| The demand for energy from economic development is increasing,and the use of coal resources accounts for 60%of the total,resulting in a dramatic increase in carbon dioxide(CO2)emissions.The most effective solution at present is to combine carbon dioxide sequestration with enhanced recovery,not only to solve environmental problems,but also to bring great commercial value.The mechanism of supercritical CO2-water-rock interaction during the process of CO2 sequestration is one of the core objectives of the current research.It combines experimental and numerical simulation methods to comprehensively analyze the water-rock reaction in the sequestration,and it has a certain guiding significance for the long-term and efficient storage of CO2.Therefore,the carbon dioxide sequestration experiment and the supercritical carbon dioxide-saline water seepage experiment were designed in this paper.On this basis,the TOUGHREACT software was used to simulate the water-rock reaction.The following studies are mainly conducted:(1)Based on the mechanism of carbon dioxide sequestration,the carbon dioxide-water-rock storage experiment was designed.X-ray diffraction experiments were performed on cores at different storage times to analyze the trend of mineral composition over time,and the relationship between carbon dioxide sequestration and time.The experimental results show that the main mineral components contributed to carbon dioxide mineralization and storage are:calcite,dolomite and clay minerals,and the calcite,dolomite and clay content have a linear change with time.(2)The non-steady state method was used to study the supercritical CO2-saline permeability experiment under different permeability,confining pressure,and displacement pressure,and discussed the influences of these three factors to permeability curve characteristics.(3)Combining the experimental results of the sequestration and phase percolation,the numerical simulation of the Liujiagou Formation in the Ordos Basin was studied using the TOUGHREACT numerical simulation software EC02N module.The simulation results show that:a)At the initial stage of carbon dioxide injection,the pressure near the injection point is the lowest and the temperature is the highest.When the injection time reaches 10 years,the pressure reaches the maximum value,and the temperature near the injection point reaches the minimum value,after which the pressure and temperature change range is very small.b)The change of potassium feldspar is extremely small,the content of plagioclase and dolomite decreases with the increase of storage time,and the content of calcite increases with the increase of storage time;c)The concentration of Ca2+ and Mg2+ increase as a whole.In the trend,the concentration of Na+ increased rapidly during the initial stage of CO2 injection.After 15 years of storage,the concentration of Na+ remained basically unchanged;the concentration of K+ did not change significantly;d)The overall porosity of the reservoir increased with time,and the time was longer.The less obvious.e)There is a certain difference between the experimental results and the numerical simulation results.The reason is that compared with the simulation time,the experimental time is short and the dissolution and precipitation equilibrium of the minerals is not reached.The research results have a certain theoretical guiding significance for the long-term and high-efficiency of geological storage of CO2,and also have a certain reference value for the analysis and evaluation of other CO2 geological storage areas. |
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