泥浆帽控压钻井裂缝漏失规律

Study on lost circulation methods in mud cap managed pressure drilling

泥浆帽控压钻井是针对严重漏失地层的一种前沿钻井工艺,漏失压力的确定是泥浆帽钻井参数设计的关键。由于裂缝边界条件的复杂性,漏失压力预测目前还没有可靠的方法。通过对不同形式组合缝以及弯曲缝的数值模拟,分析漏失压差和裂缝参数对漏失量的影响规律。研究表明:不同形式裂缝可通过等效裂缝开度进行描述,漏失量与裂缝开度之间基本满足立方定律,但随着串联缝漏失速度的增大和弯曲缝弯曲度的增加误差增大,因此在一定范围内可根据立方定律对漏失压力进行预测。为泥浆帽钻井漏失压力的预测和参数设计提供了理论依据。

Mud cap managed pressure drilling is an advanced technique that used on severe lost circulation formations, the key parameter in mud cap drilling design is the determination of lost circulation pressure. Because of the complexity of the fracture boundary condition, there is still no reliable method to predict lost circulation pressure so far. The influence rules of lost circulation pressure difference and fracture parameters to loss rate is analyzed through the numerical simulation of different types of multiple fractures and curved fractures. The research shows that different types of fractures can be described by equivalent fracture aperture, the relationship between loss rate and fracture aperture would follow Cubic Law, but the inaccuracy increases as the loss rate of the series fractures increasing and the curvature degree of curved fractures increasing. So the lost circulation pressure can be predicted by Cubic Law and this provides theoretical criterion for the prediction of lost circulation pressure and other parameters in mud cap drilling.