考虑温度效应的高温高压直井井壁稳定性规律

Wellbore stability law of high temperature and high pressure vertical wells considering temperature effect

吴怡 谢仁军 刘书杰 蒋凯 邓金根 蔚宝华3

中海油研究总院有限责任公司，北京 100028 中国海洋石油国际有限公司，北京 100028 中国石油大学（北京）石油工程学院，北京 102249

CNOOC Research Institute Co., Ltd., Beijing 100028, China CNOOC International Limited, Beijing 100028, China School of Petroleum Engineering, China University of Petroleum, Beijing 102249, China)

海外A区块探井的高温高压井段因频繁发生井漏、卡钻等井下复杂情况，井壁不稳定，导致原井眼报废。根据经典的坍塌压力和破裂压力计算模型，钻井液安全密度窗口为0.2 g/cm3，但实际作业过程中发现在高温高压井段安全密度窗口更窄。由于温度变化产生的温变应力会对井壁稳定性造成影响，因此考虑井壁温度效应，探索了温度变化对高温高压直井井壁稳定性的影响。通过分析井壁附加温变应力场，建立了考虑温度效应的坍塌压力和破裂压力计算模型，发现了温度变化对井壁稳定性的影响规律。低温钻井液在高温地层循环产生的附加温变应力，使地层坍塌压力和破裂压力减小。该方法为该区块后续生产井的顺利实施提供了技术支撑，相比探井，钻井周期大幅缩短。考虑温度效应的地层坍塌压力和破裂压力计算模型，对今后窄安全密度窗口高温高压直井的井壁稳定性研究具有参考价值。

In the high temperature and high pressure section of exploration wells in Block A overseas often occurs complex downhole conditions such as leakage and sticking, resulting in unstable wellbore and abandonment of original wellbore. The safe window is determined to be 0.2 g/cm3 by classical wellbore stability analysis, but it is found that the safe window is narrower in high temperature and high pressure section during actual operation. After consulting the literature, it is found that the temperature?鄄dependent stress produced by temperature change will affect the wellbore stability. Therefore, this paper takes the wellbore temperature effect into account and explores the influence of temperature change on the wellbore stability of high temperature and high pressure wells. Through the analysis of the additional temperature?鄄dependent stress field on the borehole wall, the calculation model of collapse pressure and fracture pressure under the coupling effect of temperature and pressure is established. The influence of temperature change on the stability of the borehole wall is found. The additional temperature?鄄dependent stress generated by the circulation of low temperature drilling fluid in the high temperature formation reduces the formation fracture pressure and the collapse pressure. The conclusion supports the successful implementation of the follow?鄄up production wells in this area, which greatly reduces the working time of exploration wells. The calculation model of formation collapse pressure and fracture pressure under the coupling action of temperature and pressure established in this paper has reference value for the future study of sidewall stability of high temperature and high pressure wells with narrow density windows.

10.6056/dkyqt201902025