动态平衡固井技术与实践

Technology of Well Cementing under Dynamically Balanced Pressure and Its Application

随着川西北地区勘探层位不断加深,川西勘探对象以深部下二叠统、寒武系地层为主。川西复杂超深井固井普遍面临纵向上多压力系统、窄安全密度窗口特点,常规尾管固井工艺已不能满足上述井况下环空有效封固。为解决该区块超深井尾管固井漏喷同存难题,针对压力敏感地层开展了动态平衡压力固井技术现场实践,形成以窄密度窗口固井环空压力控制和防窜水泥浆体系为核心的固井配套工艺,在LG70井φ114.3 mm控压尾管固井作业中进行了首次应用,确保了小间隙、井温高、漏喷同层复杂井况下的封固质量。该技术在后续超深井固井作业中推广应用也取得良好效果,为窄密度窗口井筒条件下防窜、防漏提供了一种切实可行的全新固井工艺。

Wells in northwest Sichuan are being drilled deeper and deeper. In west Sichuan, exploration activity has extended to the depths of the lower Permian Series and the Cambrian System. In the west of Sichuan cementing of complex ultra-deep wells has to be faced with multi pressure systems along the wellbore, and narrow drilling windows. Using conventional liner cementing techniques, the ultra-deep wells are unable to be cemented effectively. To address the problems in liner cementing, i.e., the coexistence of blowout and lost circulation in ultra-deep wells, well cementing under dynamically balanced pressure was practiced in wells penetrating pressure sensitive formations, and a set of techniques, including annular pressure control when cementing a well with narrow safe drilling windows and anti-channeling cement slurries. The techniques have first been successfully applied in cementing the φ114.3 mm liner in the well LG70 under managed pressure, ensuring the job quality of cementing a well with small annular clearance, high temperature and coexistence of blowout and lost circulation. These techniques have also been successfully used on many other wells, providing a whole new technology for the prevention of channeling and lost circulation in cementing wells with narrow safe drilling windows.