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ABSTRACT: In-Situ Stress and Fluid Pressures of Brunei Darussalam

Tingay, Mark R. P.1, Richard Hillis1, Richard Swarbrick2, Scott D. Mildren1, and Eugene C. Okpere3
(1) University of Adelaide, Adelaide, SA, Australia
(2) University of Durham, Durham, England
(3) Brunei Shell Petroleum, Seria, Brunei

An investigation has been undertaken of the in-situ stress and fluid pressures of the Baram Basin in Brunei. The Baram Basin is a Tertiary delta with several major petroleum fields. The basin is subject to extreme overpressures that, in some cases, reach the lithostatic gradient. The implication of in-situ stress and overpressure for sub-surface fluid flow, specifically improving hydrocarbon recovery and examining the sealing potential of faults, are discussed.

Leak-off tests and borehole breakouts have been used to determine the minimum horizontal stress magnitude and direction. Density logs are used to calculate the vertical stress magnitude.

Repeat formation tests and mudweights were used to determine pore pressure profiles and identify zones of abnormal fluid pressures. Log data and modeling are used to examine whether overpressuring is caused by disequilibrium compaction or fluid expansion mechanisms.

The relationship between stress and fluid pressure within Brunei has been examined and compared with results from Breckels and van Eekelen (1982).

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