| Title | NUMERICAL INVESTIGATION OF COUNTER-FLOW PROCESSES IN GEOTHERMAL WELLS |
|---|---|
| Authors | R. Tonkin, J. O’Sullivan, M. O’Sullivan |
| Year | 2021 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Transient, wellbore, simulation, counter flow, heat up |
| Abstract | One of the complex transient phenomena that can occur within geothermal wellbores is counter-flow. In geothermal wells, counterflow occurs when steam flows up the well while water flows down. Here we discuss numerical experiments with a recently developed transient geothermal wellbore simulator that is capable of modelling counter-flow scenarios. We use our simulator to investigate the role of counter-flow in two test cases involving shut-in geothermal wells. In the first test case, counter-flow occurs as a shallow geothermal well heats up and a vapour cap is formed. The results of this simulation suggest that the vapour cap develops because of the heat transport in a counter-flow zone that occurs in the two-phase fluid. For this reason, counterflow processes cannot be ignored when simulating flow in a shut-in geothermal wellbore, even though the mass flows that occur during this process are small. A second test case simulates the opening of a multi-feed well to flow, starting with realistic shut-in initial conditions. These initial conditions, which were found using simulation, involve inter-zonal flow and counter-flow processes. They demonstrate that temperatures in the well differ from those in the reservoir when these processes occur. Additionally, this second test case highlights that counter-flow capabilities are required to fully model many transient wellbore processes, even something as fundamental as opening a well to flow. The test cases show that simulation can be used to help in the interpretation of data from shut-in wells. However, the investigation shows that if a wellbore simulator is to be used in this capacity it must be able to model counter-flow processes. |