莺歌海盆地超高温高压井挤水泥承压堵漏技术

南海西部莺歌海盆地X构造具有超高温高压地质特征，最高地层温度204 ℃，最大地层压力系数2.19，但地层承压能力低，安全密度窗口窄，钻井过程中极易发生井漏等复杂情况，严重影响钻井安全。为提高地层承压能力，保证超高温高压井段钻井安全，设计了“前置液+抗高温水泥浆”注挤水泥浆体系，通过优化堵漏水泥浆配方，提高了堵漏水泥浆的耐温性能，增强了其封固性能；采用“试挤清洗液+注挤水泥浆”间歇式注挤水泥浆工艺，并利用Drillbench软件模拟分析了井筒温度场，根据井筒温度场精准控制注挤水泥时的水泥浆用量及胶凝时间，提高了堵漏效果。现场应用结果表明，X构造应用挤水泥承压堵漏技术，提高了地层承压能力，扩大了安全密度窗口，为后续超高温高压井段安全顺利钻进提供了重要条件。超高温高压井挤水泥承压堵漏技术可以满足莺歌海盆地X构造安全钻井的需求，并可为类似超高温高压井钻井提供借鉴。 

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.