SEQUENCE STRATIGRAPHY APPLIED IN WELL LOGS, CORES, AND OUTCROPS: CONCEPTS FOR HIGH RESOLUTION CORRELATION OF TIME AND FACIES TO STIPULATE FURTHER HIDROCARBON PROSPECT OF FIELD WITH DELTAIC ARCHITECTURE COMPLEX: CASE STUDY OF SEMBAKUNG FIELD, TARAKAN BASIN

摘要

Sembakung field is located in the Tarakan Basin, North Kalimantan. The reservoir in this field is mainly deposited as sandstone from deltaic depositional environment. Series of prograding deltaic deposit were developed since Late Miocene in this basin. The subsurface data, includes well logs, high quality 3D seismic which showed that the field is controlled by a simple four-way anticline trending NW-SE. However, based on the production data statistically distributed in the field, it shows non-linier relation between the production and the structural configuration. Better producing wells are located at the flank. A high-resolution sequence stratigraphic interpretation at the 3~(rd) order sequence to parasequence (5~(th) order sequence) from subsurface data (core and well log) combined with the outcrop observation became a comprehensive input for the geological model of the area. Based on this framework, series of transgressive and early regressive deposit showing consistent relationship in production history as the major perforated oil zone with various oil initial rate - which means it does not connect to each other. The RMS amplitude volume from multi attribute seismic analysis demonstrate the reservoir distribution. Other seismic attributes such as frequency and sweetness give hint for hydrocarbon presence. Combination of those farthermost data revealing that stratigraphic traps are majoring the reservoir configuration in this field. The development is now focusing at the North -East area, in early regressive and transgressive phase of parasequences set (4~(th) order), that have high promise of virgin reservoir in this marginal field rather than well-connected and sand-rich maximum regressive reservoir facies. This early-regressive and transgressive phase of parasequences set (4th order) at the North-East area show big oil reserve potential of 78.47 MMSTB not developed. The outstep wells SBK-PXA and SBK-PYA, SBK-PXB haveinitial oil production was 931 bopd and 675 bopd, 548 bopd at the North-East of Sembakung area. This prove that in early regressive and transgressive phase of the parasequences set (4~(th) order) show very good of oil prospect and oil production.