Numerical Simulation Study Of High Temperature Mixed Gas Displacement Stimulation Of Shale Gas

my country is a big country with shale gas resources and has established shale gas fields with reserves of more than 100 billion cubic meters in the southwest region.Guizhou area has well-developed Cambrian black shale,among which shale gas of Niutitang Formation and Longmaxi Formation are widely distributed,and they have good hydrocarbon generation conditions and exploitation potential.However,the production of shale gas has the characteristics of high cost of reservoir reconstruction and rapid decline in daily production.In order to increase the single well production of shale gas,it is necessary to use advanced production stimulation methods to extract adsorbed shale gas.This paper studies the means of increasing production by injecting different proportions of displacing agents(CO₂and N₂)under high temperature conditions.This technology can not only increase single well shale gas production,but also store CO₂underground and reduce greenhouse gas emissions.Based on the effects of temperature and pressure on shale gas pores and gas adsorption characteristics,this paper puts forward a research concept for shale gas displacement and production enhancement by injecting high-temperature displacing agents.Under different temperature and pressure conditions(60°C-100°C,1-11 MPa),the changes in the adsorption characteristics of the reservoir and the displacement effect were studied,and a multi-field coupled numerical simulation was carried out.By optimizing the operating temperature and pressure,making full use of the competitive adsorption advantages of the displacing agent for CH₄,and increasing the production of shale gas through the displacement desorption method.Aiming at the situation of shale gas reservoirs in Guizhou area,the Longmaxi Formation shale and Niutitang Formation shale have been studied by numerical simulation of the displacement and increase of methane production with three different displacing agents at three different temperatures.It is found that the use of mixed gas to displace shale gas in the Niutitang Formation has a better effect.On this basis,a sensitivity analysis of the factors affecting methane production in shale by mixed gas displacement was carried out.The analysis found that shale gas production was positively correlated with Langmuir pressure,and negatively correlated with Langmuir volume.It is inferred from this that,in the reservoirs with higher Langmuir pressure but lower Langmuir volume,the displacement operation can achieve better results.This conclusion can be used to guide the identification of favorable target areas in production practice.