Simulation of complex transient flows in geothermal wells

Abstract

In a recent paper we discussed the development of a new transient geothermal wellbore simulator. In the present paper we discuss the application of this simulator to the modelling of challenging and interesting flows that occur in a geothermal wellbore. The first group of problems involve the opening and closing of hot geothermal wells with rapid transient flows. In some cases, this involves counter-flow with steam flowing upwards and liquid water flowing downwards. The final test case in this category is the simulation of a completion test which involves four stages: cold water injection, heating up of a shut-in well, discharge of the well to the atmosphere, connection of the well to a separator.Simulation of well stimulation by air-lifting and air-compression demonstrate the capability of the simulator for modelling flows of air-water mixtures with a moving interface between the phases.Finally, we demonstrate the ability of the simulator to model injection of water-carbon dioxide mixtures, with an increasing proportion of CO2. This is of particular importance as operators look to carbon sequestration as a way of mitigating green-house gas emissions from geothermal power plants.These are a selection of the more interesting problems of the many test cases that were used during the development of our simulator to ensure that it is robust and can simulate the full range of complex transient flows that can occur in a geothermal well.