A BREAKTHROUGH OF BEKAPAI CONVERTED S-WAVE PROCESSING AND ITS POSITIVE IMPACT TO STRUCTURAL INTERPRETATION

摘要

Bekapai, a mature oil & gas field located in thernMahakam PSC, had been discovered in 1972.rnProduction started in 1974. The field consists of anrnanticline, compartmentalized by normal faults. Therninterval of interest consists of a 3 km thick multilayeredrnsediments sequence.rnThe first 3D streamer seismic was acquired in 1994rnand a reprocessing of PSDM had been completed inrn2010. However, several subsurface uncertaintiesrnremained; essentially fault shadow/push-down,rnseismic signal absorption due to gas cloud in thernshallow zone, and missing data due to alreadyrnexisting surface facilities prior to seismic acquisition.rnTo remedy these pitfalls an OBC 4C wide azimuthrnseismic was acquired in 2012. The 4C receiversrnallow recording and processing in conventional Pwavern(PP) and converted S-wave (PS).rnThe nature of S-waves with a lower velocity than Pwavesrnand being insensitive to fluid effect, promisesrna better image of the subsurface. Advanced seismicrnprocessing such as converted S-wave (PS) DepthrnMigration is one of the techniques being used.rnBuilding an accurate depth model is the key for PSrndepth migration. It is not only requires getting eventrnfocusing and gather flattening, but also needs tyingrnthe depths of corresponding horizons to the P wavernimage.rnPS processing gave a breakthrough in solving thernmain issues. This paper shows the evolution ofrnseismic imaging and how significant improvementsrnof the PS seismic contributed to the structuralrninterpretation that helps to optimize the field redevelopment.