Results of flow-meter measure- ments in Soultz-sous-Forêts well GPK4 and implications for the fracturing mechanism in crystalline rock R. Jung, M. Pfender, P. Nami, T. Tischner ENGINE Workshop 3 Ittingen 29./30.06.2006
Relevant features of the wells
STIMULATION GPK4 – Part 1 – Pressure in GPK-4
STIMULATION GPK4 – Part 2 – Pressure in GPK-4
Temperature logs in GPK4 below 3500 m Temperature [°C]
caliperlog & flow logs GPK4
Post-Frac Test GPK4; Test 05FEB22 580 80 downhole pressure 4700m (bar) Data Fit Injection rate (l/s) 540 60 500 40 460 20 q 420 0 22-Feb 24-Feb 26-Feb 28-Feb 100 derivative (bar) pressure delta_p / 10 derivative T f = 0.06 Dm 1 �� Data Fit 0.1 0.01 0.1 1 10 100 time after start injection (h)
a b Soultz GPK1 a) before b) after stimulation 0 2.5 l/s
Soultz GPK1 (1970 – 1990 m) after stimulation before stimulation
GeneSys-Project 3600 Solling Teufe (m) 3700 3700 m Perforation & Detfurth Frac 2 3800 3800 m 20.000 m³ Perforation & 3900 3900 m Volpriehausen Frac 1 1.000 m³ 4000 4000 m 130 140 150 160 Temperatur (°C) 4100 m GeneSys-Horstberg
GeneSys-Project Steigung ½ 10 Druck 1 T f > 10 Dm 0.1 1E-3 0.01 0.1 1 10 Zeit Log-Log plot
Großschönebeck 4050 Silt- stone 2. Frac 4100 Sand- 4150 1. Frac stone 4200 Conglo- 60m merates 4250 Volcanics 4300 0 10 20 30 Inflow (m 3 /h)
Großschönebeck 100 pressure pressure difference / derivative (bar) 10 factor 4 derivative 1 data fit 0.1 0.01 0.1 1 10 100 1000 time (h), since 14.01.03 Parameter (h=60m): T f ⋅ 4 k T f = 0.1 Dm at k = 0.35 mD 2 Slope of pressure/derivative x f > 120m Duration of bilinear flow
Conclusions • Massive waterfrac-tests created long axial fractures in granite and in sedimentary rock • Fractures were not stopped by natural fractures or lithology changes • Fractures are kept open by self propping • Fracture conductivity insufficient in two cases, sufficient in one case • Hydraulic fracturing has to be re-considered as the dominant stimulation mechanism also in granite
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