Strain Design and Experimental Study of Casing in Thermal Recovery Well Based on the Elastic-Plastic Constitutive Model

When using thermal recovery for the exploitation of heavy oil, the casing is the only channel of steam injection and crude oil extraction. Keeping the casing safe is critical to the operation. The authors conducted low-cycle experiments using strain-controlled material and the MTS809 material testing system. Mechanical property parameters of thermal recovery casing in high-temperature conditions were obtained. The experimental data and stress-strain constitutive relation led to numerical models of formation-cement sheath-casing based on actual geological structure and rock parameters of the recovery wells. Mechanical responses of casings in the thermal recovery wells were simulated for different high-temperature constitutive models and creep constitutive models of casing materials. Under Results indicate that the stress and strain caused by bending loads on casings change greatly at the dogleg part. Moreover, creep has a remarkable effect on casing strain in a thermal recovery well, which cannot be neglected in design. This research provided the basic parameters and technical references for strain design of casing in a thermal recovery well.