Geochemical Investigations in the Michigan Basin: Vernon Field and Springdale
James R. Wood1 and David Seneshen2
1 Michigan Technological University, Houghton, MI
2 Direct Geochemical, Golden, CO
Two case studies were conducted in the Michigan Basin during the time period 1998-2005 to test the efficiency of surface geochemistry in reducing exploration risk. These studies were sponsored by the DOE Class Revisit Program and were conducted at Vernon Field in Isabella County and in Springfield Township in Manistee County. In the Vernon study, microbial geochemical sampling was carried out on appropriately spaced grids prior to and after the demonstration drilling occurred. Most of these samples were send to GMT in Ochelata, OK for microbial processing. Weak microbial anomalies were detected that proved non-commercial. An expanded sampling program was then conducted over the entire Vernon Field and the surrounding area to determine to what extent the field had been depleted and whether any further drilling should be contemplated. Results from over 1100 gridded samples revealed that a severe depletion halo existed over the entire field, with several bright spots, thought to be shallow (Stray ?) gas, on the margins of the field. At Springdale, a different approach was taken in which shallow soil samples were taken over the proposed trajectory of a horizontal well and the absorbed soil gases were analyzed for light hydrocarbons (C1-C8+) from the fine-grained fraction by Direct Geochemical in Golden, CO. These data were then compared with the light hydrocarbon data (C1-C4) collected during drilling by the mud logger. The subsurface gas data clearly delineates the productive intervals and work is in progress to see to what extent the surface data reflects those trends.