Progress and Prospect on the Study of Full Life Cycle Sealing Integrity of Cement Sheath in Complex Environments

Influenced by many factors such as downhole high temperature and high pressure, acidic fluid, large-scale multi-stage fracturing after cementing, and oil and gas exploitation, the sealing integrity of the cement sheaths is vulnerable to damage, which leads to interlayer channeling, wellhead pressure, and even blowout. At present, the sealing control technology of cement sheaths centered on improving cement sheath cementation quality can no longer meet the demand for long-term development of complex oil and gas wells, and with the increasing number of deep wells, ultra-deep wells, and unconventional oil and gas wells, the environment and working conditions faced in the future will be even more complex, which will require even higher requirements for the sealing integrity of cement sheaths. To this end, the progress of research on the full life circle sealing integrity of cement sheaths in complex environments was reviewed, and the main problems existing in the sealing integrity control of cement sheaths were analyzed. The basic theoretical and scientific problems that should be solved in the future were pointed out, and related technologies were prospected. It is concluded that on the basis of continuous research on the theory of cement slurry hydration and anti-channeling in high-temperature and high-pressure environments, the failure law of cement sheath sealing in dynamic load environments, and the corrosion mechanism of cement stone in acidic environments, it is necessary to highlight the concept of full life cycle control and solve the key scientific problems such as “channeling, damage, and corrosion” leading to the failure of cement sheath sealing. It is also of great significance to innovate full life circle sealing integrity monitoring technology of cement sheaths and long-lasting sealing integrity control technology centered on “anti-channeling, anti-damage, and anti-corrosion” and establish the full life circle sealing theory and control method of cement sheaths in complex environments, so as to support the high-efficiency development of deep and unconventional oil and gas resources.