NGWA Event and Education Recordings Archive

Energy and water supply projects in the southwest are looking to deeper sources of water. Development of deep aquifers is often limited by the scarcity of data. Water quality can vary and permeable units such as channel sands or fracture zones are often limited to narrow zones that are hard to predict. Drilling is expensive and failures are costly. Surface geophysics can give you more subsurface information and improve your odds of putting your well where you really want it. 

Several electrical methods can image the structure of an aquifer and estimate water quality. Time Domain Electromagnetic Induction (TEM) and Magnetotellurics (MT) can image aquifers to depths of several thousand feet. Case histories will be presented that demonstrate how these methods can be used to map aquifers, find faults and fractures, and map saline water to depths of more than 3000 feet. 

Seismic reflection can be used to image geologic strata to depths of tens of thousands of feet. The attributes of the reflections can also be used to estimate the lithology of the units and detect facies changes within the aquifer. A case history will be presented where seismic reflection was used to map a sandstone aquifer at a depth of about 6000 feet and identified a facies change where the sandstone graded into a shale unit to pick drilling targets in permeable zones.

Gravity methods can be used to map deep geologic structures and are often used to map the basement of a groundwater basin or the depth to dense aquifer units such as carbonates. A case history will be presented where gravity measurements were used to map a carbonate aquifer in a complex structural basin where the depth to the aquifer varied from less than a thousand feet to more than 8000 feet over distances of a few miles.