Abstract: Application of 3-D Seismic Amplitude Studies in Porefill Prediction, Baram South Field, Offshore Sarawak, Malaysia

John Voon Wei Khin, Kho Siak Chung, Ton Ten Have

The Baram South field comprises two separate fault-bounded dip closures in the intermediate to deep reservoir levels of upper Miocene age in a depth interval between 4000 and 7000 ft. The western culmination was proven hydrocarbon bearing by three wells, but the eastern closure remained partly untested. As both closures are covered by 3-D, a seismic amplitude study was conducted to see if the presence of hydrocarbons in the eastern closure could be inferred from amplitude anomalies similar to those seen in the western accumulation.

Four key seismic horizons were mapped and auto-tracked over the whole 3-D volume. Special care was taken to enhance reliable amplitude measurements over an area that is masked by shallow gas. Using a Bayesian approach, a probabilistic porefill prediction was made based on the measured seismic amplitudes, calibrated with the well data.

The result shows that amplitude anomalies are likely to be hydrocarbon-related, which is in agreement with the postulated hydrocarbon charge model. Some uncertainties remain regarding the differentiation between oil and gas. Also, at some levels, amplitudes are affected by tuning.

This study gives a good example of how 3-D can provide vital information beyond better structural definition.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994