Effect of the hydraulic fracturing-induced slippage of regional natural fracture on casing deformation in horizontal shale gas wells: A case study on the Weiyuan block

Abstract

Casing deformation problems are widespread in the shale gas field, and the dominant natural fracture reactivation and slippage are treated as the main reasons for these casing deformations. This study establishes a mechanical model and uses the field data of Weiyuan to study the fracture slippage and the casing deformation. According to rock mechanics, the dominant natural fracture can be reactivated by the fluid injected into the fracture. A higher fluid pressure in the fracture can induce a larger slippage and a higher shear stress on the casing. The fracture slippage is not uniform along the fracture. Moreover, the maximum slippage is located at the center of the reactivation zone. The in-situ stress, friction coefficient, and angle between the fracture and the maximum in-situ stress can affect the slippage. Case studies on the casing deformation of two wells in Weiyuan have shown that the calculated slippage according to the analytical model herein is in accordance with the detected data in the field. In summary, this study provides a reliable and quick method for determining the slippage of the dominant fracture reactivation based on the distance from the fracture center.