Glossary

apical - the type of anomaly that occurs in a one to one relationship with the reservoir. Hydrocarbons and Eh anomalies are examples.

biogenic - hydrocarbons, primarily methane, derived from biological processes.

conductivity - a measure of the total ion content. The ions present represent the halogen, carbonates, sulfates, or inorganic compounds found in the soil at specific sample locations.

Eh - a measure of the reduction/oxidation potential. Low values occur over the potential reservoir.

halo - the type of anomaly that occurs towards the edge of the reservoir, outside of the anomaly, or forms a circular pattern around an apical anomaly. pH and conductivity are examples.

headspace - the volume between the top of the sample and the top of the sample container where the hydrocarbon sample is collected.

indirect - geochemical methods that do not directly detect hydrocarbons but are a measurement of alteration phenomena associated with hydrocarbon micro seepage.

normalization - a method by which multiple surveys are brought together under a single mean or average value.

occluded - hydrocarbons trapped within the carbonate matrix. These hydrocarbons are released upon acidization.

pH - a measure of soil alkalinity. High values occur beyond the edge of hydrocarbon anomalies and can be made up of carbonates, sulfates, or halogens. These high areas indicate the beginning of the non-productive areas.

Pixler Intercept - the intercept of the line that connects the C₁/C₂, C₁/C₃, C₁/C₄, and C₁/C₅ ratios of the Pixler Plot. The productive window is from 1.5 to 3.0.

Pixler Plot - a graphical representation of the C₁/C₂, C₁/C₃, C₁/C₄, and C₁/C₅ ratios. This plot is used to determine the presence of gas or oil as well as help isolate samples in the non-productive ranges.

Pixler Slope - the slope of the line that connects the C₁/C₂, C₁/C₃, C₁/C₄, and C₁/C₅ ratios on the Pixler Plot. The productive window is from 0.5 to 1.0.

residual methane - the difference between the estimated methane value and the measured methane values.

saturated hydrocarbons - contains only the elements carbon and hydrogen and have all single bonds.

thermogenic - hydrocarbons from the reservoir which have been derived from geologic processes.

unsaturated hydrocarbons - a hydrocarbon containing less than four single bonds.