Publications

Bekapai, a mature oil & gas field located in the Mahakam PSC, had been discovered in 1972. Production started in 1974. The field consists of an anticline, compartmentalized by normal faults. The interval of interest consists of a 3 km thick multi-layered sediments sequence. The first 3D streamer seismic was acquired in 1994 and a reprocessing of PSDM had been completed in 2010. However, several subsurface uncertainties remained, essentially fault shadow/push-down, seismic signal absorption due to gas cloud in the shallow zone, and missing data due to already existing surface facilities prior to seismic acquisition. To remedy these pitfalls an OBC 4C wide azimuth seismic was acquired in 2012. The 4C receivers allow recording and processing in conventional P-wave (PP) and converted S-wave (PS). The nature of S-waves with a lower velocity than P-waves and being insensitive to fluid effect, promises a better image of the subsurface. Advanced seismic processing such as converted wave (PS) Depth Migration is one of the techniques being used. Building an accurate depth model is the key for PS depth migration. It is not only requires getting event focusing and gather flattening, but also needs tying the depths of corresponding horizons to the P wave image. PS processing gave a breakthrough in solving the main issues. This paper shows the evolution of seismic imaging and how significant improvements of the PS seismic contributed to the structural interpretation that helps to optimize the field re-development.