Stratigraphic framework for oil exploration in Sarawak

Ho, Kiam Fui; Berhad, Lutong Sarawak Shell

doi:10.7186/bgsm10197801

Cited by 105 publications

(55 citation statements)

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“…Early models of the BDP therefore postulated a single‐sourced wave‐dominated delta model, based on the analogous modern Baram delta (e.g. Ho, ; Scherer, ; Johnson et al ., ). However, a wave‐dominated delta front fed by multiple rivers is likely to show much greater lateral variability in sand distribution, as a result of spatial and temporal variations in sediment transfer across the multiple drainage basins; this is supported by numerous subsurface studies of reservoir‐scale stratigraphic architecture (e.g.…”

Section: Discussionmentioning

confidence: 99%

Coupled ‘storm‐flood’ depositional model: Application to the Miocene–Modern Baram Delta Province, north‐west Borneo

et al. 2017

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The Miocene to Modern Baram Delta Province is a highly efficient source to sink system that has accumulated 9 to 12 km of coastal-deltaic to shelf sediments over the past 15 Myr. Facies analysis based on ca 1 km of total vertical outcrop stratigraphy, combined with subsurface geology and sedimentary processes in the present-day Baram Delta Province, suggests a 'storm-flood' depositional model comprising two distinct periods: (i) fair-weather periods are dominated by alongshore sediment reworking and coastal sand accumulation; and (ii) monsoon-driven storm periods are characterized by increased wave-energy and offshore-directed downwelling storm flow that occur simultaneously with peak fluvial discharge caused by storm precipitation ('storm-floods'). The modern equivalent environment has the following characteristics: (i) humid-tropical monsoonal climate; (ii) narrow (ca <100 km) and steep (ca 1°), densely vegetated, coastal plain; (iii) deep tropical weathering of a mudstone-dominated hinterland; (iv) multiple independent, small to moderate-sized (10 2 to 10 5 km 2 ) drainage basins; (v) predominance of river-mouth bypassing; and (vi) supply-dominated shelf. The ancient, proximal part of this system (the onshore Belait Formation) is dominated by strongly cyclical sandier-upward successions (metre to decametre-scale) comprising (from bottom to top): (i) finely laminated mudstone with millimetre-scale silty laminae; (ii) heterolithic sandstone-mudstone alternations (centimetre to metre-scale); and (iii) sharp-based, swaley cross-stratified sandstone beds and bedsets (metre to decimetre-scale). Gutter casts (decimetre to metre-scale) are widespread, they are filled with swaley cross-stratified sandstone and their long axes are oriented perpendicular to the palaeoshoreline. The gutter casts and other associated waning-flow event beds suggest that erosion and deposition was controlled by high-energy, offshoredirected, oscillatory-dominated, sediment-laden combined flows within a shoreface to delta front setting. The presence of multiple river mouths and exceptionally high rates of accommodation creation (characteristic of the Neogene to Recent Baram Delta Province; up to 3000 m Ma À1 ), in a 'stormflood'-dominated environment, resulted in a highly efficient and effective offshore-directed sediment transport system.

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Section: Discussionmentioning

confidence: 99%

Coupled ‘storm‐flood’ depositional model: Application to the Miocene–Modern Baram Delta Province, north‐west Borneo

et al. 2017

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“…The identification of sequence boundaries is based on recognition of regionally correlatable seismic reflectors as unconformities, and further confirmed by interpretation of the well data. Within the Sarawak basin, seven sequences are recognized which range from early Oligocene to Holocene in age, and their correlation with the eight cycles of previous workers, based on Ho (1978), is shown in Fig. 2.…”

Section: Data and Techniquesmentioning

confidence: 80%

“…4) Ho (1978) into eight cycles. The base of each cycle is marked by the maximum transgressive unit and the top is represented the maximum regressive unit.…”

Section: Eastern Sub-basinmentioning

confidence: 99%

The tectonic evolution and associated sedimentation history of Sarawak Basin, eastern Malaysia: a guide for future hydrocarbon exploration

Mat-Zin

Swarbrick

1997

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A seismic-stratigraphic study of the reprocessed regional lines for the offshore Sarawak area was undertaken with the aim of reviewing the present understanding of the tectonics and the palaeo-depositional environments of the Sarawak Basin. The study was integrated with biostratigraphy and wireline-log data from the wells drilled throughout the basin.Seven unconformities were identified within the Tertiary sediments and these were used as the markers for the seismic correlations. Where the unconformities become conformable, well data were used to guide the correlation of the conformities. Palaeoenvironment maps were generated which document the interaction of tectonics and sediments throughout the basin history. The development of the Sarawak Basin commenced in late Oligocene times with deposition along a coastline running in a NW-SE direction, which is almost perpendicular to the present-day coastline. The coastline was oriented to the present-day NE-SW during late Miocene times.Geochemistry of Sarawak Basin oils shows generation of hydrocarbons from land plant dominated source rocks. The distribution of these types of source rocks are favoured in the Coastal Fluvial, Coastal and Lower Coastal Plain environments. The quantity and quality of the source rocks deteriorates with the distance from the coastline. The palaeoenvironment maps illustrate the likely distribution of Sarawak Basin source rocks which will help in effectively planning for future exploration in Sarawak.The study also revealed that the Sarawak Basin was formed as a result of NW-SEtrending right-lateral fault movement during late Oligo-Miocene times. This dextral movement was responsible for creating the NW-SE coastline and divided the offshore Sarawak area into two sub-basins. Deposition and preservation of coastal plain and shallow marine sediments continued in the eastern area while the western area remained as a 'high' until late Miocene times. The dextral strike-slip movement which controlled the evolution of the Sarawak Basin is sub-parallel to a number of lineaments elsewhere in Sarawak. The timing of movement of these suggests progressive younging in an eastward direction. It is also believed the late structuration of the sediments and the formation of structural traps is linked to these tectonic movements.

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“…The sedimentary sequences in offshore Sarawak from Oligocene to Recent consists of a series of "Cycles" (Ho, 1978). Subsequent movement during Mid Oligocene created transform faults with a NW-SE orientation forming the boundary of Tatau and Luconia microplates .…”

Section: Regional and Prospect Geologymentioning

confidence: 99%

Recent Hydrocarbon Discovery in Pre-Carbonate Clastic Reservoir: Unlocking Deeper Potential in Sarawak Offshore!

et al. 2014

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A recent Oil and Gas discovery in an exploratory well in the Balingian Province could be the prelude to a new era of hydrocarbon exploration in deeper stratigraphy (Cycle-I) of the Sarawak offshore. In spite of various hydrocarbon discoveries made previously, only few wells flowed naturally from Cycle-I due to low permeability. Hence, natural oil flow during a DST from the well is a first of its kind in the block and nearby area. With limited data, few well penetrations and poor seismic data quality, Cycle-I exploration remains challenging and less understood. Hence the success is more of a "challenge" to "cherish" story. An extensive regional study, including preparation of time/depth structure maps, regional isopach maps, well penetration charts, play fairway maps and post drill analyses (PDA) of available wells was carried out for the prospect de-risking. Poor seismic data (mainly due to lower frequency in deeper section and shallow gas clouds overlying the objective at the well location) and the uncertainty of reservoir quality (low permeability) observed in the block become the major challenges in finding the best spot to test hydrocarbon prospectivity of Cycle-I. Despite of being low permeability, the reservoir of Cycle-I sand flowed around 400-500 bopd. This flow rate is significant as this is the first recorded data that the Cycle-I reservoir has been production tested in the block and nearby area. Usage of a robust workflow, state-of-art software and cutting edge technology contributed to the success in this well. Apart from various technical studies carried out during the project, the decisive factor behind the success of the well is the "explorer mindset" of the team and full support from the management. The discovery has wider implications for the hydrocarbon exploration of the deeper stratigraphy in this mature basin.

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Stratigraphic framework for oil exploration in Sarawak

Cited by 105 publications

References 0 publications

Coupled ‘storm‐flood’ depositional model: Application to the Miocene–Modern Baram Delta Province, north‐west Borneo

Coupled ‘storm‐flood’ depositional model: Application to the Miocene–Modern Baram Delta Province, north‐west Borneo

The tectonic evolution and associated sedimentation history of Sarawak Basin, eastern Malaysia: a guide for future hydrocarbon exploration

Recent Hydrocarbon Discovery in Pre-Carbonate Clastic Reservoir: Unlocking Deeper Potential in Sarawak Offshore!

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