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Article Dans Une Revue Journal of Applied Geophysics Année : 2017

Quantification of tracer plume transport parameters in 2D saturated porous media by cross-borehole ERT imaging

Résumé

Cross-borehole ERT imaging was tested to quantify the average velocity and transport parameters of tracer plumes in saturated porous media. Seven tracer tests were performed at different flow rates and monitored by either a vertical or horizontal dipole-dipole ERT sequence. These sequences were tested to reconstruct the shape and temporally follow the spread of the tracer plumes through a background regularization procedure. Data sets were inverted with the same inversion parameters and 2D model sections of resistivity ratios were converted to tracer concentrations. Both array types provided an accurate estimation of the average pore velocity vz. The total mass Mtot recovered was always overestimated by the horizontal dipole-dipole and underestimated by the vertical dipole-dipole. The vertical dipole-dipole was however reliable to quantify the longitudinal dispersivity λz, while the horizontal dipole-dipole returned better estimation for the transverse component λx. λ and Mtot were mainly influenced by the 2D distribution of the cumulated electrical sensitivity and the Shadow Effects induced by the third dimension. The size reduction of the edge of the plume was also related to the inability of the inversion process to reconstruct sharp resistivity contrasts at the interface. Smoothing was counterbalanced by a non-realistic rise of the ERT concentrations around the centre of mass returning overpredicted total masses. A sensitivity analysis on the cementation factor m and the porosity ϕ demonstrated that a change in one of these parameters by 8% involved non negligible variations by 30 and 40% of the dispersion coefficients and mass recovery.
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Dates et versions

hal-01517827 , version 1 (03-05-2017)

Identifiants

Citer

G. Lekmine, Harold Auradou, M. Pessel, J.L. Rayner. Quantification of tracer plume transport parameters in 2D saturated porous media by cross-borehole ERT imaging. Journal of Applied Geophysics, 2017, 139, pp.139:291-305 (IF 1,355). ⟨10.1016/j.jappgeo.2017.02.024⟩. ⟨hal-01517827⟩
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