Badania anomalii sejsmicznych w strefach pionowej migracji gazu
Abstract
INVESTIGATIONS OF SEISMIC ANOMALIES IN THE AREAS OF VERTICAL GAS MIGRATION
Summary
Direct seismic survey and surface geochemical investigation play an important role in prospecting for oil and gas. As a result of hydrocarbons diffusing from a deposit to the surface (England & Fleet, 1991), the anomalous wave field is observed over some hydrocarbon deposits (Van den Bark & Thomas, 1980) what is confirmed by surface geochemical anomalies. Hence, hydrocarbon leakage zones identified on seismic sections and correlated with surface geochemical anomalies may be an additional indicator of hydrocarbon deposit. This research problem was considered during prospecting for hydrocarbon deposits in the Palaeozoic (Carboniferous and Devonian) formations on the West Pomerania (NW Poland). The Mesozoic and Zechstein reflecting horizons were exactly located by seismic survey made by Geophysical Company Zaklad Geofizyka - Toruń. The sub-Zechstein reflections were observed occasionally (Pietsch et aI., 1995a). Therefore detecting seismic anomalies caused by the vertical gas diffusion might help located hydrocarbon accumulation. The main goal of completed modelling study is to find whether seismic anomalies related to the vertical gas migration might be generated on the territory of West Pomerania. The first stage of investigation included the studies of velocity changes with different gas saturating ratios. At the second stage the possibility of the anomalous wave field generation was estimated by means of the theoretical modelling. The correctness of the proposed approach was tested by interpreting seismic data and correlating seismic anomalies with geochemical anomalies.
Summary
Direct seismic survey and surface geochemical investigation play an important role in prospecting for oil and gas. As a result of hydrocarbons diffusing from a deposit to the surface (England & Fleet, 1991), the anomalous wave field is observed over some hydrocarbon deposits (Van den Bark & Thomas, 1980) what is confirmed by surface geochemical anomalies. Hence, hydrocarbon leakage zones identified on seismic sections and correlated with surface geochemical anomalies may be an additional indicator of hydrocarbon deposit. This research problem was considered during prospecting for hydrocarbon deposits in the Palaeozoic (Carboniferous and Devonian) formations on the West Pomerania (NW Poland). The Mesozoic and Zechstein reflecting horizons were exactly located by seismic survey made by Geophysical Company Zaklad Geofizyka - Toruń. The sub-Zechstein reflections were observed occasionally (Pietsch et aI., 1995a). Therefore detecting seismic anomalies caused by the vertical gas diffusion might help located hydrocarbon accumulation. The main goal of completed modelling study is to find whether seismic anomalies related to the vertical gas migration might be generated on the territory of West Pomerania. The first stage of investigation included the studies of velocity changes with different gas saturating ratios. At the second stage the possibility of the anomalous wave field generation was estimated by means of the theoretical modelling. The correctness of the proposed approach was tested by interpreting seismic data and correlating seismic anomalies with geochemical anomalies.