页岩气水平钻井延伸极限预测与参数优化

大位移水平井是页岩气开采的主要方式,其极限延伸的合理预测备受关注.针对涪陵地区的页岩气水平钻完井进行研究,借助钻井延伸极限预测模型,计算了不同工况下的钻井延伸极限,分析了钻机性能、钻具组合、井眼曲折度、钻井液密度等因素对钻井延伸极限的影响.结果表明,滑动钻进模式是约束水平段延伸的主要工况,当摩阻系数比较高时,螺旋屈曲锁死导致无法钻达设计井深;高井眼曲折度限制了井眼延伸长度,钻进作业中要尽量减少轨迹调整次数,保证轨迹平滑;此外,邻井压裂作业可能导致正钻地层压力上升,会降低钻井延伸极限,需要对钻井液密度进行优化.该研究对页岩气水平钻井的设计及施工具有重要指导意义.

Prediction of extension limit and parameter optimization of shale gas horizontal drilling

Extended reach horizontal well is the main way of shale gas exploitation, and the reasonable prediction of its limit extension has attracted much attention. In this paper, the horizontal drilling and completion of shale gas in Fuling area is studied. With the help of the prediction model of drilling extension limit, the drilling extension limit under different working conditions is calculated, and the influence of drilling rig performance, drilling tool assembly, hole tortuosity and drilling fluid density on drilling extension limit is analyzed. The results show that sliding drilling mode is the main working condition to restrict the extension of horizontal section, and when the friction coefficient is high, the helical buckling locks up, which leads to the failure to drill to the design well depth; High hole tortuosity limits the extension length of the hole, so the times of trajectory adjustment should be reduced as much as possible in drilling operation to ensure smooth trajectory; In addition, fracturing operations in adjacent wells may lead to an increase in formation pressure while drilling, which will reduce the drilling extension limit, and it is necessary to optimize the drilling fluid density. This study has important guiding significance for the design and construction of shale gas horizontal drilling.