Home – Home – Jornals – Russian Geology and Geophysics 2021 number 8

We substantiate certain ideas concerning the key role of fluid-geodynamic processes in the evolvement of hydrocarbon accumulations at great depths in the Earth’s crust. The presented geodynamic model of oil and gas accumulation is based on updated ideas of the structure of the Earth’s tectosphere, which includes plate, preplate, and folded complexes. The model makes clearer the spatial scale of the organic-matter transformation into hydrocarbons of the oil series. In the bottom layers of the Earth’s crust, we predict the existence of a special stagnation type of water drive systems with the following distinguishing features: (a) different scales of manifestation, from local to regional; (b) a limited water exchange with the external environment; (c) the absence of persistent drainage horizons (beds and interbeds); (d) alignment of hydrodynamic potentials in terms of depths and laterals; (e) certain growth in the role of lithohydrochemical and organic chemical factors in the development of the void space of the fluid-host medium. In their inner space, systems with difficult water exchange can control the evolvement and preservation of autoclave hydrocarbon systems for a long time, the key feature of the autoclave systems being spatial coincidence (localization) of the processes of oil and gas generation and accumulation. We assume that in the settings of all-round compression, hydrodynamic instability, and no drainage, the position of productive zones must be controlled by foci of low pore (reservoir) pressures rather than local hypsometric highs. We present results of the prediction for the development of water drive stagnation systems in the subsalt deposits of the Caspian depression. A prediction for reservoir pressures was made for the sedimentary cover at great (and supergreat) depths. It can be regarded as a necessary component of prediction of oil and gas potential because it makes it possible to delineate new (previously unknown) commercial zones of hydrocarbon accumulation.