Publications

Lematang Depression, located in the southern part of South Sumatra Basin, is adjacent to the main producing areas for MedcoEnergi E&P. Previously, exploration targets in this area were primarily focused on the post-rift sedimentary section of early to middle Miocene Baturaja limestone and late Miocene Palembang clastics. More recently, the deep syn-rift sequence of Talang Akar and Lemat Formations is becoming promising targets. High-pressure, high-temperature (HPHT) associated with deep exploration targets typically becomes the main concern for drilling operations. However, HPHT section may be a favorable environment for hydrocarbon generation and secondary migration. Understanding the regional subsurface pressure distribution is a vital part of basin evaluation. 1D (well-log) and 2D (seismic) based pore pressure was computed and structural restoration was incorporated to understand the basin migration flow mechanism. The basin rifting phase continued until late Oligocene and was then follow by a period of basin-sag up to middle Miocene. Pliocene-Recent oblique compression resulted in existing depo-center uplift and inversion structures within the syn-rift section. Basin modeling results indicate that hydrocarbon expulsion from gas prone syn-rift sediment started from middle Miocene. Rate of erosion, effective stress mapping and seal integrity estimation were also utilized to assess the potential for seal breach as well as a validation tool for hydrocarbon entrapment. As a result, the integration of basin modeling empowering structural development evaluation and subsurface pressure evaluation shows that inverted syn-rift structures initially could have been the location of hydrocarbon generation and eventually served as traps as well where the overpressured post-rift sequences provide a good seal in the relatively undeformed section. Keyword: Overpressure, secondary hydrocarbon migration, hydrocarbon entrapment