温度和化学耦合作用对泥页岩地层井壁稳定性的影响

Influence of temperature and chemical on wellbore stability in clay shale formation

 丁乙 梁利喜 刘向君 许丽

 （西南石油大学“油气藏地质及开发工程”国家重点实验室，四川 成都 610500）

 clay shale; temperature difference; chemical seepage; instability area; wellbore stability

 钻井工程中，泥页岩地层井壁失稳问题严重。由于泥页岩地层的强水化膨胀性，目前大部分研究都集中于此，从而弱化了其他因素对井壁稳定性的影响。基于热孔隙弹性理论，考虑泥页岩的半透膜效应，对钻井过程中泥页岩地层温度和化学渗流作用对井周应力和坍塌压力的影响程度进行了分析。结果表明：钻井液与地层的温差和化学渗流均会产生相应附加应力，该附加应力会造成地层坍塌压力上升。同时由于温差和化学渗流的附加应力存在，井周应力分布发生变化。井周应力的重新分布使井周失稳区域改变，近井地带岩石稳定性较差，造成扩径率增大。因此，对于泥页岩地层井壁稳定性分析，在着眼于泥页岩水化特性的同时，温度和化学渗流作用不能忽视。

 In drilling operation, wellbore instability is a serious problem. Due to its strong hydration capacity, at present, most of research pay attention to inhibiting hydration to solve instability problem. However, this phenomenon makes people ignore the influence of other factors. Based on thermal porous elasticity theory and semipermeable membrane of clay shale, the influence of temperature and chemical seepage on state stress around borehole and collapsing is analyzed. The results indicate that temperature difference between drilling fluid and formation and chemical seepage can make extra stress around wellbore, which cause collapsing pressure increase. Meanwhile, this extra stress makes stress distribution change. And this redistribution leads to change instability area around borehole. The stability of rock close to borehole is decreased, which makes the ratio of expanding diameter large. Therefore, except for strong hydration, the analysis of wellbore instability in clay shale cannot ignore the influence of temperature and chemical seepage.

10.6056/dkyqt201605027