中文摘要：

井壁稳定是实现页岩气水平井低成本、安全、高效钻井的核心技术之一,科学的井壁稳定性评价理论及方法是保障井壁稳定的前提与基础。页岩储层力学性能取决于结构面的发育程度、几何形态、组合特征及其力学性质等因素;受结构面产状及其力学参数获取困难的制约,目前普遍采用的弱面理论与莫尔–库仑准则相结合的井壁稳定性评价方法,仅局限于理论研究,尚未得到有效工程应用。鉴于此,开展了基于霍克–布朗强度理论的页岩地层井壁稳定性评价研究。通过构建含有不同裂隙的数值模型,进行不同围压下的三轴压缩数值仿真模拟,分析了参数mb、S与岩体结构的关系,建立了基于结构面发育指数J的mb、S量化方法。分析表明：基于该理论所得地层坍塌压力与实钻井垮塌失稳导致的井眼不规则具有较好的一致性,评价结果可靠,为页岩气井的井壁稳定性科学评价提供了新方法。

英文摘要：

The wellbore stability is one of the key technologies in order to achieve rule horizontal well bore in shale with low cost.Due to the occurrence and the difficulty in obtaining mechanical parameters of the underground structural planes,the evaluation method of borehole stability by weak surface theory and Mohr-Coulomb criterion has not yet been applied in engineering,and was only studied in theory. In this paper,wellbore stability has been evaluated by using Hoek- Brown criterion. The core numerical model with different fractures has been created,and the triaxial compression test with different confine pressures has been carried out by means of the numerical simulation. Relationship between the parameters mb,S and rock mass structure has been analyzed using the result of the numerical simulation. And the method to determine the parameters mb,S has been established with fracture development index. The analysis of engineering example shows that collapse pressure obtained with the theory are consistent with the actual drilling performance in shale formation and a new method for evaluating borehole stability of shale gas wells has been provided.