P110T Casing Material's Relation of Creep and Relaxation for the Sealing Surface of Premium Connection in High Temperature Gas Well

摘要

Creep or stress relaxation is considered as a mainly factor of reducing the contact pressure on the sealing surface of premium connection, causing the gas leakage in the high temperature gas well. In this paper, the creep tests of P110T casing material were conducted under different temperatures (120, 200, 300°C). According to the experimental data, the fitting mathematical model of P110T casing material's steady creep strain rate was obtained under the different temperature and loading by the Least Square method. Then, the relation of creep and relaxation was presented, and an innovation stress relaxation model was put forward from the creep strain rate. Finally, applying with the stress relaxation model, P110T casing material's stress relaxation varying with time was obtained. The results show that, the stress relaxation was obvious in the initial phase and it decreased with time increasing. The stress decreased significantly and tended to a stable value. And the environmental temperature and initial stress had a significant influence on the stress relaxation. This study can be used for the designing of the premium connection's structure, or prediction their service life in the high temperature gas well.