作　　者： (姚军）; (宋文辉）; (李阳）; (孙海）; (杨永飞）; (张磊）;

机构地区： 中国石油大学华东石油工程学院,青岛266580

出　　处： 《中国科学：物理学、力学、天文学》 2017年第9期51-62,共12页

摘　　要： 页岩中存在有机质孔隙和无机质孔隙,目前页岩气表观渗透率模型忽略了孔隙类型、孔隙半径分布对气体流动能力的影响.本文基于页岩二维剖光扫描电镜图像数值重建页岩三维数字岩心,并提取孔隙相中轴拓扑结构.根据地质上对有机质孔隙空间分布、有机质孔隙和无机质孔隙半径分布的认识,在对应孔隙喉道位置,充填满足对应孔隙半径分布以及空间分布关系的有机质孔隙和无机质孔隙,建立3种不同有机质孔隙分布模式的页岩孔隙网络模型:有机质孔隙条带状分布、有机质孔隙连片分布、有机质孔隙分散在无机质孔隙中.有机质孔隙中气体流动考虑吸附解吸、表面扩散、黏性流、努森扩散,无机质孔隙中气体流动考虑黏性流、努森扩散,气体性质计算考虑真实气体效应以及在微纳米孔道中相态变化.结果表明,当有机质孔隙半径分布小于无机质孔隙半径分布,有机质孔隙成条带状分布模型气体流动能力最强,有机质孔隙连片分布模型气体流动能力最弱.当有机质孔隙半径分布大于无机质孔隙半径分布,有机质孔隙成条带状分布模型气体流动能力最强,有机质孔隙分散在无机质孔隙模型气体流动能力最弱.本文的研究对认识页岩气流动能力具有显著意义. In shale gas reservoirs, gas is stored in organic pores and inorganic pores with nm-scale pore size. Conventional single tube apparent permeability model is based on homogeneity assumption and neglects the influences of organic pores spatial distribution pattern, pore size distribution on gas flow ability. In this study, three dimensional shale digital core is reconstructed by Markov Chain Monte Carlo （MCMC） algorithm and medial axis in the pore space is extracted. According to geological study on the organic pores distribution pattern and pore size distribution, different sizes of organic pores and inorganic pores are assigned to corresponding spatial location of pores and throats. Three different types of shale pore network are built： shale pore network model with dense continuous layers of organic pores; shale pore network model with sparse continuous layers of organic pores; shale pore network model with discontinuous organic pores. Gas transport mechanisms of adsorption and desorption, surface diffusion, viscous flow, Knudsen diffusion are considered in organic pores. Gas transport mechanisms of viscous flow, Knudsen diffusion are considered in inorganic pores. Gas property calculation takes the influences of real gas effects and phase behavior change into account. Analysis results indicate that when the organic pores size distribution is smaller than inorganic pores size distribution, the permeability of shale pore network model with dense continuous layers of organic pores is larger than that of the other two types of shale pore network model. The permeability of shale pore network model with sparse continuous layers of organic pores is smallest. When the organic pores size distribution is bigger than inorganic pores size distribution, the permeability of shale pore network model with dense continuous layers of organic pores is also larger than that of the other two types of shale pore network model. The permeability of shale pore network model with discontinuous organic pores is smallest. Our study

关 键 词： 页岩气 运移机制 孔隙网络模型 有机质孔隙 无机质孔隙