SHALLOW GEOPHYSICS PROJECT WITHIN THE WASATCH FORMATION TO DETERMINE THE FEASIBILITY OF MINING URANIUM DEPOSITS BY IN SITU METHODS

The Eocene Wasatch Formation is composed of well lithified sandstones and interbedded mudstones. In-situ leaching of uranium in sedimentary rocks requires seals above and below the host ore deposit, which can maintain a minimum of 45 psi pressure during production. Locating the water table (100 feet above the ore body is a minimum) within a sandstone/mudstone sequence can determine if an ore body can be economically mined. Uranium companies drill holes to achieve this, which is expensive and does not give a continuous line of data. We are testing if improved shallow geophysical technologies can quickly and cheaply locate the water table and verify if in-situ leaching is feasible.

Using electrical resistivity (ER) and ground penetrating radar (GPR) we test the capability of each technique in locating ore host reservoirs (sandstones), seals (mudstones), and water tables within the sequence. An AGI SuperSting R8/IP/S/WIFI instrument was used to test ER with a 275m linear array of electrodes, at 3.6s intervals. GPR data was collected along the same transit using a Noggin 100 MHz instrument.

Four uranium test holes with Gamma Ray, Resistivity, and SP well logs are located along the project line to be used as controls for geophysical accuracy. Geologic log cross sections are compared to geophysical interpretations. Uranium mineralization is indicated at roll front boundaries in several of the well sites.

Preliminary results indicate good lithologic identification to 50 meters depth using ER. GPR results are still pending further processing. Data from this project will be compared to previous ER and GPR surveys from Quaternary gravel/boulder unconsolidated deposits overlying the Cody Shale along the North Platte River.

Further research will focus on improving data acquisition by adjusting field parameters, improving processing, and possible additional instruments, such as magnetometers and gravimeters. Instruments and funding for this research were supported by WyCEHG and EPSCoR at University of Wyoming in partnership with Casper College. Thanks to Stakeholder Energy and Allemand Ranch for well data and surface access.