NGWA Event and Education Recordings Archive

The scarcity of water in arid and semi-arid regions has increased interest in sources of water much deeper than traditionally considered economic. Many projects have targeted fresh to brackish water sources at depths of 2000 to 5000 feet, with some projects looking deeper. In many formations the potential yield of a well varies based on stratigraphic changes in the unit and it is difficult to predict the potential yield of a given location without more information. The cost of drilling to such depths limits the availability of data and makes developing these resources risky and expensive.

Seismic reflection surveys are able to map fine scale stratigraphic details to depths of several thousand feet. Modern processing and interpretation techniques can identify permeable sand zones, faults, and other stratigraphic and structural features that control well yield. Unfortunately the cost to acquire high resolution seismic reflection data is relatively high, which has limited the application of the method for water supply applications. Fortunately many areas have existing reflection data from previous oil and gas exploration activities. This data can often be acquired for a few thousand dollars per mile and reinterpreted to map units that can potentially serve as aquifers.

These units are frequently shallower than the oil exploration units, so the surveys have not been optimized for the water exploration targets. In many cases the data quality is adequate to investigate the shallower units as it was originally processed. In some cases it is possible to obtain the original field data and reprocess the data to optimize shallower targets. Several case histories will be presented to demonstrate how modern interpretation methods can be used on older 2-dimensional or more modern 3-dimensional seismic reflection data to map features such as sand channels, faults, and shale pinch outs of aquifer units.