欠平衡钻井条件下地层造斜特性研究

Research on deflecting characteristic of formation while underbalanced drilling

张辉 高德利 段明星 杨建旭

ZHANG Hui GAO Deli DUAN Mingxing YANG Jianxu

中国石油大学石油工程学院，北京　102249

College of Petroleum Engineering, China University of Petroleum, Beijing102249, China

钻井实践中发现，由于对欠平衡钻井条件下的地层造斜特性不够了解，不能有的放矢地采取措施有效控制井斜。因此，欠平衡钻井条件下地层造斜特性的研究，是一项迫切需要开展的工作，对于欠平衡钻井技术的发展具有重要意义。应用有限元方法分析了不同井底压差下倾斜地层近井底岩石应力的分布状态，得出了井底压差和地层倾角对井底应力分布的影响规律；同时分析并确定了井斜趋势的判定依据，进而研究了欠平衡钻井条件对地层造斜作用的影响。结果表明，欠平衡钻井中井底保持负压差，放大了井底上倾和下倾两侧岩石应力的不对称性，增强了地层的造斜作用；地层倾角越大，这种增强作用越显著。

In drilling practice, Because of the lack of understanding of deflecting characteristic of anisotropy formation while underbalanced drilling, a appropriate measure can not be taken accordingly. So research on deflecting characteristic of anisotropy formation while underbalance drilling will play an important role in underbalace drill technology and should be carried out immediately. In this thesis, the stress distribution of bottomhole rock in various pressure difference and formations with various angle of bedding is analyzed by means of finite element method, the influence of pressure difference and formation angle on the stress distribution of bottom hole is founded, the discrimination criteria of inclination trend is established, the effect of underbalance drilling condition on the deflecting characteristic of anisotropy formation is further discussed. The result shows that the negative pressure differences while underbalanced drilling amplify the asymmetry of stress distribution and strengthen the deflecting tendency of formation. This will be more remarkable with the increase of angle of bedding.

文章编号：1000 – 7393（ 2012 ） 02 – 0001 – 03