Publications

Pre-stack depth migration has proven useful in the structural interpretation of the Banyu Urip field located in the Cepu KKS (Kontrak Kerjasama), East Java. Imaging the field is particularly difficult owing to a combination of several factors - lateral velocity complexity caused by a carbonate build-up with steep flanks encased within slower velocity siliciclastic rocks, presence of shallow gas accumulations, and a land 3-D survey that lacks both adequate fold coverage in the target zone and adequate near offset coverage. The last two factors create a challenging data regularization problem. Several high-effort processing techniques were used to mitigate the surface noise problems (ground roll and linear coherent noise), and to regularize the data (offset extension along with trace weighting and balancing). Shallow gas creates anomalous attenuation zones that required use of ExxonMobils proprietary Q-compensation algorithm for optimized Pre-Stack Depth Migration (PSDM). Velocity model building outside of the carbonate build-up was done by combining refraction tomography results using first break picks to determine velocities in the shallow portion of the subsurface, with deeper velocities estimated using PSDM migrated gathers. Inside the carbonate buildup, gather quality was so poor that a velocity scanning technique was used to determine the internal velocity structure.