Experimental Study On The Effect Of Surfactant On The Imbibition Capacity Of Tight Reservoir

Spontaneous imbibition using surfactants has become an important technology to enhance oil recovery in tight reservoirs,so it is very important to study the influencing factor of surfactant spontaneous imbibition in tight reservoirs.This paper based on the fractal geometry theory firstly,combined with the means of conventional mercury injection,scanning electron microscopy and the casting thin sections,classified study the pore structure of the cores of chang 8 reservoir in block J in the west of the ordos basin and chang 6 reservoir in block Z in the east of the ordos basin,and use the method of imbibition to evaluate the wettability of the reservoir in the study area,then,the basic properties of the different types of surfactant formula system were evaluated and screened in the laboratory,finally,the selected surfactant was used to carry out the surfactant imbibition experiment on the natural core of the reservoir in the research area.Through comparative analysis of the differences between the imbibition characteristics of the surfactant in the reservoir core,the influence of the surfactant on the imbibition characteristics of the reservoir core and the mechanism of action were studied,mainly obtained the following understanding and research:1.The larger the pore radius of the reservoir core in the study area,the better physical properties,the greater the volume proportion of the large pore throat,the smaller the volume proportion of the fine pore throat and the micro pore throat,the fractal dimension of the large pore throat is closer to that of the fine pore throat,the imbibition efficiency of reservoir is higher,the imbibition speed is slower,the imbibition balance time is late,and the more easily to be affected by the surfactant and change the imbibition characteristics.2.The composition and content of reservoir interstitial materials,the pore structure of reservoir rocks,the salinity of formation water and the concentration of KCl can indirectly affect the imbibition efficiency of the reservoir by changing the wettability of the reservoir.3.For the reservoir in the study area,the surfactant formulation solution with low interfacial tension(IFT<0.32mN/m),weak hydrophilicity(0=45.8°)and strong emulsification(Ed=75.0-90.0%)can obtain high imbibition efficiency in a short time,and the oil-water interface is relatively clear and easy to separate.It is suggested to apply surfactant formula 5#to the reservoir in the study area;4.The emulsification of surfactant is the main control factor affecting the efficiency and speed of imbibition,and the interfacial tension is the main control factor affecting the balance time of imbibition.This paper lays a theoretical foundation for further improving the oil recovery efficiency of tight reservoir and understanding the influence of surfactant on the imbibition process,and has guiding significance for the development of similar reservoirs.