温压变化下CO2−水−油−石英体系接触角的演变规律OA

[Objective]CO2-enhanced oil recovery(CO2-EOR)serves as a vital technology that simultaneously realizes crude oil production increase and geological carbon sequestration.However,existing research lacks systematic comparative investigations on wettability evolution under coupled temperature-pressure conditions and different gas phases(CO2,N2)in deep high-temperature high-pressure sandstone reservoirs,and the interfacial evolution mechanism of the CO2-water-oil-quartz multiphase system remains unclear,which restricts the optimization of field injection-production parameters for CO2 flooding.This study carries out microscopic experimental research to clarify the coupling mechanism of contact angle and wettability controlled by temperature,pressure,and gas composition.[Methods]A high-temperature high-pressure visual quartz capillary experimental setup was constructed,with n-hexadecane adopted to simulate formation crude oil.Continuous temperature gradients ranging from 25℃to 200℃and pressure gradients from 5 MPa to 30 MPa were set up for testing.Contact angles of two-phase CO2-water,water-hexadecane systems,and three-phase systems filled with CO2 or N2 were measured separately.Combined with the variation patterns of interfacial tension and fluid viscosity,the internal control mechanism of gas composition on reservoir wettability was analyzed quantitatively.[Results]The test results indicated that the CO2-water contact angle increased slightly with the growth of temperature and pressure,while the water-hexadecane contact angle decreased remarkably with temperature rise and showed weak response to pressure variation.Gas injection could adjust oil-water interfacial tension to alter reservoir wettability,and CO2 exerted a stronger viscosity-reducing effect on crude oil than N2.The critical temperature range for complete wettability transition of quartz mineral was from 120℃to 150℃.Above this threshold,the quartz surface completely transformed from oil-wet to water-wet.Heating could effectively reduce crude viscosity and enhance the seepage capacity of oil phase,while pressure had a limited effect on the physical properties of oil and water fluids.[Conclusion]Higher temperature facilitates the hydrophilic transformation of quartz matrix in sandstone reservoirs.Reasonable regulation of flooding temperature can greatly improve the recovery efficiency of CO2-EOR.This study innovatively conducts comparative micro-capillary experiments with CO2 and N2 as contrasting gas phases,and reveals the coupled controlling effect of temperature,pressure,and gas species on multiphase contact angle.The experimental conclusions can provide a reliable basis for optimizing temperature-pressure operation schemes for CO2 flooding in deep quartz sandstone oil reservoirs.