Abstract

Cambay basin is one of the highly prolific and most exploited rift basins in India. Hazad member of Ankleshwar formation is main reservoir unit with strati-structural hydrocarbon entrapment system for several small to giant size fields in this area. The sand distribution pattern is guided by deltaic depositional processes; hence the sands distribution is very discrete in nature. Identifying such subtle and laterally less extensive sand packages is challenging due to resolution limitation of seismic data. This paper presents how subtle stratigraphic traps in Hazad formation are delineated and characterized through integration of spectral decomposition, rock physics and AVO analysis, which led to Jaya gas and condensate discovery. The first step in the integrated workflow is the application of CWT based spectral decomposition method on seismic data which helped in delineating the stratigraphic channel features at different levels within Hazad interval. The identified channel features were then validated with existing wells and nearby fields data. Next, the amplitude responses of these channel bodies were characterized in terms of lithology and fluids with aid of rock physics analysis and AVO analysis. This study revealed that amplitude responds dominantly to changes in lithology than fluid. And amplitude variations within channel fairway illustrating sand thickness changes rather than hydrocarbon presence. Finally, the exploration risk was mitigated by defining the robustness of the strati-structural trap for identified Prospect by integrating the channel sand geometry and its extension against raising structural setting information. Based on this study results, an exploration well was drilled in the channel sand fairway and made Jaya discovery with good production rates of gas & condensate from Hazad formation.