Abstract: During hydraulic fracturing in shale oil and gas horizontal wells, fault slip can induce shear deformation of the casing, while conventional passive mitigation measures, such as increasing the casing steel grade and wall thickness, have shown limited effectiveness. Based on an active prevention concept that uses structural flexibility to accommodate rigid formation movement, an adaptive elastomer-composite casing capable of absorbing formation shear displacement was developed. Tests on water-swellable elastomers, numerical simulations of casing running, and simulated cementing tests were conducted to select the elastomer material and optimize its swelling ratio, elastomer-layer thickness, and casing structural parameters. By integrating seismic interpretation with drilling, mud-logging, and well-logging data, a method was established to identify small-scale subsidiary faults and intervals at high risk of casing deformation. Supporting tools, including a hinged roller centralizer, were also developed to ensure safe casing deployment. Comparative field trials of conventional casing, thick-walled casing, and adaptive elastomer-composite casing were conducted in six horizontal wells intersecting the same fault zone in the Jimsar shale oil block. Casing deformation occurred in both conventional-casing wells and both thick-walled-casing wells. Of the two wells completed with adaptive elastomer-composite casing, one remained free of casing deformation, whereas the other experienced only slight deformation. In the latter well, casing deformation occurred 6-8 fracturing stages later than in neighboring wells, and the deformation magnitude was reduced by approximately 14 mm. These results demonstrate that adaptive elastomer-composite casing can effectively accommodate fault-slip displacement, eliminating low-magnitude casing deformation and reducing the severity of high-magnitude deformation. This technology shifts casing-deformation mitigation from passive parameter adjustment toward active prevention and provides a practical solution with broad application potential for shale oil and gas wells.