| Title | Assessment of Probability of Success for Hydrogeothermal Wells |
|---|---|
| Authors | R¸diger Schulz, Reinhard Jung and R¸diger Schellschmidt |
| Year | 2005 |
| Conference | World Geothermal Congress |
| Keywords | hydrogeothermal wells, geological risk, insurance, possibility of success |
| Abstract | The quantification of geological risks, respectively the estimation of probability of success is one of the most important factors for investors and decision makers. Although the data base is often not optimal because of nonexistent comparing objects, a good quantitative assessment of the geological risks is required. We have gained experience by writing some expert reports about geological risks for geothermal wells for insurance companies and investors. In this paper a concept of the assessment of probability of success (POS) will be discussed. Data base for the estimation of POS is the information about the water productivity, the drawdown of the water level and the aquifer temperature. The depth of the aquifer has to be determined as exactly as possible by seismic measurements. The project manager has to declare, at which flow rate and at which temperature the geothermal well will be (partly) successful. Then the POS can be calculated. Information about the hydraulic parameters of the aquifer can mostly be determined in a regional scale only. Information from boreholes nearby or other boreholes having similar conditions can be weighted in a suitable manner. For the temperature prognosis, local conditions must be considered besides regional trends. An area of 1000 km? was normally chosen in the previous studies. Because of the small data base the simplest way to calculate the POS of a project is to multiply the single POS of flow rate and temperature. The POS was calculated in this manner for a geothermal well drilled in 2004 in the south of Munich (Bavaria). This POS was the base for a private insurance contract. To our state of information, this is worldwide the first hydrogeothermal borehole which is insured by an assurance company. |