Impact of fracture networks on borehole breakout heterogeneities in crystalline rock

Sahara, David P.; Schoenball, Martin; Köhl, Thomas; Müller, Birgit

doi:10.1016/j.ijrmms.2014.07.001

Cited by 28 publications

(30 citation statements)

References 31 publications

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“…However, stress rotations of 20° or more are frequently observed locally in borehole data. Such rotations can be explained by slip on faults and reflect the heterogeneity of the state of stress (Barton and Zoback, 1994;Sahara et al, 2014;Schoenball and Davatzes, 2017).…”

Section: Retrospective Estimations Of Fspmentioning

confidence: 99%

How faults wake up: The Guthrie-Langston, Oklahoma earthquakes

et al. 2018

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Large-scale wastewater disposal has led to a fast-paced reawakening of faults in the Oklahoma/Kansas region. High-resolution earthquake relocations show that the inventory of ancient basement faults in the study region differs from results of seismic surveys and geologic mapping focused on the sedimentary cover. We analyze the evolution of seismic activity in the Guthrie-Langston sequence in central Oklahoma in greater detail. Here, seismic activity has reactivated a network of at least 12 subvertical faults in an area less than 10 km across. Recorded activity began in late 2013, peaked about six months later, and includes two M 4 earthquakes. These earthquakes characteristically occur at about 4 km depth below the top of the basement and do not reach the sedimentary cover. The sequence shows a radial growth pattern despite being no closer than 10 km to significant wastewater disposal activity. Hydrologic modeling suggests that activity initiated with a time lag of several years relative to early injection activity. Once initiated, earthquake interactions contribute to the propagation of seismicity along the reactivated faults. As a result, the spatiotemporal evolution of the seismicity mimics a diffusive pattern that is typically thought to be associated with injection activity. Analysis of the fault slip potential shows that most faults are critically stressed in the contemporary stress field. Activity on some faults, for which we find low slip probability, suggests a significant contribution of geomechanical heterogeneities to the reawakening of these ancient basement faults.

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Section: Retrospective Estimations Of Fspmentioning

confidence: 99%

How faults wake up: The Guthrie-Langston, Oklahoma earthquakes

et al. 2018

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“…This theory was investigated on the basis of breakouts, identified by Sahara et al (2014). They analyzed breakouts in the deeper part of the well GPK4.…”

Section: Impacts Of Hydrothermal Alteration On Rock Mechanicsmentioning

confidence: 99%

“…They analyzed breakouts in the deeper part of the well GPK4. On Figure 4, a total of 2,440 breakouts from Sahara et al (2014) together with the SCCL for this depth interval are illustrated. A correlation between clay content and the appearance and size of the breakouts is obvious.…”

Section: Impacts Of Hydrothermal Alteration On Rock Mechanicsmentioning

confidence: 99%

The significance of hydrothermal alteration zones for the mechanical behavior of a geothermal reservoir

Meller

Köhl

2014

Geotherm Energy

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“…[64] At such depths,s light variations in stress magnitude and orientation play as ignificant role.I na ddition, the deeply seated reservoir is highly fractured. Fractures are repeatedly accompanied by mineral alteration, acting as weak zones,w hich potentially promote failurea long such heterogeneities.…”

Section: Borehole Failurementioning

confidence: 99%

“…However, recent observations made in deep boreholes (see previous sections) indicate complex coupleda nd time-dependent damage or mechanisms (Figure 14), [72] as-yet undetected transient microphysical processes, [74] and the severei nfluence of local material or structural instabilities. [64] Fort hese microprocesses, naturally encountered at elevated temperatures at which EGSs are located (depth > 5km), lower deviatoric stresses and/orl onger geological timescales are requiredt oi nduce localization instabilities. [75] At this point, evenu nconventional brittlem aterial assumptionsf ail to correctly predict the rock strengthb ecause the material reveals as evere temperature and rates ensitivity.…”

Section: 18f Ailure Mechanismsand Materials Behaviormentioning

confidence: 99%

Integrated Research as Key to the Development of a Sustainable Geothermal Energy Technology

et al. 2017

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As estimated by the International Energy Agency, geothermal power can contribute to 3.5 % of worldwide power and 3.9 % to heat production by 2050. This includes the development of enhanced geothermal systems (EGSs) in low‐enthalpy systems. EGS technology is still in an early stage of development. Pushing EGS technologies towards market maturity requires a long‐term strategic approach and massive investments in research and development. Comprehensive multidisciplinary research programs that combine fundamental and applied concepts to tackle technological, economic, ecological, and safety challenges along the EGS process chain are needed. The Karlsruhe Institute of Technology (KIT) has defined a broad research program on EGS technology development following the necessity of a transdisciplinary approach. The research concept is embedded in the national research program of the Helmholtz Association and is structured in four clusters: reservoir characterization and engineering, thermal water circuit, materials and geoprocesses, and power plant operation. The proximity to industry, closely interlinked with fundamental research, forms the basis of a target‐orientated concept. The present paper aims to give an overview of geothermal research at KIT and emphasizes the need for concerted research efforts at the international level to accelerate technological breakthrough of EGS as an essential part of a future sustainable energy system.

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Impact of fracture networks on borehole breakout heterogeneities in crystalline rock

Cited by 28 publications

References 31 publications

How faults wake up: The Guthrie-Langston, Oklahoma earthquakes

How faults wake up: The Guthrie-Langston, Oklahoma earthquakes

The significance of hydrothermal alteration zones for the mechanical behavior of a geothermal reservoir

Integrated Research as Key to the Development of a Sustainable Geothermal Energy Technology

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