Risk assessment and prevention measures for casing deformation in the geological–engineering integration of a block in Jiaoshiba shale gas field

Abstract

Casing deformation is a widespread problem in a certain block of Jiaoshiba Shale Gas Field in Sichuan Basin, China, and it severely limits the development benefits of shale gas in that block. Based on the spatiotemporal characteristics of block formation, fracture development, and casing deformation occurrence, this paper employs an integrated geological–engineering research approach to identify the primary mechanisms governing casing deformation within the block and proposes countermeasures to prevent such deformation. The present research indicates the following findings: (1) The block has undergone multiple phases of tectonic superposition, with fracture development serving as the geological factor causing casing deformation. (2) Fracturing activation constitutes the engineering factor causing casing deformation, with 4 mm of formation slip inducing deformation. (3) The fracture activation risk map shows that Class I and Class II fractures account for 73.36 % of the total recorded in the block. Within the most susceptible Class I risk zone, the critical activation pressure increment for fracturing operations ranges from 13.43 MPa to 13.99 MPa. Based on the distribution of casing failure risk zones identified in the fracture activation risk map, this paper proposes relevant technical countermeasures for preventing casing failure from three perspectives: shale gas well location deployment, drilling techniques, and fracturing techniques. These measures provide robust support for safeguarding the integrity of casing systems within the studied block.