Abstract

This paper is a case history about determining favourable carbonate reservoir facies in the Lower Batu Raja formation from a 3-D seismic survey over the Krisna-Yvonne A oil fields located in the Java Sea. Seismic attributes are easily calculated from 3-D data and are becoming commonly used predictors of "sweet spots" in a variety of production environments. Our experience has shown that the seismic response to variations in lithology is complex and non-unique in the Krisna-Yvonne fields. Consequently seismic attributes, in isolation, have no unique interpretation . The frequency content of the seismic data and the acoustic contrast and bed thickness of the rocks remain the basic constraints to resolving the seismic response.

However, because of the complete and consistent coverage provided by a 3-D seismic survey, conventional maps such as structure and isochron maps have a much greater lateral resolution than those based on 2-D data. Models and cross plots can discriminate where seismic attributes provide meaningful information about the reservoir. Rather than using seismic attributes in isolation we have found that the most effective way to find favourable carbonate reservoirs is to use seismic attributes in combination with the conventional methods of seismic interpretation such as structural mapping, isochron mapping to determine the paleogeography and seismic morphology. An integrated geologic facies model based on appropriate modern analogs was developed from the integration of the seismic information and the geologic data. The integration of the various data sources results in a product which is greater than the sum of the various parts. This model is the basis for sound reservoir management and a successful infill drilling program in the Krisna-Yvonne carbonate reservoirs and for development of exploration plays and concepts elsewhere in the basin.