HR: 1340h
AN: MR33A-0148    [Abstracts]
TI: Downhole Measurements of Electrokinetic Potential to Monitor Flow in Oilfields
AU: * Saunders, J
EM: j.saunders@imperial.ac.uk
AF: Imperial College London, Department of Earth Science and Engineering Exhibition Road, London, SW7 2AZ United Kingdom
AU: Jackson, M
EM: m.d.jackson@imperial.ac.uk
AF: Imperial College London, Department of Earth Science and Engineering Exhibition Road, London, SW7 2AZ United Kingdom
AU: Pain, C
EM: c.pain@imperial.ac.uk
AF: Imperial College London, Department of Earth Science and Engineering Exhibition Road, London, SW7 2AZ United Kingdom
AU: Addiego-Guevara, E
EM: ernesto.addiego-guevara@imperial.ac.uk
AF: Imperial College London, Department of Earth Science and Engineering Exhibition Road, London, SW7 2AZ United Kingdom
AB: Oil companies currently produce an average of three barrels of water for each barrel of oil, which is expensive and environmentally unfriendly: the produced water is contaminated and must be treated and disposed of carefully. Ideally, water production would be prevented or minimised by monitoring its movement within the reservoir and responding appropriately. We suggest that measurements of electrokinetic (or ' streaming') potential during oil production, using permanently installed downhole electrodes, could be used to monitor water encroachment towards a well before water breakthrough occurs. Electrokinetic potentials are generated when fluids flow through rock, and although they are increasingly being used in other areas of earth science to monitor subsurface flows, there has been little investigation of their utility in hydrocarbon reservoirs. We have used a new numerical model to simulate the electrokinetic potential measured at a well during oil production, with reservoir pressure maintained by water injection or aquifer influx. Our results suggest that encroaching water causes changes in the electrokinetic potential at the well which could be resolved above background electrical noise; indeed, water approaching the well could be monitored several 10s to 100s of metres away. Our results differ from those obtained previously, because we include the results of recent laboratory experiments which provide new insight into the nature of the coupling between fluid and electrokinetic potentials as the oil saturation changes. Moreover, we investigate a range of production rates which are more appropriate for modern offshore developments, and simulate the potential measured at electrodes installed at the producing well rather than at a nearby monitoring well or at the surface. Electrodes mounted downhole on insulated casing have been successfully applied in subsurface resistivity surveys during oil production, and similar technology could be used to measure electrokinetic potential. If the producing well is equipped with downhole inflow control valves (so called ' intelligent' well technology), then oil production can be significantly enhanced if encroaching water is detected before it arrives and flow into the wellbore properly controlled. These findings raise the prospect of an oil field in which the wells can monitor 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.
DE: 0545 Modeling (4255)
DE: 0915 Downhole methods
DE: 0925 Magnetic and electrical methods (5109)
DE: 3914 Electrical properties
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005