Streaming potentials at hydrocarbon reservoir conditions

We have examined the behavior of the streaming potential under multiphase conditions, and under conditions of varying temperature and salinity, to evaluate the feasibility of using downhole streaming-potential measurements to determine fluid distributions in a reservoir. Using new insights into the pore-scale distribution of fluids and of electric charge, we found that the saturation dependence of the streaming potential coupling coefficient is important in determining the resulting streaming potential. Through examination of the four independent physical parameters which comprise the coupling coefficient, we developed an understanding of the behavior of the coupling coefficient under conditions of elevated temperature and brine salinity. We found that although increasing salinity substantially reduces the magnitude of the coupling coefficient, and therefore also the magnitude of the predicted streaming potential, increasing temperature has only a small effect, showing about a 10% change between 25°C and 75°C, depending on salinity.