| Title | Monte Carlo flow rate simulations for the multi-stage EGS stimulation concept of the Haute-Sorne pilot project (Canton Jura, Switzerland) |
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| Authors | Meier, P; Ollinger, D |
| Year | 2016 |
| Conference | European Geothermal Congress |
| Keywords | EGS, multi-stage stimulation, Haute-Sorne pilot project, monte carlo flow rate simulations |
| Abstract | The Basel Deep Heat Mining project was the first attempt to produce electricity using EGS technology in Switzerland (Häring et al. 2008). It was stopped in 2006 after an earthquake of magnitude ML = 3.4 occurred during the stimulation of the crystalline basement. At that time, the Basel project had produced a unique dataset of seismic and hydraulic data which lead to a better understanding of the stimulation process. Based on that knowledge, Geo-Energie Suisse developed a new reservoir stimulation concept which minimizes seismic risk and at the same time enhances well productivity. The new concept shall be implemented in a pilot project in the crystalline basement in the community of Haute-Sorne in the Canton Jura (Switzerland). The pilot project aims at proving the technical feasibility of the concept and producing up to 5 MW electricity by 2020.summarise here the main developments in your country. In contrast to a massive stimulation in a vertical borehole (Basel), Geo-Energie Suisse uses a multistage hydraulic stimulation in highly deviated wells in combination with open-hole packer technology. We use Monte Carlo simulations in combination with a reservoir model to derive probability density functions for the flow rates in crystalline rocks (granite, gneiss) in order to evaluate the success chances of the project. As a basis for the simulations we use geo-statistical parameters for transmissivity values from the Gotthard base tunnels and other tunnels in the Swiss central alps which intersect large gneiss and granite bodies at depths up to 2000 m (Masset, O. and Löw, S., 2010 and 2013). Although the geological setting of the central alps is not directly comparable to the crystalline basement in northwestern Switzerland we believe that the fundamental statistical characteristics of flow within tight crystalline rocks are well captured by the extraordinary data set from the Swiss alps. Besides of the natural variability and a depth dependency of transmissivity a failure probability of the multi zonal isolation technique is taken into account. The results show clearly the advantages of using a multi-zonal stimulation approach in comparison to using massive hydraulic stimulation in a large openhole section. The chances of success – defined as a higher probability of larger circulation flow rates – are higher in granites than in gneisses, which is in principle agreement with data from crystalline rocks reported in Stober, I. & Bucher, K. (2007). |