Cyclic waterfrac stimulation to develop an Enhanced Geothermal System (EGS)—Conceptual design and experimental results

Abstract

The design and results of a cyclic hydraulic fracturing experiment performed to enhance the productivity of the geothermal research well at Groß Schönebeck (Germany) are presented. The stimulation carried out in the low-permeability volcanics of the Lower Rotliegend (Lower Permian) included alternating stages with cyclic changes of low and high flow rates with up to 150 L/s over six days in conjunction with the addition of quartz sand to support fracture opening. There was rapid water level increase in an adjacent well due to the stimulation (i.e. water injection). The subsequent production test showed the success of the fracture treatment, with the overall productivity of the treated well being increased by a factor of four.

Microseismicity induced during fluid-injection: A case study from the geothermal site at Groß Schönebeck, North German Basin

“…Low enthalpy geothermal reservoir rocks (see Zimmermann et al, 2009a, Zimmermann andReinicke, 2010, for details) are to be found here as siliciclastic sediments and volcanics of the lower Permian at an average depth of about 4000 m and at formation temperatures of up to 150°C. The existing well EG was used for repeated stimulation treatments to investigate scenarios of enhancing productivity of thermal fluid recovery from the underground (Zimmermann et al 2009b).…”

“…The sensor is located at only 500 m distance to the injection point providing the opportunity to monitor induced seismicity as low as M W~-2.0. (Zimmermann et al, 2009a, Zimmermann andReinicke, 2010), at maximum well-head pressures of 49.5 MPa and 38.0 MPa, respectively. In the following analysis we primarily focus on the major injection in volcanic rocks.…”

Life-cycle analysis results of geothermal systems in comparison to other power systems.

“…According to the literature, the average highest flow rate achieved during stimulation is 97 L/second (s) (36.6 barrels [bbl]/minute [min]) (Asanuma et al 2004;Michelet and Toksöz 2006;Zimmermann et al 2009). Fuel consumption was determined by using the average highest flow rate and from industry input.…”

Hydraulic fracturing process by using a modified two-dimensional particle flow code - case study

“…This method has been widely used in energy industry to enhance the recovery of hydrocarbons from tight reservoir rocks, through the creation of hydraulic fractures and coupling of these new higher permeability flow paths with the natural fracture networks in the rock (Fu et al, 2013;Wang, 2015). In addition, hydraulic fracturing can be applied in fields of the disposal of radioactive waste in the underground spaces (De Laguna et al, 1968), heat production from hot dry rock geothermal reservoirs (Zimmermann et al, 2009(Zimmermann et al, , 2010, as well as the measurement of in-situ stresses (Fairhurst, 2003;Haimson and Cornet, 2003;Yokoyama et al, 2014).…”