Onshore Sarawak Research Articles

Field And Well Evidence For Major Unconformities In North Sarawak, Compared To Southwest Sabah, Malaysia

A review of biostratigraphic and lithofacies data is used to show that there is no major unconformity in the stratigraphic record of north Sarawak or southwest Sabah near the end of the Early Miocene (approximately 17-15 Ma). The existence of such an unconformity has been cited in many papers in the past decade and used as a data point in the construction of regional geological hypotheses. Exploration well and outcrop data identifies two major unconformities in SW Sabah (the base and top of Stage III; BMU and DRU; roughly 24 and 13-12 Ma), and in offshore west Sarawak a third unconformity (MMU c. 16 Ma) which fades in effect towards onshore Sarawak. In recent years the names of these distinct unconformities have become conflated as workers had overlooked the origins and definitions of these features. This history is reviewed here in order to clarify future work.

Application of transient electromagnetic method (TEM) technique in South-East Asia: Case studies from onshore Sarawak and North Sumatra

Application of transient electromagnetic method (TEM) technique in South-East Asia: Case studies from onshore Sarawak and North Sumatra

Erratum to: Liquid hydrocarbon generation potential from Tertiary Nyalau Formation coals in the onshore Sarawak, Eastern Malaysia

Erratum to: Liquid hydrocarbon generation potential from Tertiary Nyalau Formation coals in the onshore Sarawak, Eastern Malaysia

Liquid hydrocarbon generation potential from Tertiary Nyalau Formation coals in the onshore Sarawak, Eastern Malaysia

Tertiary coals exposed in the north-central part of onshore Sarawak are evaluated, and their depositional environments are interpreted. Total organic carbon contents (TOC) of the coals range from 58.1 to 80.9 wt. % and yield hydrogen index values ranging from 282 to 510 mg HC/g TOC with low oxygen index values, consistent with Type II and mixed Type II–III kerogens. The coal samples have vitrinite reflectance values in the range of 0.47–0.67 Ro %, indicating immature to early mature (initial oil window). T max values range from 428 to 436 °C, which are good in agreement with vitrinite reflectance data. The Tertiary coals are humic and generally dominated by vitrinite, with significant amounts of liptinite and low amounts of inertinite macerals. Good liquid hydrocarbons generation potential can be expected from the coals with rich liptinitic content (>35 %). This is supported by their high hydrogen index of up to 300 mg HC/g TOC and Py-GC (S 2) pyrograms with n-alkane/alkene doublets extending beyond C30. The Tertiary coals are characterised by dominant odd carbon numbered n-alkanes (n-C23 to n-C33), high Pr/Ph ratio (6–8), high T m /T s ratio (8–16), and predominant regular sterane C29. All biomarkers parameters clearly indicate that the organic matter was derived from terrestrial inputs and the deposited under oxic condition.

Integrated Interpretation of Airborne Gravity, Magnetic, and Other Geophysical Data in Block SK-12, Onshore Sarawak, Malaysia: ABSTRACT

An airborne gravity and magnetic survey of Overseas Petroleum and Investment Corporation's concession Block SK-12 in Sarawak, Malaysia, and its interpretation were completed by Carson Service Inc. in 1990. The survey and its integration with other geophysical data from the area were undertaken to make well-constrained subsurface structural interpretations and to evaluate the petroleum potential of an area that includes both a very rugged mountain range and deltaic swamps, across which it would be too difficult and expensive to conduct comprehensive seismic prospecting. The Bouguer gravity anomalies were correlated with the regional configuration of the basins of Sarawak, and residual gravity anomalies were correlated with the local structures within these basins. The magnetic anomalies were used to estimate the depth of the magnetic basement. Stripping of the gravity effects of the known shallow structures aided by insertion of the gravity data allowed interpretation of deeper structures.