A numerical study on the effects of initial water saturation of a geothermal reservoir on well characteristics

The effects of initial water saturation on well characteristics in two-phase geothermal reservoirs were evaluated. A vertical wellbore model of uniform diameter coupled with a radial horizontal flow in a reservoir of uniform thickness was employed. The momentum equation for two-phase flow in a wellbore was numerically evaluated with a method introduced by Orkiszewski. The energy equation in the wellbore was assumed to be isenthalpic. Mass flow rate and pressure at a feed zone of the well were calculated using a steady radial flow in a reservoir. The numerical calculation showed that the lower initial water saturation in the two-phase reservoir leads to less total flow rate at a given wellhead pressure. However, the decrease in the initial water saturation results in an increase in the maximum discharge pressure. The initial water saturation does not affect the steam flow rate significantly for low wellhead pressure.