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ABSTRACT: Integrated Subsurface modelling of a Miocene reefal buildup, offshore Sarawak, Malaysia

Singh, Updesh1, Son Huu Do2, Lee Siew Sin2, and Norizah Othman2
(1) Sarawak Shell Berhad, Miri, 98100, Sarawak, Malaysia
(2) Sarawak Shell Berhad, Miri, Malaysia

The F6 Field is the largest producing gas field offshore Sarawak and is located some 180 km NNW of the LNG plant in Bintulu, Sarawak. It has been in production since January 1987 from 10 producers drilled at the crest. The F6 reservoir is a Miocene reefal buildup which forms a relatively flat-topped, platform type structure capped by a central pinnacle. As part of a petroleum engineering effort to increase reserves, an integrated subsurface study involving static and dynamic modelling was performed. The main subsurface uncertainties in the F6 field are the reservoir properties at the flank areas away from existing well control. Especially significant is a tight layer separating the reservoir into upper and lower compartments. Based on the results of a seismic inversion study and the 3D static models, the lateral variability in the reservoir quality was mapped, especially of the tight layer. History matching of the upscaled static models was performed with relatively minor changes to the original static model input. Results from the flow simulation of the F6 field showed that installing additional compressors for lowering the well-head abandonment pressure, THP, from 500 psi to 170 psi will increase the recovery factor, RF, from 80% to 87% of GIIP. The flow simulation was used to test recovery factor sensitivity to the tight layer. This study showed that in the extremely unfavorable case where the tight layer is a significant barrier to vertical gas flow the RFs of the 500 psi THP and 170 psi THP are reduced to 76% and 82% respectively.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia