Technical Reports Document Library

In October, 2003, the Edwards Aquifer Authority engaged Frontera Exploration
Consultants, in particular Dr. Thomas E. Ewing its senior geoscientist, to interpret
licensed seismic data, integrate the data with available well control, and prepare a
structure map of the Edwards Aquifer in the Knippa Gap area of eastern and central
Uvalde County (Figure 1).

Better understanding of the ‘Knippa Gap’ constriction in the Edwards Aquifer,
and of flowpaths from western Uvalde County eastward towards Medina County, are a
high priority for Aquifer research. An important part of the constriction, lying south of
Old Sabinal Road near and east of the Frio River, has little well control. This area contains the apparent downdip limit of fresh water through the constriction, and is key to understanding flowpaths. Fortunately, a sparse network of 2D seismic reflection data was acquired by the oil and gas industry in and near this key area. Interpretation of this data, integrated with all available well and outcrop control, can yield a much more complete and more reliable intepretation of fault patterns and depths to the Edwards Group in the area.

The seismic reflection lines were acquired for deep exploration targets within the
Paleozoic Ouachita thrust belt. However, modern acquisition techniques provide enough
fold and coverage at shallow depths that the structural configuration of the aquifer can be
mapped.