Sequence stratigraphy of the North Aceh Offshore area, North Sumatra, Indonesia
Year: 1996
Proceedings Title : Proc. Indon. Petrol. Assoc., 25th Ann. Conv., 1996
Sequence stratigraphic work in the North Aceh Offshore and southern Mergui Basins has established a basic geological framework for evaluating the petroleum potential of the area, based on wellestablished biochronostratigraphy, lithostratigraphy (7 wells) and seismic records (ca. 15,000 km 2-D seismic data).Seismically defined P22 Bampo sandstone structural plays were tested in two deep-water wells in 1994 (BLD-1 1,224 mST >n the southern part of the Mergui Basin. and on the cnIitinental slope, and ITU-1A 864 mSS at the nortben? extent of the North Aceh Offshore Basin) The d l s resulted in dry holes. but basically confirmed pre-drilling prognoses of the seismic stratigraphy.An N14 Baong stratigraphic play was identified based on biochronostratigraphy and seismic stratigraphy. Detailed biostratigraphic analyses were performed using Foraminifera, calcareous nannoplankton and pollen. The global sea level fluctuation curve of marine sequences was used to calibrate the biochronostratigraphic data from wells. All seismic records were enhanced in quality as much as possible by reprocessing. Relatively deeper seismic reflections were focused with fine-tuning in the reprocessing. The deeper reflectors are generally covered by long-path multiples due to large waterdepths.The main results of the stratigraphic prospecting in the region are :(1) The 30 Ma P21 sequence boundary (SB) marks the most significant event in this region's sedimentary history - a sudden remarkable depositional break from non-marine to bathyal. A downlap or onlap surface of the P22 SB represents a favorable combination of porous sandstone and top-sealing compact deep-water mudstone. P21 and P22 SBs overlap on seismic sections because of the thin sedimentary separation between them. The P22 SB was traced as a practical reference marker for structural analysis.(2) SBs of N11 through N14 should be markers that identify an exploration target in the Baong sandstone. An N14 Baong lowstand fan was identified as a stratigraphic prospect.
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