一种利用毛管压力确定致密储层岩石润湿性的方法

A Method for Confirming Rock Wettability by Capillary Pressure in Tight Reservoir

致密砂岩储层孔隙尺度微小,孔隙结构复杂,毛管效应明显,为明确该类储层岩石润湿性,提出一种利用毛管压力确定岩心润湿性的方法。首先,通过压汞实验明确致密砂岩储层孔隙结构特征,明确孔隙结构参数与毛管压力关系,确定毛管压力主要影响因素;其次,开展动态毛管压力测定实验,建立毛管压力和喉道半径关系;最后,开展不同渗透率岩心油驱水和水驱油实验,确定岩石润湿性。研究结果表明:致密砂岩储层喉道半径呈对数正态分布,其分布参数与渗透率的相关性很好,喉道半径是渗流能力的主控因素;当渗透率大于10×10^(-3)μm^(2)时,毛管压力的动态效应影响较弱,当渗透率小于1×10^(-3)μm^(2)时,毛管压力的动态效应明显;通过测定岩心两端的压差,可以利用毛管压力能够确定岩石润湿性,结果准确,与接触角法与吸入法结果相同,验证了该方法的准确性。

There are some characters including small pore scale and complex pore structure and obvious capillary effect in tight sandstone reservoir.To confirm the wettability of reservoir core,a method measuring the wettability of core by capillary pressure was proposed.Firstly,the pore structure characteristics of tight sandstone reservoir were determined by mercury injection experiment to clarify the relationship between pore structure parameters and capillary force and ensure the main influencing factors of capillary pressure.Secondly,the dynamic capillary pressure tests were carried out to establish the relationship between capillary pressure and throat radius.Finally,experiments on oil flooding and water flooding of core with different permeability were carried out to determine the wettability of rock.The results show that the throat radius of tight sandstone reservoir presents lognormal distribution,and there are some good correlations between the distribution parameters and permeability.Throat radius is the main controlling factor of seepage capacity.The dynamic effect of capillary pressure is weak when the permeability is greater than 10×10^(-3)μm ^(2).However,the dynamic effect of capillary pressure is obvious when the permeability is less than 1×10^(-3)μm ^(2).By measuring the pressure difference of the two ends of the core,the capillary pressure can be used to determine the rock wettability.The results are accurate and it is the same as the results of the contact angle method and the suction method,which verifies the accuracy of the method.