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ABSTRACT: An integrated petroleum system study, northern Gulf of Thailand: applications to the Block B8/32 area

Teerman, Stan C.1, Leah N. Smith2, Christopher, N. Denison3, and Roger W. Marzi4
(1) Chevron Research Technology Company, San Ramon, CA
(2) Pogo Producing Company, Houston, TX
(3) Chevron Overseas Petroleum, San Ramon, CA
(4) Hydrocarbon System Associates, Katy, TX

Tantawan and Benchamas fields (Miocene) are located in Block B8/32 in the northern Gulf of Thailand. Tantawan field, to the south, produces primarily gas with associated oil and condensate; Benchamas field, to the north, produces primarily light oil. Post-rift faulting has compartmentalized the reservoirs, requiring a continuous in-fill and exploration drilling program to maintain production levels. Successful exploration for additional reserves in adjacent areas of the Gulf of Thailand requires a full understanding of the regional petroleum systems.

The main source rock area is in the deeper graben areas to the east of the fields, in the Pattani Trough. A regional decrease in thermal gradient from concession areas to the south puts Block B8/32 in a favorable location for both gas and liquids generation. Faulting strongly controls migration pathways and seals.

Restricted penetration of potential source rock intervals and lateral facies changes limits interpretation of source rock occurrence. Both oils and condensates display variations in isotopic composition and their capillary gas-chromatography character, suggesting differences in source input. Characterization of Type II and II/III kerogens by pyrolysis and organic petrology indicate the occurrence of several different source facies and depositional environments.

New source rock data have been generated in collaboration with biostratigraphic data, to understand the control of depositional environments on source rock distribution and their age. This information is integrated with stratigraphic and depositional models developed from wireline logs and 3-D seismic data to produce a predictive source facies model and to define variations in organic facies. This source model is calibrated with biomarker data.

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