Tight Gas Sand Rock Physics Analysis and Hybrid Pre-Stack Iterative Inversion for Reservoir Characterization

Tight sand reservoir is one of unconventional reservoirs. Such reservoir has low porosity, low permeability, complex pore structure and strong heterogeneity. Traditional rock physics models are no longer suitable for such reservoir, and reservoir characterization using post-stack inversion method to estimate P-impedance alone is not able to differentiate the reservoir and non-reservoir. In this study, a combination of rock physics and pre-stack hybrid iterative inversion is used. Firstly, a new rock physics model is established that takes account of the complex pore structure and poor fluidity of fluids, to predict S-wave velocity. Then obtain sensitive elastic parameters of reservoir identification by rock physics analysis to guide the pre-stack inversion. Next, based on the more accurate P and S wave information obtained from pre-stack hybrid iterative inversion, the sensitive parameters data are calculated. The predicted result of high-quality reservoir is in good accordance with drilling wells, which prove the combination of rock physics and pre-stack hybrid iterative inversion can be applied to identify the gas reservoir in tight sand.