致密油藏自渗吸提高采收率影响因素研究

Key Impact Factors of Spontaneous Imbibition EOR in Tight Oil Reservoirs

针对致密油藏现有开发方式下产量递减快、可采储量低的问题,通过建立双孔双渗致密油自渗吸提高采收率数学模型,研究裂缝密度、基质渗透率、毛管力、原油黏度等因素对自渗吸提高采收率效果的影响。研究发现,注入表面活性剂使亲油致密储层产生润湿性反转,诱导产生自发渗吸,从而可有效提高基质原油的动用程度;渗吸采油效果与裂缝密度正相关,裂缝越密,基质比表接触面积越大,渗吸强度及采油速度也越快;渗吸采油效果与毛管力正相关,改变润湿性的同时应尽量保持界面张力水平;渗吸法采油适用于原油黏度较低、基质渗透率较高的亲油致密油藏。

With regards to low recoverable reserves and rapid production declining in tight oil reservoirs,a dual porosity and dual permeability spontaneous-imbibition EOR mathematical model is developed for the oil-wet tight reservoirs to investigate the impact of fracture spacing,matrix permeability,capillary pressure,oil viscosity on increased recovery efficiency.The results show that the injected surfactant can alter reservoir wettability from oil wet to medium or even water wet,then trigger spontaneous imbibition and finally favor oil movement from matrix into fracture.EOR results is positively related with fracture density and capillary pressure.The specific surface area of matrix grows with increasing fracture density,which boosts strength of spontaneous imbibition and oil production rate.Capillary pressure should be retained as big as possible to ascertain EOR results,combined with wettability alternation.Spontaneous imbibition EOR method is favorable for oil-wet tight reservoirs with relatively low viscosity of oil and high permeability of matrix.