Publications

In this abstract, a case study from offshore Indonesia is discussed and examples are shown in a complex geological setting in a very shallow water environment. The subsurface is characterized by large carbonate pinnacles containing large amount of karst features with thinning and thickening carbonate layers. The complex shallow overburden has significantly impacted and introduced ambiguity in the deeper target images. The vintage data indicates large amount of sagging effects that masks small scale pinnacle and karst images at the deeper target zones. Here the total wave field has been separated into specular reflections and diffractions. Diffraction energy, in general is much lower in amplitude and separate imaging of these, unveils small scale geological features such as channels, voids, karst, fractures, faults, caves, etc. Refined efforts have been undertaken to calibrate possible karsts images with production well data from carbonate reservoirs. Diffraction imaging also indicates edges from subsurface discontinuities in addition to the karst findings. These have been cross checked with the edges of high velocity contrasts found by reflection and refraction full waveform. Exhausting all efforts of detailed velocity determination and accurate anisotropy workflows has removed sagging effects. Further refinement through absorption compensation has recovered significantly the important signals in the deeper target zones and opened up new doors to deeper exploration. With the cascaded application of all these refined latest technologies, a significant amount of small size carbonate pinnacles has been imaged with very high resolution. The diffraction imaging process indicates possible karst within these small carbonate pinnacles. For accurate diffraction imaging, a specialized workflow has been implemented to minimize leakage of specular reflections and internal multiples after bandwidth extension. In addition, wave field separation provides advantages of processing the specular reflections separately to determine more accurate velocities.