Study On Microscopic Mechanism Of Electrokinetic Coupling In Unsaturated Reservoir Rock

Electrokinetic effects of complex porous media mainly involve the streaming potential effects and electroosmotic effect,which are the basis of seismo-electrc prospecting and acoustic electric logging. Therefore, the reseach on the electrokinetic of complex porous play an important role in the oil-air-water logging evaluation. So far, the electrokinetic effect of complex porous focuses on completely water-saturated porous media. Although the electrokinetic effect in oil-water porous media has been early discovered, it still in the experiment research phase, and the miscroscopie mechanism study also does not make a substrantive breakthrough. Moreover, the study does not from mathematically descriptive methods and the theoretical systerm with universal significance, which affects the promotion and development of the technologies in electrokinetic effects. This paper is based on capillary model and combined the electrochemisty transfer dynamics in the complex pore medium for studying electrokinetic effects in complex pore medium.Firstly,according to the different absorption characteristic of complex pore medium’s solid-liquid interface, building the hollow billet model with the wetlability in pore medium, thereby we can instablish the micro coupling mechanism among completely oil-water saturated in pore medium seepage field, electroknetical and ion flow field under the stable condition.Then based on the two states of concentration polarization effect and the non-concentration polarization effect, we can deduce the miscrosopic parameter’s computational formula of streaming potential in water-oil saturated mediun, and discuss the relation among streaming poteneial parameters, rock physical properties(porosity,penetrance,saturation), solution concentration, cation exchange capacity and other factors.Secondly,on the basis of the fluid flow equation and mass transfer electrochemical kinetics theory under the periodic pressure field condition, combining the hollow billet model under the water-wet condition, we can build the mathematic model with the dispersion of describing water-wet rock’s periodic electrokinetic effect. According to the four capillary bundle’s internal qualities, and the Dary law and Ohm law in flow rate, the relation of streaming potential coupling coefficient can be deduced. Finlly, we can make mathematical simulation relating with the streaming potential effect under the condition of flow rate in water-wet rock.Thirdly,based on the micro-pore structure in gas-water saturated pores media, and combining the gas-water slug frow’s capillary model, we can establish relation between seepage field and current field in the gas-water slug frow’s pore medium under the stable condition. Thus, the new streaming potential computational formula can be deduced and the quantitativw relation between the pore parameters/electrochemical factors amd streaming potential in air-water saturated pore mediun can be explained.