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Abstract: Reservoir Geology of the F6 Field, Offshore Sarawak, Malaysia

Dietert Van Der Baan, Updesh Singh

The central Luconia province, offshore Sarawak, is a significant gas province, characterized by extensive development of late Miocene carbonate buildups. The F6 gas field is presently the largest gas accumulation in the province (approximately 170 km2). Its gas is supplied to the Malaysian Liquefied Natural Gas (MNLG) plant in Bintulu. The field has been in production for almost seven years, beginning January 1987.

The F6 field is a large platform-type carbonate buildup, having a relatively flat top and steep flanks. The seismic data quality is good, consisting of 2-D seismic data with coverage varying from 0.5 to 0.7 km at the crest to 2.0 to 2.5 km at the flanks. A total of 16 wells have been drilled mainly in the crestal or central part of the buildup. Extensive core data of the reservoir interval are available from four of these wells. Current production is from 10 development wells situated at the crest of the buildup with one observation well used for compaction monitoring.

The gas-bearing interval in the F6 reservoir has two highly porous zones, which are separated by a tighter zone that appears to form a permeability barrier. Current estimates indicate that 35% of the GIIP is in the upper two zones and 65% in the lower zone. The remaining geological uncertainties in F6 mainly relate to (1) lateral reservoir property variation, especially of the tight zone and the buildup flank areas and (2) the strength of the aquifer. Lateral permeability variations, e.g., permeability reduction along the buildup flanks could affect ultimate recovery. The results of a reservoir geological review, including results of a porosity lateral prediction study, are presented.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994