Research and Development of High-performance SEW Q125 Casing for Service in Shale Gas Well

According to the special requirements for the oil casing performance to meet the need by domestic shale gas production,the chemical composition design of the Cr-Mo-V series coil is optimized.Then the Φ139.7 mm×12.7 mm Q125 SEW oil casing is developed with the manufacturing process of hi-frequency ERW+hot-stretch reducing+full-length quenching-tempering treatment.The geometric dimensions,the mechanical properties and the collapse strength of the trial-manufactured casing are tested.The test results demonstrate that the casing has high dimensional accuracies,i.e.,ovality≤0.5%and uneven wall thickness≤5%,and good strength-toughness mating,and that the casing has yield strength≥862 MPa,tensile strength≥931 MPa,impact energy at 0℃≥60 J,and excellent anti-internal pressure and collapseresistant performances.Therefore the casing is up to the requirements for safe service in shale gas production.