Measurements of Streaming Potential for Downhole Monitoring in Intelligent Wells: SPE Middle East Oil and Gas Show and Conference

Abstract Downhole monitoring of streaming potential, using electrodes mounted on the outside of insulated casing, is a promising new technology for monitoring water encroachment towards an intelligent well.  However, there are still significant uncertainties associated with the interpretation of the measurements, particularly concerning the streaming potential coupling coefficient.  This is a key petrophysical property which dictates the magnitude of the streaming potential for a given fluid potential.  The coupling coefficient can be measured experimentally, but previous studies have obtained data for sandstone cores saturated with relatively low salinity brine (less than seawater).  Formation and injected brine in hydrocarbon reservoirs is typically more saline than this.  Extrapolating data obtained at low salinity into the high salinity domain suggests that the coupling coefficient falls to zero at approximately seawater salinity.  If this is the case, then streaming potential signals will be very small in most hydrocarbon reservoirs. We present the first measured values of streaming potential coupling coefficient in sandstone cores saturated with brine at higher than seawater salinity.  We find that the coupling coefficient is small, but still measurable, even when the brine salinity approaches the saturated concentration limit.  Consistent results are obtained from two independent experimental set-ups, using specially designed electrodes and paired pumping experiments to eliminate spurious electrical potentials. We apply the new experimental data in a numerical model to predict the streaming potential signal which would be measured at a well during production.  The results suggest that measured signals should be resolvable above background noise in most hydrocarbon reservoirs, and that water encroaching on a well could be monitored while it is several tens to hundreds of metres away. Introduction Permanently installed downhole sensors are increasingly being deployed to provide reservoir data during production.  These data help reduce uncertainty in the reservoir description, and contribute to reservoir management decisions (e.g. Laurence and Brown, 2000; Tolan et al., 2001; Manin, 2002; Brown et al., 2003, 2004; Bui and Jalali, 2004; Kragas et al., 2003, 2004; Silva and Kato, 2004; Webster et al., 2004).  In wells equipped with inflow control valves, it is possible to develop a feedback loop between measurement and control to optimize production (e.g. Nyhavn et al., 2000; Addiego-Guevara et al., 2008).  Wells equipped with downhole sensors and control valves are often described as ‘intelligent' or ‘smart' (e.g. Robison, 1997; Glandt, 2005) and it is widely recognized that they have the potential to significantly enhance production (e.g. Robison, 1997; Rester et al., 1999; Storer et al., 1999; Nyhavn et al., 2000; Lie and Wallace, 2000; Armstrong and Jackson, 2001; Tolan et al., 2001).