Remote Detection of Anomalous Mineralogy Associated With Hydrocarbon Production, Lisbon Valley, Utah

Abstract

Examination of a variety of remotely sensed data and geochemistry suggest that specific diagenetic mineral assemblages within the Wingate Formation are closely associated with hydrocarbon production at Lisbon Valley, Utah. The Wingate Formation, exposed along the southwestern flank of the anticline has a relatively uniform composition and appearance over the entire Colorado Plateau, except at isolated localities such as Lisbon Valley, where it is locally bleached. Previous workers have suggested that hydrocarbon microseepage may account for the bleaching of the Wingate Sandstone and the presence of uranium mineralization in rocks overlying the reservoir at Lisbon Valley. Broad-band Landsat Multispectral Scanner (MSS) and airborne Thematic Mapper Simulator (TMS) data were used to map the bleached facies on the basis of brightness and lack of ferric iron. The TMS data provided further discrimination of bleached facies based on the relative abundances of clay minerals detectable with this sensor. Analysis of high-resolution airborne spectroradiometric data, thin sections, and x-ray diffraction data suggests that bleached rocks overlying the reseNoir at Lisbon Valley contain abundant kaolinite and minor amounts of feldspar. Unbleach­ed exposures contain substantially less clay and abundant feldspar. This study shows a correlation between the abun­dance of clay minerals, particularly kaolinite, and hydrocarbon production at Lisbon Valley. Because one of the principal mineralogical differences between the bleached and unbleached rocks is the relative abundance of clay minerals, and the TMS (and Landsat Thematic Mapper) data are very sensitive to clays, areas of potential hydrocarbon induced diagenetic alteration may be mapped using broad-band sensors.