Experimental Study On The Interaction Of CO₂/CO₂-H₂S Fluid With Sandstone In Liujiagou

With the development of the global economy, there is a large amounts of CO₂produced when burning fossil fuels, which caused global greenhouse phonomenonthat is widespread concerned. The geological storage of CO₂is an effective way toreduce and control excess emissions of CO₂in the atmosphere. supercritical CO₂（SCCO₂）storage in deep saline aquifers which is considered as the most potentialway to deal with it.CO₂fluid-formation water-rock reaction and CO₂-H₂S mixed fluid-formation water-rock reaction was carrying on in the autoclave under the pressure ofthe sandstone formation in Liujiagou （18MP） and in different temperaturesconditions（60°C,80°C,100°C）, in order to investigate the mineralization capturemechanism of CO₂fluid and H₂S-CO₂mixed fluid injected into saline aquifers Theresults are as follows:（1） In SCCO₂-formation water experiment, reaction time to balance betweenCO₂and formation water is about5hour; in CO₂-H₂S mixed fluid-formation waterexperiment, the balancing time is about3hour. Adding H₂S made the formationwater more acidic and accelerated carbonate equilibriumof CO₂and formation water.（2） The results indicate that dissolution and corrosion of feldspathoid, such asalbite and potash feldspar, and clay mineral become more severe as time goes by andtemperature higher during the reaction under conditions that one is SCCO₂-formationwater-rock, and the other is CO₂-H₂S mixed fluid-formation water-rock, and underthe latter condition dissolution and corrosion are more severe. Under both reactionconditions, the quartz dissolution is weak and maintain a more complete polymorph.（3） After24days, new minerals were produced under both two reactionconditions which one is SCCO₂-formation water-rock, and the other is CO₂-H₂Smixed fluid-formation water-rock. Under the former condition, there produced Secondary clay minerals-chlorite and calcite at60°C,80°C and100°C, and thecalcite crystal form is the best at the80°C condition. There produced secondarychlorite under the latter condition at every temperature, but did not produce secondarycalcite with a good crystal form, and there produced new mineral sulfur and fishscales iron pyrite at80°Cand100°C respectively.（4） Injecting CO₂and CO₂-H₂S mixed fluid into underground caused thedissolution and corrosion of feldspar, and then transformed into clay minerals andcalcite as the increase of pH. The production of calcite stabled minerals in the SCCO₂-formation water-rock reaction indicated that CO₂could achieve stable mineralizedand capture. The production of new mineral sulfur and Fish scales iron pyrite butwithout a good crystal form indicated that injecting H₂S is not conducive to the stableproduction of calcite at a short time. But H₂S also can achieve stable mineralized andcapture.