影响元坝气田超深井钻井提速的工程地质因素及技术对策

元坝气田工程地质特征异常复杂,钻井难度大,存在井漏、井涌、卡钻、井塌、高含硫化氢、高压水层等工程地质复杂问题,钻井效率低,周期长,建井成本高.从油气藏的基本地质特征、岩石力学性质、井壁稳定性等方面,分析认为,储层埋藏超深,钻遇地层岩性复杂、储层特征多样、油气立体成藏、油气水分布复杂、各油气藏特征差异大,岩石致密、强度大、可钻性差,异常高压-超高压、纵向多压力系统、井壁力学稳定性差、安全钻井液密度窗口窄,是钻井提速的工程地质影响因素.结合工程地质特征,提出了优化井身结构设计,优选空气钻井、泡沫钻井、液体欠平衡钻井、“螺杆+PDC钻头”和“涡轮+孕镶金刚石钻头”复合钻井、旋转导向钻井等钻井技术,以及优选高效钻头,优选钻井液体系等钻井提速技术对策,能够满足元坝气田海相超深井安全、快速钻井的需要.

Engineering Geological Factors of Influencing Drilling Speed Acceleration and Drilling Technical Countermeasures of Yuanba Gas Field

Drilling engineering is difficult in Yuanba gas field for the problems of well leakage,well kick,the card drilling,wall collapse,high hydrogen sulfide-bearing,high-pressure water layers and so on.Drilling efficiency is low with long drilling cycle and well construction cost is high because of abnormal complex engineering geological characteristics.After basic geological characteristics of oil reservoirs,rock mechanics properties and borehole stability are analyzed,it shows that the engineering geological factors of influencing drilling speed acceleration include ultra-deep buried depth of the reservoir,complex lithology of drilled formations,various reservoir characteristics,reservoirs stereo accumulation,complicated oil and water distribution,dense and hard and poor drillability of the rocks,abnormal high pressure and ultrahigh pressure,multi-pressure systems in the longitudinal,poor mechanical stability of sidewall and narrow safe drilling fluid density window.Combined with the engineering geological characteristics of the gas field,drilling countermeasures are proposed including optimizing hole structure design,optimizing air drilling,foam drilling,liquid underbalanced drilling,composite drilling of screw & PDC bit and turbine & impregnated diamond drill bit,rotary steering drilling,optimizing efficient bit,optimizing drilling fluid and other drilling techniques.It will achieve safe-fast drilling in marine ultra-deep wells of Yuanba gas field.