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PGCE 2008
- Conference date: 14 Jan 2008 - 15 Jan 2008
- Location: Kuala Lumpur, Malaysia
- Published: 14 January 2008
61 - 79 of 79 results
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3D Basin Simulation Controlled by Capillary Threshold Pressure – A Case Study in the North Malay Basin (2)–
More LessThe relationship between capillary threshold pressure of seal formations and buoyancy of hydrocarbons is considered as one of the most important aspects for petroleum exploration (Sales, 1997; Nakayama and Sato, 2002). As high quality 3D seismic data is acquired in common, high resolution 3D basin simulation of capillary-dominated, multi-phase flow regimes is the effective technique to realize the generation, migration and accumulation of hydrocarbons in basin scale. This paper presents the case study of
3D basin simulation in the North Malay Basin which was carried out by JGI and CPOC in 2007.
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Two-Dimensional Stratigraphic Simulation of the Malay Basin
More LessStratigraphic simulation is a computer modelling technique that can be applied in petroleum exploration to understand the depositional geometries and architecture of a sedimentary basin. By making geologically reasonable assumptions about certain process parameters (e.g. sediment supply and tectonic subsidence rates), realistic stratigraphic geometries and attributes of sedimentary basins can be replicated by forward modelling. There are a number of proprietary and a few commercially available stratigraphic
simulation packages designed for this task; ranging from simple 1D to more sophisticated 3D techniques (Ku Rafidah & Mazlan Madon, 2007). In this study we have used SEDPAK™, a 2D modelling package developed by the Stratigraphic Modelling Group at the University of South Carolina (Kendall et al., 1991), to simulate the stratigraphic evolution of the Malay Basin, offshore Peninsular Malaysia. The objective of the study is to investigate the relative influence of the main factors that controlled sedimentation in the basin. In a previous study of overpressure development in the basin (Madon, 2007), subsidence and sedimentation (burial) rates were found to be the main controlling factors in overpressure development. In this study, SEDPAK™ was used to reconstruct a depositional history of the basin by varying the rates of tectonic subsidence, sediment supply and eustatic sea-level change. We have used an interpreted seismic section across the basin as a starting model (Figure 1) and, upon applying a time-depth conversion, constructed a geologic cross-section to be simulated. Based on the published geologic ages of the seismic horizons and the measured thicknesses of the stratigraphic units, their average sediment accumulation rates were derived along the profile as input to the simulation. Figure 2 shows the three main input parameters. The input value for the modelling parameters is varied by trial-and-error iteration until there was agreement between the model result and the observed geometries in the seismic depth-section.
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Advanced Mud Gas Logging Technology: Application for Fluid Identification and Characterisation, Offshore Sarawak, Malaysia
Authors Patrick Gou and Sven ScholtenConventional mud gas data has been available for a long time from mudlogging operations. For several reasons, it has been under-utilised for fluid characterisation, although still acquired routinely in the drilling of oil and gas wells. However, the introduction of some advanced mud gas logging methods like FLAIR (Fluid Logging and Analysis in Real-Time) by Geoservices have made near real-time geochemical analysis of mud gas data possible. Advanced mud gas logging is also referred as Gas While Drilling (GWD)
in some literature. This article will describe how such mud gas data are utilised to identify and characterise different fluid types encountered by wells drilled in Shell operations. Two wells drilled offshore Sarawak in 2006-2007 are presented as examples (see Figure 1). The first example is an appraisal well while the second is a development well. The appraisal well was drilled to appraise the stacked sand reservoirs of Late Miocene age within the Baram Delta Province while the development well was drilled to produce gas from a sour (high H2S and CO2) carbonate reservoir in the eastern part of Central Luconia Province.
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Developing Remaining Oil in K1.1 Sand Reservoir with Horizontal Well in Baram Field, Sarawak Basin
Baram field is located in Miri Sarawak Basin, East Malaysia. (Figure1).The field was discovered in 1963 and brought into production in 1969. In it’s nearly 40 year production period, optimal well placement is critical for drainage of the remaining reserves. The field was developed with 8 drilling platform, three surface facilities, and two compressor platforms. STOIIP was estimated at 1400 MMSTB with a EUR of 390 MMSTB from more than 170 wells. Some of the remaining reserves are left behind in the oil column <60 ft, reservoir thickness <20 ft, and dipping angle >4deg which was economically unattractive to be developed. This study is mainly focused on how to maximize oil recovery with respect to horizontal well in thin reservoir by using azimuthal geosteering technology. (Figure 2)
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Using Acoustic Impedance Data for Tabu Field Subsurface Mapping and Reservoir Characterization
More LessThe Tabu oil and gas field, located in the southeast part of the Malay basin, was discovered in 1978 by Esso Production Malaysia Inc with the drilling of the Tabu-1 well. Oil production commenced in 1986 and is currently producing from Tabu-A and Tabu-B platforms. A field study was conducted from 2004-2006 utilizing a recently acquired 3D seismic survey to exploit the non-associated gas (NAG) and gas-cap blowdown (GCBD) resource at Tabu. Accurate reservoir characterization is required for a successful development. For Tabu field, seismic inversion was carried out with the objective of improving reservoir characterization. Acoustic impedance inversion is a process of generating an acoustic impedance volume from the seismic reflection data. It has several advantages over a seismic reflectivity volume. The acoustic impedance data has improved resolution due to the contribution of very low frequencies from the well log data. Representing the subsurface as layers instead of layer interfaces by removing the complexity caused by the seismic wavelet, results in an improved link to the petrophysical properties of the subsurface formations. Seismic inversion was carried out using the JASON Constrained Sparse Spike inversion (CSSI) algorithm. High quality well ties are important for determining the low frequency acoustic impedance trend, seismic wavelet extraction, and inversion of the seismic trace. Careful selection of CSSI parameters and the merge point between the low-frequency model and the inverted band-limited acoustic impedance are required for a successful inversion. The results of the acoustic impedance volume have had a significant impact on the interpretation of the Tabu Lower "J" reservoirs, one of the key gas reservoirs. Improved reservoir characterization, including geometry and reservoir properties has resulted. Based on the results of the interpretation a seven well development of the reservoir was initiated. Initial drilling has confirmed the validity of the interpretation model.
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Borehole Images and VSPs as Aid to Attribute and Inversion Analysis
More LessBorehole images have inherent information on sedimentary structure and lithofacies that are typically used qualitatively. There are ways of unlocking this potential by doing a comprehensive facies analysis and obtaining quantitative outputs with new applications like neural network or multivariate histogram techniques. However even with these approaches the high-resolution quantitative facies data is still only at the borehole, capturing near-wellbore characteristics which are difficult to translate and propagate into the interwell space. Needed at this critical barrier, is a tool to tie-in high-resolution borehole image and log derived facies with something that will also have a correlation with attributes that characterize the interwell and 3D-space. We test rock-physics attributes like acoustic impedance and Poisson’s-ratio and attributes generated from vertical seismic profiles (VSP) as being the likely links between high-resolution near-borehole information and interwell/3D space represented by seismic data.
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Ichnofossils from the Tertiary Sediments of the West Crocker Formation in Kota Kinabalu Area, Sabah
Authors Nizam A. Bakar and Abdul Hadi Abd Rahman and Mazlan MadonDetailed facies analysis on several well-exposed successions belonging to the West Crocker Formation reveals well-preserved trace fossils, which has not previously described. The ichnofossil assemblage in this area is associated with turbidite deposits, which indicates benthic or deep marine environments. They can be grouped into two different ichnofacies namely Zoophycos and Nereites.
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Facies Characteristics and Stratification of Debrites Within the West Crocker Formation (Early Oligocene to Middle Miocene), Kota Kinabalu, Sabah
Authors Nizam A. Bakar and Abdul Hadi Abd Rahman and Mazlan MadonThe West Crocker Formation in Sabah has always been referred to as sediments of turbidite systems. However, field observations have revealed the presence of thick sandstone bodies which display distinct facies characteristics such as very thick beds, poor sorting, lack of internal layering and sedimentary structures, randomly distributed mudclasts, loadcasted bases and irregular tops. These features reflect deposition by debris flow; hence, these deposits are debrites.
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Sedimentary Facies Characteristics and Reservoir Properties of Tertiary Sandstones in Sabah and Sarawak, East Malaysia
Authors Teoh Ying Jia and Abdul Hadi Abd RahmanSandstones are very important as reservoirs for oil and gas; more than 50% of the world’s petroleum reserve is estimated to occur in sandstones. Depositional environments, and thus facies characteristics, determine the overall reservoir properties of sandstones. The purpose of studying the reservoir sedimentological characteristics and petrophysical properties of Tertiary reservoir quality sandstones from Sabah and Sarawak is to investigate and determine the relationships between sedimentological and facies characteristics, and reservoir properties of the different types of sandstones.
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Anding Utara Fractured Basement Modeling an Integrated Workflow from Seismic-3D Static-Fracture Model
More LessThe Anding Utara Field located in PM 12 Block in production sub-block of Malong-Anding-Sotong within the Angsi-Duyong sub-basin of the South Malay Basin, offshore Peninsular Malaysia in area of water depth approximately 74 m with 4 wells drilled (Figure 1.0). The productive reservoir in Anding Utara Field is a fractured Jurassic Metamorphic Basement High within a pull-apart basin formed by extensional faulting during basin development. It is about 12 km long and 7 km wide. Correlation indicated that Anding Utara Jurassic Metamorphic Basement underlain by very thick Oligocene shale as a cap rock (Figure 2.0). The 3D fractured modeling was created using by collaborating well log, well tests, seismic attributes and outcrops analogs. The shared knowledge and flexible workflows have been conducted to get the best-fit model, manageable data and easier-way to be re-run. Dual Porosity and permeability modeling was generated for fracture and matrix properties (Figure 3.0). The fracture properties are divided into 2 major fracture sets; Distance to fault fracture set as representative for tectonic mechanic and bed contained fracture set as representative for stratigraphic mechanic (Figure 4.0). The matrix properties are developed in weathered basement. The matrix becomes the
major oil storage, while the open fracture becomes the oil flow conduit.
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Structural Style and Structural Evolution in the Hawke's Bay Region, New Zealand
More LessThis poster presents the analysis of regional 2D seismic lines across the Hawkes Bay region offshore east coast of the North Island of New Zealand. The study area is located in the outer forearc and contractional domain of the Hikurangi subduction complex. Detailed intrerpretation of long regional 2D seismic lines has indicated that the area underwent rifting in the Cretaceous, thermal sag and subsidence in the Paleogene, followed with contraction and thrusting in the early Miocene, extensional faulting in middle to late Miocene together with continued thrusting and inversion in the Pliocene to Present Day. Within the Neogene section three principal depositional sequences were identified representing growth strata deposited during different deformational phases - a syn-thrusting sequence, a syn-extensional sequence and a syn-inversional growth stratal sequence. Within the study area three tectono-sedimentary domains were identified based on the difference structural styles and sedimentary architectures. In the north the Raukumara Shelf is characterized by thrust fault-related folds, inverted extensional faults and gravitational sliding structures. In the central domain of Hawkes Bay itself, a series of Present Day active thrust faults occur associated with folds and inverted
extensional faults. The southern structural domain, the North Wairarapa Shelf, is characterized by thrust related folds and gravitational sliding structural elements. Fold amplification characteristics, overall shortening and thrust fault spacings indicate that the
shortening rates were relatively higher towards southwest of the study area. The extensional faulting in the Raukumara Shelf may indicate that subduction underplating and gravitational collapse of a supra-critical Coulomb wedge in this region.
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Controlled-Source Electromagnetic (Csem): Complementing AVO as Prospect Qualifier, Offshore Sabah, NW Borneo
Authors H. Maulana, S. Tanner and S. Algar and K. AzlanAmplitude versus Offset (AVO) analysis has been utilised to evaluate potentially hydrocarboninduced seismic amplitude variation with offset. One major uncertainty is that reservoirs with 10% gas saturation will have similar AVO responses to commercially saturated reservoirs (>60% hydrocarbon saturation). In frontier deepwater areas that lack of well control, an independent, non-seismic method like marine controlled-source electromagnetic (CSEM) survey becomes an important technique to assess the risk
of low saturation gas reservoirs. The CSEM measurement is sensitive to resistivity contrasts, it can potentially differentiate hydrocarbon saturated reservoirs (highly resistive) and the surrounding conductive sediments. Furthermore, it may also be able to discriminate reservoirs with commercial saturation (tens-thousands m resistivity) from those with residual saturation. Stochastic AVO modelling performed on Prospect X in Offshore Sabah, NW Borneo, indicates the presence of hydrocarbons as well as a chance of having low saturation gas. The CSEM interpretation on the Prospect X, however, reveals a 20-60% electric magnitude increase of the target response over a chosen background, which indicates a hydrocarbon-related resistive body. Further interpretation suggests that significantly thick sand with resistivity of 100 m is the most likely cause for the CSEM anomaly; hence, it derisks the possibility of low saturation gas being present in the prospect. The combined AVO-CSEM interpretation is a compelling prospect qualifier in the Sabah deepwater setting, where (1) drilling an expensive deepwater well is not justified based on amplitude anomaly alone, particularly when gas-charged siltstone and “fizz” gas reservoirs are common, (2) the absence of nonhydrocarbon highly resistive lithologies such as salts, volcanics, and thick limestones avoids misleading resistivity interpretations, (3) the water depth is sufficient to suppress the air-wave effect that might otherwise mask any potential highly resistive anomalies, and (4) the reservoir depth below seabed is suitable for this combined interpretation to be successful in finding commercially saturated hydrocarbon reservoirs.
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The Structural and Stratigraphic Evolution of Shale Detachment System in the Ceduna Basin, Australia
More LessThe Ceduna sub basin, part of the Bight basin, covers an area of 95,000 sq. km and is located at the southern margin of the Australian continent. The basin was formed by the Mid-Late Jurassic to Early Cretaceous separation of southern Australia from Antarctica. Four principal tectono-stratigraphic phase have been identified in the Ceduna Sub-Basin. Mid-Late Jurassic rifting was followed by two phases of post-rift thermal subsidence in the Cretaceous with southern margin breakup occurring in the Late Santonian. From the Late Cretaceous through the Cenozoic the passive margin phase was characterized by progradational sediment deposition from a major delta system – the Ceduna delta. Four episodes of thermal subsidence have been identified and these events are related to a massive sediment influx into the passive margin basin. Two major delta complexes have been identified. Rapid progradation of Turonian –Santonian and Campanian –Maastrictian deltas on the unconsolidated Albian deep marine shale have produced series of syn –depositional listric faults and shale detachment systems. Two episode of shale detachment systems have been recognized - a Mid Albian and a Late Santonian detachment systems. The Mid Albian event is more widespread than the late Santonian event which only dominated the outer margin of the delta. The Mid-Albian event produced a series of southward dipping listric fault systems which are associated with syn depositional growth sequences and contractional toe- thrust systems.
The Ceduna sub-basin shale detachment systems are characterized listric extensional growth faults and roll–over anticlines. Sediment depocentres are controlled by the syn–depositional fault structures with the initial sedimentation infilling the basin center followed by a shift to the outer delta margin after the basin center has been filled, together with reactivation of the fault along the delta margin. Sediment accumulation in the fault hanging-walls caused the propagation of growth faults, hanging wall rotation and the development of roll–over anticlines. Small scale roll-over anticlines dominate the western part of the study area and large scale anticlines dominate the middle sector of the basin.
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Integrated Fracture Evaluation af a Malaysian Basement Well Drilled with the Oil-Based Mud
Hydrocarbons discovered in the naturally fractured basement reservoir around the Malay basin are being explored for additional reserves for the Malaysian oil and gas industry. The fractured basement reservoirs are much more difficult and expensive to evaluate when compared to a conventional reservoir due to its challenging environment. Many new technology tools are target s for such reservoirs. However, the optimized formation evaluation program is required to obtain as much reservoir information to enable an
estimation of the most prospective hydrocarbon bearing intervals in this reservoir. This information is essential for field development decision in fractured basement reservoirs. This paper presents the challenges and results of the formation evaluation program in the fractured basement reservoir in Malaysia. This particular well example is a highly-deviated well drilled with oilbased mud (OBM) as it was believed that the borehole wall failures, formation damage and fracture damage which occurred in previous wells was due to being drilled with a water-based mud (WBM). Current image-based fracture evaluation techniques were developed for water-based mud systems. However, a comparatively limited fracture analysis can still be done with the Dual Oil-base MicroImager (OBMI2) in oil-based muds. There are inherent limitations that prevent interpreters from performing a full fracture analysis beyond fracture identification, orientation and fracture density quantification in OBMs. OBM makes differentiating between open and closed/healed fractures impossible as both appear as resistive events although one is filled with the OBM and the latter with resistive cement. This in turn prevents the calculation of fracture aperture and fracture porosity. This uncertainty can be fulfilled by combining the borehole image results with dual packer wireline formation tester (WFT), Sonic Scanner reflection imaging and Stoneley data. The borehole image was crucial in selecting testing zones for the dual packer WFT, and in turn the WFT results were especially helpful in determining whether fractures within a certain zone were open or healed (productive or not). Reservoir parameters and fluid sampling were obtained using the WFT. In addition, the combination of the borehole image and Stoneley was an important factor in reducing uncertainties. The Stoneley fracture analysis is intended to detect open fractures with significant fluid flow in/out of them. Also Borehole Acoustic Reflection Survey imaging delivers highresolution acoustic images around the wellbore to identify sub-seismic inter beds, faults or fractures far beyond the resolution obtained from any seismic surveys. Using a combination of data from all of these disciplines, the uncertainties of fracture analysis in OBM can be lessened and the resulting integrated solution giving significant value to the characterization of complex fractured reservoir.
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Trace Fossil or Soft Sediment Deformation? An Enigmatic Structure from the Balingian Cycle II Sequence, Offshore Sarawak
By David InceThe Early Miocene Cycle II interval in the D35 field contains the principal hydrocarbon bearing reservoirs. The majority of the Cycle II section however comprises a variety of mudstone facies and minor coal horizons. Recent analysis of the sedimentology and ichnology of these rocks has revealed a variety of distinctive trace fossil assemblages that reflect variations in salinity of the water column. As detailed in a parallel poster presentation the predominant facies is interpreted as having been deposited under brackish water conditions with somewhat restricted ichnofaunas reflecting this environmental stress. As well as the readily identified trace fossils that can be assigned to known Ichnogenera, there are structures of unknown origin that, to date, have not been recognized as trace fossils but are not satisfactorily explained by physical processes. The presentation describes these structures and presents the suggestions that have so far been advanced to explain their origin. A physical process involving loading of starved ripples has been put forward, however the viability of this process is unclear. An alternative interpretation is that the structure represents an organic trace reflecting an aspect of animal behaviour previously unrecognised in these sections. Evidence is
presented and the reader is encouraged to weigh and debate the options for interpretation.
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Trace Fossil Assemblages and Palaeoenvironmental Re-Evaluation \of Miocene Reservoir Intervals, Offshore Sarawak, Malaysia
Authors Kerrie L. Bann, David M. Ince and Abdul Hadi A. and Ahmad Munif B.This study integrates ichnology and sedimentology to re-define the palaeoenvironmenal and sequence stratigraphic interpretation of Miocene reservoir intervals in the D35 Field in Offshore Sarawak, Malaysia. The succession has been interpreted previously to reflect predominantly fluvial and lacustrine environments of deposition. Analysis of the trace fossil assemblages throughout the succession strongly suggests, however, that it is exceedingly difficult to reconcile the majority of these units with a fluvial and fresh water interpretation. Instead, the interval reflects a variety of lower coastal plain deposits, most of which were moderately to significantly affected by marine influence.
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Application of Walkaway VSP for Improved Seismic Imaging Beneath a Gas Cloud
More LessThe Vertical Seismic Profiling technique (VSP) has been widely used in oil and gas exploration in Malaysia over recent years. During 2007, a well was drilled to access the hydrocarbon prospect within a gas cloud area by Carigali and a walkaway VSP acquired over the area to delineate reservoirs underneath the gas cloud. VSP utilizes the advantage of placing the receivers in the ground that are close to the target reflectors and thus reduce seismic signal attenuation by half of that encountered by conventional surface seismic acquisition. The results show a much clearer image enabling the interpreter to define the top reservoirs which were not possible to track on the surface seismic. Based on these findings, the PCSB team decided to reevaluate the technical and economic impacts to the initial field development plan (FDP).
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Tectonic Evolution, Sedimentation and Chronostratigraphic Chart of Sabah, Malaysia
More LessA stratigraphic chart incorporating all the Tertiary tectonic evolution and sedimentation phases of the Sabah Basins (North Borneo) was constructed based on onshore and offshore exploration data. This chart reflects the most recent interpretations of Sabah stratigraphy and correlations of onshore and offshore areas of Sabah. It includes major lithostratigraphic units and biostratigraphic markers. The diverse structural trend and depositional framework of Sabah (North Borneo) were contributed by several regional tectonic events occurred since the early Tertiary. At least three major episodes were linked to NW-SE compressions coinciding with the ongoing subduction of the proto-South Chine Sea during the Late Eocene (Sarawak Orogeny), middle Early Miocene (22-20Ma, Sabah Orogeny-BMU) and early Middle Miocene (15.5Ma, MMU/DRU).
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A Comparison of Geochemical and Petrographic Features of Oil Prone Coals from the Balingian Province with those of the Malay Basin, Malaysia
Authors Peter Abolins and Wan Hasiah AbdullahThe role of coal as a source for oil continues to be debated in geochemical circles. This paper attempts to present the case for Malaysian Tertiary aged coals as a source rock for oil, as well as for gas. The Malay Basin of offshore Peninsular Malaysia and the Balingian Province of offshore Sarawak, are petroliferous Tertiary basins. Both basins are known to contain coal-bearing sequences of Lower Miocene age (Group I in the Malay Basin; Cycle II in the Balingian Province.) This paper compares and contrasts the respective geochemical and petrographic characteristics of the Balingian and Malay Basin coals with the purpose of assessing their oil generating capability and their source facies. The oil-prone nature of these coals can be envisaged visually under reflected light microscope, in particular using fluorescence mode visualization, and by evaluating their chemical composition in terms of hydrocarbon content. Based on the current investigation, it is most apparent that both sets of coals possess many similar oil-generative features, such as the extensive development of exsudatinite crack network, common occurrence of oil haze, significant occurrence of oil-prone liptinite macerals e.g. suberinite, including its derivatives, and show some common biomarker distributions. The use of biomarker distributions as an aid to correlating the coals to the oils of the respective basins is also demonstrated. Combined use of biomarker assemblages, calibrated with biostratigraphic data, helps constrain the source facies of produced oils. The application of detailed maceral analysis is described and is shown to be able to categorise the coal depositional settings of these basins into diferent sub environments.
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