深部煤层力学参数反演和气体钻井井壁稳定性

发布时间：2018-08-14 12:42

【摘要】：如何确定深部煤层的地质力学参数是气体钻井井壁稳定评价的关键。基于量化的地质强度指标GSI和Hoek-Brown强度准则分析了反演深部煤层地质力学参数的方法,结合DB1井氮气钻井,以弹塑性方法分析了侏罗系炭质泥岩和煤层的井壁稳定性。研究表明,塔里木盆地依奇克里克区块侏罗系煤GSI介于45~55,变形模量约在1 560~2 850 MPa之间。井眼钻开后炭质泥岩和煤层井周存在塑性区,炭质泥岩层井周塑性区约为1.37倍井眼半径,煤层井周塑性区约为2.07~2.59倍井眼半径。塑性区应力松弛造成围压减小,导致节理岩体抵抗工程扰动的能力减弱。以工程允许塑性半径等于1.5倍井眼半径为临界稳定条件,井眼钻开后煤层会出现大面积坍塌失稳,不宜采用气体钻井;工程扰动造成炭质泥岩井眼扩径,扩径后井眼仍能保持稳定。
[Abstract]:How to determine the geomechanical parameters of deep coal seam is the key to evaluate the stability of gas drilling shaft. Based on the quantitative GSI and Hoek-Brown strength criteria, this paper analyzes the method of retrieving the geomechanical parameters of deep coal seam, and analyzes the stability of Jurassic carbonaceous mudstone and coal seam by elastic-plastic method combined with nitrogen drilling in DB1 well. The results show that the GSI of Jurassic coal in Ichikrik block in Tarim Basin is between 450.55 and the deformation modulus is about 1 560,2 850 MPa. After borehole drilling, there is a plastic zone around the carbonaceous mudstone and coal seam. The plastic zone around the carbonaceous mudstone layer is about 1.37 times of the borehole radius, and the plastic zone around the coal seam is about 2.07 ~ 2.59 times the borehole radius. Stress relaxation in plastic zone reduces confining pressure and weakens the ability of jointed rock mass to resist engineering disturbance. If the allowable plastic radius of engineering is equal to 1.5 times the radius of borehole as the critical condition, the coal seam will collapse and lose stability in a large area after borehole drilling, so it is not suitable to use gas drilling, and engineering disturbance causes hole expansion of carbonaceous mudstone. The hole can remain stable after expanding.
【作者单位】：油气藏地质及开发工程国家重点实验室西南石油大学;水力学与山区河流开发保护国家重点实验室四川大学;
【基金】：油气藏地质及开发工程国家重点实验室开放基金(PLN1421) 教育部博士点基金项目(20125121110001) 四川省教育厅科技基金(14ZB0060)
【分类号】：TE21

【相似文献】