CO2-盐水-岩石相互作用对砂岩储层孔隙结构及润湿性的影响OA

During the process of CO2 injection into saline aquifers for geological sequestration,the dissolution of CO2 in for-mation water can create an acidic environment,leading to the dissolution of reservoir minerals and resulting in changes of pore-throat structure and wettability of the reservoir rock.In this study,based on the reservoir and formation water data of sa-line aquifer A in South China Sea,the influence of CO2-brine-rock interactions on the physical properties of sandstone reser-voir during CO2 sequestration was studied using scanning electron microscopy(SEM)and CT scanning under the reservoir conditions of 50℃and 10 MPa.The experimental results show that with the increase of fluid/rock interaction time,the pH value of the formation water decreased from 7.62 to 5.11,the Na+concentration increased from 5634 mg/L to 6533 mg/L,and the conductivity increased from 5.15 ms/cm to 9.58 ms/cm.XRD and SEM-EDS analysis results indicate that sodium feldspar and potassium feldspar in the formation rock dissolve preferentially,leading to an increase in detrital particles,form-ing more dissolution pores and microcracks.Meanwhile,layer shaped kaolinite clay minerals were formed.In addition,CT scanning experiments show that the pore volume of the core sample increased due to the dissolution of minerals,with the av-erage pore radius increasing from 22.20 μm to 28.38 μm and the average throat radius increasing from 10.70 μm to 18.48 μm.Using an in-situ contact angle measurement technique to quantitatively characterize the wettability of rocks,it was found that the CO2 contact angle of rocks increased from 119.78° to 135.23°,due to mineral dissolution,kaolinite formation,and surface erosion of rocks,which can make the rock surface more hydrophilic.