Publications

Time-lapse seismic is a geophysical technique for reservoir evaluation based on the change of seismic attributes (reflection amplitude, impedance, etc.) over time as a result of production depletion. This technique has been developed since the middle of the last century. Widuri Field was discovered in 1989, and put on production at the end of 1990, with original oil in place 796MM barrels. The field encompasses an oil-bearing area of 35 km2, the largest offshore oil field in Southeast Asia, with characteristic deltafluvial facies and faulted anticlinal structures. Conventional exploration seismic at Widuri Field was followed by a 3D seismic program in 1991, followed by two time lapse 3D seismic programs in 2000 and 2004. Typical processing included time migration before stack, seismic inversion, reservoir fluid index inversion and oil-bearing probability inversion in 1991, 2000 and 2004. These efforts had numerous beneficial results including 1) regional pressure depletion identification, especially areas where formation pressure is lower than bubble point pressure, 2) recommendations for optimal injector locations, 3) increased oil production by water flooding, delaying production decline rates and enhanced oil recovery and, 4) formation pressure detection after water flooding and determination of water migration paths, mastery of oil water displacement range and optimization of infill well locations to enhance oil recovery. Results from time-lapse seismic technique in Widuri Field successfully supported water flooding and stimulation, decreasing oil production decline rates and effectively improving oil recovery rates yielding substantial economic benefits. * CNOOC SES, Ltd.