Tectonic Control on Fluid Dynamics and Efficiency of Gas Surveys in Different Tectonic Settings

For the Caspian Sea region an analysis is given of the relationship between gas field parameters for the near-surface lithospheric layer, hydrosphere and surface atmosphere. Strong distinctions were established between mobile, highly dislocated, folded regions and tectonically stable ancient cratons, linked through tectonic control on the intensity and distance of subvertical migration of gases. Tectonic control becomes evident in studying the efficiency of near-surface (1-2 m) gas surveys - about 80% in folded regions and about 60% within ancient cratons. The efficiency of gas surveys in cratonic regions becomes comparable with that of near-surface (1-2 m) gas surveys in mobile folded regions only at depths greater than 50 m.