Abstract: History of Hydrocarbon Generation in Tembungo Area, Northwest Sabah Basin
Mohammad Jamaal Hoesni, Mohd Nasir Che Mood
Tembungo field in Sabah Basin produces oil from upper Miocene turbidite reservoirs. The oil, with low sulfur and wax contents and API gravity of 38-40°, was derived from terrigenous source rock of mainly land-plant origin. The history of hydrocarbon generation in the Tembungo area--that is, the burial, fluid pressure and fluid-flow, thermal, hydrocarbon generation, and migration history--has been studied with the help of a two-dimensional finite difference basin model.
Backstripping shows that high sedimentation rates occurred during middle to late Miocene. The Tembungo structure itself began to grow in late Miocene (7.24 Ma), with an accelerated growth rate in the early Pliocene. A constant basement heat flow of 55 mW/m2 was determined for the area. The faults are known to be sealing, with very low associated permeabilities. The presence of barrier faults and thick shales resulted in development of overpressure in the area. Contribution of hydrocarbon generation to overpressure is insignificant.
Maturation models based on kinetic chemical reaction indicate that upper Miocene sediments underlying the reservoir section in the adjacent syncline to the northwest and west began to enter the hydrocarbon generation window at 8.4 Ma and that the hydrocarbons began to be trapped in the Tembungo structure in the late Miocene (6.0 Ma). The oils most likely were sourced from these upper Miocene sediments underlying the reservoirs. Hydrocarbons sourced in middle Miocene sediments were largely retained due to thick overlying shales, and they eventually were cracked to gas.
AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994