Strain-Based Casing Design for Cyclic-Steam-Stimulation Wells

An oil field in Xinjiang, China, experienced a casing failure rate of 15 to 30% in thermal wells, mainly relating to inadequate protocols of casing design. This paper presents a new strain-based casing-design method. New material parameters are proposed to build safety-evaluation principles throughout the service life of a thermal well. In addition, a gas-tight thread joint is applied to prevent steam leakage that otherwise would cause a large transversal stress between different formations, and result in slip deformation of the casing string. Field practices have shown that the new method's fitness works better for thermal wells than previously used methods.