oa Surface Geochemistry of Gas and Volatile Compounds above an Oil & Gas Field as Baseline Monitoring Tool for CO2 Storage

Surface geochemistry has been used in Janovice oil & gas field in NE Czech Republic aiming at providing a set of monitoring patterns, which may serve as a baseline for future monitoring of the pilot CO2 geological storage. Soil probes from the area of interest were sampled and analyzed. The probes were taken from the soil depth of 80 cm using a regular grid of 11 x 11 monitoring points with a 50 m step. The results are evaluated and presented as contour-line maps. Adsorbed volatile compounds are compared with the light hydrocarbons of the wet gas in the accumulation. The differences are attributed to the migration and in shallow subsurface alterations including biodegradation. The isotopic composition of hydrocarbons and carbon dioxide suggests further aspects, such as thermal maturity of petroleum compounds, potential source rocks in respect to the reservoir rocks. The elevated contents of higher hydrocarbon gases coincide with lower oxygen content in soil. Aromatic hydrocarbons show elevated values in similar locations to the maxima of saturated hydrocarbons. The CO2 anomaly will serve as a baseline pattern for future monitoring of CO2 storage in the abandoned wet gas field.