煤系地层坍塌压力预测与井眼轨迹优化

由于煤岩割理交错发育，采用常规井眼坍塌压力预测模型不能准确指导钻井作业，甚至有可能引发井壁失稳事故。通过分析煤岩理化性能和微观结构，确定井壁失稳类型以力学失稳为主；结合弹性力学、岩石力学、单一弱面破坏准则等理论，建立了煤岩地层水平井坍塌压力计算模型；以DB-X01井、DB-X04井与红河油田煤层段为例，根据所建模型进行井眼轨迹优化，得出最佳钻进井斜角与方位角；结合DB-X01井J₂kz煤层，分析了割理产状、地应力机制以及井眼轨迹对坍塌压力的影响，为煤系地层水平井井眼轨迹优化研究提供参考。

Collapse pressure prediction and borehole trajectory optimization for coal measure strata

Coal cleats are developed in a stagger manner, so conventional models for predicting borehole collapse pressure cannot accurately guide drilling operations or even may cause borehole wall instability incidents. The physical and chemical properties and microstructure of coal were analyzed and then mechanical instability was determined as the main type of borehole wall instability. A model for calculating the collapse pressure of coal in horizontal wells was established based on the theories of elastic mechanics, rock mechanics and single weakness plane failure criteria. With this model, borehole trajectories in coal intervals of the DB-X01 and DB-X04 wells and the Honghe Oilfield were optimized and the best inclination and azimuth for drilling were obtained. The influences of cleat occurrence, geostress mechanism and borehole trajectory on collapse pressure were analyzed using the J₂kz coal in Well DB-X01 as an example, which provided an idea and reference for the optimization of borehole trajectories of horizontal wells in coal measure strata.