Pitfalls in seismic amplitude interpretation: Lessons from Oligocene channel sandstones

Abstract

A high-amplitude anomaly was identified in the Upper Oligocene Daman Formation clastic sequence during initial interpretation of newly acquired 3D seismic data in the Tapti-Daman sub-basin offshore western India. This anomaly exhibited the depositional signature of a channel and was interpreted as bright spots associated with gas sands, consistent with the occurrence of thin gas pays in the sandstone reservoirs of Daman Formation in the area. Considering thickness and areal extent, thick gas sands were predicted, upon drilling; however, thick water-bearing sands were found. The predrill interpretation was mainly based on windowed amplitudes without validation through character of reflection events and other supporting evidence such as frequency, velocity, and AVO.