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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
41 - 60 of 132 results
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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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