南海超大水垂比大位移M井钻井关键技术

为开发南海东部某油田边际油藏，设计了一口水垂比高达4.90的大位移井M井，钻井过程中面临储层埋深浅、稳斜裸眼井段长、安全密度窗口窄、井眼清洁困难和套管下入摩阻大等技术难点。通过研究与应用井眼轨迹控制、井身结构优化、井筒当量循环密度ECD控制工艺和安全高效下套管工艺等技术，顺利完成了该井的钻井作业。应用结果表明，五开井身结构显著提高了井壁稳定性；使用连续循环阀系统及岩屑床破坏器，井底ECD变化率降低至小于1.9%；应用漂浮下套管及全掏空旋转下尾管工艺，顺利下入?244.5 mm套管×4 200.00 m及?177.8 mm尾管×5 772.00 m。超大水垂比大位移井钻井关键技术在M井应用后，创下了中海石油海上油田最大水垂比大位移井钻井作业纪录，为后续类似大位移井的开发积累了经验。 

Key Drilling Technologies in Extended-Reach Well M with Ultra-High HD/VD Ratio in the South China Sea

In order to develop marginal oil reservoirs in an oil field in the eastern South China Sea, an extended reach Well M with a HD/VD (horizontal displacement to vertical depth) ratio of up to 4.90 was designed. During the drilling process, technical problems were encountered, such as shallow reservoir buried depth, long tangent open-hole section, narrow safe density window, difficult borehole cleaning, and strong casing-running friction resistance, etc. The drilling operation was completed owing to research and application of technologies including borehole trajectory control and casing program optimization, ECD (equivalent circulating density) control of drilling fluids in the wellbore, and safe and efficient casing-running technology. The application results showed that the borehole wall stability was greatly enhanced by the five-section casing program. The ECD change rate of the bottomhole was reduced to less than 1.9% by the continuous circulating valve system and cuttings bed destroyers. The ?244.5 mm casing was run to the designed depth of 4 200.00 m via the floating casing-running technology, and the ?177.8 mm liner was run to the depth of 5 772.00 m by the hollowed-out rotating liner-running technology. The application of the key drilling technologies of extended-reach wells with ultra-high HD/VD ratio in Well M sets a new record for China National Offshore Oil Corporation in the drilling of such wells, and provides valuable experience for the subsequent development of similar extended-reach wells.