Numerical Analysis of Transient Behaviours of Geothermal Well Deliverability

Abstract

Deliverability of geothermal production well is evaluated by measuring wellhead pressure versus mass flow rate at several wellhead pressures. Controlling a main valve of the well results in the changes in wellhead pressure and mass flow rate. However, duration required for these variables to stabilize depends on flowing behaviour of steam-water two-phase fluid in the wellbore. The well deliverability is also affected by the reservoir parameters such as reservoir permeability, reservoir pressure and temperature. Thus, transient behaviours of well deliverability were analyzed numerically using a wellbore simulator WELBORE (Miller, 1980). To evaluate the effects of the duration of valve controlling operation on well deliverability, a step change and linear changes with several time intervals in mass flow rate at wellhead were given. The results showed that the duration required for wellhead pressure to stabilize for a given mass flow rate increase in a form of step change is longer compared to that in a form of linear changes. The longer time required for opening valve will result in the faster stabilization of wellhead pressure.