It　is　ubiquitous　that　the　rock　of　porous　media　is　composed　of　multiple　minerals　expressing　distinct　geochemical　properties　and　spatial　distributions,　which　may　influence　the　geochemical　processes,　the　flow　field　by　changing　the　size　and　connectivity　of　the　pores.　Numerical　modeling　is　an　effective　means　to　investigate　the　impact　of　heterogeneous　mineral　composition.　However,　it　is　challenging　to　represent　a　successful　and　reliable　spatial　distribution　of　minerals　as　the　prerequisites　for　numerical　simulations.　In　this　study,　a　novel　approach　for　realizing　a　reasonable　spatial　distribution　of　mineral　composition　was　presented,　and　the　effect　of　mineral　heterogeneity　on　the　geochemical　reactions　was　evaluated.　Based　on　the　available　data　from　a　CO2　geological　storage　site,　the　random　field　with　lognormally　distributed　permeabilities　was　firstly　generated　by　employing　the　geostatistical　theory,　and　then　porosities　obeying　normal　distribution　were　obtained　with　a　regressed　log-linear　model.　Finally,　the　two-dimensional　joint　normal　distribution　model　was　adopted　to　realize　the　mineralogical　heterogeneity.　By　using　＂3　sigma　law＂,　the　generated　permeabilities,　porosities　and　mineral　contents　were　limited　to　the　corresponding　ranges　of　site-specific　available　data　with　probability　of　as　high　as　99.74%.　Aforementioned　processes　have　been　coupled　into　the　existing　software　TOUGHREACT.　The　proposed　approach　was　applied　to　a　CO2　geological　storage　site　to　estimate　the　effects　of　spatial　variation　of　minerals　on　the　evolution　of　caprock　sealing　capacity.　The　generated　spatial　distribution　of　minerals　is　reasonable　compared　with　the　measured　data　from　the　CO2　geological　storage　site　in　the　Ordos　Basin,　China　The　500-year　simulated　results　imply　that　the　spatial　variation　in　mineralogical　composition　slightly　enhanced　the　sealing　capacity　of　caprock.