页岩气田压裂区加密调整井绕障轨道优化设计方法

在页岩气丛式水平井设计中，针对压裂区的加密调整井井眼轨道设计需要考虑绕开已钻井压裂段影响域及压裂段影响域之间互相干扰等问题。为了快速评估加密调整井压裂段井眼轨道设计方案的合理性，运用矢量代数方法对页岩气压裂区障碍物进行了几何建模，该几何模型考虑了压裂裂缝影响域；然后根据所建立的障碍物几何模型，建立了以设计轨道总长度最短、轨道势能最小为优化目标，以轨道间防碰为约束条件的页岩气压裂区绕障轨道优化设计模型，并给出了判断页岩气压裂段影响域之间是否存在干扰的几何校核方法；最后依据四川盆地涪陵页岩气田现场实钻数据，对所建立的设计模型进行了验证。研究结果表明：①在压裂区，忽略压裂影响域的障碍物尺寸会被严重低估；②忽略压裂影响域，所设计出的绕障轨道可以避开老井的井眼轨迹，但是有可能会与已钻井的压裂影响域相交，进而引发钻井事故。结论认为，所建立的页岩气压裂区绕障轨道优化设计模型能够满足防碰绕障约束的要求，相应的设计计算避免了繁琐的试算和校核，并且能够实现井眼轨道设计总长度和轨道势能达到最小值的优化目标。

Optimization design method for the bypass trajectories of infill adjustment wells in the fracturing areas of shale gas fields

In the design of a shale-gas cluster horizontal well, it is necessary to consider the bypass of the fracturing influence domains of existing wells and the interference between fracturing influence domains when the wellbore trajectories of infill adjustment wells in the fracturing areas are designed. In order to quickly evaluate the rationality of the design scheme of fracturing wellbore trajectory in an infill adjustment well, this paper adopted the vector algebra method to build a geometric model of the obstacles in the shale gas fracturing area. In this geometric model, the influence domains of hydraulic fractures are taken into account. Then, based on this geometric model, the optimization design model of bypass trajectory in the shale gas fracturing area was established by taking the minimization of total trajectory length and trajectory potential energy as the optimization objective and the anti-collision between trajectories as the constraint. Besides, the geometric check method to judge if there is any interference between fracturing influence domains was provided. Finally, the established optimization design model was verified based on the actual drilling data of Fuling Shale Gas Field in the Sichuan Basin. And the following research results were obtained. First, the obstacle sizes in fracturing areas will be seriously underestimated if the fracturing influence domains are neglected. Second, if the fracturing influence domains are neglected, the designed bypass trajectory can bypass the wellbore trajectories of old wells, but may intersect the fracturing influence domains of existing wells, thus inducing drilling accidents. In conclusion, the proposed optimization design model of bypass trajectory in the shale gas fracturing area can satisfy the constraint of anti-collision and bypass and achieve the optimization objective of minimizing total trajectory length and trajectory potential energy, and the corresponding design calculation avoids complex calculation and check.