动态控压固井工艺关键技术与应用

Key technology and application of dynamic managed pressure cementing

随着四川盆地常规气勘探开发目标向盆地深层、超深层发展,复杂深井、超深井受套管层序的限制,同一裸眼井段通常钻遇多个压力系统,纵向地层呈现窄安全密度窗口特征。尽管采用控压钻井(MPD,Managed Pressure Drilling)技术保证了安全有效钻进,但给后续小间隙平衡压力固井带来了巨大的挑战。初期的平衡压力固井工艺技术主要针对浆柱结构调整、注替参数优化等方面开展研究,但仍存在一些技术难题,2015—2020年在川庆钻探公司的固井作业中,常规固井技术作业井次漏失率23.8%,压力失衡导致12井次的异常套压事件,安全作业密度窗口小于等于0.10 g/cm^(3)的井况下几乎无法实施常规平衡压力固井作业。为此,针对上述瓶颈问题开展技术攻关,形成了动态控压固井工艺,研究结果表明:①以井筒安全作业密度窗口值为基础,所建立的下套管分段激动压力控制方法与“微吐—微漏”环空动态近平衡压力控制技术,小间隙尾管激动压力值降低50%,近平衡固井作业窗口阈值可达0.05 g/cm^(3),实现窄密度窗口条件下固井不同作业阶段的压力精细控制。②所开发的全参数在线监控系统和高精度伺服电驱动模式的固井专用节流控制装备,实现0.05 g/cm^(3)阈值窗口条件下固井环空压力始终处于有序可控的状态。③动态控压固井工艺关键技术在川渝地区及塔里木油气田推广应用92井次,固井成功率100%,质量平均合格率较常规固井工艺提升近20个百分点,基本解决了困扰四川盆地、塔里木山前构造等高压气区多年的窄密度窗口固井难题,为类似的复杂区块窄密度窗口井况下实施近平衡压力固井提供了技术借鉴。

The target of conventional gas exploration in the Sichuan Basin is shifting to deep and ultra-deep layers.Meanwhile,due to the limitation of casing sequence,multiple pressure systems are usually encountered in the same open-hole section in complex deep and ultra-deep wells,presenting the characteristics of narrow safe density window in the longitudinal direction.Although the Managed Pressure Drilling(MPD)technology ensures safe and effective drilling,it brings great challenges to the subsequent small-clearance balanced pressure cementing.The initial balanced pressure cementing technology mainly focuses on the adjustment of slurry column structure,and the optimization of injection and replacement parameters,but there are still some technical problems.In the cementing operations of CNPC Chuanqing Drilling Engineering Company Limited(CCDC)from 2015 to 2020,the lost-circulation rate of well times was 23.8%by conventional cementing technology.The pressure imbalance resulted in abnormal casing pressure events of 12 well times.The conventional balanced pressure cementing was almost impossible under the well condition of safe density window below or equal to 0.10 g/cm^(3).To address these problems,technical researches were conducted to form a dynamic managed pressure cementing process.Based on the value of safe density window,the casing-running segmented surge-pressure control method and the"micro-spitting to micro-leakage"dynamic near-equilibrium managed pressure technology were established.As the result,the surge pressure of small-clearance liner was reduced by 50%,and the window threshold value of near-equilibrium cementing was up to 0.05 g/cm^(3),achieving precise pressure control in different stages of cementing operations under the condition of narrow density win-dow.With the full-parameter online monitoring system and the cementing-specific throttling device of high-precision servo electrical driving mode,the cementing annulus pressure was always in an orderly and controllable state under the condition of window thresh-old value of 0.05 g/cm^(3).The key technology of dynamic managed pressure cementing has been applied to 92 well times in the Sich-uan-Chongqing region and the Tarim oil and gas field,with a success rate of 100%,and the average qualification rate nearly 20%high-er than that of conventional cementing,basically solving the problem of narrow density window cementing bothering the high-pressure gas areas in Sichuan Basin and Tarim piedmont structure for many years.The technology provides a reference for near-equilibrium pressure cementing in similar complex blocks.