Development and Application of New Downhole Technology To Detect Water Encroachment Toward Intelligent Wells

Abstract Electrokinetic potentials are generated when fluids flow through rock. We have investigated whether changes measured in electrokinetic potential using permanently installed downhole electrodes could be used to detect water encroachment towards intelligent oil wells. Downhole electrodes in cemented arrays have been successfully utilized in resistivity measurements, but have not previously been used to measure electrokinetic potential. One reason is that it has not been possible to relate changes in potential with changes in saturation. We have reviewed the existing literature and conducted laboratory experiments to determine how the electrokinetic potential varies with water saturation, brine salinity and other key reservoir parameters. We have used the results to simulate numerically the electrokinetic potential response measured at a well during oil production. Preliminary results suggest that encroaching water causes changes in the measured electrokinetic potential which could be resolved above background electrical noise; indeed, water could be detected several 10's to 100's of meters from the well. We have also investigated the optimum response of an intelligent well equipped with downhole inflow control valves. In a simple, conceptual reservoir model, production is significantly enhanced if encroaching water is detected before it arrives and flow into the wellbore is properly controlled. Our findings raise the novel prospect of an oil field in which the wells can detect the approach of water and respond appropriately. Such wells offer enormous potential economic and environmental benefits, particularly in fields which are difficult to access or dangerous to operate.