Case Study: Casing Deformation and Fault Slip Induced by Hydraulic Fracturing in Sichuan Basin

: In Changning and Weiyuan shale gas blocks, casing deformation occurred in more than 30% of wells during hydraulic fracturing, which restricted the efficient development of shale gas in China. Ning 201-H1 was atypical well which experienced casing deformation. The characteristics of casing deformation, include deformation time, deformation position and deformation shape, were analyzed, and the results indicate that the casing deformation was caused by a small fault slip. Using Microseismic monitoring data and ant tracking data, the dip and inclination angles of small faults were identified, and the mechanical activity of the fault was analyzed based on the in-situ stress and treating pressure data. The results show that under the in-situ stress conditions and treating pressure, the fault is critically stressed and was activated during fracturing, which caused casing deformation. The characteristics of cementing quality data, fracturing curve and microseismic data were analyzed. Due to poor cementing quality, the fracturing fluid may break through the gap between casing and formation during fracturing, intrude the fault and finally activate the fault. Therefore, in order to avoid casing deformation, it is recommended to improve cementing quality and avoid small faults.