Identifying Surface Alterations Caused by Hydrocarbon Microseepages in the Patrick Draw Area of Southwest Wyoming, Using Image Spectroscopy and Hyperspectral Remote Sensing

Sarah Jacobson and Shuhab Khan
University of Houston, Houston, TX

The detection of underlying reservoirs using remote sensing had its inception with the identification of macroseeps at the surface. However, today we find ourselves relying on the detection of more subtle characteristics associated with underlying reservoirs, such as microseeps. Microseepages are the vertical movement of hydrocarbons from the reservoir to the surface through networks of fractures, faults and bedding planes, which provide permeable routes within the overlying rock. They express themselves in an array of near surface alterations, such as chemical or mineralogical changes in overlying sediments. The majority of these anomalies are found to be the result of long term leakage of hydrocarbons through microseeps, which set up near surface oxidation-reduction zones, initiating diagenetic Eh/pH controlled reactions. This influence on mineral stability and chemical reactivity can then be detected at the surface remotely. Using NASA's Hyperion hyperspectral imaging sensors, geochemical and ground truthing techniques, this project develops methodologies to identify and map alterations caused by hydrocarbon microseepages and to identify their relationships to the underlying geology in the Patrick Draw area of Southwest Wyoming. Relationships between identified alterations and microseepages are then confirmed using ICP, XRD as well as Carbon Isotope analysis of field samples. Patrick Draw consists of a stratigraphic trap affected by late Tertiary deformation that resulted in the formation of fractures and faults. Associated microseepages have been documented by Lang et al. (1985), Richers et al. (1982; 1986) and Scott et al. (1989), making it an ideal location to examine relationships between microseepages and hyperspectral data.