INTEGRATING GEOLOGY AND PETROPHYSICS INTO SEISMIC INTERPRETATION FOR RESERVOIR DEFINITION AND IMPROVED FIELD DEVELOPMENT: A CASE STUDY FROM THE BANUWATI FIELD

摘要

The integration of geological and petrophysical data into a geophysical interpretation project is essential if the full potential of hydrocarbon accumulations is to be recognised and the most cost effective development plan formulated. An example of this approach is described from the Baturaja Formation in the Banuwati Field of the Sunda Basin. Detailed well tie work established the gas bearing porous carbonates unexpectedly found by the Banuwati-4 well produced a seismic event. Careful mapping revealed the full extent of this reservoir to be much larger than previous estimates. The combine'd geophysical and geological information support a reef model. Amplitude maps revealed, nearby, undrilled structures with similar seismic expression. AVA analysis and acoustic impedance data gave encouragement that similar reservoir and fluid fill would be present in the largest of these. This prospect was drilled, in 2004, by Banuwati-6, to test the model that gas bearing carbonates as found at Banuwati-4 would be present. Banuwati-6 well data is a very good match to the seismic prediction. Porous carbonate presence, thickness, and fluid fill were all successfully predicted from the seismic data. The well also was a highly successful blind test of the acoustic impedance volume created prior to drilling. Total Banuwati Field reserves have been increased 33% and reefal carbonates are now estimated to contain 25% of field reserves. The high quality acoustic logs obtained in the 2004 well were used to generate crossplots of the many seismically derivable attributes against reservoir properties. The optimum seismically derivable product to identify high porosity and low water saturation zones is acoustic impedance. This approach to the geophysical interpretation has lead to the identification of a seismically predictable gas resource. Reservoir location, geometry, reservoir sweet spots and fluid fill are all seismically identifiable, leading to more accurate and increased reserve estimates, a changed reserve distribution, reduced uncertainty and risk and a reduced cost development plan.