Novel Approach for the Exploration of the Muschelkalk Aquifer in Switzerland for the CO2- free Production of Vegetables

In Switzerland, the Grob vegetable gardening and cultivation company, with around 7 ha of greenhouses in Schlattingen, produces different types of vegetables. The heating of the greenhouses requires about 20,000 MWh of energy per year. Using a mix of fossil fuels currently produces annual CO2 emissions of about 5,000 tons, which should be substituted by the use of geothermal energy. Because of the lack of detailed geological resp. hydrogeological data sets of the region of Schlattingen it was decided to conduct an intensive investigation program in a first vertical borehole (1,508 m bgl), including drilling into the basement with partial coring. The geological and hydrogeological data acquired were used to prepare a geological and finite element hydrothermal model of the Muschelkalk aquifer for the planning of a second inclined borehole. On this basis it was decided to select a novel approach with an almost 800 m long horizontal drilling section in the Muschelkalk aquifer and a total length of 2,013 m to explore as many tectonic structures as possible to increase the chances of success for a higher flow rate. Using a rotary steerable system (RSS), the horizontal drill paths could be implemented into the 33 m thick aquifer (1,112 to 1,145 m bgl). The results of the first pumping test show that the production flow rate was slightly enhanced in comparison with the borehole Schlattingen 1. An additional sectionwise stimulation is planned to increase the flow rate further.