气体钻井岩石应力应变场对井斜的影响分析

The Influences of Stress Field and Strain Field of Rocks on Hole Deviation in Gas Drilling.

井斜问题是气体钻井技术应用过程中的主要技术瓶颈,因为井底负压差条件使地层岩石的视强度显著降低,一方面有利于地层岩石破碎与提高机械钻速,另一方面也容易在较短的时间内形成较大的井斜角。目前对气体钻井过程中的岩石力学特性研究甚少。以传统的井周应力模型为基础,考虑地层孔隙压力和原始地应力的作用,利用Ansys软件分析了气体钻井井周与井底岩石应力应变场分布。分析结果认为,气体钻井井底岩石应力分布的差异是造成井斜的主要原因,井眼轨迹有向最大水平主应力方向漂移的趋势。

Hole deviation is the main technical bottleneck in gas drilling because the negative pressures at the bottom of the hole reduces the apparent strengths of the rocks penetrated,thus in being beneficial to the increase of ROP,on the other hand,a high well angle is easy to be generated in a short time.Using the Ansys software,the stress field and strain field of rocks around the bore hole and at the bottom of the hole was analyzed based on the conventional stress model,taking into account the pore pressure and original rock stresses.The analyses showed that the difference in stress distribution of rocks at the bottom hole was the main cause of hole deviation,and the hole path tended to drift toward the maximum horizontal principal stress.