Abstract

Integrated basin modeling reconstructs the geological evolution of a sedimentary basin and can be applied to test different conceptual models of geologic evolution e.g. to reconstruct pressure and temperature histories, fluid flows, petroleum generation and explusion. In the study presented here, a Temispack study of the Sakala-Timur PSC in Indonesia, three primary objectives of the modeling work are addressed, failure analysis of unsuccessful exploration wells, calibration of modeling parameters using local well control, and the assessment of exploration risks for prospects in the licence area.

Results indicated that the reason for failure of one of these wells (ST-Alpha) was the lack of a suitable migration pathway from mature source kitchen to the trap. A second line passed through an oil-bearing structure tested previously by two wells (L46-1 and - 2) and was used as a calibrant of pressure prediction. Pressure information provides significant constraints on the degree of communication between sources and reservoirs and on the quality of potential seals.

A third line transected a dual-target prospect with prospective reservoirs in a Miocene carbonate buildup and in Eocene clastics. A fourth exploration well (L40-1) provides still more control for the models. Results of the modeling suggest that a gas charge would reach both targets in the prospect. A previously perceived risk on topseal due to an overpressured reservoir was significantly reduced as a result of the modeling work. However, a further result of the Temispack modeling served to highlight a separate problem regarding topseal. Silty Tertiary mudstones, developed at a number of levels, may not be capable of sealing a large buoyant gas accumulation. The Temispack models all showed significant leakage due to capillary failure over the predicted accumulations and highlighted a need for additional seal capacity investigations.