天然岩芯化学驱采收率机理的一些认识

CHEMICAL FLOODING RECOVERY MECHANISM OF NATURAL CORES

用牛顿流体驱替一定的均质多孔介质系统结果显示,驱油效率由驱替液的毛管数决定。用化学液驱替天然岩芯时,除毛管数以外,还有很多其他因素影响驱油效率。天然岩芯,即使在宏观上是均匀的,在微观上也不均匀;驱替时所得到的效率一般被称为驱油效率,实质上是微观波及效率和驱油效率的乘积。牛顿流体没有弹性,驱替时,体系的润湿性不发生变化,不出现渗吸作用,不形成乳液,孔隙的几何形状不发生变化。但是,用化学液驱替天然岩芯时,由于化学液为粘弹性,体系有润湿性的改变,会出现乳化现象,渗吸作用也会出现。上述因素都会影响驱油效率,尤其是当多种因素同时作用时。分析了极限采收率和经济采收率的区别。很多文章都论述极限采收率,但经济采收率对油田的作用更大。化学驱应考虑上述因素,这对设计、开发、筛选化学剂以及确定驱油体系会是有益的,将深化我们对化学驱机理的认识,促进这方面更深入的研究。

Results of Newtonian Fluids flooding very homogeneous porous media show the displacement efficiency of the system is determined by the capillary number of the driving fluid.The experience gained from chemical flooding natural cores and reservoirs that are all micro-heterogeneous or macro-heterogeneous to some degree shows that displacement efficiency is influenced,besides capillary number,by many other factors.Newtonian Fluids do not have elastic properties;when flooding,there is no change in the wettability of the system;there is no imbibition;emulsions are not formed;and there is no alteration of the geometry of the pores.However,when chemically flooding,elasticity markedly effects the displacement efficiency;change in wettability could occur;emulsions well often show up,and from core and field tests data,emulsions significantly increases the recovery,emulsions can increase the volumetric sweep of the porous systems and markedly alter the phase permeability behavior and water cut.The wettability will change and imbibition will occur;pore geometry alteration by solution and precipitation will happen,which influences the permeability,imbibition and recovery.The above factors all markedly influence the displacement efficiency of the system,especially when many factors act jointly.The concept of ultimate and economical displacement efficiency and its effect on the selection of actual field flooding systems is analyzed（Many papers analyzeul timated is placement efficiency.however,inoilfield,usuallye conomical displacement efficiencyis more important）.Besides capillary number,the above factors should be considered when developing and selecting chemicalsandfloodingsystems.The above in sights canfur the rdeepenour knowledge of the mechanism of chemical flooding,promote further research in this area and form better criteria for designing,developing,screening and selecting EOR chemicals and flooding systems in oil field.