Detrital carbonate characterization through approach of seismic data in c block

The existences of detrital carbonate distribution in C block- East Java provides new exploration opportunity in East Java Basin. The J-2 well had drilled and penetrated ~400ft gross reservoir thickness of detrital carbonate. Core plug analysis result shown Oligocene planktonic foram mixed with shallow marine bioclast which growing in isolated carbonate buildup. Therefore, it ensure the detrital carbonate in Cepu formed of a reworked Oligo-Miocene shallow marine carbonate Build up which is the main reservoir in C block. Log & petrophysical data determine the detrital carbonate is gas reservoir which has passably properties (~11% of porosity and ~40% of water saturation). The reservoir give strong positive amplitude anomaly in seismic data and reflected onlap geometry to the body of carbonate buildup. The connection between detrital and buildup carbonate will lead to potential hydrocarbon migration toward to the carbonate body instead trapped in detrital carbonate. The conventional seismic data has limitation to determine continuity in detrital carbonate layer and estimate similar lithology. The quantification and relationship between amplitude and frequencies of seismic data used to estimate the continuity and distribution of detrital carbonate facies. The frequencies of detrital had distinguished using spectral decomposition which transformed to continue wavelet. In addition, the impedance was predicted using model based inversion which build from J-2 well. Cross-plot result shown the detrital carbonate in C block has unique frequencies and impedance value. Horizon slice map identified there are no connection between carbonate build up body with detrital carbonate. In addition, CWT and Inversion identified facies changing in detrital sedimentation from carbonate to shale. As conclusion, detrital carbonate have good chance to be good gas reservoir and new play in C block.