井壁稳定性分析在靖边气田水平井钻井设计中的应用

The Wellbore Stability Application of Horizontal Well Drilling Design in Jingbian Gas Field

井壁稳定性问题(即井壁坍塌破裂)会引起系列严重的井下卡钻井漏等事故。靖边气田在钻井过程中,钻遇的地层当中存在多煤层,井壁稳定性问题十分突出,在该地区水平井钻井设计当中进行井壁稳定性分析有着重要的意义。分析了井壁围岩应力分布规律并建立地层坍塌(破裂)压力计算模式,根据库仑-摩尔强度准则和最大拉应力破裂准则,计算井壁坍塌(破裂)压力与钻井液安全密度窗口。通过实验研究分析煤层坍塌压力和破裂压力随井斜角、方位角变化规律,提出合理的方位角优选方案,指导水平井钻井方案设计。

The borehole stability problems （collapse and rupture of the borehole） cause a series of serious under- ground drilling accidents such as sticking and leaking. The borehole stability problem is very prominent as drilling strata existing multiple sets of coal seam in Jingbei gas field, so there is important significance of the wellbore stabil- ity analysis in horizontal well drilling design in the area. The paper analyzes the stress distribution of wall rock and establishes the Rocks collapse （fracture） pressure calculation model. The well collapse （fracture） pressure of ex- tended reach well and the security density window of drilling fluid wasestimated are based on the Coulomh - More strength criteria and the maximum tension stress fracture criteria. Through experimental study of coal collapse pres- sure and fracture pressure with the deviation angle, azimuth variation, the plan optimizes azimuth angle and guides the program design of horizontal well drilling.