矿物溶解作用下颗粒粗糙度对多孔岩石渗透率和电导率的影响

Effect of grain roughness on permeability and electrical conductivity of porous rock under mineral dissolution

矿物溶解过程广泛地存在于地下储层中.溶解作用的发生会在岩石内部产生新的流动通道,使地下储层的孔隙度发生变化,从而影响多孔岩石的物性参数,例如渗透率和电导率.为了定量研究多孔介质的颗粒粗糙度、渗透率和电导率在溶解作用下的关系,本研究采用线性布尔模型和四参数随机生成法(QSGS)对不同颗粒粗糙度的多孔介质进行建模.之后,采用双分布格子Boltzmann方法模拟岩石孔隙的溶解和渗透率演化过程.常见的溶解模式有均匀溶解、面溶解和虫洞溶解,主要受Péclet数(Pe)和Damkohler数(Da)这两个无量纲数控制.通过改变Pe数和Da数,我们相应地重现了不同的溶解模式.为了对岩石电导率进行数值计算,我们采用基于最小自由能的有限元法获得多孔介质的电场,然后根据欧姆定律计算岩石的有效电导率.研究结果表明,对于具有相同晶粒粗糙度的多孔介质,在不同溶解模式下,渗透率和电导率产生不同的变化规律.虫洞溶解模式下,渗透率和电导率变化最大;而面溶解模式下,变化最小.在相同的Pe和Da下,粗糙颗粒模型的渗透率和电导率变化显著高于光滑颗粒模型.

Mineral dissolution widely exists in subsurface reservoirs.Dissolution process can make new flow channels,which leads to the porosity of the underground reservoir alteration,thereby affecting the physical parameters of porous rock such as permeability and electrical conductivity.We apply a linear Boolean model and a four-parameter stochastic generation model to quantitatively investigate the relationship between grain roughness,permeability,and electrical conductivity of porous rocks under dissolution conditions.The dual-distribution function lattice Boltzmann model was used to mimic the dissolution process and permeability evolution in porous rocks.Common dissolution patterns including uniform,surface,and wormhole dissolution,are controlled by two dimensionless numbers,the Péclet number(Pe)and the Damköhler number(Da).By varying Pe and Da,different dissolution regimes were reproduced.We obtain the electric field in porous media using a finite element method based on minimum free energy and then calculated the bulk electrical conductivity based on Ohm's law.Our results indicate that for porous media with the same grain roughness,different dissolution regimes lead to different effects on permeability and electrical conductivity due to changes in pore geometric structure.The wormhole dissolution regime shows the largest variations in permeability and electrical conductivity,while the face dissolution regime exhibits the smallest variations.Under the same Pe and Da conditions,models with higher grain roughness show significantly larger variations in permeability and electrical conductivity.