长宁页岩气井钻井复杂情况及钻井液工艺技术

阐述了长宁页岩气区块嘉陵江组至韩家店组钻井过程中时常出现的复杂情况:在大段泥岩段钻井钻头被泥包；部分地层层理发育，易发生力学坍塌，上部裸眼井段垮塌，出现卡钻；裂缝发育较好，地层连通性强，易发生井下漏失；在蠕变地层钻井易造成井径扩大；泥岩污染，同时提出了钻井液维护处理存在的难题以及解决措施。根据在嘉陵江至韩家店组钻井遇到的复杂情况进行分析和实践应用，对水基钻井液配方进行优化，在长宁区块应用十余井次，大大减少了复杂情况出现的概率，顺利钻穿嘉陵江石膏层，克服了飞仙关泥岩段，避免了长兴-龙潭区域性垮塌，杜绝了因钻井液维护处理不当导致的井下复杂情况。长宁区块不同地理位置井场的地层变化较大，加深对长宁区块地层的认识，尽可能在钻井设计时更有针对性地提出建议与措施，减小复杂情况出现的频率，为页岩气优质、高效、低成本的钻井提供一定技术参考。 

Drilling Challenges and Drilling Fluid Technologies for Shale Gas Drilling in Changning Area

Challenges encountered in shale gas drilling in Changning area from the Jialingjiang Formation to Hanjiadian Formation are as follows:bit balling in drilling long section of mudstones, mechanical collapse of formation with developed beddings, borehole wall collapse in drilling the top section of well causing pipe sticking, developed fractures with good connectivity resulting in mud losses, borehole enlargement resulted from formation creep, and contamination to drilling fluid by mudstones. Challenges encountered in drilling fluid maintenance and the solution were also provided in this paper. Based on the analyses of drilling problems encountered from Jialingjiang Formation and Hanjiadian Formation, the drilling fluid formulation to be used was optimized accordingly. The optimized drilling fluid was used in 10 times in different wells in Changning area, greatly reduced the occurrence of downhole problems. With the optimized drilling fluid, the Jialingjiang gypsum formation was penetrated with no troubles, the Feixianguan mudstone formation was drilled with success, and cave-in of the Changxing-Longtan formations was avoided. Any downhole complicationsrelated with drilling fluid were all avoided. Lithology variance in the Changning area is remarkable. An in-depth understanding of the formations in this area, and specific suggestions and measures presented in drilling fluids design help minimize the occurrence of downhole complications, providing technical support to quality, efficient and cost-effective drilling of shale gas.