Bulletin of the Geological Society of Malaysia, Volume 63, June 2017, pp. 117 – 143
1JX Nippon Oil and Gas Exploration (Deepwater Sabah) Limited, Malaysia
2 Petroliam Nasional Berhad (PETRONAS), Petronas Twin Tower, KLCC, Kuala Lumpur, Malaysia
3 Retired Consultant/Sequence Stratigrapher (firstname.lastname@example.org)
4 Goldbach Geoconsultants O&G and Lithium Exploration, Germany
*Corresponding author: email@example.com
Abstract: The onshore portion of Baram Delta petroleum province in northern Sarawak is largely covered by the Block SK333 exploration permit, most recently operated by JX Nippon. It contains a complete sedimentary succession ranging in age from Mid Eocene to Holocene. A sequence-stratigraphic investigation of the area, based on 2009 2D seismic, integrated with recent biostratigraphic analyses conducted in 2010-2011, suggests that the sedimentary section has been affected by three major episodes of deformation which are: (1) Late Cretaceous to Eocene (79.5-36Ma) block faulting, (2) Late Oligocene to Mid Miocene (30-20.5Ma) wrench movement and related folding, followed by (3) Mid Pliocene to Holocene (4.0-0Ma) uplift and compressional folding. These tectonic episodes have resulted in a subdivision of the Block SK333 area into two major anticlinal trends: the Engkabang-Karap Anticline in the south, and separated by the large Badas Syncline, the northern Miri-Asam Paya Anticline.This configuration resulted in two distinct petroleum systems and respective hydrocarbon zones: (i) A southern overmature gas system sourced probably from deeply buried and carbonaceous Eo-Oligocene basinal shales containing reworked terrestrial organic matter, which charged wrench induced traps such as at the Engkabang-Karap Anticline that were later overprinted by compressional folding. The surface expression of this petroleum system is manifested by an active mud volcano on the western Engkabang-Karap Anticline axis, which emits thermogenic C1 gas. Burial history modelling indicates that an earlier oil charge probably occurred during deep Oligocene burial, preceding basin reversal during the Pliocene-Holocene inversion episode, with the wrench-induced anticlinal closure which subsequently has been charged by late gas. (ii) A block-wide oil and gas system sourced from peak mature Mid-Late Miocene carbonaceous shales and coals in the synclines, charging inversion and compressional fold structures along the northern Miri-Asam Paya anticlinal trend, and also the Miocene section at the Engkabang-Karap Anticline. Expulsion and charge to traps commenced during the Late Miocene and is continuing to the present-day. Although the exploration results of the southern Eo-Oligocene carbonate play have been disappointing to date, the onshore Baram Delta still contains a number of attractive, both untested and partially tested plays that are yet to be fully explored. Lowstand delta and turbidite plays, a highstand delta shoreface play in the Miri-Asam Paya anticlinal area and a moundform stratigraphic play in the southern limb of the Badas Syncline are among the untested play identified in the study area.
Keywords: onshore Baram Delta, northern Sarawak, petroleum systems, sequence stratigraphy, SK333