不同支护条件下开孔扰动对瓦斯钻孔局部变形的研究

Study on Local Deformation of Gas Drilling Caused by Opening Disturbance under Different Support Conditions

瓦斯钻孔的失稳破坏会严重影响瓦斯抽采效率,钻孔内布设支护管可以有效提高孔壁稳定性以及抽采效率。为获得不同支护条件下开孔扰动对瓦斯钻孔局部变形规律,实现瓦斯抽采钻孔的定点维护,采用相似模拟方法,系统分析不同支护条件下瓦斯钻孔在竖直方向、水平方向和不同钻孔深度条件下的三维变形特征。研究结果表明:在不同支护条件下,应力加载到一定程度时均发生应变骤减现象,刚性支护抵抗变形能力大于柔性支护,应变衰减总体趋势与孔径大小无关;钻孔深度的增加与应变的衰减情况不具有绝对的正相关性;水平构造应力的存在不会影响钻孔内部变形规律,随着水平构造应力程度的加剧,孔壁破坏初始阶段应变敏感性显著降低。

The instability and failure of gas drilling will seriously affect the gas drainage efficiency.The placement of support pipe in the drilling hole can effectively improve the stability of hole wall and drainage efficiency. In order to obtain the local deformation law of gas drilling caused by opening disturbance under different support conditions and realize the fixed-point maintenance of gas drainage drilling,the similarity simulation method is used to systematically analyze the three-dimensional deformation characteristics of gas drilling under different support conditions in vertical direction, horizontal direction and different drilling depth. The results show that under different support conditions, the strain suddenly decreases when the stress is loaded to a certain extent. The resistance to deformation of rigid support is greater than that of flexible support, and the overall trend of strain attenuation is independent of the size of hole diameter;There is no absolute positive correlation between the increase of borehole depth and the attenuation of strain;The existence of horizontal tectonic stress will not affect the internal deformation law of borehole.With the intensification of horizontal tectonic stress, the strain sensitivity of borehole wall in the initial stage of failure decreases significantly.