The spatial distribution of pre-exploitation conditions (i.e. temperature and pressure distribution, liquid and vapor saturations, circulation characteristics of high-temperature fluids) in the Dachny field of the Mutnovsky hydrothermal system, obtained using a three-dimensional (3-D) mapping method, are revised on the basis of natural-state simulations performed using the computer code TOUGH2. A 3-D model of the natural-state conditions at the Dachny site was developed. The fine-tuning of the model was achieved by comparing computer results to the observations made in geothermal wells tested during 1983-88. Also studied was the behavior of the field in response to different exploitation scenarios, assuming production from existing and additional wells needed to supply sufficient steam to a proposed 80 MW(e) power plant.