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  • 1
    Electronic Resource
    Electronic Resource
    Seismic and Aseismic Slips Induced by Large-scale Fluid Injections (1997)
    Springer
    Pure and applied geophysics 150 (1997), S. 563-583 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Fluid injection, induced seismicity, aseismic slip, downhole monitoring network, surface monitoring network.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract. —A 3600 m deep well has been used to conduct large water injection tests in the Rhine Graben. The total volume injected during the fall 1993 reconnaissance program reached 44000 m3. Induced seismicity was monitored with both a downhole and a surface seismic network. About 20000 events have been recorded by the downhole tools and 165 events with the surface network. The largest observed magnitude reached 1.9, as determined from signal duration observed on the surface network. Borehole televiewer observations show that some slip events were larger than 4 cm at the borehole wall, a value much larger than the slip motion associated with microseismic events, as evaluated from events' magnitude. It is concluded that these observed slip events were aseismic. This implies that induced seismicity is not a good marker for the efficiency of this hydraulic stimulation. It only helps to identify zones of high pore pressure during injection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050093
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of induced seismicity for stress field determination and pore pressure mapping (1995)
    Springer
    Pure and applied geophysics 145 (1995), S. 677-700 
    Details
    ISSN: 1420-9136
    Keywords: Induced seismicity ; stress determination ; stress heterogeneity ; fluid flow ; fault morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The focal mechanisms of some one hundred microseismic events induced by various water injections have been determined. Within the same depth interval, numerous stress measurements have been conducted with the HTPF method. When inverted simultaneously, the HTPF data and the focal plane solutions help determine the complete stress field in a fairly large volume of rock (about 15×106 m3). These results demonstrate that hydraulically conductive fault zones are associated with local stress heterogeneities. Some of these stress heterogeneities correspond to local stress concentrations with principal stress magnitudes much larger than those of the regional stress field. They preclude the determination of the regional stress field from the sole inversion of focal mechanisms. In addition to determining the regional stress field, the integrated inversion of focal mechanisms and HTPF data help identify the fault plane for each for each of the focal mechanisms. These slip motions have been demonstrated to be consistent with Terzaghi's effective stress principle and a Coulomb friction law with a friction coefficient ranging from 0.65 to 0.9. This has been used for mapping the pore pressure in the rock mass. This mapping shows that induced seismicity does not outline zones of high flow rate but only zones of high pore pressure. For one fault zone where no significant flow has been observed, the local pore pressure has been found to be larger than the regional minimum principal stress but no hydraulic fracturing has been detected there.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879595
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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