Page 239 - Geothermal Energy Systems Exploration, Development, and Utilization

4.10 Case Studies 215
1000 10

800 8
Pressure (bar) 600 6 4 Flowrate (m 3 /min)

400

200 2

0 0
09.08 10.08 11.08 12.08 13.08 14.08 15.08
Time

Figure 4.13 Pressure and flowrate data of the massive
waterfrac treatment in Groß Sch¨onebeck in August 2007.

4.10.1.7 Hydraulic Fracturing in Sandstones (Gel-Proppant Stimulation)
The stimulation treatment in the sandstones of the lower Dethlingen was carried
out from 18 August to 19 August 2007 (see Figure 4.14). The intended interval from
4204 to 4208 m was isolated with a bridge plug in 4300 m and then perforated with
big hole perforations (20 per m, circumferential). Transport of the proppants was
provided with a cross-linked gel with high viscosity. Two kind of proppants were
applied: high strength proppants coated and uncoated. Both consist of a diameter
of 0.4–0.8 mm (20/40 mesh size); the coated proppants were used at the end of the
treatment to support the sustainable fracture opening in the near-wellbore vicinity.

1400 7
Pressure (bar) & prop conc (g/l) 1000 Leak off test Step rate test Frac 5 Flowrate (m 3 /min)
6
1200

4
800
600
3
2
400
200

0 1
0
09:00 10:00 11:00 12:00 13:00 14:00 15:00
Time (hh:mm)
Figure 4.14 Pressure and flowrate data of the 1.
gel-proppant treatment in Groß Sch¨onebeck in August 2007.