APGCE 2019

The Penyu Basin is moderately explored that may still have undiscovered hydrocarbon potential, and recent studies suggest that the basin remains prospective with excellent data coverage of both 2D and 3D seismic. The basin was formed in continental crust, although the exact origin is not properly understood and most authors generally considered it as a pull-apart or “rift-wrench” basin. This is supported by the presence of major strike-slip faults and associated normal faults as being the main basin-bounding faults. The initial half-graben basins evolved into isolated lacustrine systems that provide source-rock facies habitat that could potentially charge the traps in the syn-rift and post-rift sequences. Trap styles in the Penyu Basin include the compressional anticlines, basement drape structures and syn-rift stratigraphic/structural traps. The results of the syn-rift exploration are encouraging, albeit a detailed understanding of the reservoir distribution is essential for identifying future drilling targets in this interval. Undoubtedly, more detailed mapping of new structures with application of new techniques such as basin modeling, integrated structural and high-resolution potential field data interpretation will help in identifying new play types and enable a better understanding of the structural evolution and hydrocarbon prospectivity of the basin.

The NW Borneo margin, offshore Brunei Darussalam, is characterised by high subsidence-rates (overall 1 km/MA over the last 14 MA; up to 6 km/MA locally) combined with large-scale, and rapid, syndepositional deformation driven by delta-loading and regional tectonics. Deformation includes extensional (regional and counter-regional), contractional, and strike-slip structures. Effects of eustatically driven variations in the Cainozoic sea levels, which are readily recognised in the stratigraphic records of many passive margins, including the neighbouring Sarawak-basin segment of the NW Borneo margin, have been subdued, or overwritten, by the subsidence signal on the Brunei margin. High rates of background subsidence have imposed limits on the duration of SL lowstands, while inversely amplifying the effects of eustacy-driven SL rises. This study is chiefly concerned with periods of eustatic SL lowstands, and with the imprint of subsidence-variations in space and time on the eustatic SL signal.

Typically, 2D horizons across calibrated well biostratigraphy data were done on regional lines to build consistent stratigraphic horizon framework. However, in Deep Water Sabah, the interplay of eustatic sea level change and tectonics are more complex. Each catastrophic events triggered old sediments transported further into basin and redeposited within younger sediment. This causing uncertainties to place ‘Last Appearance Datum (LAD)’ from biostratigraphic well data. At regional scales, calibration wells used are from different contractors where biostratigraphic data usually analysed and picked by different labs and contractors. These might lead to inconsistencies in some species identification especially microfossils preservation in a poorly recovered sequence. Thus made consistent stratigraphic horizon framework calibrated to well data in deep water is more challenging. In order to produce a consistent stratigraphie horizon framework in the Deep Water Sabah at basin and play scales, application of four dimension wheeler diagram (X,Y, Relative Geological Time and Thinning Attribute) was introduced.

The understanding of sequence stratigraphy study is used as a chronostratigraphic framework for the correlation and mapping of sedimentary facies and for stratigraphic prediction (Emery et. al., 2005). The idea of a new approach of refined sequence stratigraphy for West Baram Delta (WBD) came considering of current reservoir correlations within the fields in WBD are done mainly based on lithology correlation. In addition, the unstandardized zonation throughout the fields in WBD contributes to discrepancy in static and dynamic modeling. The new standardized stratigraphic framework is built by integrating 3D seismic megamerged volume, well logs, and biostratigraphic data. In order to get the full impact and to add value to the new invention, a detailed study in field scale need to be done. Therefore, this study will focus on X field where the application of the new standardized and refined sequence stratigraphy is discussed. Technically, the refined stratigraphy and new reservoir scheme are utilized for better reservoir delineation and prediction in order to explore and develop the remaining upside potential within each stratigraphie unit, and to capture the bypass oil. The study has indicated a presence of an upside potential where it will be discussed in detailed in this paper.

The study was conducted in the D field with complex compressional-extensional events causing the main field structure to have numerous compartmentalized fault blocks. In general, the relatively thin reservoirs, complex faulting and contacts are the principal challenges faced in this field. The reservoir distributions and connectivity de-risking by application of a stochastic simultaneous inversion workflow. The results then integrated and used as data input for reservoir static model. The challenges of this study are the thin beds, which justify the usage of the geostatistical inversion. The statistical component of the seismic inversion will model the results beyond the seismic resolution. At the seismic resolution, the convolution of the impedances with the wavelets will produce synthetics. The match between the seismic and synthetics must be good at the seismic resolution. Application of geostatistical inversion methodology in the D Field demonstrates that important improvements still can be made in reservoir characterization when the reservoir is below the seismic resolution. In addition, a better match of well data to inverted-results was achieved through geostatistical inversion than through deterministic inversion.

In this study, we used seismic stratigraphy mapping to optimize EOR wells through testing reservoir sand continuity and communication between injectors and producers. Grey Level Co-occurrence Matrix (GLCM) tool is used in the study to facilitate mapping of top and base of targeted sand in order to generate thickness maps, also the GLCM assisted in enhancing the homogeneous seismic amplitudes at the reservoir level which facilitated the mapping of reservoir sand. The final stratigraphic interpretation proposes a new geological model of sand distribution suggesting fluvial dominated delta. The new model is supported by the water cut rates at individual wells indicating that it is related to the sand quality. The study provided solid understanding of sand distribution at injection level, and this understanding is used to further optimize the injector wells locations and securing the project’s objectives

Offshore drilling operation in the oil and gas industry is complicated and exhibits different types of technical challenges as the mysteries of the water bottom conditions and the environments that occur at different depths. The recent drilling operations continue to encounter shallow geological hazards (geohazards) with different intensity. Many operating companies in the industry are running geohazard assessment surveys early on in the project to measure the degree of geological complexity and level of hazards associated with the drilling operation in the site. This paper is part of a geohazards study for an exploration well in the South China Sea offshore Sarawak, Malaysia. The assessment is based on integrating the interpretation of a high-resolution two-dimensional seismic data (2D) with the normal three-dimensional seismic data (3-D) to evaluate the near subsurface geology and identify the hazardous locations prior to the drilling campaign. Different seismic attributes maps such as Root Mean Square (RMS) and Variance generated to highlight features of interest and identify the hazardous areas. The results of the shallow hazard assessment were identifications of shallow gas accumulations at different levels, faults and channels in the area of interest

This paper summarizes the study that have been conducted on simulating carbonate growth and spatial distribution through time in frontier environment using new technology stratigraphic forward modeling (SFM). The area of study is located in dangerous ground deep water Sabah. It offers a unique challenge for exploration as only two wells have been drilled in this area. Very few geological studies have been conducted in this area and results of the recent drilled wells have added more to the geological ambiguitiy of the study area. For this purpose, an innovative technique has been used to improve the geological understanding and better predict reservoir distribution for future prospects and plays SFM is deterministic and mathematical process tool. It is used to model the physic of sedimentary transport and deposition of silicicalastic and carbonate. It enables the geologist to test and validate the factors controlling depositional process by comparing the simulation results with soft data. In carbonate reservoirs, SFM is designed to predict reef growth with the goal of better understanding reef evolution and carbonate facies distribution through time and space.

With few data sets and little exploration activity, frontier basins are high risk, and yet have high potential return. The offshore Sri Lanka is such a frontier basin. To date, oil companies have only drilled fifteen wells (four of the fifteen were stratigraphic tests) offshore Sri Lanka. Five wells are in the West Mannar Basin. In 2011, two wells discovered gas: Barracuda and Dorado (Sorkhabi 2013). The remaining deep-water offshore basins, south and east of Sri Lanka, remain unexplored.