Flow Simulation At Micro-and Nanoscale Considering Streaming Potential

With the production of conventional oil and gas dwindling gradually,the development of unconventional resources like tight reservoirs of low permeability have been receiving more and more attention.Compared with conventional formations,one of the outstanding characteristics of unconventional tight reservoirs is that the pores and throats are extremely small,often at the scale of several microns or even nanometers.As a result,some interfacial forces that can be safely neglected in conventional formations can have significant impact on fluid flow in these tight reservoirs.This thesis is mainly concerned with the study of the impact on fluid flow in tight porous media of streaming potential resulting from the electrical double layer on the interface of grains and fluid.Based on a thorough literature survey,models of coupled fluid flow in capillaries of constant and non-constant radius,in two and three dimensional pore networks and capillary bundle models of oil-water two phase coupling flow are established from the micro-and nanoscale.Numerical methods are employed to solve these models and the impact of streaming potential on fluid flow in tight porous media under various circumstance are analyzed.The results suggest that streaming potential can increase resistance to fluid flow when the radii of pores and throats are very small.Compared with the case in which streaming potential is not considered,the volume flow rate of coupled fluid flow is decreased at the same pressure drop.The impact of streaming potential on fluid flow is most pronounced when the radius of pore or throat is about 2 to 3 times the thickness of the electrical double layer.However,the results also suggest that the relationship between flow rate and pressure gradient in tight porous media remains linear when the streaming potential is considered and streaming potential does not have much effect on fluid flow behavior in tight formations.Besides,since the viscosity of crude oil is usually much bigger than that of water,flow resistance to oil-water two phase flow comes mainly from oil phase.Therefore,the effect of streaming potential on oil-water displacement is rater limited.