IN SITU BIOGENIC GAS PRODUCTION WITHIN A LOW PERMEABILITY LENS

The production and emission of gasses in low permeability sediments has led to the substantial discharge of methane (CH4) into the atmosphere. Quantification of gas discharge rates from low permeability horizons is often made difficult due to the lithological influences contributing to the gasses spatial distribution. In a previous study conducted in Stillwater, Oklahoma it was demonstrated that the presence of a low permeability lens beneath a hillslope, may have contributed to the depression of the water table almost five meters from its normal range. Further preliminary observations conducted in a lake adjacent to the hillslope demonstrated that bubbles discharging from the lake were composed of methane. We hypothesize the depression of the water table is also the result of biogenic gas displacing water in the low permeability lens. In this study, we quantify the permeability of the clay and utilizing reactive and non-reactive gaseous tracers to evaluate near surface gas distribution and composition.