Geochemical Assessment of Injectivity Problems in Geothermal Wells

The horticultural sector is making increasing use of geothermal heat as a renewable substitute for the burning of natural gas. However, so far many of the completed geothermal systems in the Netherlands do not function as planned. After heat extraction, the water is reinjected into the reservoir. A frequent problem with this is the poor injectivity of the injection wells.
The causes of injectivity problems at several geothermal systems used by the greenhouse industry were investigated by analysing the geochemical aspects and processes involved. This study focuses on the causes of the poor injectivity. Within this research GPC (France) focussed on the measurements of bubble point pressure and suspended particle size distributions, while KWR Watercycle Research Institute focussed on the (geo)chemical processes that occur in the geothermal systems. KWR’s research is reported here. Particular focus was on the precipitation of minerals, as mineral scaling was suspected to be a major contributor to the injectivity problems.