Coupled modeling circulating multi-layer wellbore temperature and stress field during deepwater high-temperature and high-pressure gas well testing

Abstract

During the testing of offshore high-temperature and high-pressure (HTHP) gas wells, the heat transferred by the high temperature gas flowing through the tubing frequently leads to the rupture of the wellhead cement sheath, which can directly result in the failure of the wellhead seal and pose a significant safety hazard. In this study, an advanced multi-layer temperature and stress coupling model is introduced, which combines wellbore heat transfer and the multi-layer thick-walled cylinder theory. Subsequently, commercial software and measured data are utilized to verify the validity of the coupling model. The simulation results show that the average error between the model and the commercial software is 0.84%, and the average error between the model and the measured data is 1.65%. There is the optimal gas production in testing process by calculating the temperature and stress distribution during the test of the South China Sea HTHP gas well, and the stress distribution sensitivity of the multi-layer model is analyzed. The sensitive parameters are ranked in descending order of importance as follows: the number of cement sheath layers, gas-oil ratio (GOR), performance parameters of the cement sheath, performance parameters of the formation, and casing wall thickness. Furthermore, in the three-layer model, the circumferential stress at the first interface of the cement sheath is lower compared to the two-layer model. The findings provide a theoretical reference for comprehending the distribution of wellbore temperature and stress during testing, which is crucial for accurately assessing wellbore safety and ensuring optimal operational conditions.