ISRM Suggested Methods for Rock Stress Estimation—Part 5: Establishing a Model for the In Situ Stress at a Given Site

Stephansson, Ove; Zang, Arno

doi:10.1007/s00603-012-0270-x

Cited by 68 publications

(23 citation statements)

References 48 publications

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“…We rate in situ stress the second most important parameter in EGS development after the presence of heat. One should follow International Society for Rock Mechanics standards for determining in situ stress at a given (geothermal) site, Stephansson and Zang (2012).…”

Section: Discussionmentioning

confidence: 99%

Analysis of induced seismicity in geothermal reservoirs – An overview

et al. 2014

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In this overview we report results of analysing induced seismicity in geothermal reservoirs in various tectonic settings within the framework of the European Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs (GEISER) project. In the reconnaissance phase of a field, the subsurface fault mapping, in situ stress and the seismic network are of primary interest in order to help assess the geothermal resource. The hypocentres of the observed seismic events (seismic cloud) are dependent on the design of the installed network, the used velocity model and the applied location technique. During the stimulation phase, the attention is turned to reservoir hydraulics (e.g., fluid pressure, injection volume) and its relation to larger magnitude seismic events, their source characteristics and occurrence in space and time. A change in isotropic components of the full waveform moment tensor is observed for events close to the injection well (tensile character) as compared to events further away from the injection well (shear character). Tensile events coincide with high Gutenberg-Richter -values and low Brune stress drop values. The stress regime in the reservoir controls the direction of the fracture growth at depth, as indicated by the extent of the seismic cloud detected. Stress magnitudes are important in multiple stimulation of wells, where little or no seismicity is observed until the previous maximum stress level is exceeded (Kaiser Effect). Prior to drilling, obtaining a 3D -wave ( ) and -wave velocity ( ) model down to reservoir depth is recommended. In the stimulation phase, we recommend to monitor and to locate seismicity with high precision (decametre) in real-time and to perform local 4D tomography for velocity ratio ( / ). During exploitation, one should use observed and model induced seismicity to forward estimate seismic hazard so that field operators are in a position to adjust well hydraulics (rate and volume of the fluid injected) when induced events start to occur far away from the boundary of the seismic cloud.

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Section: Discussionmentioning

confidence: 99%

Analysis of induced seismicity in geothermal reservoirs – An overview

et al. 2014

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“…5). For information on determining in-situ stress at specific sites see: Zang and Stephansson (2010); Stephansson and Zang (2012). ).…”

Section: Resultsmentioning

confidence: 99%

Stress magnitudes across UK regions: New analysis and legacy data across potentially prospective unconventional resource areas

Fellgett

Kingdon

Williams

et al. 2018

Marine and Petroleum Geology

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“…However, these data represent specific locations and may mislead the result if directly used for the interpretation of larger rock volume (larger topographic coverage). In order to integrate these data for the analysis of stress state of quite a large rock volume of the UTHP area, a final rock stress model (FRSM) concept as recommended by Stephansson and Zang (2012) is extensively utilized (Table 11).…”

Section: Stress State Assessmentmentioning

confidence: 99%

“…The FRSM concept considers stepwise evaluation of the in situ stress state integrating best estimate stress model (BESM), stress measurement methods (SMM), and integrated stress determination methods (ISD). Stephansson and Zang (2012) concluded that the resulting stress data are more relevant for larger rock volume after the ISD model and stress modeling are performed. Hence, both the ISD model and numerical analysis (FLAC 3D model) are used to develop the final rock stress model for the UTHP case.…”

Section: Stress State Assessmentmentioning

confidence: 99%

Detailed engineering geological assessment of a shotcrete lined pressure tunnel in the Himalayan rock mass conditions: a case study from Nepal

Basnet

Panthi

2019

Bull Eng Geol Environ

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The complex topography, geology, and tectonic environment prevailing in the Himalaya are the main challenges while applying the unlined or shotcrete lined pressure tunnel concept for hydropower projects. In addition, rock masses in the Himalayan region are influenced by faulting, folding, schistosity, and jointing to a varying degree representing geological complexity. Similarly, frequent occurrence of large scale earthquakes changes in situ stress dynamics. In spite of these challenges, an unlined/shotcrete lined pressure tunnel is being constructed at the headrace tunnel system of Upper Tamakoshi Hydroelectric Project (UTHP) in the Nepal Himalaya. This article studies the unlined or shotcrete lined pressure tunnel in terms of the topographical conditions, in situ stress state, and overall rock engineering aspects. First, the pressure tunnel alignment is assessed using the Norwegian confinement criteria. Second, the minimum principal stress state is assessed using numerical simulation by validating measured in situ stress conditions. Finally, a comprehensive assessment on the rock engineering aspects of the headrace tunnel is carried out. It has been found that if there exist good quality rock mass with tight joints, it is possible to apply the unlined/shotcrete lined pressure tunnel system in the Himalaya provided that the stress requirement is fulfilled. It was also found that the Norwegian confinement criteria are too optimistic for direct use in the design of high pressure headrace tunnel alignment. The detailed rock engineering assessment and stress state analysis indicated that there are some critical locations along the Upper Tamakoshi headrace tunnel alignment. This is specially the case for an about 700 m downstream stretch of the headrace tunnel from where there is a risk of hydraulic jacking, which may possibly lead to excessive water leakage during power plant operation.

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ISRM Suggested Methods for Rock Stress Estimation—Part 5: Establishing a Model for the In Situ Stress at a Given Site

Cited by 68 publications

References 48 publications

Analysis of induced seismicity in geothermal reservoirs – An overview

Analysis of induced seismicity in geothermal reservoirs – An overview

Stress magnitudes across UK regions: New analysis and legacy data across potentially prospective unconventional resource areas

Detailed engineering geological assessment of a shotcrete lined pressure tunnel in the Himalayan rock mass conditions: a case study from Nepal

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