Fluid flow monitoring in oil fields using downhole measurements of electrokinetic potential

Abstract

Downhole measurements of electrokinetic potential are a promising new technology for hydrocarbon reservoir monitoring. Using a 3D finite-element model combining both multiphase flow and electrokinetic components, we investigated the behavior of electrokinetic (streaming) potential during oil production in a range of reservoir environments. We found that streaming-potential signals originate at fluid fronts and at geologic boundaries where fluid saturation changes. As water encroaches on an oil production well, the streaming-potential signal associated with the water front encompasses the well even when the front is up to [Formula: see text] away, so the potential measured at the well starts to change significantly relative to a distant reference electrode. Variations in the geometry of the encroaching water front can becharacterized using an array of electrodes positioned along the well, but a good understanding of the local reservoir geology is required to identify signals caused by the front. The streaming potential measured at a well is maximized in low-permeability reservoirs produced at a high rate and in thick reservoirs with low shale content. However, considerable uncertainties remain, particularly relating to the nature of electrokinetic coupling at high salinity and during multiphase flow. Our results suggest that the streaming potential at low salinity [Formula: see text] is large [Formula: see text] but might become too small to resolve [Formula: see text] at high salinity [Formula: see text], depending on how the available data for the electrokinetic coupling at low salinity are extrapolated into the high-salinity domain. More work remains to determine the behavior of electrokinetic coupling and therefore the utility of this technique at high salinity.

Streaming potentials at hydrocarbon reservoir conditions

“…However, as pointed out by Saunders et al (2008), considerable uncertainties remain, particularly relating to the nature of the streaming-potential coupling coefficient in the high salinity and temperature conditions typical of hydrocarbon reservoirs, and during multiphase flow.…”

“…Recent numerical modeling work has suggested that measurements of streaming potential, acquired using electrodes permanently installed downhole, could be used to monitor water saturation changes in the vicinity of a well during oil or gas production (Saunders et al, 2006(Saunders et al, , 2008. The streaming potential is due to inflow of water to the reservoir as the hydrocarbons are extracted, either from an underlying aquifer or from water injection wells.…”

Measurement of Streaming Potential in Downhole Application: An Insight for Enhanced Oil Recovery Monitoring

“…Streaming potential measurement applying electrodes permanently installed downhole has been a promising reservoir-monitoring technology [5,6]. Jaafar et al (2009) have measured the streaming potential coupling coefficient in sandstones saturated with higher brine salinity and reported the values of streaming potential coupling coefficient changed with respect to rock texture or mineralogy, injected and formation brine salinity [7].…”

Electrokinetic Techniques for the Determination of Hydraulic Conductivity

“…However, inferring a firm link between SP intensity and water flux is still difficult. Recent modeling has shown that SP observations could detect at distance the propagation of a water front in a reservoir (Saunders et al, 2008). We distinguish 1) The steady-state and passive observations which consist in measuring the electrical self-potential (SP).…”