井壁失稳区域确定方法及影响因素分析简

井壁失稳区域及其面积能够反映井壁失稳破坏特性及其严重程度，以井壁安全系数作为识别准则，建立了井壁失稳区域识别方法，并基于Monte-Carlo 方法，给出了井壁失稳面积的计算方法. 以井壁坍塌为例，分析了钻井液密度、井斜角及方位角对井壁失稳区域特性的影响，以本文建立的失稳区面积计算方法，分析了不同地应力场中井眼轨迹对井壁失稳区大小的影响，评价结果符合工程实际，表明能够利用本文方法评价井壁失稳特性及其严重程度.

DETERMINATION OF WELLBORE INSTABILITY AREA AND ANALYSIS OF INFLUENCING FACTORS

The wellbore safety factor is used as a criterion to determine the wellbore instability area, and with the Monte-Carlo simulation, the instability area is calculated. To consider the wellbore collapse risk, the influence of the mud density, the deviation and the azimuth on the wellbore instability area is analyzed, and the effect of the well trajectory parameters on the wellbore instability in different in-situ stress fields is evaluated by the method of calculating the instability area proposed in this paper. The evaluation results agree with the actual engineering practice, which shows that this method could be used to evaluate the characteristics and the severity of the borehole instability.