CO2-水-岩石相互作用对砂岩储集层润湿性影响机理

摘要

The interactions among CO2,water and rock will result in wettability changes of reservoir rocks after CO2 is injected into formations,which will impact reservoir permeability.Contact angle and interfacial tension (IFT) measurements,and core displacement experiment are used to study the influence of CO2-water-rock interactions on the sandstone reservoir wettability under high pressure,and to investigate the relationship between rock wettability and permeability.The results show that the static water contact angle on the surface of quartz increases gradually with the increase of CO2 pressure and reaches the maximum when the pressure of CO2 is 7.2 MPa,then gradually reduces with the increase of CO2 pressure;water-CO2 interfacial tension and water adhesion work on the quartz surface gradually decrease with the increase of CO2 pressure and reach the minimum when the pressure of CO2 is 7.2 MPa,then increase with the increase of CO2 pressure.With the decrease of pH value of aqueous solution,the contact angle of water on quartz surface first decreases then increases,and reaches the maximum when the pH value reduces to 2.5.When the pH value continuously decreases,the contact angle reduces.With the decrease of the pH value of aqueous solution,the contact angle of water on sandstone surface first decreases and then increases,and the water permeability in the sandstone first decreases and then gradually increases.%CO2注入地层后,与水和岩石相互作用,导致储集层岩石润湿性发生改变,从而影响储集层的渗透性.应用接触角测量、界面张力测量、岩心驱替实验等方法,研究了高压条件下CO2-水-岩石相互作用对砂岩储集层润湿性的影响,并探讨了岩石润湿性和渗透性之间的关系.结果表明,水在石英表面的静态接触角随着CO2压力的升高逐渐增大,在CO2压力为7.2 MPa时达到最大值,然后随着CO2压力的升高有所减小;水-CO2界面张力及水在石英表面的黏附功随着CO2压力的升高逐渐减小,在CO2压力为7.2 MPa时达到最小值,然后随着CO2压力的升高而增大;随着水溶液pH值降低,水在石英表面的静态接触角先减小后增大,pH值降低至2.5时,静态接触角达到最大值,pH值继续降低,静态接触角减小;随着水溶液pH值降低,水在砂岩表面的静态接触角先减小后增大,砂岩的水相渗透率先减小后逐渐增大.