Hydrocarbon Analysis
Soil samples were collected along three lines for thermal desorption and analysis of hydrocarbons to test for a surface expression of the Glodes Corner Field. The Trenton Black River Gas anomaly associated with the field is dominated by methane and ethane with minor contributions of propane, butane, and pentane, and it is similar to that of the reservoir gas, which consists of greater than 98% methane with only traces of the heavier hydrocarbons (Fig. 1). Soil gas hydrocarbon anomalies are spatially associated with existing gas production, and these anomalies conform to a sag feature (shaded area) that is evident on seismic profiles (Fig. 2).
Redox Potential and Trace Elements
The redox potential of the near-surface environment can also serve as pathfinder to hydrocarbon microseepage and buried reservoirs. In the case of Glodes Corner, for instance, there is a higher concentration of CO2 relative to O2 over the east part of the field suggesting more reducing conditions (Fig. 3). This reduced environment probably reflects the oxidation of more hydrocarbon microseepage in this area relative to the west part of the field. The reason(s) for the change in redox potential over the field is unclear, but it could be related to fluid migration in the sub-surface. If hydrocarbons migrated into the dolomite breccia reservoir from the east, then more vertical hydrocarbon migration from this part of the reservoir might be expected. More information about the reservoir is currently being obtained to constrain this hypothesis.
The soil samples were also analyzed for 23 elements by ICP-OES analysis. Many transition elements (e.g., Vanadium) show a spatial association with the Glodes Corner Field (Fig. 4).
Figure 1.
Figure 2.
Figure 3.
Figure 4.
