Abstract

Infill horizontal wells with fracturing treatment are being widely applied to enhance the recovery from shale gas reservoirs in Sichuan basin. Frac-hits are commonly treated as a hazard for the adjacent (infill) well production and wellbore. During the infill well fracturing of the gas shale in Sichuan basin, an interesting field phenomenon has been reported: (i) the number of microseismic (MS) events close to the boundary of the parent well SRV decreases sharply. It seems that there is a barrier or a local attenuation process that inhibits significant MS activity from developing within the parent well SRV. (ii) After infill well fracturing, a transitory pressure and production regain were detected in the adjacent parent well. In this work, an integrated flow-geomechanics coupling model has been built, which includes the parent well fracturing, parent well production, infill well fracturing and production. Involving with the field researches in North America, two cases in Fuling gas shale are discussed. The first case is based on an infill well in one main productive layer, while the second case is based on a multi-layer infill wells zone. Mechanism of the field phenomenon from Fuling gas shale infill wells are investigated by the integrated flow-geomechanics coupling model and evidenced by field data. Finally, several inspirations were proposed: (1) Only in gas shale (ultra-low permeable and naturally fractured reservoir)? (2) More geomechanical mechanisms for the MSEB effect? (3) Frac-hit is good or bad? How can we utilize it? More investigations are expected from scholars in different researching fields.

Background

The well production and pressure of shale gas reservoirs in Sichuan basin (Fuling, Changning, etc) drops over 90% and 75% in two years. Infill horizontal wells with fracturing treatment are being widely applied to enhance recovery from this reservoir.

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