3D3C application in prediction of fractures of deep-seated tight reservoir: An example of gas exploration in member 2 of Upper Triassic Xujiahe Formation, Xinchang gas field

The deep-seated gas reservoirs in the realm of continental deposits of the western Sichuan depression, which are super-tight, heterogeneous, fracture-pore gas reservoirs scattering mainly in Members 2 and 4 of Upper Triassic Xujiahe Formation, formed large- and middle-sized gas fields such as Xinchang, Hexingchang, Qiongxi, Zhongba and Bajiaochang. Deep in the continental realm of the western Sichuan depression there were favorable geological conditions for forming large- and middle-sized gas fields, for example, abundant gas sources, developed reservoirs, good preserving conditions and complete structural traps; the formed deep-seated gas reservoirs have the features of super depth, super tightness and low porosity and permeability, superhigh pressure, complex gas-water relations and complex reservoir heterogeneity, creating a great challenge to the prediction and identification of so complex reservoir and fracture systems using conventional seismic exploration technologies. The 3D3C converted wave seismic exploration technology, which is able to acquire at the same time C wave data reflecting rock matrix and anisotropy and P wave data reflecting matrix and fluid characteristics, is helpful to the exploration of deep-seated, tight, fractured gas reservoirs. Through the processing, inversion, multi-wave attributes analysis and comprehensive interpretation of 3D3C converted wave data, this technology has solved such problems about the deep-seated, tight, fractured gas reservoirs in western Sichuan as identification of high-quality reservoirs and detection of fractures, and has great potentials in determining fluid characters.