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Asia Petroleum Geoscience Conference and Exhibition (APGCE)
- Conference date: November 28-29, 2022
- Location: Kuala Lumpur, Malaysia
- Published: 28 November 2022
1 - 100 of 132 results
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Carbonate Facies Description for a Large Gas Field, Central Luconia, Sarawak Basin
Authors P. Henglai, K. Poret and A. SallerSummaryRock sample analysis provides crucial information that enable creation of a robust depositional facies model, which is a key input for reservoir modelling and the field development plan. However, the conceptual facies model suggests that facies distribution in the carbonate platform varies in both vertical and lateral directions as a result of the original depositional facies and diagenesis history. Therefore, the current dataset may not be enough to capture this uncertainty, and thus we require more data to gain a clearer understanding of reservoir heterogeneity.
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Permeability Modelling using Rock Fabric Number and Neural Networks in Carbonate Reservoirs
Authors H. Zulkiply, K.H. Ling and K.S. NgSummaryDetermination of permeability is vital in the static and dynamic modelling of reservoirs. Carbonate reservoirs pose a unique challenge due to heterogeneity caused by primary and diagenetic processes. Generalized porosity and permeability relationships were developed by linking permeability and porosity with rock fabric classifications. Applications of Lucia Rock Fabric Number (RFN) method to estimate permeability is possible where specific data is available. It is postulated that spatial distribution of RFN within a field may be estimated based on Neural Networks. By combining well-based RFN classifications and Neural Network Modelling, a 3D profile of permeability and rock fabric can be obtained.
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Quantification of Mid Aptian Net Uplift and Erosion in Lower Congo Basin
Authors S.S. A Aziz, L.K. Yeap, S. Dasgupta, S. Saidi, Z.K. Gulab and R. DasSummaryThe Early to Mid-Aptian marks the cessation of rifting via seafloor spreading. Widespread uplift and erosion accompanied this early drift phase, which was likely caused by flexural rebound, though inversion due to tectonic forces may also have contributed ( Chen et al., 2013 ).
This drift phase uplift and subsequent erosion significantly impacted Aptian petroleum systems (source rocks, reservoirs, and seals; Dore & Jensen, 1996 ). In this study, our objective was to quantify the scale of uplift and erosion to develop a better picture of petroleum system dynamics and risk. Our methodology was to utilize sonic interval transit time of shale intervals in the Gamba and Dentale Formations. In addition, the results derived from sonic interval transit times were corroborated with vitrinite reflectance measurements from another 19 wells. Our analysis identified six (6) anomalous wells in southern Gabon and these were used to estimate net uplift and erosion during the Mid-Aptian.
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Predicting the Distribution and Concentration of H2S in Eastern Central Luconia
By M. ChooSummaryThe distribution of the H2S in sour gas carbonate fields in eastern Central Luconia is geographically influenced, where fields near the deep-rooted WBL generally have higher concentration of H2S likely due to their proximity of accessing the thermal fluid migration with TSR via the WBL fault system. The efficiency of the H2S-generating process relies on the proximity of the sour gas carbonate fields to the source of H2S (sulphate), the energy source and the timing of migration of the H2S into the gas reservoir. It is observed that carbonate fields with a small Hhc/Hstrc ratio have lower concentration of H2S; as opposed to the ones with high Hhc/Hstrc that exhibits higher concentration of H2S levels. This is attributed to the water-scrubbing process of removing the H2S from the sour gas that occurs naturally due to the existence of a large water column beneath the GWC. These observations are used to ascertain the maximum possible H2S concentration of the on-going B14 development; therefore, minimising the potential project and commercial risk of the project. The same observations and learnings can be transferred into the uncertainty assessment of the presence of H2S and estimation of its concentration in future exploration and appraisal wells.
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A Delineation of Multi-Formation Fluid Components Using Cased Hole Logs for Offshore Malaysia Gas-Condensate Reservoir
Authors J. Yii, A. Simanjuntak, S. Shirai and E.C. LimSummaryGas reservoir fluid properties vary during the production phase as the reservoir pressure declines below the dew point. The evaluation of formation saturation across such reservoirs may become more complicated when water saturation increases due to water influx from the aquifer.
Formation saturation analysis using conventional pulsed neutron carbon/oxygen and thermal neutron capture cross section (sigma) logs do not provide a clear sensitivity between gas and condensate. A combination of a multi-detector pulse neutron tool with an improved analysis capability has been the key to unlocking some of the challenges faced by an operator of a gas-condensate field located off the coast of Sarawak, offshore Malaysia.
Pulsed neutron logging was performed for three-phase saturation evaluation as part of a multi-well logging campaign. Production logging was also conducted in a flowing condition in one of the wells to determine the contribution from perforated intervals.
The saturation results will provide a reference to determine if there are changes required to be made on the inputs to calculate the fluid saturations (particularly water saturation, Sw) for the initial condition. This update on the inputs will improve the reservoir dynamic modelling in part with delivering actual production vs modelling.
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The Importance of PVT and Trap Analyses in the Distribution of Hydrocarbons in the Malaysian Basins
Authors F. Zainetti and N.F. Bt Ahmad SharifSummaryThis study suggests that the distribution of oil and gas accumulations of the Malaysian basins is predominately controlled by the saturation pressure regime, which defines the depth range of a dual phase system. Therefore, even though the underlying source rocks are expelling a gas-condensate hydrocarbon mixture – typically in single vapour phase, the interaction between the pressure regime and the trap characteristics still allows the accumulations of liquid pools.
In conclusion, it is important to analyze petroleum systems with a holistic approach. Once charge is established, the focus needs to be shifted to the trap geometry and its physical characteristics in relation to its seal capacity. Analyzing these relationships at a regional to semi-regional scale, would be the most effective analytical modeling method to predict and commercially exploit the remaining material liquid potentials still present in the Malaysian basins.
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CO2 Sequestration in South East Asia: Screening Methodology for Potential Storage Sites in Depleted Gas Fields
Authors N.Z. Mat Razali, L. Hong Shien, E. Intrieri, K. Mei Ching, N. Hashim and A. DimabuyuSummarySite selection is the most crucial, time-consuming, and costly process at the initial stage of a CO2 sequestration project. This paper highlights the regional screening approach and maturation study for Southeast Asia depleted gas fields. Based on the methodology, several fields situated in various basins in the region have been identified as potential candidates for future CO2 storage. Geological boundaries such as faults, stratigraphy, and hydrogeology are ideal cases for site selection characterization. However, in practice, the study area is defined by the authority on the basis of block or concession boundaries and is also limited by data availability.
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Precision Dating and Correlation from the Malay Basin to Sabah Using SEA Depositional Cycles
Authors R. Morley, S.S. Hussein, H.P. Morley, J. Jais and M.R. AripinSummaryObtaining confident age interpretations using a traditional biostratigraphic approach fail in most continental margin successions since most microfossil extinction datums are diachronous due to a combination of facies and carbonate dissolution issues, whereas evolutionary appearances are affected by both facies and caving, and so there is invariable subjectivity in placement of such datums. Sequence biostratigraphy allows confident age interpretations through the identification of transgressive-regressive cycles (SEA cycles) that faithfully capture the sedimentation ‘pulsebeat’ driven by patterns of Antarctic glaciation in the Oligo-Miocene and northern hemisphere glaciations in the Pliocene, even in very deep-water settings. Cycles are ‘fingerprinted’ by age-restricted microfossils in distal facies with correlations relying on sequence boundaries rather than first or last microfossil appearances. Based on the evaluation of 101 biostratigraphic datasets from the Malay and Penyu Basins, offshore Sarawak and offshore Sabah, a total of 46 transgressive-regressive cycles are identified. The SEA cycle succession demonstrates that other sequence biostratigraphic schemes, such as the TA and TB cycle schemes include a mixture of cycles of different rank and are thus less useful for stratigraphy prediction. To undertake sequence biostratigraphic evaluations, biostratigraphers need to become equally familiar with all three biostratigraphic disciplines of micropalaeontology, nannopalaeontology and palynology
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Improvement of FWI with Progressive Transfer Learning
More LessSummaryThe lack of low-frequency data components has been a major obstacle in FWI applications for velocity model building. Many theoretical approaches have been proposed to extrapolate low-frequency components. Progressive transfer learning was proposed to solve the problem by using a deep learning-based approach to predict low-frequency components. In this paper, we demonstrate the effectiveness of the progressive transfer learning workflow by building a practical workflow and applying it to the field data.
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Uncertainties Associated with Quantitative Fault Seal Prediction; Case Studies from Sarawak & Sabah Basins-Malaysia
By M.H. MohamadSummaryQuantitative fault seal predication concept, methodology and related software developed during last 33 years ( Allan 1989 , Knippe et al 1997, Yielding 2002 , Bretan et al, 2003 ) and became a standard technique in hydrocarbon exploration industry for predrill hydrocarbon column height and ultimately volumetric estimation. Rocks which get entrained in the faulting process- aka Shale Gouge Ratio (SGR)- is one of the main sealing mechanisms when sand juxtaposes sand on either side of the fault ( Fristad et al 1997 , Yielding et al 1997 & Yielding 2002 ). To the latter, statistical data from North Sea, Sarawak and Sabah indicate across fault pressure difference and related hydrocarbon column is a function of relative SGR ( Yielding 2002 , Hisham et al 2022 ). Increasing SGR of up to 50% results in bigger hydrocarbon column at the trap. However, overall data for SGR/pressure and/or SGR/hydrocarbon column height suggest a wide range of pressures and hydrocarbon column for the same percentage of SGR. This presentation focusses on how established methods for calculating hydrocarbon column height can benefit from newly acquired knowledge based on the integrated fault seal analysis of several fields in Sarawak and Sabah basins. This study help understanding predrill sealing capacity and hydrocarbon column height prediction.
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Machine Learning for Lithology Percentages Prediction from Cutting Photos: Massive Validation, Results, and Challenges
Authors M. Mezghani and E. TolstayaSummaryDrill cutting samples are valuable data that cover the major part of drilled well compared to the core samples that cover only a limited depth interval. Therefore, accurate and objective cutting description plays major role in decision making while drilling, in the reservoir characterization studies, and in modeling workflows. We developed an Artificial Intelligence workflow to automatically predict cutting lithology percentages using cutting photos. The workflow can be applied in near-real-time as soon as photos are acquired.
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Turning high Resolution FWI Model into Reflectivity: a Case Study Using Sparse OBN
More LessSummaryFull-waveform inversion (FWI) has been a very valuable tool for deriving accurate and detailed velocity models in various geological settings, especially for sub-salt imaging. By increasing the inversion frequency in FWI, more details and lithology related features start to show up in the inverted velocity model. It contains richer information, other than just providing a velocity model for migration. Migration image is usually considered as normal reflectivity of the sub-surface. A pseudo-reflectivity can be directly derived from the FWI velocity model without going through the migration route. The derived pseudo-reflectivity inherited the full benefits of FWI in terms of illumination compensation and noise reduction, and provides a supplementary volume to the migration image.
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Flat Spots in Carbonates: Rocks, Fluids, or Myth?
More LessSummaryQuestions are raised whether flat spots within carbonates are DHIs. High sensitivity of elastic properties to porosity and mineralogy, and the low sensitivity to fluids combined with high degree of heterogeneity all act to reduce the likelihood of strong and coherent fluid induced flat spots. In some regions of Sarawak Basin, offshore Malaysia apparent flat spots are observed within some carbonates. Where drilled the flat spots occur at or close to the GWC, but there is also a coincidence with changes in porosity and lithology. In some cases, the coincidence of changes in porosity coinciding with changes in fluid have been thought to be linked by diagenetic factors, where porosity is preserved or enhanced especially when CO2 level is high. Given not all flat spots are perfectly flat, question is raised whether these features can be predictive of gas. Recent well drilled into one of these carbonates and through the flat spot found gas but also found that the flat spot was caused by change in lithology and porosity. Further rock physics modeling showed that fluid induced flat spots might be present when the porosity and homogeneity were sufficiently high. Such examples were found on the flank of the carbonate.
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An Erosional Unconformity at the Top of the Nyalau Formation, Central Sarawak: Regional Context and Significance
Authors M. Madon, M.H. Amir Hassan and J. JongSummaryThis paper documents an erosional unconformity at the top of the Nyalau Formation (Oligocene-Early Miocene) exposed in a road-cut near Bintulu in central Sarawak. The outcrop of interest, which we call Outcrop no. 7 (longitude 113.212502°, latitude 3.325615°), is located about 25 km to the northeast of Bintulu between Tg. Kidurong and the Similajau Industrial Park. The main exposure is a 100 m-long road cut on the eastern side of the Bintulu-Miri road. It exposes sandstones of the Nyalau Formation overlain by mudstone in a channel-like feature with an erosional base. The erosional surface is irregular, and has a concave-upward surface, which is interpreted as representing a major regional unconformity.
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Crustal Structure and Evolution of the Bunguran Trough: New insights from Gravity and Seismic Data
More LessSummaryThe Bunguran Trough is an enigmatic 15 km-deep basin that straddles the Sarawak shelf-slope region, offshore Malaysia. The trough is the deepest part of the Cenozoic Sarawak Basin, comparable to the Baram Delta depocentre on the opposite (eastern) side of Central Luconia carbonate province. Despite the enormous sediment thickness, there is no gravity or bathymetric expression. A simple bouguer slab correction applied to the free-air gravity anomaly does not explain the presence of such a thick sediment-filled trough. Although its presence is known for a long time, its origin is not well understood. In this paper, we present some new insights into the nature and origin of the Bunguran Trough based on analysis of gravity and seismic data across the Sarawak Shelf. The results of this analysis have been discussed in detail by Madon & Jong (2022) . This paper only highlights some key points.
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Seisimic and Gravity Evidences of Pre-Tertiary Subcrops Beneath the Malay Basin
Authors S. Anak Suntek, M. Madon and J. JongSummaryThe “basement play” concept in the Malay Basin has been based mainly on hydrocarbon discoveries in pre-Tertiary metasediments at Anding, SW Malay Basin (e.g., Kadir, 2010 ). Hydrocarbons in these fractured “basement” reservoirs are believed to be sourced from overlying Tertiary lacustrine source rocks within the deep half-grabens. This play concept, which drew analogy from the granitic basement play in offshore Vietnam, was the main driver for the “fractured basement” exploration since the mid-1990s. Besides metasediments, other lithologies also occur beneath the Base-Tertiary Unconformity (BTU), reflecting the complex pre-Tertiary geology of the surrounding landmasses. Hence, a better understanding of the pre-Tertiary basement geology is required to explore for hydrocarbons in the pre-Tertiary. To this end, we reviewed the evidence from seismic, well, and gravity data on the nature and distribution of pre-Tertiary rocks beneath the BTU.
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Empirical Detection of Suppressed Vitrinite in Legacy Data: an Example from the Malay Basin
Authors M. Madon, J. Jong and N. Dayang AimiSummarySuppressed vitrinite reflectance (Ro) can have a big impact on exploration decisions if not recognised and corrected for. It is known to occur in the Malay Basin where optically determined Ro values have been compared with equivalent Ro analysed by the FAMM (Fluorescence Alteration of Multiple Macerals) technique. Although “apparent” suppression of Ro may be minimised through strict laboratory protocols, explorationists may have to deal with legacy data (say pre-1995) comprising only optically determined Ro of unknown quality. How then would suppression be detected? In this paper, we examine both Ro and FAMM data in the Malay Basin to see if a general suppression trend can be established and consider its potential implications for exploration.
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A Review of the Structural-Stratigraphic Framework and Petroleum Systems of the Sandakan Basin, offshore East Sabah
More LessSummarySandakan Basin, located offshore East Sabah, is one of the few regions in Malaysia that have yet to produce commercial hydrocarbons despite decades of exploration effort. The exploration history and hydrocarbon occurrences in the area up to year 2000 have been summarised by Leong & Azlina (1999) . A number of sub-commercial discoveries have demonstrated the presence of a generative petroleum system in the offshore Sandakan Basin between the Sandakan and Dent Peninsulas. These occurrences complement the numerous oil and gas seeps commonly associated with mud volcanoes and salt springs, especially on Dent Peninsula (e.g., Leong & Azlina, 1999 ). This paper provides an updated overview of the structural-stratigraphic framework and petroleum systems in the basin.
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Alteration of Mudrocks by CO2
Authors M. Sams and T. JayasangarSummaryAnomalous features observed in seismic data from parts of the Greater Sarawak Basin are believed to be diagenetic fronts associated with the presence of CO2. Measurements from well log data show that the elastic properties of shales and silts behind these diagenetic fronts have been altered through a loss of capillary bound micro-porosity. It is hypothesized that this is due to the action on the clays of carbonic acid, which diffuses along a concentration gradient away from the reservoir rocks, which contain high concentrations of CO2 that have accumulated in traps along with hydrocarbons. The velocity and density data can be corrected based on an empirical model that matches similar changes caused by normal mechanical compaction. The degree and shape of the alteration is sufficient for these effects to be observed on seismic data. The amplitudes and AVO characteristics of the seismic data drastically change due to the alteration thereby making reservoir and fluid prediction significantly more challenging. The alteration might be used as an indirect hydrocarbon indicator as there is a strong correlation within the current data between hydrocarbon presence and shale alteration.
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The Shaping and Demise of the Tusan Beach “Drinking Horse”, Southwest of Miri, Sarawak
Authors M.H. Bin Yussof, J. Jong and F. KesslerSummaryThe Miri-Bekenu coastline is formed by Neogene clastic rock formations that are poorly consolidated. These formation outcrops are shaped by weathering elements of tropical rainfalls, wind and marine erosions, and deformation processes such as tectonic uplift, structural faulting and folding. The geological monuments of the Miri area such as the iconic Tusan Beach “Drinking Horse” cliff structure generally withstand weathering degradation and marine erosion poorly. Further to this, housing projects, road constructions and encroaching new plantations had their share in destructing geological landmarks. In this article, we discuss the case study of the “Drinking Horse” starting from its creation, the impact of weathering elements and coastal erosions, and human interferences that resulted in its ultimate demise. Nonetheless, due to its present-day state of seaward-dipping sedimentary layers prefect for gravity sliding, coupled with pounding erosions, the cliff had inevitably collapsed and any prior preservation effort carried out to protect the structure were seen in vain.
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Seismic Imaging Workflow Optimization and Velocity Model Uncertainty Quantification in Carbonate
Authors M.H. Pua, M.I. Supardy, C. Lee Slind, W.H. Tang, S. Maitra and F.F. BasirSummaryThe velocity Model plays a remarkably important role in seismic processing, especially in seismic imaging, as it directly affects the final data quality. Carbonate fields velocity model building are even more complicated as they are known to be much more complicated in chemistry and physics that leading to high heterogeneity and uncertainty. Often in carbonate fields, other complications also will associate together such as shallow gas in this case study where it increases the complexity and difficulty to obtain the most optimum velocity model for seismic imaging. This accumulation of complications can be resolved mostly through advanced and modern seismic processing techniques however, there will be still some uncertainty remaining in the velocity model building. In this case study, a tailored imaging workflow that includes Q-tomography, Q-APSDM, and FWI has been applied and plays an important role in solving most of the challenges while optimizing the velocity model. The uncertainties that underlie the velocity model produced even with this sensible workflow will still be present and need to be quantified. The quantification of velocity model uncertainty will be through the tomographic inversion process and able to provide velocity standard deviation as an output that reflects velocity model uncertainty.
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Upgrading and Redefining Cycle I GDE of Deepwater Sarawak via Multi-Attributes Analysis of Cycle I Coal
SummaryThis study covered within North Luconia region which warrant a guidance towards Cycle I gross depositional environment (GDE) revision. Previous model of 2020–2021 Cycle I GDE represent separated bodies at Well C-1, Well O-1, Well P-1, Well Q-1 and Well R-1 due to those wells was sitting at paleo high as supported by Bouger anomalies and was affected by marine incursion. In general, coal deposition in Cycle I was associated with lower coastal plain (LCP). However, the coal deposition in the previous model was not extensive and this therefore, raised a possibility that it might be a single coastal body instead. Questionable on the swampy area which only pointing at Central Luconia while at North Luconia province, the coal still can be established as depicted by Well A-1, Well C-1, Well J-1, Well O-1, Well P-1, Well Q-1 and Well R-1.
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Uplifting Vintage 3D Land Seismic Dataset with Modern Processing Workflow: a Case Study from Thailand
Authors N. Wanpiyarat, R. Chakraborty, S.H. Ng and N. PhantaweeSummaryWe present a case study based on the application of modern contemporary signal processing and depth- imaging techniques to vintage data from the Phitsanulok Basin, onshore central Thailand, in which four overlapping vintage 3D land surveys were merged and imaged pre-stack to form a single volume. The vintage data processing was limited to the application of dip-filter-based noise attenuation, pre-stack time imaging and post-stack survey merging, which leads to unresolved geophysical challenges associated with each process. In the reprocessing, a cascaded application of surface-wave and coherent noise attenuation was followed by surface-consistent deconvolution that is robust against surface-inconsistent noise and suitable for stabilizing the amplitude and phase response of the embedded wavelet. 5D matching-pursuit Fourier interpolation technique was utilized for interpolation and regularization in offset-vector tile domain of the sparsely and irregularly sampled data. Anisotropic depth imaging was implemented to reduce the structural uncertainty. Additionally, pre-stack merging of the vintage seismic data facilitated accurate structural imaging in and around the overlap area of the surveys. The improvement attained in the reprocessed seismic images will reduce the risks associated with future development plans, overcoming the limitations of the suboptimal acquisition parameters.
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Understanding Stage IVD-Pink Reservoir through Hard Data-detailing Geoseismic, Integration of Updated PDA and Newly Constructed GDE
SummaryThe distribution trend of Stage IVD Pink is matches with the shelf edge cut in Southeast to Northwest direction which suggesting the entry point is coming from Baram and Champion delta. During syn-kinematic deposition of Stage IVD Pink, the sand transportation tries to find the lower structure as a main pathway towards distal toe-thrust area. The Stage IVD Pink behavior is deposited during syn-kinematic event where the deposition takes place during structuration forming ponded turbidites. Based on well and biostratigraphy analysis at Stage IVD Pink, it is correlatable to NN11/NN10. Seismic facies summary demonstrates 8 seismic facies categories interpreted in the area. The new analysis of Stage IVD Pink PDA covered 22 wells constrained within area of interest and failure analysis is generated based on 9 wells (excluding discovery and unevaluated wells) PDA shows reservoir as the main causes of exploration failure due to previous wells drilled targeting crestal part of toe-thrust area. Pink interval is deposited during syn-kinematic phase, hence thicker sands is believed to be deposited at the flank area and thinning onto the crest. The distribution of Stage IVD-Pink reservoir is limited towards distal toe-thrust as shown by NN11/NN10 zone at well 23-1.
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Chasing the Remaining Hydrocarbon in Carbonate Build-Ups of Central Luconia Field, Offshore Sarawak, Malaysia
Authors Z. Abdul Rahman, J. Baharom, N.F. Zawri and S.S. Ab RahmanSummaryOpen-winged carbonate platform characterised by thin carbonate wings were interpreted to have been deposited in situ as a thin carbonate platform during marine transgressions. 3D seismic data of the Terumbu Luconia covering an area of approximately 13,483 km2 was used in this study. The advancement in the interpretation technology allows extensive number of seismic horizons to be picked and mapped with consistent polarity. Seismic interpretations revealed that the open wings tend to extend for several kilometres away from the buildups along flat-lying surfaces and may have volumes significantly larger than the volumes of their corresponding buildup intervals. Central Luconia province is one of the major producing areas in Sarawak fields with almost 250 fields and 65 tcf recoverable gas discovered to date. However, most of the producing wells targeted to the main long-lived carbonate buildups. The results indicated that there is promising gas potential for NFE exploitation in the allochthonous play within the study area for further evaluation.
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Detached Offshore Bars. Testing a Stratigraphic Play, Offshore Sarawak, Malaysia.
SummaryOffshore bars are an enigmatic and often under-recognized constituent of the shallow marine deposition system. In the Pliocene aged, Cycle VI clastic sedimentary succession located offshore Sarawak Malaysia, offshore bars have been interpreted from sediments previously thought to be lower-to-middle shoreface deposits. The reclassification of these sediments from shoreface to offshore bars yields compelling exploration opportunities as detached bars, encased in shelfal mudstones may constitute stratigraphically isolated traps.
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Unlocking Significant Hydrocarbon Potential with Newly Identified Carbonate Play in North Luconia, Deepwater Sarawak, Offshore Malaysia
SummaryThis abstract presents the recent G&G work which led to identify Carbonate Play in North Luconia province deepwater area of Sarawak, offshore Malaysia. North Luconia, offshore Sarawak is a relatively frontier area for exploration having very sparse well density and presently low exploration activities. The understanding of petroleum system elements in this area is relatively fair to good. In the past most wells drilled in Northern Luconia deep-water, targeted Cycle I and Cycle II Clastic reservoirs. There are few wells drilled to target deep-water turbidites sands in Cycles V–VII. So far, no commercial hydrocarbon accumulation has been encountered, however there are few sub-commercial discoveries made in the region, have proven working petroleum system. Recent interpretation of Seismic 3D PSDM data leads to identification of a potential Pre-Cycle I ( Sequence-A Carbonate Play) in Late Eocene - Early Oligocene age. The integration of other G&G data, i.e., seismic, wells, and Gravity-Magnetic have been made to identify prospects in Sequence-A Carbonate Play in PETRONAS Carigali operated Blocks ND1, ND2 and ND3. Preliminary evaluation of Sequence-A carbonate play indicates evidence of huge hydrocarbon potential in deepwater area of Sarawak, which will certainly rejuvenate exploration activities in this region.
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Revealing the Reservoir Underneath Volcanic Rocks and Folding Structures in the Liaohe Basin
More LessSummaryMultiphase volcanic eruption and fault-related folding form good traps for hydrocarbon reservoirs in Liaohe-basin, China. Exploration activities in the deep Paleozoic section in the region have been limited due to poor subsurface imaging underneath complex overburden. Strong surface-related multiples are present, because of frozen surface conditions and high impedance contrasts between sediment layers and volcanic rocks. These multiples overwhelm weak primary signals in deep section. Meanwhile, drilling history revealed high spatial variation of the velocity in deep target zone due to major faults and volcanic rocks. Such complex overburden poses significant challenges for seismic imaging. Imaging is further complicated by the inadequacy of available data sets, which all have narrow-azimuth coverage and limited offsets. None of these challenges have been fully addressed in the vintage seismic processing. In this study, we first demonstrate the importance of 3D surface-related multiple elimination (SRME) after adaption for the data here, and then present iterative time-lag full-waveform inversion (TLFWI) to derive an accurate high-resolution velocity model that can correct the kinematic distortions due to the complex overburden. With a tailored flow, the Paleozoic section and the major Rongxi reverse fault are clearly revealed in our latest re-imaging, which helps reduce uncertainties for future exploration.
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Advanced Geostatistical Seismic Reservoir Characterization in the Growler Field
Authors A. Mannini, S.J. Yap, D. Cunha, E. Shirley, J. Zhou, A. Mathur, A. Mandong, R. Shaw and J. TingSummaryThe Growler field located in the Cooper–Eromanga Basin, South Australia, is an onshore field producing oil from the middle Birkhead formation of Jurassic age. The main producing area is a low relief four-way dip closed structure consisting of a channel reservoir of 15–20m thickness that has been mapped from the 3D seismic amplitudes and confirmed by the drilled wells. Interpretation of 3D seismic data has revealed relatively lower quality oil reservoir in the form of minor sandstone channels and crevasse-splay deposits. To draw strategy for optimum development of this field and to support further exploration campaign pre-stack seismic inversion has been carried out. An innovative workflow comprising iterative seismic petrophysics, rock physics modelling, preconditioning of seismic data was used to calibrate the seismic AVO response with well data. Deterministic inversion was carried out and litho-facies estimated using Bayesian inference to understand the intricacies of the aforesaid challenges before application of geostatistical inversion to derive highly detailed subsurface model. Joint facies and elastic properties inversion facilitated by geostatistical inversion using Markov Chain Monte Carlo method has resulted in good quality facies results that match wells at several blind locations and conform to the depositional setup of the area.
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Why Subsurface Uncertainties don't have to be Lognormal and other Practices to Avoid
By J. De JagerSummaryThe risks and volumes of oil and gas prospects are in most companies assessed in commercially available probabilistic Risk & Volume tools. Despite a lot of effort is put into this, the exploration community continues to over-predict (on average) the oil and gas volumes of prospects. This is in part due to some misunderstandings that lead to common practices that are best avoided. In this presentation several of these will be discussed: the incorrect assumption that subsurface uncertainties must be lognormal, incorrect truncation of uncertainty distributions at the low end, and the way that uncertainty is often confused for risk. A better understanding and application of these basic aspects of sound Risk & Volume assessments may reduce the risk of over predicting prospect volumes.
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Decomposing Zoeppritz: A Visual Interpretation of AVA
Authors M. Sams and T. KurniawanSummaryFor most people, the Zoeppritz equations are impenetrable and provide a barrier rather than an aid to interpreting seismic amplitudes in terms of key reservoir properties. Even very basic simplifications can be challenging for some. AVA blocky modelling is commonly used to visualise the AVA behaviour of half spaces, but these only provide limit use for the complexity of most geological situations where vertical variations are occurring at many scales. We propose that a deeper understanding of the AVA behaviour of seismic data is better achieved by visualising synthetic AVA gathers based on well log data, which have been decomposed into three terms representing the response to variations in acoustic Impedance, shear modulus and density. The decomposition shows how the AVA is governed by the vertical variations in the elastic properties and the inter-relationships between those elastic properties. These insights will allow the interpreter to more readily make the link back to the geology and the quantitative interpreter set expectations on the reliability of estimates of elastic properties from AVA inversion. Case studies for a soft gas sand and a hard wet sand are provided.
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Defining Reservoir Compartments and Baffles: A Case Study in Deepwater Sabah, Malaysia
Authors J. Jong, M.A. Khamis, S.M. Barker, R.C. Shoup and W.M.Z. W EmbongSummaryOne of the key challenges in deepwater exploration is the prediction of reservoir geometries. Basin floor fans, deepwater channel systems and crevasse splays, ponded turbidites and MTDs are the main depositional geometries that can result in reservoir compartmentalization and baffling in a shale-dominated environment. This study aims to define and understand the various reservoir compartments from a deepwater Sabah case study, applying both structural and stratigraphic approaches over the Kinarut to Pink stratigraphic intervals. The application of sequence-stratigraphic interpretation techniques in conjunction with sedimentary-processes enables geoscientists to unravel the complex deepwater depositional architecture. The integration of multiple G&G data is employed to define the deepwater reservoir setting and possible sand fairways. These methods include structural and sedimentary seismic analysis, seismic attribute studies and spectral decomposition analysis. The interpreted results are then related to regional deformation episodes, with a pre-kinematic phase and a post-kinematic phase observed. Their impact and controls on the sedimentation styles and the resultant variations in reservoir geometries and compartmentalization are then discussed.
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Influence of Frequency and Training Models on Physics-Guided Velocity Model Building
Authors S. Dhanapal, H. Rusmanugroho, M.D.D. Muhammed, J. Sun and J. LiSummaryVelocity model building (VMB) is subsequently used to provide subsurface velocity model for workflows such as seismic imaging and interpretation. As two widely used velocity model building techniques, ray-based tomographic approaches are not very effective in complex geological settings; and Full waveform inversion (FWI) approaches are computationally extensive and sensitive to initial model. The physics-guided deep learning based velocity model building, that involves deterministic, physics-based modelling and data-driven deep learning components, is designed to capture the subsurface salt body shapes and locations, with a small amount of training models. In this work, we further discuss the influence of dominant frequency and training models on the velocity prediction by using H-PGNN method. Our results show that, the higher the dominant frequency, the more accurate the prediction accuracy of the salt body shapes and background information. For more complicated velocity models and real datasets, simple synthetic training models are not capable of capturing the salt body shapes, nor the background information. A more practical synthetic training set with much more smoothed background layered structures is more suitable to predict complicated models.
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A Review of Digital Transformation Initiatives for Real-Time Formation Evaluation
Authors K. Katterbauer, A. Al Shehri and A. YousifSummaryWe present a thorough overview of the state-of-the-art developments of artificial intelligence and automation, including robotics, in the area of formation evaluation, well logging and reservoir monitoring. The 4IR is and will be a key component in the development of new technologies in these domains and more broadly in upstream oil operations. While there are substantial challenges that need to be overcome in the near future, there is also tremendous potential with the availability of an increased number of interconnected sensing devices for real-time monitoring and interventions [ 25 ]. The 4IR trend is clear and unrestrainable also in Formation Evaluation: automation of measurements, interpretation, interventions and decision making, with minimal human intervention; as well as extensive use of artificial intelligence to support data analytics and interpretation in a framework of indirect measurements, complex characterization, data scarcity and ill-posed problems.
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We Think we're in Control, but are we? A Case Study from Offshore Sarawak-East Malaysia
Authors S. Nazari, P.A. Restrepo-Pace, C. Lee and H.'. Ahmad MunifSummaryStructural restoration and structural forward modelling of 2D cross sections presented here are used to provide structural validation and insights into the kinematic evolution of a hydrocarbon field offshore Sarawak. Structural restoration is the primary workflow used for interpretation validation. Structural forward modelling, on the other hand, provides holistic kinematic review as it constrains deeper fault shape trends. During cross section balancing fault throw, horizon cutoffs and seismic character across faults is checked. The datasets are loaded in two different structural platforms, applying similar methodology in order to investigate how their algorithms operate in an effort to establish more efficient ways to conduct routine modelling. Software A & Software B perform restoration primarily using the block restoration, vertical slip and flexural slip as the parameters. Reference horizon is used and faults slips are removed in order to restore interpreted surfaces and seismic ( Nunns, 1991 ). Due to the uncertainty of deeper fault geometry (poor imaging), structural modelling is used to constraint fault shape. We have now conducted restoration for interpreted seismic sections and forward modelling for fault trend trajectory for Sarawak offshore. Thus, comparison between the restoration results and forward modelling using two different software to narrow down the uncertainty.
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Seismic Characterization of Carbonate Flank Deposits Delineating Upside Potential : A Case Study in Central Luconia
Authors H. Ismail, R.S. Djumeno, A.H. Abd Latiff and N.A. AzmanSummaryCarbonate Flank deposits considered as one of the emerging hydrocarbons play within the proven plays in Central Luconia Sarawak. The potential of hydrocarbon occurrences within this play has been proven by one of the producing fields. Seismic characterization and mapping techniques utilizing multi attributes extractions and well data analysis will aid in delineating the Flank deposits features and connectivity. Detail seismic evaluation of the untapped resources within the carbonate flank deposits is expected to provide good input to assist volume estimation within Central Luconia aimed for hydrocarbon monetization and future resource addition.
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Empirical Anisotropy Correction in Deviated Well Logs from the Malay Basin.
Authors S. Ronghe, A. Locke, S. Teng, S. Chee Chuan and A. ChuangSummaryShales in the Malay Basin are anisotropic. Well log measurements of p-velocity and s-velocity are affected by shale anisotropy, especially in deviated wells. Anisotropic measurements create inconsistency within the data set and impact results and interpretation. In this paper we present a novel, empirical technique to correct for anisotropic effects in velocity logs, referenced to a rock physics model.
Data comprised 22 wells from the Malay Basin including 15 with varying angles of deviation (up to 70°). The wells were spread across an area of approx 2,000 sq km, covered by seismic angle stacks. The project involved absolute seismic simultaneous inversion followed by lithology and fluid interpretation, calibrated to a statistical rock physics model.
Velocity logs from deviated wells were corrected for anisotropy. The correction involved adjusting low frequency trends of the logs to the trends from vertical wells for non-reservoir lithologies. The correction was applied proportional to the magnitude of well deviation - as the angle of deviation increased, rock physics trends from vertical wells carried greater weight.
Anisotropy corrections improved the consistency of elastic logs across wells and enabled their tighter integration with seismic for reservoir characterisation in deriving predictions of lithology and fluid distributions.
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Pore Pressure and Drilling Experience: A Deepwater Well Case Study in the Gulf of Mexico
Authors H.Y. Sau, B.C. Ong, F. Wijnands, N.N.H. C Soh, M.S. Masnan, F.A. Ismail, J. Sagahon and M.R. Paul TingaySummaryThis is a case study of the predrill pore pressure estimation and post-drill pore pressure analysis of Well X in the Gulf of Mexico. Well X is a deepwater wild cat well in the Gulf of Mexico with very sparse offset well data. The objective of Well X is to test the hydrocarbon presence in the Miocene aged deepwater stacked channels/lobes in an NW-SE trending toe thrust anticline with a reverse fault in the core and edge of the structure at a depth of ∼ 3600 m TVDDF. Conventional 1D pore pressure prediction methods have limitations and high uncertainty in structurally complex deepwater frontier exploration areas. Pore pressure predictions rely mainly on seismic interval velocities and a velocity-pore pressure transform, particularly in areas with limited offset wells. With an excellent geological understanding, pore pressure analysts integrate all the geological inputs into a robust predrill pore pressure model for the well design and planning. Nevertheless, all pore pressure models have uncertainties, and a key goal of pre-drill pore pressure prediction is to appropriately capture these uncertainties to enable safe well design.
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Unleashing Potential Stratigraphic Play via High Resolution Strata-Slicing Approach in North Malay Basin, Offshore Peninsular Malaysia
SummaryIdentifying new opportunities in the Malay Basin is challenging as heavy exploration activity has taken place with more than 700 wells drilled since 1969. Nonetheless, Yet-to-Find (YTF) estimation in 2021 indicates around 3 Bboe of remaining potential are awaiting to be explored. This paper describes the utilisation of specialised seismic interpretation technology in combination with high resolution strata-slicing, as an alternative approach in identifying exploration potential within North Malay Basin. The geological nature of the NMB reservoirs comprising lower coastal plain channelised system, provides an ideal geological setting to test this application. More than 400 horizon strata slices were generated from the top of basement to the seabed using merged 3D seismic data obtained from Relative Geological Time (RGT) model using PaleoScan™ software. The strata slices are then used for amplitude attributes extraction and spectral decomposition analysis, in combination to interpret the geomorphological features and define it’s associated geobodies where approximately 250 prospects were identified. One of the largest prospects yield a gas-initially-in-place (GIIP) of up to 2 Tscf. These findings are dominantly represented by fluvial channels within Groups F to I, which provided a new insight in a relatively mature basin.
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Enhancing Interwell Saturation Mapping via an Innovative Quantum Machine Learning Framework
Authors K. Katterbauer and A. Al ShehriSummaryUtilizing a quantum machine learning method for mapping interwell saturation based on well logs and electromagnetic tomography provides a data-driven approach to deep diagnostics of the reservoir, honoring both geology as well as reservoir dynamics. The 4IR framework has exhibited a strong estimation quality of the water saturation profile for a realistic reservoir box model via training the network with well-log data in the near-wellbore zone.
This new approach can be readily supplemented with new data to improve the accuracy of the predicted saturation maps. The 4IR framework is flexible enough to be adapted to different geological structures and petrophysical relationships and the results from this reservoir box model study exhibited great potential in a broader application of the technique for interwell saturation mapping.
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Delineating Prograding Deposit of Syn-Rift Play of North Malay Basin via Seismic Attributes and Wheeler Transformation
SummaryThis study was carried out in the Late Oligocene to Early Miocene interval of the North Malay Basin offshore Peninsular Malaysia. This paper demonstrates an integrated interpretation of geological information from seismic mapping, attributes analysis and seismic sequence stratigraphy via wheeler transformation in assessing the prograding deposit within the top synrift of the area. The result of this study shows that alternative methodologies from semi-automated interpretation and Relative Geological Time (RGT) model to the application of Wheeler Transform are able to enhance the definition and delineation of prograding sequence within the top synrift of North Malay Basin. The combined approaches of refined interpretation of the seismic supplemented by generation of instantaneous phase and thinning attribute from RGT, have successfully mapped the strata termination plus its associated thinning and thickening patterns. Together with other attributes, the clinoform outline within the interval were greatly enhanced which helps in extracting potential prospect. The overall results indicate a series of interesting stratigraphic/seismic geomorphological features representing the potential prospects (prograding sandy deposit?) that could add to the Yet-To-Find (YTF) resources candidates.
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Ultra-Shallow Water OBN offshore Sarawak - High-Resolution Model Building to Image Shallow Gas and Complex Geology
Authors A. Verba, W.L. Cheah, J.W.L. Ming, S.W. Cheok, S. Chen, S.B.A. Rahman, T.W. Hoong and A.I. YusofSummaryOil and gas fields offshore Sarawak in the Malaysian basin present a number of challenges for seismic imaging due to the shallow-water environment and uncertainties in seismic reservoir definition and reservoir characterization. These are mainly due to a complex overburden, including heavy faulted zones and shallow gas accumulations. Legacy seismic images show poor fault delineation and a lack of continuity of events beneath the shallow gas, due to the limits of both the acquisition and imaging technologies previously available.
An ocean-bottom node (OBN) survey was conducted in the offshore Sarawak area due to the low-frequency, full-azimuth, and ultra-long offset information the OBN data would provide. These benefits can be used to improve illumination of the main target reservoir. When combined with contemporary signal processing and depth imaging technology, it can reveal the geological structures and provide reliable amplitude especially beneath the shallow gas body for reservoir characterization.
This paper focuses on the earth model building and describes the combination of full-waveform inversion (FWI), common-image-point (CIP) tomography and Q tomography workflows to build detailed and accurate velocity and Q models to improve the seismic imaging, capture overburden heterogeneity, and uncover the structures masked by the gas body above the target area.
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Management and Mitigation of CO2 Emissions During Marine Seismic Surveys
Authors A. Long, M. Christiansen and C. JamesSummaryTo take urgent action to combat climate change and its impacts, we have committed to reduce relative CO2 emissions (t CO2 per CMP km) by 50% compared to 2011 within 2030. DataOps optimization of vessel and survey management has been applied to four Titan-class Ramform seismic vessels since 2020 and allows realtime tracking of fuel consumption, CO2 emissions and many vessel performance metrics. Guided by the digital platform used to measure and manage the vessel operations, the two focus areas for attention are elements of survey design and drag reduction initiatives. Tools are being developed to translate modelled dynamic loads and drag of specific acquisition configurations into modelled fuel consumption versus vessel speed. The ‘equivalent CO2 budget’ should be predictable for a survey as a function of different key acquisition parameters, at least qualitatively in terms of comparative configurations.
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Arising Play: Post MMU Clastics with Lupar-Rajang Systems as Reservoir Provenance in West Sarawak
Authors M.I. Mahmood, S.H. So, M.N. Zubir, S.N. Jamil and M.A. AriffSummaryWest Sarawak is located at the western most of Borneo, tucked to the east of Natuna Basin. The region can be divided into three provinces namely West Luconia, Southwest Sarawak and Tatau. Exploration had begun in the 1970s with many gas discoveries in Cycle V clastics and Cycle IV carbonates. Despite all, there are still more to learn about this region’s tectonic and stratigraphy. Cycle VI to VIII has been perceived as having low prospectivity with high uncertainty in reservoir presence. Recent evaluations suggest, thick package of sediments within Cycle VI to VIII have deposited in Bunguran Inboard. Based on the evidence, there is a high possibility for this package to be sandy with Lupar and Rajang as the provenance for this reservoir.
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Trends And Observations On Co2 High Uncertainty To Revitalize West Luconia.
Authors M.I. Mahmood, S.H. So, M.N. Zubir, H. Kahar and M.A. AriffSummaryWest Sarawak is located in between Central Luconia Province and Natuna. The region consists of West Luconia, Southwest Sarawak and Tatau province. Since 1970s, there are approximately 25 exploration wells drilled the region. Considering the areal extent of this region (80000 sq. km), the wells are deemed as sparse, thus making it a frontier region. Even though the drilling success rate at West Sarawak is high, CO2 in the reservoirs appeared to be ranging from 2% to 90%. Consequently, the region is well known as ‘cursed’ by CO2. Recent studies have indicated that West Sarawak tectonic and stratigraphy settings could influence the CO2 occurrence and accumulations. Deep-seated faults could be the conduit to transport CO2 from deep source to the reservoirs. In addition to that, different stratigraphy such as Cycle VI and Lower Cycle V may capture lower CO2 depending on the migration pathways. It was also observed that CO2 Halo diagenetic effect can be associated with the occurrence of CO2, however it has no correlation with the concentration of CO2.
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Deep Seated Faults Reactivation; Insight from Subsidence Analysis, West Luconia-Sarawak Basin-Malaysia
Authors M.L. LEE, S. Sherkati, S.S. Mustahim, S.H. So, M.I. Mahmood and M.N. ZubirSummaryWestern flank of Sarawak basin subdivided into 5 main geological provinces namely Bunguran Trough, West Luconia Rim, SW Luconia, Half Grabens and Sibu. The current exploration target is focusing from Pre-Cycle I to Cycle VIII (late Paleogene-Neogene). Play targets ranging from marine clastic, carbonate, terrestrial clastic and basement play. High uncertainty of CO2 concentration in West Luconia is one of the main challenges for hydrocarbon exploration, which linked with deep seated faults reactivation. Deep burial depth and poor seismic imaging prevent understanding the inherited faults reactivation timing and its impact on structuration. The aim of this study is to use subsidence analysis and 2D/3D regional structural restoration to overcome this problematic. Furthermore, paleotopography for different time steps were estimated and sedimentary distribution relation with tectonic evolution discussed. In conclusion, restoration and back striping analysis in west of Sarawak basin show deep seated faults most probably reactivated several times in the past. Deep seated faults reactivation had a major impact on seabed topography and sedimentation accordingly and CO2 migration from mantle. Our study highlighted the area with higher potential for carbonate deposition during Cycle III & IV.
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Towards a Formal Method in Tectono-Stratigraphy; Using SE Asia’s Unique Dataset
More LessSummaryAn overlooked relationship in sedimentary geology is that basins direct sedimentation, and stratigraphy records the tectonic history of the basins. In spite of this direct relationship, stratigraphy has hardly been used to help develop ideas in regional structural geology. In some cases bad stratigraphy has actually obscured recognition of natural patterns. The authors have undertaken a major review to validate and calibrate stratigraphic data from original reports, and using modern methods such as geohistory analysis to quantitatively analyse the history of accommodation space and its sediment fill across Sundaland since the Eocene. The results are startling, and indicate a very different geology and plate tectonic origin for the region. The process is evidence-based and replaces the largely model-based stratigraphic concepts that have dominated thinking over the past three decades. From this a process has evolved, where stratigraphy can be used to test and falsify geological ideas, quite unlike its limited application in “layer-cake” passive margins.
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Facies and Reservoir Property Prediction Using Deep Feed-Forward Neural Network, a Case Study from Offshore Thailand
Authors P. Boonyasatphan, O. Limpornpipat, R. Pasha Amarullah Bekti and J. TingSummaryReservoir property prediction from seismic data could be conducted by using many approaches. One of the easy-to-use approaches is to extract seismic attribute(s) that could provide a link between the observed amplitude anomaly to the corresponding geological feature, which in terms is closely associated with the deposition of a certain type, qualify of lithology, and fluid content. Reservoir property can also be predicted using elastic property obtained through the more advanced approach such as seismic inversion. However, the seismic inversion workflow usually requires more time and resources, for example, when building a robust rock physics model. This paper introduces a new prediction technique using a supervised deep neural network called Deep Feedforward Neural Network (DFNN). It can predict facies and reservoir property directly from seismic stacks. It provides a significant benefit in terms of speed and quality compared to traditional methods. From the prediction results achieved in this study, the DFNN technique can be considered as an alternative to conventional seismic reservoir characterization methodology.
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A Novel Approach to Unlock Hydrocarbon Potential in Thinly Laminated Reservoirs through Casing
Authors C. Cavalleri, S. Ahmad and Y. AkashevSummaryA novel methodology for high resolution pulsed neutron logging and comprehensive formation evaluation behind casing is presented. Multiple independent rock properties, recorded and analyzed at different resolution, are recorded and integrated for accurate assessment and characterization of laminated sequence to unlock their potential and guide well testing and completion strategy. The ability to record station log data during standard depth log acquisition, at no extra time, coupled to dedicated data processing, is instrumental to further enhance the vertical resolution of the outputs, adding confidence to the interpretation for formation evaluation.
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Basin Development, Paleogeographic Evolution and Sandstone Reservoirs Characteristics within the Early-Late Miocene Play, Northern Malay Basin
Authors N. Md Nor, A.H. Abd Rahman, S.S.W. Sy Khairulmunir Wafa, B.H. Wei, M.R. Aripin, J. Baharom and N.F. ZawriSummaryNorthern Malay Basin is located northeast offshore Peninsular Malaysia, in water depths ranging from 50m to 80m. This part of the Malay Basin, which is relatively less explored, comprises three geological terrains: basin centre, west flank and east flank. This paper summarizes the results of the evaluation of the seismic geomorphology and reservoir characteristics of the sand bodies within the stratigraphic units Groups D to J that, facilitated the evaluation of basin development and paleogeographic evolution of this area. From the mid Middle Miocene (Group F) to lower Late Miocene (Group D), the main depocentre which trends NW-SE, was dissected by a series of north-south trending faults acting near the centre-to-western part of the basin and resulted in a bending in the southern part of the depocentre. The basin developed into two connected depocentres towards the end of Group D times – a north-south and a second east-west trending depocentres. The gentle eastern flank of the basin recorded the preservation of many intervals of channelised fluvial reservoir sand-bodies. The steeper western flank recorded many intervals displaying sedimentary lobes and patches, possibly representing some form of alluvial fan deposits.
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Systematic Seismic Multi-Attributes Methodology to Uncover the Early Miocene Carbonates in Central Luconia Province.
SummaryCentral Luconia Province is characterized by the extensive development of Late Miocene carbonates build ups which has been a prolific play and regarded as one of Southern East Asia’s Super Basins (Rice-Oxley & Abu-Bakar, 2020). The Early Miocene carbonates which co-exist with the prolific Cycle IV/V Carbonates have the potential to hold substantial hydrocarbon volume for sustainable future.
Carbonate facies identification in the Early Miocene plays of Central Luconia is known to be challenging as the seismic imaging of the deeper carbonate are hindered by the energy absorption of overlying Cycle IV/V Carbonate; resulting to poor imaging and subtle lithologic changes that cannot be easily recognized. The aim of this paper is to share the proposed methodology of identifying carbonate morphology and seismic facies analysis using multi-attributes generation and spectral decomposition
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Comprehensive Approach of Reservoir Quality Through Carbonate Type Identification in Early Miocene Carbonate Plays, Central Luconia
SummaryThe Central Luconia province in offshore Sarawak, features extensive development of Middle to Late Miocene isolated carbonate platforms that developed on post-rift horst palaeo-highs. Carbonate deposition in the Central Luconia Province started during the Early Miocene and continued until the present day in some areas. Two major factors controlling carbonate sedimentation in the Central Luconia province are the regional tectonics and eustatic sea level changes ( Ting & Aljaadi, 2011 ).
The remaining underexplored of Early Miocene carbonates have very limited penetrations hence understanding the presence and quality of the reservoir persists as a challenge. The lack of analogue for these plays unveiled the comprehensive approach in determining the reservoir quality through carbonate type identification. The aim of this paper is to share the different types of carbonates identified occurs during Early Miocene. Classifying these carbonates into different carbonate types and models helps to further shift the understanding of the carbonate quality in different geological depositional settings. Both global and nearby analogue of reservoir properties were adopted to these different carbonates typing.
The details seismic facies work has identified 6 different types of Early Miocene carbonates build ups which have major impact on the understanding of Early Miocene paleogeography in Sarawak Basin.
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Fluid Inclusion Studies on Understanding Hydrocarbon Migration of Point Bar System in N Field, Malay Basin
Authors N.Z. Azmi, N.N.L. Hushin, M.A.R. Mohd Abd Rahman, K.A. Ser, M.I. Zainuddin and C.C. JiunSummaryThe N Field is one of the hydrocarbon fields within PM-3 Commercial Agreement Area (CAA) block located at the northeast margin of the Malay Basin. The sands were deposited during the Middle Miocene to Early Miocene in fluvial to marine environment. PM-3 CAA currently has over 255 wells mainly targeted the low-risk play type of structural or combination trap.
One major component of a successful exploration is evidence of hydrocarbon migration. Fluid inclusion stratigraphy (FIS) is a technique that can be used to understand the hydrocarbon charge, migration through stratigraphic interval of interest, and evaluate the petroleum type and quality. This paper demonstrates the application of FIS to identify the migration in Reservoir A in N Field. Photomicroscopy on thin sections is used to verify petroleum inclusion presence in sample as well as to observe non-relict features of FIS mass spectra.
Fluid inclusion study shows both wells that penetrated the water and hydrocarbon legs have petroleum inclusion which supports hydrocarbon migration concept in the Reservoir A’s point bar system. The result helps in improving the chance of success for PB1 and PB3 exploration.
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Intriguing Possible Calciturbidite Features seen in the North-West Borneo Trough
Authors M. Mubin, M.H.H. Mohamad, A. Bera, S. Jirin, Z.Z. Tuan Harith, Z. Zaki, S.N.A. Syed Khastudin, D. Uli and H.H. MohammadSummaryThe paper showcases seismic geomorphology analyses based on spectral decomposition performed in the western area of the North-West Borneo Trough. Two intriguing ‘fan-shaped’ features were observed coming from the NE and NW of the block boundary defined to have formed during the Late Miocene period. The features are believed to originate from Miocene aged carbonates which are believed to have survived until the Present-day as observed from satellite imagery on the Present-day bathymetry. They are inferred to be calciturbidites which formed during erosion and reworking of the carbonate buildups during prevalent sea-level fall or seismicity events which occurred during the Late Miocene. As these calciturbidites were only observed during Late Miocene period with no observable seismic occurrences in the younger shallower intervals, a possible hypothesis is that they were probably still present but ‘diluted’ by the active sedimentation coming from the Southern Baram which had an increase in influence in the northern part of the study during latter stages of the Late Miocene period onwards. This period also coincides with a major backstepping of the carbonate platform sizes as they start to have a decrease in carbonate productivity hence less available carbonate material able to be reworked.
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Utilizing Shallow Water PP-PS Seismic of Sparse Ocean-bottom Nodes for Improved Reservoir Characterization
Authors B. Chowdhury, A. Waluyo, S. Sengupta, P. Kristiansen, A. Sazykin, S. Goswami, S. Basu, S. Mahapatra, A. Prakash, A. Singh, R. Srivastava and J. DasSummaryOcean bottom node (OBN) seismic is getting more popular for providing greater interpretation certainty in areas of complex reservoirs. Its full azimuth (FAZ), high fold count, high repeatability and broadband character prove to be beneficial especially in areas with complex geological structures and these factors were a driver to record the first 4C OBN survey in D1 field, western offshore India. Despite several attempts of reprocessing legacy narrow-azimuth marine seismic with more advanced processing techniques, it was difficult to use the legacy data to resolve the thin plays of the multi-layered limestone reservoir and understand fluid distribution in the reservoir section.
We present a case study of seismic processing of PP-PS data, acquired with sparsesly distributed multicomponent ocean-bottom nodes in a shallow water environment, in order to resolve the production issues, anisotropy mapping, reservoir development, thin pay mapping and basement fracture detection. We review a number of processing and imaging challenges and demonstrate corresponding solutions using optimum processing workflows that produced a cleaner and higher resolution final image with improved reservoir characterization.
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Leveraging Full-Waveform Inversion and Multicomponent Seismic for High-Resolution Earth Model Building - a Case Study from Western Offshore, India
Authors S. Sengupta, S. Chen, B. Chowdhury, A. Sazykin, S. Goswami, P. Kristiansen, T. Barling, W. Abd El-Mawla, S. Basu, S. Mahapatra, A. Prakash, V. Saluja and R. SrivastavaSummaryWe present a case study from Western Offshore India integrating full-waveform inversion (FWI) and PP-PS joint tomography model building to derive a high-resolution tilted transversely isotropic (TTI) model to reduce depth uncertainty and improve imaging. The survey is in the Neelam-Heera fields in the Panna-Bassein block of Mumbai Offshore basin which are significant contributors to India’s oil & gas production. These mature oil and gas fields have been producing from Eocene-Oligocene carbonate reservoirs with established carbonate plays in this area.
This survey was acquired with a sparse multicomponent ocean-bottom node (OBN) technique in shallow water, with ∼ 40 m to 50 m depth. Sparse OBN acquisition in such a shallow water environment presents significant challenges to the imaging of both the PP- and PS-wave due to the sparsity of receivers greatly reducing the shallow illumination, making it a difficult scenario for signal processing, earth model building and imaging. The objective of the data processing was not only to improve the P-wave seismic images when compared to the ones obtained from legacy towed-streamer data over the area, but also to deliver equivalent high-quality, complementary PS-wave images suitable for joint PP-PS inversion, reservoir characterization, and sequence stratigraphy.
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Unlocking Post MMU Play Potential through Integration of Seismic Attribute and Geology in West Luconia, Sarawak.
Authors H. A Kahar, N. Muhammad Nizar, M.N. Zubir, O. Swee Keong, G. Malo-Paul, T. Wei Yong, S. Seng Hui and M.I. MahmoodSummaryThe newly acquired 3D Broadband survey with a total area of 6920 km2 (full fold square kilometres) was able to image Miocene to Pleistocene Clastic and Miocene Carbonate plays in West Luconia. To unlock the remaining potential for the huge area size, 3D regional seismic interpretation and mapping was first conducted for the zone of play interest on the full offset APSTM stack and QAPSDM stack volumes. The new data availability throughout the area enables spectral decomposition analysis and multi attributes generation e.g RMS amplitude, maximum/minimum amplitude and semblance. This paper aim to highlight the uplifting of new seismic data that enhance new concept and model for the reservoir deposition within the area of interest.
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Resolution Geo-sample Core Scanning: New insights for PETRONAS Digitalization Program
Authors M. Nor Kartini Suriati, A. Azimah, R. Juliza, S. Hussien Nordin and H. M. IzzuddinSummaryThis paper outlines an integrated methodology for geo-sample core digitalization utilizing advanced scanning technology from UK that has currently been used to digitalize all PETRONAS geo-sample core data in PETRONAS Geo-sample Centre (PGSC).
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Improved Reservoir Monitoring with PP and PS Time-lapse Imaging Utilizing up down Deconvolution
Authors F. Twynam, R. Ford, P. Caprioli, M. Hooke, S. Chen, P.E. Dhelie, V. Danielsen and K.R. StraithSummaryAdditional insight into the interaction between pressure and fluid saturation changes within the reservoir can be extracted through discrimination of time lapse (4D) signal from PP and PS data. Previous processing of the 4D PP dataset over the Edvard Grieg field from 2016 to 2022 yielded interpretive saturation related 4D changes due to production and injection. The PS radial data followed, centred on a co-processed up/down deconvolution (referred to here as radial/down deconvolution for PS) workflow in alignment with the PP route. The result was a unique 4D PS response to that of PP due to changes being pressure related. The UDD workflow involved spectral division of the radial with the downgoing wavefield in the 3D tau,p,q domain. The output was shaped to a user-defined wavelet and 3D deghosted. Although the condensed and optimised deconvolution process requires minimal processing, the result is sensitive to instrument calibration, source variability, and spatial sampling. Performing joint PP-PS tomography provided an uplift in depth-domain event alignment, which helped to correlate structural boundaries with the extracted 4D attributes. The 4D PS result correlates well with the predicted model and the low frequency response was observed to be significantly improved over the legacy processing route.
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Advanced Imaging Workflow Reveals New Details in 3-D Seismic Exploration Data for Near Surface Applications.
Authors J. Oukili, B. Caselitz, T.K. Karlsen, J. Beenfeldt and A. McKaySummaryReprocessing existing 3-D seismic exploration data with a state-of-the-art High-Resolution (HR) workflow can provide very fine details of the very shallow subsurface. In the paper, we focus on the very first hundred meters in a shallow water environment and suggest how 3-D seismic data, which does not meet the typical Ultra-High-Resolution (UHR) requirements, can be used to significantly reduce the overall timeline, risks and costs of future offshore new energy projects.
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Model-based CO2 Concentration Prediction for the Sarawak Basin
Authors J. Hoesni, M.N. Samsuri, S. Nayak, A.T.P. Panting, O. Swee Keong, M.A. M Diah, J. M Shah, W.A. Wan Zakaria, R. Masoudi, M.S. Razak and N.A. AhmadSummaryThis paper describes the model-based approach in the prediction of CO2 concentration for the Sarawak Basin. Such modelling approach allows us to test contribution of multiple CO2 sources, as well as identifying subsurface geological processes that plays major role leading to the accumulation of the CO2 in the traps.
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Applying Integrated Chemostratigraphy and Enhanced Mineralogy Techniques to Assess Reservoir Quality Role on Production, Offshore Malaysia
Authors T. Ishihara, M. Asraf Khamis and E. DaneshvarSummary
Chemostratigraphic and mineralogical analyses have individually the advantage that can be applicable to any lithology in any depositional environment, regardless of the sample types. In this study, these techniques were applied and integrated on the cutting samples, to investigate the cause of poor productivity in one of the sandstone reservoirs, offshore Malaysia. X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN®), and petrography techniques were applied on total 300 samples from 8 wells, and the results were fully integrated, together with wireline and core data, to determine element-mineral affinities and to get an indication of changes in bulk lithology and mineralogy. The results successfully determined all reservoir quality parameters in the studied reservoir. Given fully quantified Ca and carbonate minerals, carbonate content was differentiated into carbonate bioclast debris and calcite cemented sandstone, in which the latter one is reported as a main player in the reservoir quality in this study. Results also associate to density/sonic spikes of wireline logs and interpreted to be the thin shelly lag deposits related to storm bed. Such cemented shelly lag deposits are interpreted to be vertical barriers. These findings are being used for future development planning.
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Lower Tertiary Wilcox, Central Gulf of Mexico: Comparison of Exploration Success in Outboard and Inboard Trends
Authors P. Abbott, S. Mukherjee and A. AmirSummaryThe combination of world class Tithonian oil-prone source rock, thick reservoir intervals, the presence of numerous salt-related traps, and multiple intraformational seals, makes the Lower Tertiary Wilcox an attractive play in the CGoM. 16 out of the 64 exploration wells drilled in the play are considered economic discoveries. Seven fields are currently on production, and all are in the outboard trend. However, with the advancement of seismic technology, exploration has moved increasingly towards the inboard trend. Shenandoah, Anchor, and North Platte, with a combined size of ∼1Bboe, are likely to be the first inboard discoveries to begin production ( IHS Markit, 2022 ).
Due to the different risk elements and subsequent exploration success rates, it is important to distinguish the ILT from the OLT. The subdivision of the play into trends is a key learning that has allowed us to greater understand the Wilcox. In fact, the odds of drilling an economic discovery increase from 24% (∼1 in 4) to 32% (∼1 in 3) when exploring in the inboard trend. Trap style, reservoir architecture/quality, seal capacity, and maturity trends can all vary in the two trends and understanding these should be considered an important step during prospect maturation.
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Interplay of Salt Tectonics and Basin Evolution - Implications on Maturity Trends, Northern Gulf of Mexico
Authors S. Mukherjee, P. Abbott and A. AmirSummaryRegional fluid distributions in the northern GOM suggest that first order controls on maturity trends are a function of basin fill, salt evolution, trap modification, charge style and the permeability structure in the carrier beds, based on modeling and observed datasets. Second order controls include pressure evolution, biogenic charge, and biodegradation which could affect fluid types in the discoveries/fields and should be evaluated carefully when using regional datasets to define maturity trends.
It is further noted that during early stages of prospects maturation regional maturity trends should not be used alone when evaluating fluid predictions and instead should incorporate integrated subsurface geological understanding coupled with prospect specific basin models. Developing a basin scale model in unproven and proven plays and integrating with regional datasets with established trends can be leveraged to unravel the charge mechanisms and identification of sweets-spots for the plays from a regional petroleum systems perspective.
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Carbon Storage Resource Assessment - How to Predict Containment Risk and Effective Resources
Authors M. Neumaier and B. KurtenbachSummaryWe present an advanced Carbon Storage resource assessment workflow to consistently predict quantitative containment risk and probabilistic ranges of effective CO2 resources for an early screening phase. In addition to the standard pore volume assumptions, our workflow uses quantitative notions of Pressure-Volume-Temperature (PVT), fluid injection mass, and seal capacity.
Our probabilistic approach fully integrates subsurface uncertainty of pore volume, CO2 in-situ phase and density as well as seal properties. It explicitly includes containment risk, as the likelihood of failure due to fracturing, leakage through the top or fault seal, or structural spill based on CO2 pressure and properties.
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Prospect Assessment and the Consistent Prediction of Dual Phase Accumulations for Exploration Well Placement Optimization
Authors M. Neumaier, B. Kurtenbach and J. De JagerSummaryDual phase accumulations, or traps containing both oil and gas, are very frequent in many hydrocarbon provinces but poorly treated in prospect assessment. The possible presence of gas, competing with oil for pore space and seal capacity, complicates exploration decisions in many aspects.
First, the definition of success and the estimation of chance of success (COS, or “risk”) is often tied to the presence of hydrocarbons, which also includes gas.
Also, the composition of success-case volumes (“resources”) might contain considerable amounts of gas, which does not favor oil. Oil versus gas column height uncertainty is performed in a rather arbitrary way.
Finally, the decision of where to place a first exploration well can also be difficult for a dual phase accumulation. Especially in thin reservoirs, a well in the upper part of the structure might only prove gas, whereas in the lower part of the trap, it might encounter water.
In the presented paper, we address the confusion of well versus prospect COS and the volumes which can be proven by one well, based on a consistent assessment of oil versus gas occurrence (risk) and column heights (resources).
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The Role of Logging for Formation Evaluation during CCUS Site Screening and Performance Appraisal
By C. CavalleriSummaryAs much as for oil and gas wells, static and dynamic reservoir characterization is key in carbon capture storage. An accurate knowledge of the hosting rock and surrounding formation coupled to comprehensive modelling are fundamental to demonstrate the geological site has the required properties for safe and long-term CO2 storage. Even if dealing with a mature field where detailed knowledge of the formation and connate fluids is already available, logging measurements being recorded at the current time may be required to complement the local knowledge and provide additional information previously not accessible. Logging technology can be deployed in existing wells to check integrity and usability; with the need for newly drilled injection well there is also the opportunity to record specific logging measurements and gather information in the open hole sections.
During the site appraisal and pre-modelling stage, logging and testing measurements help defining and refining the understanding of storage capacity, CO2 injectivity and maximum injection rates, and containment. Technology deployment and evaluation strategies are optimized to enable successful operations to follow, as well as to guarantee full compliance with stringent regulations related to CCUS. We describe the roadmap to successful assessment of key rock attributes at early stage.
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Digital MEMS and Seismic Nodes – Technology Fusion
By C.J. CrissSummaryMEMS based digital sensor technology was introduced into the seismic exploration market as early as 1998. Designed to overcome the limitations inherent in analog geophone sensor technology, use of the digital MEMS sensor eliminates issues with broadband sensitivity and phase. Since the introduction of the MEMS technology, sensors have been utilized extensively in most regions of the world, primarily with cable-based systems. MEMS technology has continued to progress since the early days and the technology is currently in its 5th generation.
Robust node technology has evolved simultaneously. Current node technology can record data for up to 50 days of continuous recording. Autonomous nodes have proven to be highly flexible and reliable in a wide variety of environments and are favored by operators because of the reduced crew sizes needed to operate and the very low environmental impact. When combined with the latest MEMS sensor the fusion of the two technologies is a new and unique solution for seismic acquisition.
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Finding the Hidden Faults – Delineating Faults and Fractures with Diffraction Imaging
Authors J.H. Tan, S. Maitra, C.C. Lam, N.N.H. Che Soh, C. Onn, N. Huu Nghi, N. Hamza and N.N. Abdul RahmanSummaryWithin the deep-water part of offshore Sabah, Malaysia, faulted anticlinal structures are zone of interest for hydrocarbon exploration. Interpretation of these faults and other geological discontinuities are important to identify segmented reservoirs in the area. In this paper, we demonstrated diffraction imaging can complement conventional seismic image and aid interpretation of fault geometries, factures network and small-scale features.
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Provenance of Neogene Sediments in Deep Water Offshore Sabah, NW Borneo
More LessSummaryThis study focuses on the provenance of Neogene clastic sediments in offshore Sabah, northern Borneo, Malaysia. The area of interest is the offshore Sabah fold and thrust belt region which is a major hydrocarbon province within thick Neogene sediments. There have been no studies of the provenance of offshore sandstones and this is the first such study utilising offshore sediments from Sabah.
The primary aim was to determine the sources of the Neogene clastic sediments and link offshore to onshore geology. This was intended to identify temporal and spatial changes in provenance of offshore sands and help understand tectonic influences on their deposition. Samples of core and drill cuttings were acquired from wells located (1) northwest of Labuan Island and (2) northwest of the Kudat Peninsula. The sands were deposited within a short time interval in the Middle to Late Miocene.
The quartz-rich sandstones were analysed for through light and heavy mineral analyses as well as U-Pb detrital zircon geochronology. Two groups of sands were recognised with distinctive detrital zircon U-Pb age suites, indicating different sources. The different features observed, the potential sources and the implications for uplift history and palaeo-drainage on land are discussed.
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Imaging Solution for Highly Faulted Block – A Case Study
Authors F.F. Basir, S. Maitra, K. Kongjuk, W.D. Gan, E. Sulaeman and A. ChansaneSummaryImaging highly faulted blocks in a shallow water environment can be quite challenging. This paper outlines the strategic seismic processing and imaging techniques applied on relatively old acquisition with limited azimuth and offset, which area affected by shallow overburdens. A combination of broadband processing, a targeted demultiple strategy, comprehensive velocity model and absorption Q model building workflows and application of advanced imaging technique successfully resolves the imaging challenges and resulting in a high-quality subsurface image.
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Unearthing NW Sabah Platform & Sabah Trough Potential Through Tectonostratigraphic Evolution Understanding
Authors N.L. Zakaria, P.S. Das, A.K. Upadhyay, S.N.F. Harun, T.M.S. Tg Hassan and N. OmarSummaryNW Sabah Platform and Sabah Trough geological provinces which are situated within the Sabah Deepwater at the southern conjugate margin of the South China Sea are relatively underexplored compared to the coeval and correlatable petroliferous basins situated on the northern conjugate margin. Although there are numerous literatures on South China Sea (SCS)’s tectonic history and setting, literatures on NW Sabah Platform and Sabah Trough remain scarce. Recent hydrocarbon discovery in Sabah Trough which proves a working petroleum system has sparked a renewed interest in this area. This paper focuses on the tectonostratigraphic evolution and the petroleum system elements of these areas diving deep into the tectonic phases and their associated depositional environments based on detailed geological interpretation of the seismic data, well logs, petrographic analysis, and comparison with results by previous researchers. Based on a wholesome understanding of the tectonostratigraphic evolution, this paper hopes to demonstrate the vast play potential each of the stratigraphic interval holds, and in turn encourage more exploration initiatives in the NW Sabah Platform and Sabah Trough region.
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Offshore-Onshore Geological Model to Define Deformation Zone in West Timor and Its Implication to Petroleum System
Authors A. Andaru, M.B. Wiranatanagara, M.Y.A. Madjid, N. Ardiansyah and J. KristianSummaryWest Timor is a promising frontier area for petroleum exploration known for its complex geological and structural condition in its onshore area. Notwithstanding its complexity, the petroleum system in this area was found to be functioning.
This study aims to integrate gravity data and subsurface results to construct an onshore-offshore geological model of West Timor and to estimate the basement depth and model in the onshore area by conducting gravity analysis. The result shows a significant impact in proposing a new extensive geological model that stretches out from onshore to an offshore area of West Timor. The research concludes that there are 4 deformation zone based on how deep and old the detachment surface cut the sediment sequence into. The detachment surfaces lie in older sediment from zone to zone, or northward, as it also cuts deeper sediment and lift older sediment in each zone. Petroleum system potential has its highest opportunity in zone 1 and decreasing towards zone 4, northward, since it is highly deformed.
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A Rock Physics Feasibility Workflow for 4D Seismic Monitoring of Injected CO2
Authors F. Sinclair Smith, A. Mur and W. HarbertSummaryCCS initiatives require a program of monitoring, verifying, and accounting of injected CO2. 4D seismic reflection surveys can be used to monitor the injected CO2 over the lifespan of the project. As with traditional seismic interpretation for oil and gas exploration, seismic reflectivity data pose the problem of non-uniqueness, thus multiple forward models need to be built, first to model if there would be sufficient 4D seismic signal to make time-lapse seismic monitoring effective, and subsequently, once multiple time lapse surveys are acquired, multiple forward models should be generated to understand uncertainty around the observed signal.
This work presents a rock physics modelling workflow, built on traditional quantitative interpretation techniques, to model the predicted 4D seismic signal for different CO2 injection scenarios and time steps. Here we present the Vernik-Kachanov rock physics model, which places both pores and microcracks into the average effective stress field in the solid matrix of the material, allowing for the stress sensitivity component of the rock physics model. We then account for fluid changes using Biot-Gassmann theory and published empirical and semi-theoretical fluid models for CO2-pore fluid mixing. Finally, synthetic seismic models are built using Zoeppritz equations for reflectivity and amplitude changes and time-thicknesses estimated.
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Predicting Hydrogen Sulfide Concentrations in Sarawak Hydrocarbon Fields through Petroleum System Modelling: Its Feasibility and Reality
Authors Z. A Kadir, P. Abolins, N.A.A. A Hamid and Z.A. ZulkifliSummaryHydrogen sulfide (H2S) and carbon dioxide (CO2) are among the common contaminants associated with the hydrocarbon fields in Offshore Sarawak. Current production plant could only handle up to 400 ppm of H2S concentration. H2S modeling is suggested to forecast and predict upcoming prospects to meet facilities limitation. Petroleum system modeling (PSM) software was proposed as the tool to model H2S generation, migration, and accumulation. H2S concentration and isotope data are collected and interpreted to determine the possible origin of H2S. Hypothetically we propose that areas of high H2S could be identified based on circumstantial evidence of having Cycle II carbonate body with more than 120°C temperature. However, we could not be certain of the actual intensity of the generation nor the loss of H2S and therefore, there is no certainty that having Cycle II carbonate with more than 120°C will result in high H2S concentration. In addition, we are looking at H2S as contaminant to hydrocarbon, where any modeling for H2S concentration need to include both hydrocarbon and H2S thus increasing the complexities and uncertainties. The H2S source and process could be tweaked to match measured data but it is not possible to generate a predictive H2S model.
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Integrated Studies in Defining Cycle V in Block “X” of Baram Delta
Authors M.A. Khamis, T. Ishihara and K. TsuzukiSummaryCycle V of the Baram Delta is the least explored interval in the Block “X”. The deep target posed multiple challenges, including seismic resolution, high pressure, high temperature and critically unknown hydrocarbon prospectivity. JX Nippon drilled an exploration well in Block “X”, named X-1 with the objective to test the prospectivity of high amplitude seismic reflectors in the predicted Cycle V. With the new data acquired in X-1 well, integration of geological and geophysical datasets was important to address the challenges and in defining Cycle V.
The geological and geophysical elements being used for this study are seismic, well-to-well correlations and biostratigraphy zonation. Integration of these geological and geophysical elements lead to the confirmation of the Cycle V sequence in Block “X”
All information obtained from each element – seismic, well-to-well correlations and biostratigraphy zonation – are crucial in supporting each other. The Cycle V is finally well defined as all of these elements are in agreement, and thus indicates that X-1 well achieved testing its main objective to explore the Cycle V sequence.
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Imaging Thrust Belt with Multi-Azimuth FWI and Least Squares Migration
Authors B.Y. Ong, J.H. Tan, S. Maitra, C.C. Lam, N.N.H. Che Soh, C. Onn, N. Huu Nghi, N. Hamza and N.N. Abdul RahmanSummaryWe dive into the application of high frequency multi-azimuth (MAZ) full waveform inversion (FWI) and least-square Q reverse-time migration (LS-QRTM) to address the challenges brought about by the fold-thrust belt system within the offshore deep-water Sabah. The imaging of the main structure of the study area has been challenging due to complex velocity variation, steeply dipping complex geological structure and structural uncertainties below shallow gas bodies.
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Structural Analysis of the Distal Stretches of Rift System: Case study from prolific Pre-salt Campos Basin
Authors H. Wahab, S. Sherkati, Z. A Kadir, A.A. Hashim, M. M Nor, N.Q. Salim, N.A. Razali, S.F. Jabbar and L.W. ChingSummaryDistal stretches of prolific Campos Basin remain poorly understood for crustal evolution and salt deformation, which may have significant impact on the development of effective source rock, reservoir, and hydrocarbon charges. salt thickness variation through time, duration of rifting and heat flow evolution are some of the main uncertainties. So heat flow evolution of those frontier zones, which is crucial for petroleum system modelling is still subject of debate. In this paper we aim to use 3D seismic and well data for 3D structural restoration and paleo heat flow estimation of distal Campos margin.
The study integrates both 2D & 3D structural restoration techniques, a leading edge technological application for structural analysis mainly used to estimate initial salt thickness, update subsidence curves and to estimate heat flow. By doing this, the model successfully incorporates the complex tectonic and paleo-salt movements (halokinesis) in the outboard Campos. The robust thermal model is expected to predict hydrocarbon phases correctly further outboard provided the other petroleum system elements remain consistent.
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Importance of estimating original source potential: A case study in the South China Sea
More LessSummaryTotal organic carbon (TOC) content and hydrocarbon index (HI) are one of the basic parameters to evaluate source potential. However, the measured values of TOC and HI from the samples have been decreased from their original one differentially to the buried depth as the rock samples from a source rock have gone through different thermal maturity stages. Hence, it is required to get an accurate estimation of the original total organic carbon (TOCo) content and original hydrogen index (HIo) from measured values of thermally mature organic matter.
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Improvement on Structural Mapping in Tinjar Province through Air-FTG
Authors S.N.F. Jamaludin, C. Murphy and R. KittrellSummaryWith the advancement in data acquisition and processing, the interpretation of data in the complex geological area of Tinjar Province is now being re-look. Variations in the wavelength of the gravity data acquired via this method allow structural interpretation at shallow and intermediate ranges to be compared with the existing work on SAR analysis. Prominent NE-SW orientation Meanwhile, the aeromagnetic data acquired along with the Air-FTG provides understanding for deeper section of subsurface. The aeromagnetic data focus on the top of basement, which deduce E–W orientation. This E–W orientation reflects the potential basement orientation underneath northern Sarawak. Similar orientation of E–W structures are commonly found in central Sarawak representing igneous or metamorphic origin, which better captured by the magnetic signals. Apart from useful in locating new or adding to our understanding of the existing hydrocarbon sites in Tinjar Province, airborne gravity and aeromagnetic data are also useful in improving the understanding of regional geology for onshore Sarawak.
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Mapping the Distribution of Reservoir Facies on 3D Seismic Data using Convolutional Neural Networks
Authors H. Pratama, A. Latiff, D. Markus and E. PurnomoSummaryUnderstanding the distribution of facies in a reservoir is important for reservoir characterization and can be used to aid in identifying the locations of hydrocarbons. However, due to the complexity of the earth’s subsurface, predicting the facies distribution information is often a very challenging task. Recently, the growth of computing power has enabled the application of Machine Learning models in service of studying many geoscience challenges, including the classification of facies using seismic data. Although, many previous studies have mainly relied on the use of multiple seismic attributes to build and train the model, in this work, we develop a Convolutional Neural Network (CNN) model using a U-Net architecture that can accurately map the facies distribution using only the original 3D Post-Stack seismic data. The approach was applied on a reservoir from a real oil field in the Malay Basin. We have improved the model using transfer learning that allows us to use learned parameters from a pre-trained model. The results obtained from the U-Net CNN model provide an accurate and realistic facies distribution compared with the true facies distributions. The model obtained 94% of accuracy for the training dataset and 89% of accuracy for the validation dataset.
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Improving Stratigraphic Interpretation of Sarawak Wells Using Detrital Zircon Geochronology
More LessSummaryThe interpretation and correlation of Cycles I and II in Teres-6 and Tenggiri Marine-1 is difficult due to the wells’ poor biostratigraphic data and seismic quality. Many attempts to re-evaluate them using the same old, inadequate dataset were inconclusive. Therefore, this study used the under-utilised drill cuttings for detrital heavy minerals study, particularly zircon, that aims to resolve the stratigraphic uncertainty of the wells. The result reveals an interesting finding, especially in the characterisation of Cycle I and Cycle II defined by detrital zircon U-Pb ages. Hence, a new stratigraphic revision is proposed, which re-assigns the reported Cycle I section to Cycle II based on the age-provenance signature of the Phanerozoic imprint (i.e., Permo-Triassic, Jurassic and Cretaceous age population). It also updates the regional palaeodepositional model of Cycle II, interpreting that Teres-6 and Tenggiri Marine-1 were part of a large and connected drainage system sourced from the Kuching-Rajang Range.
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Source, Origin of H2S in Central Luconia, Sarawak Offshore. How much do we know?
Authors N.A.A. A Hamid, A.T.P. Panting, S. Nayak, J. M Shah, W.A. Wan Zakaria, R. Masoudi, M. Dubille, I. Kowalewski, J. Hoesni, M.S. Razak and A. AznanSummaryThis paper presents an integrated approach to understand the potential source and prediction of H2S (undrilled prospects) in Central Luconia through an integrated subsurface modelling workflow. Possible sources for H2S and related subsurface processes leading to H2S accumulation is discussed.
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Geochemical Data Characterization and Spatialization for Petroleum System Analysis-An Example from Offshore North Gabon Basin, Africa
Authors N.S. Mohd Pauzi, R. Das and A.K. UpadhyaySummarySpatialization of multiple geochemical variables is a strong and well-established method to investigate, analyze variations of source potential, hydrocarbon fluid types, and source organofacies through time and space in a petroleum system. In our findings, the Post Salt Petroleum System of offshore North Gabon Basin of Africa is characterized by 4 key source-stratigraphic intervals: Albian, Ceno-Turonian and Coniacian-Santonian and Upper Cretaceous that can be correlated with OAE. Two dominant fluid families associated with organofacies classes B and C (Pepper & Corvi, 1998) were identified from multiple key biomarker ratios and cross plots along with tricyclics and hopane profiles within post salt reservoir system. The work summarily helps to recognize and focus on the desired play and petroleum system elements for further opportunity evaluation and petroleum system modelling.
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Combining Automatic Carbonate Detection with Dynamic Matching FWI to Improve Imaging of Jurassic Reservoirs, Timor-Leste
Authors D. Cavalin, D. Mondal, J. Twigg, A. MacDonald, S. Stokes, J. Rogers, S. Notiyal and N. HandSummaryIn shallow water environments where usable offsets are limited, Full Waveform Inversion (FWI) has become a tool-of-choice to generate high-resolution velocity updates. Traditional approaches such as refraction and reflection traveltime tomography can struggle with capturing sharp lateral and vertical velocity variations responsible for structural distortions deeper in the section. Classical implementation of FWI works at its best when very low frequencies and long offsets are recorded. This allows the inversion scheme to start from a smooth initial velocity model. However, the absence of quality low frequencies below 4 Hz and offsets limited to 6000 m in this project meant that the initial model built from legacy stacking velocities had to be improved prior to running FWI.
We first demonstrate a methodology to automatically detect the top of the shallow carbonate platforms and pinnacle reefs present near the seabed. The small-scale velocity variations added to the starting model bring immediate structural improvement down to the reservoir level and enable FWI to start at a higher frequency band. Alternating between passes of FWI and conventional reflection tomography leads to an updated velocity model conforming to the complex geology. The resulting depth migration enables better fault positioning and mapping of key reservoir horizons.
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Exploration Potential of NW Borneo – Latest Regional MultiClient 3D Opens New Petroleum Plays
Authors T. Choi, J. Beenfeldt, E. Mueller and A. VartanSummaryThe Sabah Basin is situated in offshore NW Borneo and is filled principally with marine Tertiary strata typically more than 8km thick. The basin received major sediment input from the Baram Delta and the now abandoned Champion and Meligan deltas and is a prolific hydrocarbon province extending throughout NW Borneo. Gravity loading and thin skinned deformation has resulted in a fold and thrust belt in the inboard area. Loading was initiated near the shelf in the mid-Miocene, which then propagated north-westward in the Pleistocene. The fold and thrust belt, which hosts turbidite reservoirs within anticlinal structures, has been the major focus for E&P oil companies and represents the most successful hydrocarbon play type in the basin to date. The newly acquired dataset has enabled detailed seismic mapping of the basin fill which has historically been a challenge to image below the regional unconformity (MMU). Furthermore, QI/AVO workflows applied to the broadband data of the fold and thrust belt show that the reservoirs trapped in the low side of the folds, present a low Vp/Vs response, similar to that of nearby discovered fields. These additional stratigraphic trap anomalies occur widespread throughout the Sabah fold and thrust belt.
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Unbiased Prospects Assessment and Portfolio Management with Machine Learning
By F. SchneiderSummaryThis work has made it possible to develop a method and a tool using outranking and machine learning techniques for the evaluation of plays and the unbiased ranking of prospects. The methodology is based on the generation of two indices: The PPI (Play Preference Index) and the OPI (Opportunity Preference Index).
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Partnering Geological Concepts with Seismic Imaging Velocity and its Impact to Quantitative Interpretation Results
Authors C.L. Lai, M. Choo, A. Fahmi Abdullah and S. RongheSummaryThis paper is to demonstrate the importance of geology and its impact on seismic imaging and QI study. By comparing the result from the previous against current seismic processing; PSTM vs QPreSDM, there is quite a big improvement on the 3D seismic data and QI results. During the exploration phase, limited geological information was available, hence in the PSTM processing, no geological input was incorporated. In the most recent QPreSDM processing, geological information was incorporated as more geological information was obtained from drilling the exploration well. The study shows result optimization can be achieved even with the subtle variation.
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Seismic Polarity-Based Sequences to Enhance Seismic Imaging of Carbonate Depositional Environments via the Application of Attributes
Authors R. Rosli, N.A. Zakaria, M.H. Baharuddin and S.S. Abd RahmanSummaryCarbonate rocks although it is prolific are known to be challenging to characterise on seismic data due to its heterogeneity and unique sedimentologic. However, increased knowledge of carbonate deposits and their petrophysical parameters, and higher quality geophysical tools now permit a better understanding of carbonate rocks using seismic images.
This study was carried out to illustrate the advantage of seismic attribute analysis on the high-resolution seismic sequences in imaging carbonate depositional environments. The workflow of imaging carbonate using attributes has been applied on carbonate platform in Central Luconia, offshore Sarawak. Amplitude-based seismic attributes and spectral decomposition (CWT and matching pursuit) were used to inferred the depositional environments. Result shows that spectral decomposition produced better image compared to amplitude-based seismic attribute.
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Well Site Gas for Reservoir Evaluation
Authors J. Moore, T. Dodd, E. Michael and L. JonesSummaryOur presentation discusses the applications of well site gas to reservoir evaluation. It is an under used dataset and opportunities exist to improve how this data is utilised both in future wells and in the large datasets that are available. In the presentation we review this data type, discuss data processing and corrections. We then describe how well site gas data can be used to determine pay and phase in a well. Examples from the Northwest Shelf of Australia are used to demonstrate the work flow.
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Integration of Production Data and Modelling Inventory for 3D Static Model Stratigraphic Framework in Brownfield Development
SummaryPost production data for stratigraphic trap of brown field infers vertical and lateral connectivity in a previously compartmentalized areas. Pressure plot, water cut trend and salinity data concludes that area of unintended multiple water injections received such pressure supports which pose threats to RMP, infill opportunities and production attainability by reducing well life. History matching and AI-driven modelling also supports connectivity throughout the reservoirs. An integrated static model is required to understand the connectivity by building a robust structural vertical and lateral framework, while incorporating detailed stratigraphic concept for baffle and fluid pathway through seismic and geological depositional concept. The static model should no longer be limited to pre-production geological concept but extend into production insights during geological modelling to facilitate dynamic simulation.
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FWI Imaging: Achieving AVA Reflectivity Faster than the Conventional Workflow
Authors J. McLeman, T. Rayment, K. Dancer and T. BurgessSummaryMany seismic processing and imaging workflows have been developed over the years to attenuate aspects of the recorded wavefield which cannot be properly mapped into the image domain through conventional migration algorithms. These workflows, including techniques such as deghosting, designature, and demultiple, have become extensive and time-consuming to execute due to the linear-like fashion they must be applied. Each stage in the workflow must undergo a range of parameter testing with success judged on a subjective basis. We present the application of a novel multi-parameter full-waveform inversion (FWI) imaging technique as an alternative to the conventional workflow. It uses the raw field data to simultaneously perform model building and least squares imaging with all the recorded reflection wavefield. This approach uses the primaries, multiples, and ghosts to generate standard model parameters (like velocity and anisotropy) and high-resolution true amplitude AVA reflectivity images fit for structural and amplitude analysis faster than the conventional workflow. In this paper, we compare the FWI derived reflectivity-with-angle outputs to that of a standard Kirchhoff preSDM workflow to highlight the suitability of FWI imaging to directly supersede the conventional workflows.
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Automated Denoising of Seismic Horizon Interpretations using a Convolutional Neural Network
Authors L. Souche, L. Marcelin and W. GuistelSummaryAcquisition, imaging and interpretation errors may impact the quality and accuracy of structural maps built from seismic data - yielding maps which should not be used directly for model building purposes. Nevertheless, such maps are ubiquitous in legacy datasets and it is often not practical to go back to the source seismic data for fixing the original issues. A common practice in the industry has therefore been to use naïve smoothing strategies, such as Gaussian filtering, for minimizing the impact of geophysical noise. This approach, however, tends to eliminate useful information while retaining some of the artifacts. Better filtering techniques, which rely on geostatistical methods, either require human expertise and interpretation or additional input data, which limits their applicability.
In this paper, we present an automated methodology based on Artificial Intelligence for filtering geophysical noise from faulted structural surfaces. It is composed of a stochastic generator for creating synthetic clean and noisy training data, of a polynomial trend estimator, able to handle fault surfaces, and of a Convolutional Neural Networks similar to the ones used for de-noising digital photographs. We show that it can outperform geostatistical approaches while requiring no expertise or parameterization.
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Applying Reservoir Filling Techniques to the CO2 Storage Modelling Challenge
By G. WilliamsSummaryTraditional reservoir simulation methods have proven challenging in matching known CO2 distribution in subsurface CO2 storage sites. This paper demonstrates how reservoir filling techniques using invasion percolation can be applied to modelling plume migration and better history match known CO2 distribution, and also be used to better predict CO2 migration in potential sites to better understand capacity and containment potential. Examples are shown from the Sleipner storage site in Norway and the In Salah storage site in Algeria to demonstrate how this approach can be applied to different subsurface challenges.
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Application of Machine Learning Technologies on Unstructured Data for Sustainable Exploration Activities – Brazil Pre-salt
Authors T. Looi, F. Baillard, N.M. Hernandez, M.H. Minhat, T.S. Tuan Abd Rashid and M.D.M. RamlanSummaryDuring the exploration activities, one way to obtain the geoscience insights is to interpret the basin regional trends and identify the anomalies. Regional information can be analysed through the vast amount of unstructured data accumulated over the years of exploration. This paper demonstrates a data driven strategy implementing the latest advancement of Machine Learning (ML) and Analytics applied on the massive amount of unstructured data. A case study is performed using the data driven strategy on pre-salt carbonates prospects of Campos and Santos basins in Brazil. This paper has shown by adopting the ML/AI technologies, geoscientists can effectively analyse a massive amount of unstructured data and to gain knowledgeable insights of the regional trends and anomalies for crucial parameters. This is vital to minimize the risk of exploration and promote sustainable development.
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Managing Top of Carbonate Uncertainties via Real-Time Geological Operations Interventions in Extended Reach Drilling Well
Authors F. Yusoff, M.K.A. Mohd Bukhari, N.A. Razali and M.T. ElshafeiSummaryThe paper discusses a key part of subsurface risk management that is often overlooked, especially in carbonate field development - mitigating the impact of uncertainties in Top of Carbonate (TOC). The well, located in a highly prolific gas-bearing carbonate platform was planned as Extended-Reach-Drilling (ERD) well. It was planned to penetrate TOC at the less explored area of the field which then raises two key uncertainties on depth of TOC, and drilling issues at the top of TOC. The actual TOC was observed to be 166 m MD (23.4 m Total Vertical Depth) deeper than prognosis. Real-time interventions were then required to ensure well objectives and ultimately overall production targets are met. In the case that the trajectory was not revised during drilling, the target might have been missed altogether. The agility to change the trajectory in real-time and holistic approaches critically mitigated these challenges. The well was completed with the required open-hole-length (OHL) with maximum stand-off distance from GWC and ultimately delivering production in a relatively unexplored area within the field. The critical decision in real-time ensured the well success as part of subsurface risk management from geological operations standpoint.
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