Abstract

The offshore Northwest Java (ONWJ) contract area is typical of basins approaching exploration maturity in which substantial production has been established from structurally controlled traps. However, a strong element of stratigraphic control on hydrocarbon accumulation has always been apparent and this offers the opportunity for significant incremental hydrocarbon potential in ONWJ. One example of such potential is the FWS area.

The FWS area 150 km east of Jakarta, is located in the northwestern corner of the "F" High Trend. The area is adjacent to and downdip from the HZE, FW and FN fields which currently produce oil from Miocene "Main" and "massive" intervals. Two exploratory wells tested oil in the area, but these wells have not been put on production because structural closures have not been identified. Subsequent mapping and stratigraphic studies suggest that, whereas the originally anticipated structural trap is not present, the two wells penetrated a possible stratigraphic trap within the "Main" interval. Based on a combined stratigraphic structural trap model, the FWS area has significantly larger potential reserves than those estimated from the earlier structural interpretation. The area is currently being re-evaluated for additional drilling utilizing the stratigraphic model.

This stratigraphic approach can be applied elsewhere to enhance the reserve potential of an area and to locate new plays in mature provinces.