Casing Shearing Failure in Shale Gas Wells Due to Fault Slippage Caused by Hydraulic Fracturing-Case Study

Abstract

Abstract According to the analysis of casing deformation events and the achieved micro-seismic data in four shale gas wells, the slip of the fault is treated as the main reason for casing deformation problems in shale gas wells in Changing. Analytical model for calculating fault slippage is established based on elastic mechanics and the slippage of faults around 4 shale gas wells is calculated. The calculated results show that both the height of fault reactivation area and the angle between the maximum in-situ stress and fault have significant effect on the fault slippage. The location of the intersection point where casing goes through the reactivation area of fault can significantly affect the casing deformation. The closer the intersection point is to the center of reactivation area, the larger fault slippage and the serious casing deformation occurs. Case study in well Ning201-H1 shows that the slippage of fault at total depth 3490 of this well is 30.5mm, and the corresponding casing deformation is 10.5mm which is in agreement with field data. The casing deformation in drilling platform H19 is much more serious due to the extremely complicated faults and the large reactivation area. The maximum casing deformation reaches 35mm in well H19-5. The results of this study have significant reference value for understanding the mechanism and controlling methods for casing deformation in shale gas wells during hydraulic fracturing treatment.