Abstract

Horizon slices of 3-D seismic data are used to control seismic facies of 2-D data in the Aru area, North Sumatra Basin, with Sembilan Sand (a part of Middle Baong Sand) and Lower Keutapang Formation as the hydrocarbon producer in Securai and Paluh Tabuhan Timur (PTT) oil fields.

The 2-D seismic facies of Sembilan Sand, submarine fan environment during lowstand system tract, can be divided as shelf-landward, shelf slope and shelf to basinward. Most of the 3-D seismic area present at shelf slope, and the northwest 3-D seismic area, is where the Sembilan Sand has not developed. The boundary of its sand and developing channel complex, can be observed clearly and directly from horizon slices reconstructed from 3-D seismic data.

The Lower Keutapang Formation deposited in several deltaic sequences and barrier bar complex environments during highstand and transgressive system tracts. The 2-D seismic facies from the lower part of the deltaic sequences (zone 1100) can be mapped, as well as the 3-D seismic area present for this sequence in the delta front and prodelta area. The high amplitude of the 2-D seismic data at the upper part of Lower Keutapang Formation (zone 860), was observed and interpreted as a barrier bar complex. Horizon slices of 3-D seismic data can be observed and mapped both for the boundary and development of deltaic and barrier bar complex with northwest southwest direction respectively in the 3-D seismic area.

The result of this study gives more accurate seismic facies of Sembilan Sand and Lower Keutapang Formation and a basic strategy for the future exploration.