The electrokinetic process is an emerging technology for in situ soil decontamination, in which chemical species, both ionic and nonionic are transported to an electrode site in soil. These products are subsequently removed from the ground via collection systems engineered for each specific application. Electrokinetics refer to movement of water, ions and charged particles relative to one another under the action of an applied direct current electric field. In a porous compact matrix of surface charged particles such as soil, the ion containing pore fluid may be made to flow to collection sites under the applied field.
The work presented here describes part of the effort undertaken to investigate electrokinetically enhanced transport of soil contaminants in synthetic systems. The results of the laboratory study presented here indicate that electrokinetic enhancement of contaminant transport in soils is a viable technology; development of this technology for wide range of applications hinges upon better understanding of the transient chemical and physical processes during application of current through soil/contaminant systems.
The probable relation between diffuse double-layer
processes and redox reactions that enhance degradation
or conversion of contaminants under an applied electric
field were examined in a clay medium. Kaolinite clay,
precontaminated with hexavalent chromium, was the test
soil medium. Analyte, containing ferrous iron, was
transported through the kaolinite clay using direct electric
current. The Cr(VI) reduction to Cr(III) was followed by
measuring the soil redox potential and pH at discrete locations
in the clay bed. The post-test distribution of Cr showed
significantly more Cr(III) than Cr(VI) at low to slightly acidic
pH distribution (2 < pH < 6) in clay. The stoichiometric
analyses of measured chromium and iron species
concentrations versus the measured redox potentials
were compared to Nernst equation predictions of an
equivalent aqueous system. An average of +0.37 V shift
was measured from the linear Nernstian prediction of cell
potential. The applied electric field appeared to provide
additional “cathodic current” to drive forth the redox reactions.
The redox potential shift was explained by possible
overpotential development at the clay−water interfaces
due to double-layer polarization under the applied field.
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AbstractAmong the leading emerging technologies for in-situ oil recovery is the use of an electrokinetic technology known as electrically enhanced oil recovery (EEOR TM ) i . Electrokinetic methods are continually tested and improved both in the laboratory and in the field to render them highly feasible for increased oil recovery. The effectiveness of the process to enhance the flow and production of both light and heavy crude oil from sandstone reservoirs have been demonstrated in the laboratory by researchers for the last four decades. Successful but limited field applications, both in-situ and ex-situ have also been reported for the same duration of time. There has been little work done on the applicability of the technology to carbonate rock reservoirs, owing to predicted high energy consumption due to low clay content formations and high salinity environments. Yet, compared to currently incurred high costs of conventional electrical oil recovery which depends on joule heating of the formation , electroosmotic mass transport may offer a feasible option to augment the flow of these large volumes of crude oil both onshore and offshore.A great additional incentive is that EEOR TM can be engineered as a truly green technology, where there is no water consumption, and no air, water, and formation pollution. The technology can be applied with no depth limitation in-situ rendering it even more attractive in remote operating locations as well as the environmentally challenging ones. This paper addresses the first attempt undertaken at the newly-established Electrokinetic Laboratory of the Petroleum Institute in Abu Dhabi, U.A.E. to determine the efficacy of electrokinetic technology in EEOR TM tested on field collected data samples of Abu Dhabi. The results of the initial tests conducted on field retrieved specimens of Abu Dhabi on-shore carbonate reservoir rock candidates from several formations in high salinity environments that contained various crude types are reported.
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