Macrodispersion in sand-shale sequences

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Water Resources Research; (USA)

DOI:https://doi.org/10.1029/WR026i001p00153· OSTI ID:6797316

Desbarats, A J ^[1]

---

1. Geological Survey of Canada, Ottawa, Ontario (Canada)

Macrodispersion in sand-shale sequences is investigated by a series of numerical tracer tests. Hydraulic conductivity is modeled as a binary, spatially correlated random function. Realizations of the random conductivity field are simulated on a nodal grid discretizing the heterogeneous formation. Corresponding realizations of the random velocity field are obtained by solving the equation for saturated steady state flow. Particle tracking, with flux-weighted tracer injection and detection, is used to generate experimental residence time distributions (RTDs). Moments of the RTD are used to characterize longitudinal tracer spreading. Results show that macrodispersive transport in sand-shale sequences cannot be represented by a Fickian model. RTDs display a bimodal structural caused by the fast arrival of particles traveling along preferential sandstone and shale. The relative importance of channeling and tortuous flow transport mechanisms is determined by sand-shale conductivity contrast, shale volume fraction, and conductivity spatial correlation structure. Channeling is promoted by high conductivity contrasts, low shale fractions, and flow parallel to bedding in anisotropic media. Low contrasts, high shale fractions, and flow perpendicular to bedding act to break up channels and to enhance tracer spreading.

• OSTI ID: 6797316
• Journal Information: Water Resources Research; (USA), Journal Name: Water Resources Research; (USA) Vol. 26:1; ISSN 0043-1397; ISSN WRERA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
FLOW MODELS
FLUID FLOW
FLUID MECHANICS
GROUND WATER
HYDRAULIC CONDUCTIVITY
HYDROGEN COMPOUNDS
HYDROLOGY
ISOTOPE APPLICATIONS
MATHEMATICAL MODELS
MECHANICS
OXYGEN COMPOUNDS
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SHALES
TRACER TECHNIQUES
WATER