废弃石油井周围煤层中油层气扩散-渗流规律

(1.西安科技大学 能源学院,陕西 西安 710054; 2.西安科技大学 西部矿井开采及灾害防治教育部重点实验室,陕西 西安 710054; 3.神华宁夏煤业集团 双马煤矿,宁夏 银川 750011)

废弃石油井; 油层气; 扩散-渗流; 数值模拟; 影响半径

Diffusion-seepage law of oil-bed gas in coal seam around abandoned oil well
SUO Yong-lu1,2,LIU Ying-kai1,XIAO Jiang1,2,ZHANG Gang1,3,LI Fan1,QU Hui-sheng1

(1.College of Energy Science and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China; 2.Key Laboratory of Western Mine Exploitation and Hazard Prevention,Ministry of Education,Xi'an University of Science and Technology,Xi'an 710054,China; 3.Shuangma Coal Mine,Shenning Group,Yinchuan 750011,China)

abandoned oil well; oil-bed gas; diffusion-seepage; numerical simulation; influence radius

备注

为揭示煤矿废弃石油井周围煤层内油层气流动的压力与影响半径的变化规律,基于煤体孔隙裂隙二重介质假设,考虑孔隙率与渗透率动态变化,结合煤体变形特征,建立了油层气流动的扩散-渗流耦合模型,针对油层气组分的特殊性,运用COMSOL Multiphysics软件进行模拟计算。结果 表明:流动过程中,煤层各处油层气压力的增加速度都先加快后减慢直至趋于稳定,距离废弃石油井越近,油层气压力短时间内变化越快,压力也越大; 随着时间的推移,油层气影响半径逐渐增加,最后趋于稳定,井内压力恒定时,影响半径增加速度一直衰减,井内压力线性增加时,影响半径增加速度先增后减; 第30年时,当井内压力线性增加至15 MPa时,影响半径为310 m.模拟结果与现场实测结果基本吻合,说明该耦合模型合理,该研究为受废弃石油井威胁的煤层的安全高效开采提供理论指导。

In order to reveal the changing laws of the pressure and influence radius of the oil-bed gas flowing in the coal seam around the abandoned oil wells in coal mines,based on the hypothesis of dual-porous media,the diffusion-seepage coupling model of oil-bed gas flow was established withthe dynamic changes of porosity and permeability as well as the deformation characteristics of coal in mind.The coupling model with the specificity of oil-bed gas composition was simulated by COMSOL Multiphysics software.The results shows that:during the flow,the increase rate of the oil-bed gas pressure in the coal seam accelerates first,then slows down until it stabilizes.The closer to the abandoned oil well,the faster the pressure changes in a short time and the greater the pressure is.As time went on,the influence radius gradually increases,and finally stabilizes.The increase speed of influence radius has attenuated when the pressure in the well is constant while it increases first and then decreases when the pressure in the well increases linearly.At 30 years,when the pressure in the well increases linearly to 15 MPa,the influence radius will be 310 m.The simulation results are roughly consistent with the reality.So this coupling model is proved to be right.This study provides a theoretical guidance for safe and efficient mining in the coal seam threatened by abandoned oil wells.