Investigation of the effects of in situ chemical oxidation on the electrical and diffusive transport properties of porous fractured rock.
University of New Brunswick
Two sets of diffusion-reaction experiments were conducted to: 1) to investigate the reaction mechanisms of the oxidation of naturally occurring reductants by permanganate during In-Situ Chemical Oxidation (ISCO) in porous fractured rock and 2) to study the effects ISCO has on the electrical and transport properties of the rock. The first set of experiments was carried out on black shale samples that were soaked in permanganate solution for up to 24 months. Results of SEM and (S)TEM image analysis suggest that permanganate can react with pyrite present in the rock in a two-step reaction process that is first transport limited, with permanganate diffusion and reaction with organic carbon and reduced mineral particles in pores to form MnOx(s), then electronically driven as permanganate oxidizes the mineral grains via solid state electron transfer through the MnOx(s) network in the pores. The second set of diffusion-reaction experiments was carried out on sandstone samples that were treated alternately with dextrose and permanganate with the goal of producing MnOx(s) inside pores of the matrix. The bulk resistivity values of the samples were monitored over the course of the treatment, and the porosity and pore diffusion coefficients of the treated sandstone samples measured. There was an overall decrease in resistivity and an increase in pore diffusion coefficients for treated sandstone samples compared to untreated samples. These observations are consistent with a decrease in tortuosity of the treated samples. Tortuosity factors Ꞇfd and Ꞇfe changed by factors of 2.1 to 2.6 times for samples treated with permanganate compared to untreated samples. The decrease in tortuosity could be the result of oxidation of small reduced particles such as organic carbon in the pore throats of the treated rock.