Risk analysis and characteristic experiment of oil and gas explosion during high-pressure air injection process for oil recovery
Air injection displacement is an economically effective enhanced oil recovery technology,and the explosion-proof safety of hydrocarbon and air mixtures also attracts much concern.At present,explosion risk assessment is carried out mostly based on the characteristics of oil and gas explosion under low temperature and pressure,and there is less research on actual high-temperature and high-pressure conditions in oil fields.Using a self-developed experimental device for high-temperature and high-pressure oil and gas explosion,this paper simulates the working conditions of air injection in wellbore,and studies the effects of pressure,density,and gas composition on the explosion limit of natural gas.The experiment results show that when the pressure increases from 5 MPa to 15 MPa at 100 ℃,the explosion limit range can expand by 10.25％,accompanied with increased explosion risks.In the experiments on auto ignition explosion of light and heavy oil,the evaporation of light components is caused by high temperature.The auto igni-tion explosion temperature of light oil and heavy oil increases with the increase of density;at 15 MPa,the auto ignition explosion temperature can be as low as 190-207 ℃ The explosion risks are analyzed for different air injection processes and hydrocarbon explo-sion mechanisms.When the gas injection well pressure is lower than the reservoir pressure,the mixture of hydrocarbons flowing back into the wellbore and air is mainly contributed to the explosion.In production wells,incomplete oxidation of crude oil or gas breakthrough leads to an oxygen concentration exceeding the critical oxygen content,which is the most important factor that causes explosions.Finally,based on experimental and theoretical analysis results,the paper proposes effective wellbore explosion-proof measures for different air injection processes.
air injectionoil and gas explosionauto ignition explosionhigh temperature and high pressuredensity
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