Remote Sensing Mapping of Hydrocarbon-Induced Rock Alterations In Lisbon Valley, Utah

Long-term hydrocarbon microseepages develop diverse arrays of chemical and mineralogical changes in rocks and soils above petroleum reservoirs. Alterations that are reported to have affected the Wingate Sandstone in Lisbon Valley, Utah, include bleaching of redbeds, precipitation of high limonite and carbonate concentrations, anomalous weathering patterns, and high clay content. Using spectral reflectance, HyMap hyperspectral, and ASTER multispectral data new methodologies have been developed and different types of rock alterations have been identified and mapped through combinations of several remote sensing techniques: Band Ratio, Spectral Angle Mapper classification, Principal Component Analysis, and Gram-Schmidt Spectral Sharpening. Our results show the presence of the altered Wingate Sandstone in the southwest and northwest part of a Lisbon Valley anticline. Based on sandstone color alteration patterns three different zones were identified in the Wingate Sandstone: the southwest zone is the most altered, the middle part is unaltered, and the northwest part shows minor alteration. Spectral reflectance data were acquired from rock samples collected during the field work in Lisbon Valley. ASTER image was then used to detect, map and classify all altered areas, while HyMap has been used for detailed observation and comparison of altered and unaltered areas at the SW part of the anticline, as well as for creating mineral maps (for calcite, kaolinite, and hematite) based on the information gained from spectral reflectance data. All remote sensing results have been confirmed by field verification, but geochemical analyses are planned as well. Our future work will be based on creating the spectral library for rock alterations in the Lisbon Valley area. We also plan to develop and look at spectral indexes characteristic for rocks affected by leaking hydrocarbons. Methodology being developed in this work can provide new techniques for petroleum exploration, especially in remote regions of the world where field work is difficult.