Experimental investigation of the geochemical and mineralogical interaction between CO2 and carbonate: Evaluation of CO2 sequestration in dolomite-calcite formations

Abstract

Abstract Sequestration of CO2 in saline aquifers has become a renowned procedure owing to the availability of this type of reservoir. This study aims to identify the induced rock and fluid interactions during CO2 injection and their influence on the reservoir rock properties like porosity and permeability. A systematic study is required for further evaluation of these interaction effects. The experiments were collected from Iranian Asmari formations in Fars province with significant quantities of dolomite revealed by XRD analysis. The carbonate rock sample is considered for this study since most of the oil reservoirs in Iran are produced from carbonate Asmari formation. A series of core-flood experiments were carried out to assess the potential of dolomites to buffer brine and further promote mineral precipitation over time. Carbonate samples were exposed to CO2 for 2 weeks and 4 weeks. The dissolution and precipitation of minerals were investigated using CBCT to determine the impact of these processes on rock properties. The result of 4-weeks experiments showed that the reaction with CO2 causes salt precipitation which is observed in FE-SEM and EDS. The ICP and IC analysis tests showed that long-term CO2 reaction also creates a significant CO2 drying-out effect and salt (NaCl) crystallization in the aquifer s rock pore space by altering the pore structure. Such mineralogical alterations considerably affect the saline aquifer properties, producing noteworthy outcomes in the sequestration process. For example, the core permeability (C2) at 1\xa0ml/s CO2 injection rate and confining pressure of 22\xa0MPa decreased considerably from 51.8 to 15.06 mD with decrease in porosity from 22.90 to 15.56 using imaging technology (dental X-ray CT). Furthermore, CO2 storage capacity of both core samples was measured for a brine system with a salt concentration of 150,000\xa0ppm.