HIGH-RESOLUTION SEISMIC STUDY IN THE GAS HILLS URANIUM DISTRICT, WYOMING

A study was undertaken to evaluate the effectiveness of the high-resolution seismic technique for the mapping of stratigraphic and structural controls in the Gas Hills uranium district, Wyoming. The test area is one in which uranium deposits are in Tertiary sediments which unconformably overlie a Mesozoic Paleozoic section. Paleochannels on the unconformity appear to control the localization of the uranium. Drilling in the area allows an evaluation of the effectiveness of the study. Using both sonic and density logs, we computed synthetic seismograms to evaluate the feasibility of predicting the success of the seismic reflection technique and to test this prediction using surface seismic methods. The field study was undertaken utilizing primarily two energy sources - a high-frequency vibrator (40-350 Hz), and one-pound dynamite charges shot in 10-ft holes. A limited amount of data was also acquired using detonating cord on the surface. Some three-dimensional (3-D) data were also acquired, and a later study acquired passive seismic data. The seismic reflection data were successful not only in delineating the unconformable surface and in mapping paleodrainages on the unconformity, but also in defining channel deposits within the Tertiary section. Correlation with the logs shows the success of the study. Several areas were delineated where one would undertake tight drilling patterns, and other areas were delineated in which one might minimize or eliminate exploratory drilling. The synthetic seismograms also could have predicted the success of the seismic work. © 1982 Society of Exploration Geophysicists.