Hydrology of an Evaporite Aquitard Permian Evaporite

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Date

1984

Authors

Kreitler, Charles W.
Fisher, R. Stephen
Senger, Rainer K.

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Abstract

Permian evaporite strata of the Palo Duro Basin, Texas Panhandle, are considered to have low permeabilities but are capable of some leakage. Cross-sectional and areal modeling of regional groundwater flow in the Palo Duro Basin indicates leakage from the Upper aquifer through the Evaporite aquitard that contributes approximately 30 percent of the water in the underlying Deep-Basin Brine aquifer. The regional estimate of permeability of the aquitard (~ 10^-4 md) is in general agreement with laboratory testing of salt permeability. Oxygen and hydrogen isotopic composition and the Cl/Br ratio of the deep-basin brines also suggest leakage through the aquitard. Isotopically non-equilibrated meteoric waters are found to depths of 8,000 ft.

Leakage through the aquitard may occur as either matrix or fracture flow. According to petrographic and geochemical studies of the evaporite strata, halite dissolution and minor recrystallization occurred predominantly during Permian time. Post-Permian waters may have altered the top of the Evaporite aquitard. Fracturing is prevalent in the rock strata in the basin; the greatest density of fracturing occurs in areas with tectonic deformation. The potential for leakage may be greatest in these areas.

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