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Miscible Displacement Measurements within Laboratory Columns Using the Gamma‐photoneutron Method

1970; Wiley; Volume: 34; Issue: 6 Linguagem: Inglês

10.2136/sssaj1970.03615995003400060014x

1435-0661

J.C. Corey, Richard H. Hawkins, R. F. Overman, R. E. Green,

Geothermal Energy Systems and Applications

Abstract When fluid in a porous medium is displaced by a second fluid that is miscible with the first, a transition zone exists between the two. The length and location of this transition zone in a soil column is difficult to measure in situ . When one of the fluids contains D 2 O as the major component, a new procedure, the gamma‐photoneutron method, readily measures this transition zone. This method permits precise measurements of the average concentration of heavy water (D 2 O) at selected locations in a soil column. The utility of the method is illustrated by two experiments; the downward displacement of D 2 O (specific gravity of 1.105 g/cm 3 ) by H 2 O, and the downward displacement of H 2 O by D 2 O + NaNO 3 (specific gravity of 1.291 g/cm 3 ). The mathematical model which describes the shape of the transition zone between the miscible fluids requires the apparent diffusion coefficients to be constant. The experiment showed the apparent diffusion coefficient was not constant as the zone moved through a 100‐cm column. Unstable flow due to viscosity differences between fluids was probably responsible for increases in the apparent diffusion coefficient when H 2 O displaced D 2 O.