Study On The Interaction Of C0₂Fluid With Sandstone In Shiqianfeng

CO₂as the end product of burning fossil fuels, as a result of the greenhouseeffect is a serious threat to human living environments. A key way to reduce CO₂emissions into the atmosphere is deep into the stratum of permeable reservoir rock,the geological storage of CO₂. CO₂dissolved in water to form acidic fluids can causein reservoir rock of soluble minerals such as feldspar dissolution and precipitation ofnew minerals such as carbonates, substance to achieve the CO₂traps.This simulation of underground environment using high pressure reactor forgas-water-rock interaction experiment and computer simulation, reveal and explorethe effective mechanism of interaction between the CO₂fluid and reservoir rock, theeffect that dissolving, dissolution of CO₂fluid on reservoir rock, and formation ofnew generation of CO₂capture.By3groups of high pressure reactor experiment, scanning electron microscopeobservation of mineral samples before and after reaction, chemical compositionanalysis of remaining after the reaction solution and numerical simulation of theinitial,which were discovered:（1）In different temperature conditions （55°C，70°C，85°C and100°C）, with theincreases in temperature, the samples dissolution strength gradually increased, and itcould be confirmed according to the amount of quality loss after the response ofsamples. Degree of dissolution of feldspar, quartz and clay minerals graduallyincreased with temperature rises. Under the same conditions of temperature, thedissolution rate of sodium feldspar is faster than potassium feldspar’s.（2）In interaction experiments of CO₂-ground water-sandstone, under55°C and 70°C, there are kaolinites and chlorites in the surface of the samples. However, thegibbsites generated on the samples surface, under70°C，85°C and100°C. Theinteraction experiment of CO₂-ground water-sandstone under the differenttemperature, the gibbsite, chlorite and albite were generated respectively. That allconfirmed that CO₂could be captured between the rock in the form of mineral, andthe geological storage of CO₂through a material traps are feasible.（3）The changes of chemical components in the remaining reaction solutionconfirm that the intimate interaction, which was between the dissolving andprecipitation of minerals and hydrolysis reaction that CO₂dissolved in water formscarbonic acid in interaction experiments of CO₂-ground water-sandstone, such as pHand the concentration of HCO₃.（4）The artificial simulated the changes of pH and the porosity after CO₂fluidinjection, by using of TOUGHREACT software. Results showed that, pH graduallyreduces in the initial phase of CO₂injection, but pH rise back again when the injectionof CO₂is stopping. The change of pH was bound up with the solubility of CO₂andthe dissolving and the precipitation of minerals. The porosity hardly decreased. Thatall account for the balance that the dissolution and the precipitation of the reservoirminerals. But the new mineral precipitation is slightly larger than the main mineralsdissolve.