When a deep water high temperature and high pressure well delivers fluid upward, the casing column undergoes thermal deformation, and the circumferential fluid generates circumferential pressure, resulting in wellhead lift. In this paper, the temperature field of deep water high temperature and high pressure wells is analyzed, and the wellhead lift model of deep water high temperature and high pressure wells is established by taking into account the thermal stress of the casing caused by the temperature effect. The article carries out the simulation test of wellhead lift to verify the accuracy of the model and study the influence of casing thermal stress on wellhead lift. The results show that: the amount of tubing column lifting is more obviously affected by temperature, and the temperature and casing elongation basically increase linearly. Combined with the data of a deep water high temperature and high pressure well in the South China Sea, the actual lifting amount is compared with the predicted lifting amount, which verifies the adaptability of the model and provides a basis for the formulation of preventive and control measures of wellhead lifting in deep water high temperature and high pressure wells.
Along with the continuous deepening of oil exploration and development, oil and gas exploration is shifting from land to sea. According to statistics, 74% of new oil and gas discoveries in the world in the past 10 years are distributed in the sea, of which 23% are in deep water and 36% are in ultra-deep water. With the progress of oil and gas development technology, more and more high temperature and high pressure oil fields have been discovered, such as the Yingge Basin in the South China Sea, the shallow waters of Malaysia, the Krishna Godavary Basin and the South Texas Basin on the east coast of India. During the extraction process of deep water high temperature and high pressure wells, high temperature fluid at the bottom goes up along the wellbore, and the temperature of casing and annular fluid in each layer rises by heat conduction. In addition to the obvious axial load on the free end of the casing, the temperature increase also causes the fluid in the confined annular space to generate a large expansion pressure due to heat, which leads to wellhead lift. By establishing a computational model of wellhead growth caused by temperature and pressure effects and performing computational analyses in case wells, Qiao et al. (2018) concluded that the axial load caused by multiple annular pressures is second only to the axial load caused by casing axial temperature differentials; wellhead growth increases with the increase of the thermal expansion coefficient of the annular fluid, and decreases with the decrease of the isotherm of the annular fluid. Introducing annular pressure management in production improves production efficiency by optimizing the well structure and production plan as well as installing wellhead monitoring equipment. Shi et al. (2019) studied the spiral buckling effect, temperature effect and bulging effect all as the lifting influencing factors in deep water high temperature oil and gas wells, and established a wellhead lifting model and solved it. Almulhem K (2020) proposed that the thermal expansion of the casing is an important effect of wellhead lifting in high temperature and high pressure gas wells, analyzed the effect of the wellhead temperature on the wellhead lifting, the integrity of the wellbore wellhead temperature on wellhead lift, wellbore integrity, and suggested measures for the causes of wellhead lift. Zheng et al. (2021) established a wellhead lift height calculation model by considering the influence of cement ring cementing strength, and based on the self-developed high temperature and high pressure wellhead lift simulation experiment device, carried out wellhead lift simulation experiments under the conditions of double-layer tubular columns with different cementing heights and multi-layer tubular columns coupled and cemented, and obtained the influence law of cement stone cementing on the elongation of tubular columns. In this paper, Yu et al. (2022) used the finite element method, according to the site conditions of a well in Shunbei block, and established a thermal-solid coupling analysis model of multilayer casing-cement ring-formation multi-body system under different working conditions by using the ABAQUS software to analyze the heat-solid coupling analysis model of the return casing from the beginning of the cementing stage to the time of production. The stress and displacement changes were analyzed, and the wellhead stress and lift height change process and the influence law of its related parameters were obtained. Wang et al. (2023) simulated the nonlinear heat transfer process and thermal expansion phenomenon of multi-stage casing-cement ring-formation by finite element method based on the multi-stage heat transfer theory, put forward a new calculation method of wellhead lift, and carried out the risk evaluation analysis of the wellhead of all levels of tubular columns under different working conditions by taking a well of a certain block in Xinjiang oilfield as an example. At present, the research on temperature effect mainly focuses on land high temperature and high pressure wells and offshore thick oil hot recovery wells, so it is necessary to carry out an in-depth study on the temperature effect of offshore deep water high temperature and high pressure wells. Deep water high temperature and high pressure wells face a more hostile environment, where the vertical distance from the mud surface to the seafloor exceeds 500 m water depth, the temperature at the bottom of the well is higher than 150 °C, and the pore pressure of the formation is greater than 69 MPa. Therefore, during the production process of deep water high temperature and high pressure wells, the temperature and pressure of the borehole undergoes a huge change, which may lead to the occurrence of wellbore cementing damage and the phenomenon of borehole uplift.
