Streaming Potential in Porous Media - Single and Two-Phase

Master's thesis in Petroleum engineeringThe streaming potential method is a promising method to measure how surface potential change when different fluids are injected into a rock. The understanding of how and why the surface potential changes can give important information about the transport of oil and water, and which brines to use in a water flood to improve the oil recovery. The interpretation of streaming potential measurements are straightforward for single-phase flow in homogenous, porous rocks. In the presence of oil, the interpretation is much more complicated. Recent experimental studies claim that a change in the streaming potential is independent of saturation, and only indicates wettability change, while simple analytical models predict a correlation between fluid saturations and streaming potential. In this thesis, appropriate theory for the interpretation of streaming potential measurements are first presented. Further, the well-known Helmholtz-Smoluchowski equation for single phase streaming potential, in addition to simple analytical models of two-phase streaming potential developed by Sherwood (2007) are derived from first principles. The two-phase models are analysed and discussed in order to investigate the effects of an oil phase on the measured streaming potential. The results of the analysis indicate that the total streaming potential in a water-oil system most likely represents a combination of effects arising from wettability and movement of charged- and uncharged oil particles. The total effect is highly dependent on the interface properties at the particle surface