Bulletin of the Geological Society of Malaysia, Volume 42, Dec. 1998, pp. 47 – 53
Sarawak Shell Berhad, Locked Bag No.1, 98009 Miri, Sarawak
Abstract: The D35 oil field in the Balingian province offshore Sarawak was discovered in 1983. It came on-stream in late 1994 and currently produces around 14,000 stb/d. An infill development drilling campaign has been planned for late 1997. A multi-disciplinary study for the D35 field, including quantitative interpretation of the seismic for porefill prediction, was undertaken to support the development drilling.
A high resolution 3D seismic survey was acquired over the D35 field in 1995. As the seismic data was of reasonably good quality, an AvO study was initiated. True amplitude near and far offset migrated sub-stacks were created, and amplitudes extracted at objective levels. AvO attributes were calculated and the responses at the infill target locations were evaluated by comparing the results with those observed at well locations.
The results of this study showed that the brine-bearing and oil-bearing reservoirs have different AvO responses. Thus, the results gave an indication of the porefill at the reservoir level, and this in turn assisted in optimising the revisit target locations.
In conclusion, AvO is an additional tool that can be used in screening drilling targets and for risk management in a multi-disciplinary team environment. The technique offers added information to reduce uncertainties as presented here in the D35 study.