Mechanical behaviour of Australian Strathbogie granite under in-situ stress and temperature conditions: An application to geothermal energy extraction

Kumari, W.G.P.; Ranjith, P.G.; Perera, M.S.A.; Shao, Shishi; Chen, Bernard; Lashin, Aref; Arifi, Nassir Al; Rathnaweera, T.D.

doi:10.1016/j.geothermics.2016.07.002

Cited by 175 publications

(81 citation statements)

References 39 publications

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“…We further note that our estimates of rock mass elastic modulus do not consider the influence of pressure or temperature. Published data show that static elastic modulus of the same lowporosity, fresh granite increases slightly with increasing pressure and temperature (from ~ 22 GPa at room temperature up to ~ 26 GPa at 200 °C; Kumari et al 2017). Despite these data, it is unclear whether, or to what extent, such temperatures will influence granites from the URG, which are more hydrothermally altered than the granites studied in the aforementioned studies.…”

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 92%

“…It is known from experiments and modelling that high temperature (from 100 up to 1000 °C) can influence the short-and long-term strength of granite in the brittle regime (e.g. Wong 1982b; Xu et al 2008Xu et al , 2017Shao et al 2015;Kumari et al 2017;Chen et al 2017;Violay et al 2017). However, a recent experimental study has shown that the strength of a low-porosity fresh granite is largely unaffected at temperatures of 140-150 °C (Kumari et al 2017).…”

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 99%

“…Wong 1982b; Xu et al 2008Xu et al , 2017Shao et al 2015;Kumari et al 2017;Chen et al 2017;Violay et al 2017). However, a recent experimental study has shown that the strength of a low-porosity fresh granite is largely unaffected at temperatures of 140-150 °C (Kumari et al 2017). These new data are in agreement with previously published data that show that temperatures of a couple of hundred degrees Celsius do not appear to greatly influence the short-term strength of granite (Xu et al 2008;Shao et al 2015).…”

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 99%

“…It is well-known that the long-term strength of rock is much lower than its short-term strength, due to the increased influence of time-dependent deformation mechanisms such as stress corrosion cracking (Brantut et al 2013). Further, in contrast to the short-term strength of granite (Xu et al 2008;Shao et al 2015;Kumari et al 2017), the long-term strength and time-to-failure in granite are considerably reduced by temperatures of a couple of hundred degrees Celsius (Kranz et al 1982;Xu et al 2017;Chen et al 2017). We highlight the long-term strength of granite from the URG (at room temperature and at elevated in situ temperatures) as an interesting avenue for future study.…”

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 99%

“…Brace et al 1966;Byerlee 1967;Tapponnier and Brace 1976;Wong 1982a;Lockner 1998;Eberhardt et al 1999;Oda et al 2002), and high-temperature uniaxial and triaxial experiments have studied the influence of temperature on brittle failure (e.g. Wong 1982b; Xu et al 2008;Shao et al 2015;Kumari et al 2017) and "transitional" and ductile behaviour (e.g. Tullis and Yund 1977;Violay et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

et al. 2018

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Knowledge of the strength and elastic modulus of a reservoir rock is important for the optimisation of a particular geothermal resource. The reservoir rock for many geothermal projects in the Upper Rhine Graben, such as those at Soultz-sous-Forêts and Rittershoffen (both France), is porphyritic granite. High fracture densities (up to ~ 30 fractures/m) in this reservoir rock require that we consider the strength and elastic modulus of the rock mass, rather than the intact rock. Here we use uniaxial and triaxial deformation experiments performed on intact rock coupled with Geological Strength Index assessments-using the wealth of information from core and borehole analyses-to provide rock mass strength and elastic modulus estimates for the granite reservoir at Soultz-sous-Forêts (from a depth of 1400 to 2200 m) using the generalised Hoek-Brown failure criterion. The average uniaxial compressive strength and elastic modulus of the intact granite are 140 MPa (this study) and 40 GPa (data from this study and the literature), respectively. The modelled strength of the intact granite is 360 MPa at a depth of 1400 m and increases to 455 MPa at 2200 m (using our estimate for the empirical m i term of 30, determined using triaxial and tensile strength measurements on the intact granite). Strength of the rock mass varies in accordance with the fracture density and the extent and nature of the fracture infill, reaching lows of ~ 40-50 MPa (in, for example, the densely fractured zones in EPS-1 at depths of ~ 1650 and ~ 2160 m, respectively) and highs of above 400 MPa (in, for example, the largely unfractured zone at a depth of ~ 1940-2040 m). Variations in rock mass elastic modulus are qualitatively similar (values vary from 1 to 2 GPa up to the elastic modulus of the intact rock, 40 GPa). Our study highlights that macrofractures and joints reduce rock mass strength and should be considered when assessing the rock mass for well stability and rock mass deformation due to stress redistribution in the reservoir. We present a case study to demonstrate how a simple and cost-effective engineering method can be used to provide an indication of the in situ strength and elastic modulus of reservoir rock masses, important for a wide range of modelling and stimulation strategies. We recommend that the effect of macrofractures on rock mass strength and stiffness be validated for incorporation into geomechanical characterisation for geothermal reservoirs worldwide.

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Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 92%

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 99%

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 99%

Section: Rock Strength and Elastic Modulus Characterisationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

et al. 2018

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Experimental study on the mechanical properties, acoustic emission characteristics, and permeability evolution of sandstone under triaxial hydromechanical coupling

Wang

Song

Wang

et al. 2022

Energy Science & Engineering

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In situ stress and groundwater have important effects on the deformation and stability of deep underground rock masses. Therefore, it is extremely important to study the mechanical properties and permeability evolutionary processes of rocks under hydromechanical (HM) coupling. The purpose of this study was to investigate the mechanical properties and permeability evolution of sandstone using triaxial compression tests under different confining and seepage pressures. The test results show that the confining pressure can increase the strength of sandstone, whereas the seepage pressure has the opposite effect. The initial and maximum permeabilities were positively correlated with seepage pressure and negatively correlated with confining pressure. The confining and seepage pressures had little effect on the change in initial permeability. As a common parameter of acoustic emission (AE), cumulative AE counts can intuitively reflect the permeability evolutionary process in the sandstone failure process. A permeability evolutionary early warning model for the sandstone failure process under HM coupling is proposed. The results are helpful for understanding the influence of in situ stress and seepage pressure on deep sandstone and the permeability evolutionary mechanism, and they can be used to provide early warning of water inrush disasters in deep underground structures.

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Study on rock mechanics characteristics of deep shale in Luzhou block and the influence on reservoir fracturing

Han

Liu

et al. 2022

Energy Science & Engineering

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This paper aims to study the influence of deep formation conditions on the mechanical properties of shale, which is of great significance for the engineering application of efficient development of deep shale gas. In this study, a real-time high-temperature (25°C-170°C) triaxial compression experiment was first carried out on shale samples. Then, based on the analysis results of rock mineral components and discrete element numerical simulation technology, a thermo-mechanical coupling model (TMCM) was constructed, and the accuracy of the numerical model was verified. Finally, based on the micromechanical parameters, a numerical fracturing mechanism model considering the influence of temperature, natural fracture density, and fracture length was established, and the influence of current reservoir conditions on hydraulic fracturing was discussed. The results show that confining pressure has a greater effect on rock mechanics than temperature.When the temperature exceeds 110°C, the plasticity of rock samples increases, and the fracture morphology becomes complex. In addition, the increase in temperature promotes the fracture of microcracks to a certain extent. The research results are expected to provide a sufficient theoretical basis for the development and utilization of deep shale gas resources. K E Y W O R D Sdeep shale gas, PFC, rock mechanics, temperature, XRD | INTRODUCTIONShale gas, an unconventional energy source with abundant reserves, is a clean and environmentally friendly natural gas that has become an important strategic resource in China. 1,2 Deep shale gas in China has a great potential for exploitation. 3 However, a series of technological difficulties exist. 4 In particular, the high-temperature (HT) and high-pressure (HP) geological environment of deep reservoirs results in the transformation of rock mechanical properties, 5 which has a significant impact on geological evaluation, drilling technology, and fracturing. [6][7][8][9] Therefore, this requires considerable attention.In recent decades, several studies have focused on understanding the mechanical behavior of progressive damage and microscopic damage mechanisms of rocks

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Mechanical behaviour of Australian Strathbogie granite under in-situ stress and temperature conditions: An application to geothermal energy extraction

Cited by 175 publications

References 39 publications

Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

Experimental study on the mechanical properties, acoustic emission characteristics, and permeability evolution of sandstone under triaxial hydromechanical coupling

Study on rock mechanics characteristics of deep shale in Luzhou block and the influence on reservoir fracturing

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