Current status of seismic and borehole measurements for HDR/HWR development

Niitsuma, Hiroaki; Fehler, Michael; Jones, R. Clark; Wilson, Stephen; Albright, James N.; Green, Andrew; Baria, Roy; Hayashi, Kazuo; Kaieda, Hideshi; Tezuka, Kazuhiko; Jupe, A.; Wallroth, Thomas; Cornet, François; Asanuma, Hiroshi; Moriya, Hideshige; Nagano, Koji; Phillips, W. S.; Rutledge, James; Beauce, A.; Alde, D.; Aster, R. C.

doi:10.1016/s0375-6505(99)00024-3

Cited by 29 publications

(16 citation statements)

References 51 publications

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“…Induced seismicity accompanies hydraulic stimulation and can be detrimental to deep geothermal projects when magnitudes of induced earthquakes are perceptible to the public (Ellsworth, 2013;Evans et al, 2012). However, in many industrial projects in the context of both hydrocarbon and heat extraction, including this study, it is an indispensable tool that is used to map the stimulated fracture system (Maxwell et al, 2010;Niitsuma et al, 1999;Warpinski et al, 2013). When the hydraulic fractures propagate beyond the vicinity of the injection point, they will inevitably interact with natural fractures to some degree.…”

Section: Seismic Response and Seismic Cloudmentioning

confidence: 99%

Hydraulic fracture propagation in a heterogeneous stress field in a crystalline rock mass

Dutler¹,

Valley²,

Gischig³

et al. 2019

Preprint

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Abstract. As part of the In-situ Stimulation and Circulation (ISC) experiment, hydraulic fracturing (HF) tests were conducted in a moderately fractured crystalline rock mass at the Grimsel Test Site (GTS), Switzerland. The aim of these injection tests was to improve our understanding of processes associated with high-pressure fluid injection. A total of six HF experiments were performed in two inclined boreholes, where the surrounding rock mass was accessed with twelve observation boreholes, which allow high-resolution monitoring of fracture fluid pressure, strain and micro-seismicity in an exceptionally well-characterized rock mass. A similar injection protocol was used for all six experiments to investigate the complexity of the fracture propagation processes. At the borehole scale, these processes involved newly created tensile fractures intersecting the injection interval while at the cross-hole scale, the natural network of fractures dominated the propagation process. The six HF experiments can be divided into two groups based on their injection location (i.e., south or north to a brittle ductile shear zone), their similarity of injection pressures and their response to deformation and pressure propagation. The injection tests performed in the south connect upon propagation to the brittle ductile shear zone. Thus, the shear zone acts as a dominant drain and a constant pressure boundary. The experiments executed north of the shear zone, show smaller injection pressures and larger backflow during bleed-off phases. From a seismic perspective, the injection tests show high variability in seismic response independent of the location of injection. For two injection experiments, we observe re-orientation of the seismic cloud as the fracture propagated away from the wellbore. In both cases, the main propagation direction is normal to the minimum principal stress direction. The re-orientation during propagation is interpreted to be related to a strong stress heterogeneity and the intersection of natural fractures striking different than the propagating hydraulic fracture. The seismic activity was limited to about 10 m radial distance from the injection point. In contrast, strain and pressure signals reach further into the rock mass indicating that the process zone around the injection point is larger than the zone illuminated by seismic signals. Furthermore, strain signals indicate not just single fracture openings but also the propagation of multiple fractures. Transmissivities of injection intervals increase about 2–4 orders of magnitudes.

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Section: Seismic Response and Seismic Cloudmentioning

confidence: 99%

Hydraulic fracture propagation in a heterogeneous stress field in a crystalline rock mass

Dutler¹,

Valley²,

Gischig³

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Such induced microseismicity can be used as a diagnostic tool to define the geometry and nature of failure of the individual events, regardless of HF scale (e.g., Ishida, 2001;Falls et al, 1992;Majer and Doe, 1986;Lockner and Byerlee, 1977). For this reason, microseismic monitoring is routinely used for monitoring stimulations of EGS reservoirs (Niitsuma et al, 1999) and more recently in oil and gas fracturing operations (e.g., Caffagni et al, 2016;Warpinski et al, 2013;Maxwell et al, 2010). At the other extreme of the HF scale, it is also used to study the failure process of rock in laboratory tests (e.g., Chitrala, 2013) During small-scale HFs, the orientation of the seismicity cloud is generally considered indicative of the fracture propagation directions and is thus assumed to be normal to the minimum principal stress (σ 3 ) direction.…”

Section: Introductionmentioning

confidence: 99%

On the link between stress field and small-scale hydraulic fracture growth in anisotropic rock derived from microseismicity

et al. 2018

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Abstract. To characterize the stress field at the Grimsel Test Site (GTS) underground rock laboratory, a series of hydrofracturing and overcoring tests were performed. Hydrofracturing was accompanied by seismic monitoring using a network of highly sensitive piezosensors and accelerometers that were able to record small seismic events associated with metre-sized fractures. Due to potential discrepancies between the hydrofracture orientation and stress field estimates from overcoring, it was essential to obtain highprecision hypocentre locations that reliably illuminate fracture growth. Absolute locations were improved using a transverse isotropic P-wave velocity model and by applying joint hypocentre determination that allowed for the computation of station corrections. We further exploited the high degree of waveform similarity of events by applying cluster analysis and relative relocation. Resulting clouds of absolute and relative located seismicity showed a consistent east-west strike and 70 • dip for all hydrofractures. The fracture growth direction from microseismicity is consistent with the principal stress orientations from the overcoring stress tests, provided that an anisotropic elastic model for the rock mass is used in the data inversions. The σ 1 stress is significantly larger than the other two principal stresses and has a reasonably welldefined orientation that is subparallel to the fracture plane; σ 2 and σ 3 are almost equal in magnitude and thus lie on a circle defined by the standard errors of the solutions. The poles of the microseismicity planes also lie on this circle towards the north. Analysis of P-wave polarizations suggested double-couple focal mechanisms with both thrust and normal faulting mechanisms present, whereas strike-slip and thrust mechanisms would be expected from the overcoring-derived stress solution. The reasons for these discrepancies can be explained by pressure leak-off, but possibly may also involve stress field rotation around the propagating hydrofracture. Our study demonstrates that microseismicity monitoring along with high-resolution event locations provides valuable information for interpreting stress characterization measurements.

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“…Injection-induced slip in fractures is understood to be one of the mechanisms causing the microseismicity observed during hydraulic stimulation (Pearson, 1981;Pine and Batchelor, 1984;Talebi and Cornet, 1987;Cornet and Yin, 1995), that has been associated with fluid injection within a number of different geological environments, including geothermal reservoirs (Pearson, 1981;Pine and Batchelor, 1984;Niitsuma et al, 1999;Baisch et al, 2006aBaisch et al, , 2006bMajer et al, 2007), oil/gas reservoirs (Phillips et al, 2002;Rutledge and Phillips, 2003;Rutledge et al, 2004), crystalline rocks (Zoback and Harjes, 1997;Baisch et al, 2002), and active faults (Tadokoro et al, 2000(Tadokoro et al, , 2001. Since induced seismicity and its role in the creation or enhancement of geothermal reservoirs have recently been the subject of debate (Bommer et al, 2006;Majer et al, 2005Majer et al, , 2007, it is to be hoped that a better understanding of the mechanisms of change in fracture permeability associated with induced slip events will provide information of fundamental significance for future interpretations of the relationship between fluid flow and microseismicity.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and hydraulic coupling of injection-induced slip along pre-existing fractures

et al. 2008

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Current status of seismic and borehole measurements for HDR/HWR development

Cited by 29 publications

References 51 publications

Hydraulic fracture propagation in a heterogeneous stress field in a crystalline rock mass

Hydraulic fracture propagation in a heterogeneous stress field in a crystalline rock mass

On the link between stress field and small-scale hydraulic fracture growth in anisotropic rock derived from microseismicity

Mechanical and hydraulic coupling of injection-induced slip along pre-existing fractures

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