Application of Well-Bore Flow Modelling in Geothermal Systems - Lessons Learned from Oil and Gas Production Systems

Abstract

Proper operation of geothermal wells is important for ensuring reliable heat production from them over a long period. The geothermal production could suffer from several production issues, such as corrosion, scaling, erosion and hydrocarbon production, which can limit the performance of these systems. They can lead to unstable production, a decline in the flow rates or endangering the integrity of the geothermal doublets. Similar problems are also occurring in upstream oil and gas and there are numerous studies and experimental data available on understanding, monitoring and mitigating these issues. For better identification of operational issues in geothermal wells combining the relevant reaction and thermodynamics models with flow solvers could be of added value. The prediction of production issues, such as scaling and corrosion, is currently being done globally without considering the local changes in flowing conditions in the well-bore and top-side facilities (e.g. in pumps, filters, separators). These issues could be enhanced or suppressed by changing the local pressure, temperature and flow properties of the produced geothermal fluid. Thus, detailed information on the local flow properties of the geothermal fluid in the well-bore and top-side facilities is crucial for preventing production issues. In this study, simulators for multiphase flow in the well-bores which are used for assessing production issues in oil and gas wells were employed. Several models are applied on a well which is exemplary for Dutch geothermal wells and conditions (doublet brine systems, with a temperature range of 70 to 100 ˚C). The dynamic multiphase flow solver provides useful information of the local operating conditions in the well (flow velocities, pressures and temperatures). This information was fed to the relevant models for scaling, erosion and corrosion. The simulations showed that trends/sensitivity of scaling, erosion and corrosion to several operating parameters were captured accurately. The predicted trends by the simulator were validated with the observations from the field. The results showed the applicability and potential of well-bore flow models, developed for oil and gas, for maximizing the geothermal production while minimizing the operational and integrity risks.