Modeling of the thermal-hydrodynamic and chemical regime of Geyser reservoir (Valley of Geyser, Kamchatka)

Abstract

The thermal-hydrodynamic and chemical eight-decade history of the Geysers production reservoir in the Valley of Geysers (Kamchatka) shows either linear multiyear trends, seasonal cycles, or stepwise changes synchronized with geological catastrophes. Recent changes, apparently caused by surface meteoric water inflow into the productive Geysers reservoir as a result of caprock erosion from the 2007 catastrophic landslide and 2014 mud-flow, include: (1) seasonality of deep component discharge, (2) a drop in CO2 fraction of the gas content of geysers followed by a decrease in geyser eruption capacity, (3) increases in standard geothermometers (Na/K and SiO2) and (4) increases in the sulfate component. 2D numerical thermal-hydrodynamic (TH) model was developed and applied to explain the seasonal decrease in deep component discharge as an effect of gas phase condensation and upflows capture caused by cold water infiltration from the surface during flood periods. Thermo-hydrodynamic-chemical (THC) models and total chemical discharge/recharge balances were used to explain CO2 sequestration, increased sulfate component, and increased standard geothermometers due to gypsum/calcite transformation in surface water infiltration pathways rather than reservoir heating.