Non‐Fickian dispersion in porous media: 1. Multiscale measurements using single‐well injection withdrawal tracer tests

[1] We present a set of single-well injection withdrawal tracer tests in a paleoreef porous reservoir displaying important small-scale heterogeneity. An improved dual-packer probe was designed to perform dirac-like tracer injection and accurate downhole automatic measurements of the tracer concentration during the recovery phase. By flushing the tracer, at constant flow rate, for increasing time duration, we can probe distinctly different reservoir volumes and test the multiscale predictability of the (non-Fickian) dispersion models. First we describe the characteristics, from microscale to meter scale, of the reservoir rock. Second, the specificity of the tracer test setup and the results obtained using two different tracers and measurement methods (salinity-conductivity and fluorescent dye–optical measurement, respectively) are presented. All the tracer tests display strongly tailed breakthrough curves (BTC) consistent with diffusion in immobile regions. Conductivity results, measured over 3 orders of magnitude only, could have been easily interpreted by the conventional mobile-immobile (MIM) diffusive mass transfer model of asymptotic log-log slope of −2. However, the fluorescent dye sensor, which allows exploring much lower concentration values, shows that a change in the log-log slope occurs at larger time with an asymptotic value of −1.5, corresponding to the double-porosity model. These results suggest that the conventional, one-slope MIM transfer rate model is too simplistic to account for the real multiscale heterogeneity of the diffusion-dominant fraction of the reservoir.

[1]  P. Cloetens,et al.  Permeability assessment by 3D interdendritic flow simulations on microtomography mappings of Al–Cu alloys , 2005 .

[2]  D. P. Hartmann.  Measurement and analysis. , 1988 .

[3]  L. Gelhar,et al.  Field study of dispersion in a heterogeneous aquifer: 2. Spatial moments analysis , 1992 .

[4]  Philippe Gouze,et al.  WTFM, software for well test analysis in fractured media combining fractional flow with double porosity and leakance approaches , 2004, Comput. Geosci..

[5]  Olivier Bour,et al.  Characterization of the velocity field organization in heterogeneous media by conditional correlation , 2006 .

[6]  X. Sanchez‐Vila,et al.  On matrix diffusion: formulations, solution methods and qualitative effects , 1998 .

[7]  Sean Andrew McKenna,et al.  On the late‐time behavior of tracer test breakthrough curves , 2000 .

[8]  S. Gorelick,et al.  Multiple‐Rate Mass Transfer for Modeling Diffusion and Surface Reactions in Media with Pore‐Scale Heterogeneity , 1995 .

[9]  E. Simpson,et al.  Laboratory evidence of the scale effect in dispersion of solutes in porous media , 1987 .

[10]  C. Noiriel,et al.  Hydraulic Properties and Microgeometry Evolution Accompanying Limestone Dissolution by Acidic Water , 2005 .

[11]  Philippe Gouze,et al.  Non‐Fickian dispersion in porous media: 2. Model validation from measurements at different scales , 2008 .

[12]  M. Dentz,et al.  Transport behavior of a passive solute in continuous time random walks and multirate mass transfer , 2003 .

[13]  Brian Berkowitz,et al.  Anomalous transport in laboratory‐scale, heterogeneous porous media , 2000 .

[14]  Y. Tsang,et al.  Study of alternative tracer tests in characterizing transport in fractured rocks , 1995 .

[15]  Rina Schumer,et al.  Fractional Dispersion, Lévy Motion, and the MADE Tracer Tests , 2001 .

[16]  Richard L. Beauheim,et al.  Tracer tests in a fractured dolomite: 1. Experimental design and observed tracer recoveries , 2001 .

[17]  Ralf Metzler,et al.  Physical pictures of transport in heterogeneous media: Advection‐dispersion, random‐walk, and fractional derivative formulations , 2002, cond-mat/0202327.

[18]  P. Callaghan,et al.  Reversible and irreversible dispersion in a porous medium , 2003 .

[19]  Lorene M Nelson,et al.  Measurement and Analysis , 2004 .

[20]  Rina Schumer,et al.  Fractal mobile/immobile solute transport , 2003 .

[21]  K. H. Coats,et al.  Dead-End Pore Volume and Dispersion in Porous Media , 1964 .

[22]  M. A. Collins,et al.  General Analysis of Longitudinal Dispersion in Nonuniform Flow , 1971 .

[23]  L. Pomar,et al.  Reservoir-scale heterogeneity in depositional packages and diagenetic patterns on a reef-rimmed platform, upper Miocene, Mallorca, Spain , 1999 .

[24]  Allen M. Shapiro,et al.  Interpreting tracer breakthrough tailing from different forced‐gradient tracer experiment configurations in fractured bedrock , 2002 .

[25]  P. Gouze,et al.  Density contrast effects on tracer dispersion in variable aperture fractures , 2005 .

[26]  Ivars Neretnieks,et al.  The Channel Network Model—A Tool for Transport Simulations in Fractured Media , 1999 .

[27]  Sean Andrew McKenna,et al.  Tracer tests in a fractured dolomite: 2. Analysis of mass transfer in single‐well injection‐withdrawal tests , 1999 .

[28]  B. Berkowitz,et al.  Measurement and analysis of non-Fickian dispersion in heterogeneous porous media. , 2003, Journal of contaminant hydrology.