Estimated Effect of the Exploitation Induced Infiltration in the Pauzhetsky and Mutnovsky Geothermal Fields, Kamchatka, Russia

Abstract

A three-dimensional numerical model of the Pauzhetsky geothermal field has been developed based on a conceptual hydrogeological model of the system (Kiryukhin et al, 2008). The model is calibrated, combining natural-state and 1960–2006 exploitation data. Heat and mass balances derived from the calibrated model helped identify the sources of the geothermal reserves in the field. With the addition of five makeup wells, simulation forecasts for the the period 2007–2032 a sustainable average steam production of 29 kg/s, which is sufficient to maintain the generation of 6.8 MWe at the Pauzhetsky power plant. Nevertheless, significant inflow of the meteoric waters in Pauzhetsky accounted for 30% of the total withdrawal of the fluids and was found to be occuring not only in areas of the former hot springs discharge, but mostly in areas of the abandoned wells, where no natural discharge was observed before exploitation started. This leads to the conclusion that some of these poorly cemented abandoned wells may conduct infiltrated meteoric water into the reservoir, cooling production zones and negatively impacting production parameters. Re-modeling scenarios were conducted under the assumption that the artificially created infiltration zones could be isolated.
Extremely low water levels in Mutnovsky geothermal field (500-600 m below surface) induce vertical infiltration of meteoric waters in production zones too, especially if poorly cemented abandoned wells conduct downflows. Integrated analysis of the production data from 2000-2006 combined with numerical simulation shows the possibility of such phenomena.