油包水钻井液研究与应用

The Research and Application of Water-in-oil Drilling Fluid

与水基钻井液相比,由于油基钻井液具有抗高温、抗盐钙侵、有利于井壁稳定、润滑性好和保护油气层等优点,成为钻遇深井、大斜度定向井、水平井和各种复杂地层的首选体系。油包水钻井液具有油基钻井液的优点。针对非常规油气藏及强水敏、易坍塌地层钻井的需要,研制了油包水钻井液,优化了钻井液配方:基液(油水体积比为8∶2)+3%主乳化剂+3%辅乳化剂+3%有机土+4%降滤失剂+3%的CaO+重晶石。室内评价结果表明,该油包水钻井液具有良好的流变性、悬浮稳定性、润滑性、乳液稳定性和抗污染能力。同时,完善了现场施工工艺,并在中原、新疆、西南等现场应用了7口井。应用证明,油包水钻井液稳定性好,破乳电压大于600V,抗污染、抗温能力强,遭受20%的水和岩屑污染后,钻井液性能稳定,易于维护处理;且钻井过程中井壁稳定,定向施工顺利,减少井下复杂,平均井径扩大率小于5%。该钻井液配制工艺简单,可以回收利用,满足页岩气水平井、易塌地层钻进的需要。

Compared with water base drilling fluid, oil base drilling fluid has the advantages of high temperature resistant,salt and calcium erosion resistance,being good for stable sidewall,good oiliness,giving protection for reservoirs and so on,which has become the preferred system for drilling in deep well,high angle deviated hole,horizontal well and every complex formations.Water-in-oil drilling fluid has many advantages of the oil base reservoirs and as base fluid drilling fluid.It has been developed for the need of the drilling in nonconventional oil and gas formations with strong water sensitivity and being easy to cave.Its formula has been optimized （8：2 of oil/water volumetric proportion） ＋3% primary emulsion＋3% assistant emulsion＋3% organ- ic clay＋4% fluid loss control agent＋3% CaO＋baroselenite.Laboratory in-oil drilling fluid has good rheological property,suspension stability, evaluation results show that this water- oiliness,emulsion stability and antipollution capability.Field operation has been perfected,and the formula has been applied in seven wells in Zhongyuan,Xinjiang,and Southwestern China.The application strong pollution resistance and heat resistance capacity and proves that the water-in-oil drilling fluid has good stability with demulsification voltage higher than 600V.The drilling fluid can keep stable performance after 20% water pollution and rock power pollution and be easy for maintenance.It can ensure directional drilling smoothly and keep wellbore stable and reduce complicated downhole problems with the rate of hole enlargement less than 5%.The drilling fluid has simple preparation technology and the characteristic of recovery the shale-gas horizontal well and and utilization,which can meet the requirements of drilling of stratum easy to cave.