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耦合理论模型与数值模拟方法,详细分析了煤储层孔隙结构分形特征对煤层气运移的控制作用.首先,采用Menger海绵体构造思想模拟了三维煤岩介质的非线性孔隙结构;随后,借助多孔介质渗透率的串联,并联模式预测模型,推导出分形多孔介质渗透率同孔径分布特征之间的关系,并采用格子波尔兹曼方法验证了其有效性.基于耦合方法,系统分析了分形多孔介质孔隙度,孔隙结构分形维数Db,孔径范围[rmin,rmax]等参数对其渗透率的影响,结果表明:①最大孔径rmax形成的通道主宰,呈近2次方关系;②最大孔径同最小孔径比越大,渗透率越高;③Db与之间呈负幂乘关系,并表现出分段特征,拐点为Db=2.5附近.综合以上分析结果,推演出分形多孔介质渗透率预测模型为max n Cfr,其中C为常量,n为接近2的常量,f是同孔隙结构信息相关的表达式.最后,本文还讨论了Db=2时,本文预测模型与Kozeny和Carman模型=Crn的等效性.
Coupling theoretical model and numerical simulation method, the fractal characteristics of coal reservoir pore structure on the control of coalbed methane transport are analyzed in detail.Firstly, the nonlinear pore structure of three-dimensional coal and rock media is modeled by Menger’s sponge structure theory. The relationship between the permeability of fractal porous media and the pore size distribution is deduced, and the validity of the method is verified by the lattice Boltzmann method.Based on the coupling method, the fractal features of fractal The porosity of porous media, the fractal dimension of pore structure Db, the pore size range [rmin, rmax] and other parameters on the permeability. The results show that: ① the channel formed by the maximum pore size rmax is dominated by nearly quadratic relationship; ② the maximum pore size (3) The relation between Db and negative power exponentiation shows segmented characteristics with inflection point near Db = 2.5. Based on the above analysis results, the prediction model of permeability of fractal porous media is deduced Is max n Cfr, where C is a constant, n is a constant close to 2, and f is an expression related to the pore structure information.Finally, we also discuss that when Db = 2, the prediction model of this paper is similar to Kozeny and Ca rman model = equivalence of Crn.