Development and Creep Stress Analysis of Super High Strength TP165V Casing

Addressing the problem of damage of the casing serving in the creep formation, a new type of ultra-high strength casing is designed and developed featuring the steel grade up to 165 ksi, the transverse impact value at least 55 J, the longitudinal impact value at least 70 J, and the collapse resistance strength exceeding 182 MPa. The creep stress and elastic stress of the casing are analyzed by finite element method. It is found via the test that the ultimate collapse strength of the casing exceeds 200 MPa. Taking the maximum in-situ stress of the production layer of Zhongyuan Oil Field as an example, the actual collapse strength of the casing reaches 4 times of the maximum formation pressure. Furthermore it is revealed via relevant the study that the elastic stress and creep stress of the casing increase along with the increase of the difference between the two-dimensional in-situ stresses, and the creep stress increases more than the elastic stress. When the salt layer dissolves and produces voids, the stress at the cementation surface increases first, then decreases, and finally tends to be stable.