Mechanism of Casing Deformation of Shale Gas Platform Wells in Luzhou Block Before Fracturing and Countermeasures for Prevention and Control

The deep shale gas resources in the Luzhou area of the southern Sichuan Basin are abundant and have been identified as a key replacement field for natural gas development following the medium-to-shallow shale gas fields in Changning and Weiyuan. However, the frequent occurrence of “pre-deformation without fracturing” in horizontal wells has significantly restricted large-scale production. In this study, the Lu203 and Yang101 well areas were analyzed to investigate the characteristics of casing deformation and the correlation with faults and natural fractures (fracture systems). A numerical model of multi-stage fracturing for platform wells was established based on microseismic event data, and the effects of fracturing on the stress and casing stress of adjacent wells were simulated and analyzed. The results indicate that the development of fracture systems is the primary cause of the “pre-deformation without fracturing” phenomenon. The propagation of fracturing fluid through fractures significantly increases the stress and loading around adjacent wells, causing casing stress to exceed its yield strength. To mitigate this issue, a method involving the injection of approximately 10 MPa of internal casing pressure into unfractured wells was proposed, effectively reducing the risk of casing deformation and failure. This provides technical support for the efficient development of deep shale gas.