Applications of Streaming Potential Transient Tests to Electrokinetic Characterization of Oil Reservoirs

Abstract Electrokinetic techniques have proven to be a valuable tool in providing direct information on charge solid/liquid interface. Today, oil industrial companies are looking into electrokinetic techniques with great interest, in order to describe the oil reservoir physics occurring in and near the well bore during production. This paper introduces a new method, which uses streaming potential transient testing to characterize the electrokinetic properties of oil reservoirs. Streaming potential exists in the movement of part of electrical double layers from the charged pore surfaces when fluid flow is induced by an applied pressure gradient. A fully computerized high pressure and high temperature core holder device is utilized to simultaneously measure streaming potential and pressure transient tests. The time behavior of the transient steaming potential is identical to that of fluid pressure when laminar flow is maintained. The transient streaming potential data is a useful quantity for determining the electrokinetic (zeta) potential values produced at the reservoir rock/fluid interface, and is considered an important electrokinetic characteristic that can play a role in reservoir rock properties. In low conductivity liquids, such as petroleum fluids, the surface conduction of reservoir rocks will cause errors in streaming potential measurements and therefore any derived electrokinetic potentials are also affected. The latter is corrected by determining the total electric conductivity of reservoir rocks, including the surface conductivity. The compressibility of reservoir fluid has been shown to affect streaming potential measurements and the results of electrokinetic potentials. We believe that this work is an important addition to the hydraulic and electrokinetic characterizations of oil reservoirs.