The GeneSys Project : Development of concepts for the extraction of heat from tight sedimentary rocks

Within the GeneSys geothermal energy project of the GEOZENTRUM Hannover, massive water-frac tests were carried out in the Horstberg Z1 abandoned gas exploration well. The tests were carried out in the low permeable sediments of the Middle Buntsandstein Formation. During the test, 21 000 m 3 of fresh water were injected at rates of up to 50 l/s and maximum wellhead pressures of 460 bar. No proppants were added. Fracture propagation was monitored by a comprehensive geophysical programme, including microseismicity, electric self-potential and tiltmeter measurements. Analysis of hydraulic data show that a large frac was created in the Detfurth Sandstone Formation. It exhibits a large fracture area, high storage capacity and substantial transmissivity, even at pressures well below the fracture propagation pressure. The results are encouraging for alternative concepts which are also the subject of experimental investigations. The GEOZENTRUM Hannover operates the Horstberg Z1 well as an in-situ laboratory to test and develop concepts. This reflects the need to offer tailormade solutions for specific geological situations.