--> --> Comparison of Permeability Calculated from Geophysical Logs, Aquifer Tests, and Grain-Size Distribution at SAWS Aquifer Storage and Recovery Site, Bexar County, Texas

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Comparison of Permeability Calculated from Geophysical Logs, Aquifer Tests, and Grain-Size Distribution at SAWS Aquifer Storage and Recovery Site, Bexar County, Texas

Abstract

San Antonio Water System (SAWS) operates an Aquifer Storage and Recovery (ASR) facility that is developed within an interval of a “massive sand” of the Carrizo formation on a 3000 acre site in southern Bexar County, Texas. Spatial variations in permeability reflect heterogeneity in physical properties that could affect the injection, movement, storage, and recovery of water at the site.

Several independent estimates of permeability at various wells were made from nuclear magnetic resonance (NMR), resistivity, and porosity well logs. Estimates of permeability from well tests and from Kozeny-Carman equation calculations, which used grain-size distribution data from partial core recovery, provide a comparison to the geophysical log interpretations. Permeability estimates are distributed into a layered 3D geocellular grid using geostatistical methods.