A new approach for post-fracturing evaluation and productivity prediction based on a reservoir fracability index model in shale gas reservoirs

Multistage fracturing technology is the primary means of reservoir stimulation in shale gas wells. However, the productivity contribution of each stage varies greatly. It is essential to evaluate the fracturing effect in order to make an optimized treatment design. In this study, we adopted an integrated workflow to assess the main control factors of geological and engineering parameters and a novel approach was proposed for post-fracturing evaluation. For this purpose, the H block in Zhaotong shale gas demonstration zone in Sichuan, China, has been taken as an object of study. The production predicting model was built based on the reservoir fracability index (RFI) which took both fluid type and proppant size differences into consideration. The results demonstrated that (1) if the reservoir quality index (RQI) in the target zone is greater than 5.0, then the area has good reservoir quality and development potential. (2) The RFI of H Block is generally at 4.0-6.0, it can be used as the key parameter to screen out the sweet spot. This method not only serves as a set of practical fracturing evaluation methods but also as a set of productivity prediction and fracturing optimization methods, which can provide strong support for the development of shale gas reservoirs.