摘要
掌握煤水两相体系中多态水分布及动态运移特征对评价煤层注水效果和煤层气开发利用有重要意义。利用低场核磁共振实验系统,在标定多孔介质中不同状态水分弛豫时间的基础上,对试验煤样进行了浸润实验和核磁共振CPMG序列测试,基于煤体多态水分布结果建立了煤体自由态水弛豫特征与润湿性的定量关系,依托动力学理论研究了煤体吸附态水峰面积随时间变化的规律,揭示了煤储层与水分子间微观作用机制。研究结果表明:吸附态水峰对应的弛豫时间在0.1~10 ms,纯自由态水峰对应的弛豫时间在800~10000 ms,多孔介质中自由态水的弛豫速率会加快,束缚态水峰位于吸附态水和自由态水峰中间;不同煤样的自由态水弛豫特征与其自身润湿性有紧密联系,润湿能力越强的煤样自由态水弛豫速率越快,弛豫时间越短,对应峰的左移能力越强;接触角θ与煤样的自由态水峰闭合所需浸润时间t及对应时刻自由态水峰值对应的弛豫时间T_(2)存在定量关系,符合θ=51lg T_(2)+2.4t^(0.3)-87;煤体吸附态水峰面积可以用来评估煤层注水降尘效果,其随浸润时间的变化规律符合一级动力学模型,煤粉表面仅存在一种吸附位点;煤体中发生的水分子吸附过程由2部分组成:主吸附过程受扩散作用控制,发生在煤体表面极性官能团上;次吸附发生在煤体外层吸附态水分子形成的吸附位点上,该过程形成的水分凝聚是水锁效应的成因。水锁效应能否产生与煤样自身润湿性强弱有较大关系。
It is of great significance to understand the distribution and dynamic transport characteristics of polymorphic water in the coal-water two-phase system for estimating the water injection effect of coal seam,and the development and utilization of coal-bed methane.With the calibration of the moisture in different state relaxation times in porous media,the test coal samples were infiltrated and the CPMG sequence test was conducted with the low-field nuclear magnetic resonance experimental system.Based on the results of coal polymorphic water distribution,the quantitative relationship between the relaxation characteristics of free-state water and the wettability of coal bodies was established.According to the kinetic theory,the tendency of water peak area of the adsorption state of coal with time was studied,and the microscopic mechanism between coal reservoirs and water molecules was revealed.The brief conclusions are described below.The relaxation time corresponding to the water peak in adsorbed form is between 0.1 and 10 ms.The relaxation time of pure free-state water peak is in the range from 800 to 10000 ms,and the relaxation rate of free-form water in porous media will be accelerated.The bound water peak is located in the middle of the adsorbed water and the free-form water peak.The relaxation characteristics of free water peaks of different coal samples are closely related to their own wettability.The faster the relaxation rate of coal-like free-state water with better wetting capacity,the shorter the relaxation time,and the stronger the ability to shift to the left of the corresponding peak.There is a quantitative relationship between the contact angleθand the infiltration time t required for the closure of the free-state water peak of the coal sample and the relaxation time T_(2)corresponding to the apex of free-state water peak at the corresponding time t,which is consistent withθ=51lg T_(2)+2.4 t^(0.3)-87.The adsorbed water peak area of coal can be used to evaluate the effect of water injection and dust reduction in coal seams.The law of the peak area of water in the adsorption state with time conforms to the first-level adsorption kinetic model,indicating that there is only one adsorption site on the surface of pulverized coal.The adsorption process of water molecules in the coal body is composed of two parts.The main adsorption process is controlled by diffusion and occurs on the polar functional groups on the surface of the coal body.The secondary adsorption occurs on the adsorption sites formed by the adsorbed water molecules in the outer layer of the coal,and the water condensation formed in this process is the cause of water lock effect.Whether the water locking effect can be generated is greatly related to the wetting ability of the coal sample itself.
作者
杨明
徐靖
何敏
高建良
张学博
刘佳佳
王淞民
YANG Ming;XU Jing;HE Min;GAO Jianliang;ZHANG Xuebo;LIU Jiajia;WANG Songmin(School of Safety Science and Engineering,Henan Polytechnic University,Jiaozuo 454003,China;State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization,Jiaozuo 454003,China;State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Jiaozuo 454003,China;Yongmei Group Co.,Ltd.,Yongcheng 476600,China;China Pingmei Shenma Group,Pingdingshan 467000,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2023年第2期787-794,共8页
Journal of China Coal Society
基金
国家自然科学基金资助项目(52274186,52074106)
河南省高等学校青年骨干教师培养计划资助项目(2020GGJS053)。
关键词
煤
润湿性
核磁共振
煤层注水
水锁效应
coal
wettability
nuclear magnetic resonance
coal seam water injection
water blocking effect
