Petrogenic Gas
Petrogenic Gas: In geology, petrogenic gas refers to natural gas that is the byproduct of the thermal decomposition of biological and organic matter. In fact, this is the same process that results in the geological formation of petroleum underground. For instance, methane soil gas hazards in Los Angeles Methane Zones are typically resulting from underlying pockets of petroleum and near-surface tar pits. Alternatively, natural gas can be biogenic gas, meaning the gas forms by the microbial decomposition of buried organic materials.