低渗透砂岩润湿性对水驱和复合驱采收率的影响

Effect of wettability of low-permeability sandstone on waterflooding and ASP flooding recovery

在砂岩岩心渗透率小于50×10-3μm2条件下,考察驱替相润湿接触角分别为37,86,126和167°的驱油效果,对应水驱采收率平均值依次为16.18%,15.47%,13.94%和9.02%,复合驱采收率依次为21.12%,17.33%,13.53%和5.26%。结果表明,除强亲油性外,其他润湿性对岩心水驱采收率的影响不显著。复合驱提高采收率幅度随润湿性由亲油到亲水变化逐渐提高,其平均值与润湿接触角呈二阶线性负相关关系,即润湿接触角越小,采收率越高,接触角为37°时提高采收率最大。低渗透孔隙微毛细管对原油的捕集作用是制约驱油效率的关键因素,应用复合驱应重点从降低油水界面张力和改变岩石润湿性2方面考虑克服毛管对原油的捕集束缚。

The core flooding tests were conducted in order to investigate the influence of wettability of low permeability sandstone core bellow the permeability of 50 md on waterflooding and ASP flooding recovery factor.Experiments showed that the wetting angle of oil displacement phase is 37°,86°,126° and 167° respectively.The average value of waterflooding recovery is 16.18%,15.47%,13.94% and 9.02% correspondingly.The average value of ASP flooding recovery is 21.12%,17.33%,13.53% and 5.26%.Results indicate that the influence of the other wettabilities,except for the lipophilicity,on core waterflooding recovery is approximately similar.The more stronger the water wettability is,the more higher ASP flooding recovery is.It shows a negative second-order linear relationship between the water wetting angle and average value of ASP flooding recovery.Especially,the average value can amount to 21.12% for strongly water wetting with the contact angle of 37°.The oil entrapment in low-permeability pore and micro-capillary trap is the key factor of controlling the oil displacement efficiency.When the ASP flooding technology is used,it should be mainly considered lowering the oil-water interfacial tension and changing the rock wettability to overcome the constraint of oil entrapment.