塔里木油田库车山前超高压盐水层精细控压钻井技术

Precise Managed Pressure Drilling Technology for Ultra-High Pressure Brine Layer in the Kuqa Piedmont of the Tarim Oilfield

刘伟 周英操 石希天 王瑛 雷万能 李牧

LIU Wei ZHOU Yingcao SHI Xitian WANG Ying LEI Wanneng LI Mu

中国石油集团工程技术研究院有限公司，北京 102206 中国石油天然气股份有限公司塔里木油田分公司，新疆库尔勒 841000

CNPC Engineering Technology R & D Company Limited, Beijing, 102206, China PetroChina Tarim Oilfield Company, Korla, Xinjiang, 841000, China

塔里木油田库车山前巨厚盐膏层普遍发育超高压盐水，且盐膏层中夹杂破裂压力低的泥岩层，导致安全钻井密度窗口窄, 易发生井涌、井漏、井塌和卡钻等井下故障。通过精细描述钻井液循环系统流量变化特征，定量化钻井液出入口流量差与溢流量、漏失量及高密度钻井液弹性变形量间的相互关系，可以实时快速判断溢流和漏失，计算求取地层压力，并将自动控压排水与控压压回相结合，精确控制地层与井底的压力差，有效控制合适的盐水返出量，大幅降低溢流、井漏等井下风险，形成了超高压盐水层微流量精细控压钻井技术。该技术在克深A井和克深B井进行了现场试验，均安全快速钻穿超高压盐水层，大幅提高了机械钻速，缩短了钻井周期，降低了钻井成本。研究与应用表明，超高压盐水层微流量精细控压钻井技术可快速发现溢流和漏失，精确控制地层盐水返出或者钻井液漏入地层，实现可控微溢流或漏失,大幅减少了盐水排放时间，确保了井眼稳定，实现了安全快速钻穿超高压盐水层的目的，为超深井复杂地层高效钻进提供了新的技术手段。

Ultra-high pressure brine development (pressure co-efficient of up to 2.65) is common in the thick salt formation of the Kuqa Piedmont in the Tarim Oilfield, and the salt formation contains a mudstone layer with a low fracture pressure gradient, which leads to a narrow drilling safety density window, prone to downhole problems such as spill, lost circulation, collapse, stuck pipe, etc. By precisely describing the flowrate change characteristics of drilling fluid circulation system, and quantifying the correlation among the inlet/outlet flowrate difference of the drilling fluid, the spill volume, leakage volume and the elastic deformation volume of high-density drilling fluid, it is possible to realize the rapid and real-time identification of spill and leakage and calculate the formation pressure. By combining the automatic pressure-controlled drainage and pressure-controlled bull-heading, it is possible to accurately control the difference between the formation pressure and bottomhole pressure, and effectively control the appropriate amount of brine return. In this way, it is possible to significantly reduce the downhole risks of both spill and leakage, forming the managed pressure drilling technology by a fine controllable micro-flowrate in an ultra-high pressure brine layer. The technology has been tested in Well Keshen A and B, and drilled through the ultra-high pressure brine layers safely and quickly, which greatly increases the ROP, shortens the drilling cycle and saves the drilling cost. Research and application showed that the managed pressure drilling technology by fine micro-flowrate control in ultra-high pressure brine layer could quickly detect spill and leakage, accurately control formation brine return or lost circulation of drilling fluid, and achieve a controllable micro-spill or leakage, which can reduce the brine discharge time greatly, ensure the borehole stability, and achieve the purpose of drilling through ultra-high pressure brine layer safely and quickly. The technology has provided a technical means for the efficient drilling of ultra deep wells in complex formations.

国家科技重大专项课题“深井超深井井筒安全钻井技术与装备”（编号：2016ZX05020-003）资助

https://doi.org/10.11911/syztjs.2020034