Cement Squeezing for Pressure-Bearing Plugging in Ultra-High Temperature and High Pressure Wells in the Yinggehai Basin

Cement squeezing in deep, hot, harsh environments presents special challenges The X structure of Yinggehai Basin in the western South China Sea oilfield is one such example. It has an ultra-high temperature and high pressure structure, with the formation temperature of up to 204 ℃ and formation pressure coefficient of up to 2.19. However, cement squeezing has been dangerously weak due to the low formation pressure-bearing capacity and narrow safety density window, and complications such as leakage could easily occur during drilling, which seriously affect the safety and integrity of operations. In order to improve the formation pressure-bearing capacity and ensure the safe and smooth drilling of ultra-high temperature and high pressure sections, a cement squeezing system “preflush + high temperature resistant cement slurry” was designed to improve the temperature resistance properties of leakage plugging slurry and enhance its sealing performance by optimizing the formulation of plugging cement slurry. The intermittent cement squeezing process of “cleaning pilot squeezing fluid + cement squeezing slurry” was adopted, and Drillbench software was used to simulate and analyze the wellbore temperature field, which accurately controls the slurry volume and gelation time based on the wellbore temperature field and effectively improves the plugging effect. Field application results showed that the technology could improve the pressure-bearing capacity of formation, and expand the safety density window in the X structure, as well as provide important conditions for the safe and smooth drilling in subsequent ultra-high temperature and high pressure sections. This technology can provide technical support for the successful drilling of the X structure in the Yinggehai Basin, which is worthy of reference for similar ultra-high temperature and high pressure wells.