国内页岩气长水平井JY2-5HF井钻井液技术

JY2-5HF井是中石化在重庆涪陵页岩气田部署的一口开发评价井，完钻井深5965 m，水平段长3065 m。该井二开中下部钻遇地层主要为泥页岩井段，存在井壁垮塌、卡钻、漏失等潜在风险，使用多元协同防塌水基钻井液（BT-200钻井液）钻井，主要处理剂有抑制剂BT-200、K-HPAN、KCl、井壁稳定剂、乳化沥青、非渗透处理剂、聚合醇、多功能固体润滑剂和QS-2。水平段要求钻井液除了具有较强的化学及物理防塌能力，还须具有良好的润滑及悬浮性能，采用了油水比为90:10的油基钻井液，水相为26% CaCl₂水溶液，破乳电压控制在900 V以上。现场实践表明，该套钻井液较好地满足了井下和钻井工程的需要；页岩气井长水平段钻进较适宜采用旋转导向和油基钻井液；压裂后测出的地层压力系数普遍比钻进时高0.1~0.2，建议设计钻井液密度时减去。 

Drilling Fluid Technology for Long Horizontal Shale Gas Well JY2-5HF in China

Well JY2-5HF, completed at depth of 5,965 m, is an appraisal well drilled in Fuling shale gas feld, Chongqing, by Sinopec. The length of the horizontal section of this well is 3,065 m. The second interval of this well penetrated shale formations in its middle and lower sections and is at risk of borehole wall sloughing, pipe sticking and mud losses. An anti-sloughing drilling fluid, BH-200, formulated with synergetic additives, such as shale inhibitor BT-200, K-HPAN, KCl, a wellbore stabilizer, an emulsifed asphalt, a non-penetration additive, polyglycol, a multi-function solid lubricants and QS-2, was used to drill the well. The horizontal section of the well required that the drilling fluid should have good physical and chemical wellbore stabilizing capacity, good lubricity and good suspending capacity. An oil base mud, with O/W of 90:10 (26% CaCl2 solution) and electric stability of at least 900 V, was used to drill the horizontal section. Field operations showed that the drilling fluids used well satisfed the needs of downhole and drilling engineering. Rotary steering and oil base drilling fluid are suitable for long horizontal drilling in shale gas wells. Formation pressure coeffcient measured after fracturing was generally higher than the pressure coeffcient during drilling by 0.1-0.2, and it is thus advised that this value be deducted when designing the density of a drilling fluid.