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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 - 20 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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