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Method for Estimating the Increase in Permeability of Reservoirs during Hydro-fracturing Stimulations. |
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Hydro-fracturing stimulation is a classical method to achieve better flow rate in
hard geothermal rock reservoirs. The stimulation is performed by maintaining a
high fluid pressure (several MPa) into pilot boreholes. The pore pressure
increases gradually from the injection source to the surrounding rocks, implying
local changes in the stress field that induces shears and/or opening of sealed
micro fractures or faults, and, when the differential pressure is greater than the
rock cohesion, leads to normal faulting. Each of these events induces small
magnitude micro-seismic events which can be recorded from the surface by tri-axial
geophones located deep in observation boreholes. This induced micro-seismicity
provides indirect information on the reservoir permeability. A new methodology is
proposed to characterize the geothermal reservoir potentialities by estimating its
3D anisotropic heterogeneous diffusivity and its time evolution during the
stimulation. This approach has been applied to the Soultz-s-Forêts, France HDR
geothermal reservoir for depths ranging from 3500 to 5000m. It provides a detailed
map of the permeability and of its variations before and after stimulation with a
resolution of tenths of meters over an extension of several hundred meters around
the injection source. Then, by interpreting and processing the boreholes UBI
images, the main active fractures zones were identified on the three available
wells. Orientation and opening of each fracture were evaluated using the GMI
software, and integrated into a comprehensive 3D model using the gOcad geomodeler.
The 3D fracture network seems to be coherent with a strike slip model related to
the formation of the Soultz horst. The relationship between the induced miro-
seismicity and the identified fracture zones are then discussed in terms of
hydraulic potentialities.
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Id: |
19 |
Place: |
GeoForschungsZentrum Potsdam (GFZ) 14473 Potsdam, Telegrafenberg
Germany |
Starting date: |
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Duration: |
03' |
Contribution type: |
Poster |
Primary Authors: |
Dr. ROYER, Jean-Jacques (CRPG/CNRS, gOcad Research group, Nancy School of Geology, Nancy – France) |
Co-Authors: |
Mr. LALOS, Pierre (ENSG, Nancy, France) Dr. VOILLEMONT, Jean-Charles (2 Earth Decision, Paris – France) Ms. CONIN, Mariane (ENSG, Nancy, France) Dr. SAUSSE, Judith (, UHP – Université Henri Poincarré, Nancy, France) Dr. GERARD, André (4EEIG Heat Mining, Kutzenhausen, France) |
Presenters: |
Dr. ROYER, Jean-Jacques |
Material: |
Slides Poster |
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