A Modeling Study of the Role of Hydrothermal Processes in the Formation of Production Reservoirs in Volcanogenic Rocks

The paper describes the role of hydrothermal fluid circulation in the creation of porous reservoirs bounded by low–permeability layers in volcanogenic rocks, which can accumulate fluids of different origin and phase conditions. The Rogozhnikovsky oil-bearing volcanogenic production reservoir in west Siberia, hosted in Triassic rhyolite tuffs and lavas, and the Mutnovsky high temperature geothermal reservoir hosted in recent rhyolites and andesites, are considered as benchmark examples. TOUGHREACT modeling scenarios show that formation of production reservoirs due to hydrothermal circulation may result from chemical fluid-rock interactions. The model shows short- term pressure drop conditions in the early stage of circulation (favorable for fluid migration into the reservoir), followed by reservoir self-sealing at the last stage of hydrothermal circulation (favorable for fluid trapping and formation of mineral resource deposits).