| Increasingly tense energy and environmental problems promote the transformation of energy structure,and geothermal energy stands out for its clean and environmental protection.Because of the reservoir characteristics of deep geothermal energy,it is necessary to construct thermal reservoirs artificially in order to achieve commercial development and utilization.Because the number of cracks and fractures in natural hot-dry rock reservoirs can not meet the production needs,it is necessary to increase reservoir permeability artificially.Based on the modification of hot-dry rock reservoir,this paper studies the mechanism of chemical stimulation method of hot-dry rock reservoir,and focuses on the evolution law of rock physical and mechanical properties under the action of organic acid-soil acid system.In this paper,chemical stimulation method is used to modify hot-dry rock reservoir.Through theoretical analysis,experimental research and numerical simulation,the evolution law of physical and mechanical properties of granite in the process of chemical transformation and the later operation of EGS in Gonghe Basin of Qinghai Province is studied.The reaction principle and theory of chemical excitation of granite are analyzed,and the reaction mechanism between water or chemical solution and rock is revealed.The evolution law of macro and micro physical properties of granite under the action of organic acid-soil acid is obtained by combining experiment and numerical simulation,and the cause of dissolution reaction is analyzed.The deterioration of mechanical properties of granite under different chemical dissolution is tested by mechanical test,and the mechanical parameters are used.Deterioration characterizes the improvement of soil acid by organic acids.The results show that:1)The chemical excitation theory of hot-dry rock is analyzed and divided into hydro-petrochemical reaction and acid-rock reaction according to the degree of reaction.The results show that there are obvious differences in chemical reaction between different chemical reagents and rocks,as well as the interaction between different acid liquids.Long-term working fluid circulation in high temperature reservoirs will also affect the porosity and physics of rocks.Mechanical properties will have a greater impact.2)The evolution of macrophysical properties of hot-dry rock reservoirs under chemical excitation is studied by chemical dissolution experiments of organic acid and soil acid.The results show that the rock undergoes weak hydro-rock chemical reaction in water,and the dissolution reaction between soil acid and organic acid-soil acid solution and granite is more obvious than that between water solution and granite,and the chemical reagent group added with acetic acid has more obvious effect.The mass loss per unit surface area is 0.7g/mm~2 after 12 days.3)Using COMSOL numerical simulation software,the chemical excitation of hot-dry rock reservoir is simulated,and the porosity evolution of core micro-physical properties is analyzed.The results show that chemical excitation can significantly increase the porosity of core,from 0.1 to 0.22.4)Evolution rules of chemical excitation mechanical properties of hot-dry rock reservoirs are obtained by mechanical experiments of granite under different chemical dissolution.The results show that the mechanical properties of hot-dry rock reservoir obviously deteriorate with the increase of chemical excitation time.After 12 days of organic soil-acid solution,the deterioration of tensile strength,uniaxial compressive strength and shear parameters of rock specimens are greater than those of traditional soil-acid solution.5)The research proves that the dissolution of organic earth acid to granite is better than that of traditional earth acid.The addition of acetic acid can effectively increase the reaction radius of rock and reduce secondary precipitation.The chemical reagent group added with acetic acid has more severe deterioration of the core properties.Successful improvement scheme of organic acid addition is obtained,which has certain guiding significance for the production and construction of hot-dry rock reservoir construction in Gonghe Basin,Qinghai Province. |
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