深部煤层注气强化开采的流-固-热耦合数值模拟研究

Numerical simulation of fluid-solid-thermal coupling for CO_(2) injection enhanced mining in deep coal seams

为研究温度效应对深部煤层注CO_(2)增抽瓦斯的影响规律,根据煤体变形特征和瓦斯渗流特性基本理论,建立了同时考虑非等温吸附、二元气体竞争吸附、气体渗流和扩散、热传递和热对流的注CO_(2)强化煤层抽采的流-固-热耦合模型,探究了温度效应对煤储层参数和产气演化规律的影响。结果表明:煤层温度降低引起的煤基质收缩促进了CH_(4)解吸,忽略温度效应的流-固耦合模型会低估瓦斯产气量;在初始渗透率为3.95×10^(-17) m^(2),CO_(2)注气压力为8 MPa时,对于韩城矿区3#煤层埋深1400 m的深部煤体而言,考虑温度效应(319.5 K)的流-固-热耦合模型相比流-固耦合模型,瓦斯抽采3650 d,煤层平均瓦斯压力下降0.69%,A点渗透率增幅11.02%,产气速率增幅13.51%,累计产气量增幅13.76%。

In order to study the effect of temperature effect on CO_(2) injection and gas extraction in deep coal seams,a fluid-solidthermal coupling model for CO_(2)-injection enhanced coal seam extraction was established based on the basic theory of coal deformation characteristics and gas seepage characteristics,which also considered non-isothermal adsorption,binary gas competitive adsorption,gas seepage and diffusion,heat transfer and heat convection.The influence of temperature effect on coal reservoir parameters and gas production evolution law is investigated.The results show that the shrinkage of coal matrix caused by coal bed temperature decrease promotes CH_(4) desorption,and the fluid-solid coupling model ignoring temperature effect will underestimate gas production.When the initial permeability is 3.95×10^(-17)m^(2) and the CO_(2) injection pressure is 8 MPa,for the deep coal body buried 1400 m in the No.3 coal seam in Hancheng Mining area,compared with the fluid-solid-thermal coupling model considering the temperature effect(319.5 K),the gas extraction time of 3650 days is higher than that of the fluid-solid coupling model.The average gas pressure of coal seam decreased by 0.69%,the permeability of A point increased by 11.02%,the gas production rate increased by 13.51%,and the cumulative gas production increased by 13.76%.