中文摘要：

有效防止水平井段孔眼坍塌是煤层气多分支水平井钻井成功率的有利保障之一，而煤体结构和地应力是影响成孔的两大主要因素。基于目前多分支水平井井身结构和煤体孔裂隙系统特征及弹性力学理论，分别建立了Ⅰ、Ⅱ类煤相关切向应力模型。根据该模型，分析了Ⅰ、Ⅱ类煤中垂直地应力与水平地应力不同大小、与主支和侧支钻进方向不同情况下的受力情况。结果表明：Ⅰ类煤中沿水平最小主应力钻进成孔最难，沿水平最大主应力方向成孔最容易；Ⅱ类煤中钻进方向由外生主裂隙与水平最大主应力夹角决定。

英文摘要：

It is one of effective measures to guarantee success rate about multi-lateral horizontal well drilling to prevent hole collapse, coal structure and situ stresses are two main factors to effect hole forming. Based on casing program about multi-lateral horizontal well and pore and fissures characteristics about coal body, elastic mechanics and coal with Ⅰ and Ⅱ structures, the corresponding targential stress models were established. Based on targential stress models, the force conditions in different states such as different sizes among horizontal stress and vertical stress, different drilling directions about main branch and collateral branches in multi-lateral horizontal well were analyzed. The results showed tha it is the easiest to hole-forming to drilling along the direction of the minimum horizontal stress to the coal with I structure, it is the hardest to drilling along the direction of the maximum horizontal stress to the coal with Ⅰ structure; the drilling direction was controlled by the angle between the surface of exogenous fracture and the direction of the maximum horizontal stress to the coal with Ⅱ structure.