Abstract:

The second member of Xujiahe Formation in Gaomiaozi Gas Field, located in Xinchang fault zone of western Sichuan Depression, Sichuan Basin, is a typical tight sandstone gas reservoir with multiple layers of superimposed sand bodies. The sand bodies exhibit clear transverse phase transitions, characterized as “overall sand rich, locally gas rich”. However, due to the impedance of the high-quality reservoir being similar to that of mudstone, traditional post-stack inversion methods struggle to accurately delineate the boundaries of the sand body and the distribution of high-quality reservoir zones.To address these challenges, the study initially focused on identifying and predicting the boundary of the favorable facies zones based on the geological characteristics of the second member of Xujiahe Formation. This was complemented by an analysis of sensitive petrophysical parameters. Subsequently, a pre-stack geostatistical inversion study was conducted under phase control constraints. This approach enabled the differentiation between effective reservoirs and mudstone, culminating in an accurate prediction of phase-controlled effective reservoirs. The results of this predictive technology not only enhanced the accuracy of identifying sand bodies but also improved the reliability of predicting effective reservoirs. The outcomes closely matched the actual drilling results. This prediction technology has significantly supported the reserve submission and the strategic deployment of exploration well locations in the Hexingchang gas field, yielding substantial oil and gas benefits.

Key words: tight sandstone, seismic facies, sensitive parameter, prestack geostatistical inversion, effective reservoir prediction