| Title | The Stimulation of a Sedimentary Geothermal Reservoir in the North German Basin: Case Study Gro? Schˆnebeck |
|---|---|
| Authors | Ernst Huenges, Heinz-Gerd Holl, Bjˆrn Legarth, G¸nter Zimmermann, and Ali Saadat |
| Year | 2004 |
| Conference | Stanford Geothermal Workshop |
| Keywords | reservoir stimulation, GRO? SCH÷NEBECK, low permeablity reservoir |
| Abstract | In order to make the generation of geothermal electricity in a sedimentary reservoir rocks possible a deep former gas exploration well was reopened and deepened in 2000 to 4294 m depth. An in-situ downhole laboratory was established in this well with the purpose of developing appropriate stimulation methods to increase permeability of deep aquifers by enhancing or creating secondary porosity and flow paths. The goal is to learn how to enhance the inflow performance of a well from a variety of rock types in low permeability geothermal reservoirs. Proppant-gel- frac techniques as well as waterfrac techniques were used in several different experiments. During the proppant-gel-frac two intervals of Rotliegend sandstones were hydraulically stimulated in January 2002. The experiment design comprised isolating the bottom boundary of the interval of interest by filling the bottom of the well with sand. The top of the interval was sealed with a mechanical packer. High-viscosity fluid with proppant was employed for stimulation. Flow rates were increased significantly, and a fracture with a length of 150 m was generated due to this operation. However, the productivity observed was insufficient for power production. Further stimulation of the reservoir rocks in this well was performed in two experiments in winter and fall 2003 using the waterfrac technique. More than 15000 m? water was injected in different pressure steps with flow rates up to 80 ls -1 . Mechanical reacting reservoir properties were observed at injection flow rates above 9 ls -1 . Recent data of a production test show a productivity of 14 m?h -1 MPa -1 . |