Prospect of HDR geothermal energy exploitation in Yangbajing, Tibet, China, and experimental investigation of granite under high temperature and high pressure

Zhao, Yangsheng; Feng, Zhiwei; Xi, Baoping; Zhao, Jinchang; Wan, Zhifeng; Zhou, Anchao

doi:10.3724/sp.j.1235.2011.00260

Cited by 31 publications

(14 citation statements)

References 6 publications

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“…The creep strains are larger and the creep lifetimes are shorter under the higher creep stresses. These creep behaviors under uniaxial tension were observed in the previous experiments 17,18) and are similar to those under compression, 34,35) which indicates that the proposed model is applicable to the creep deformation under uniaxial tension.…”

Section: Comparison Between the Simulated And Experimental Resultssupporting

confidence: 83%

“…These calculations were repeated under the control method of eq. (18). The simulated results reproduce the loading-rate dependence of peak strengths as well as residual strengths although the spaces between curves just after the peak strengths are wider in the simulation than those in the experiment.…”

Section: Comparison Between the Simulated And Experimental Resultsmentioning

confidence: 70%

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Modeling of Complete Stress-Strain Curves and Time-Dependent Behaviors of Rocks under Uniaxial Tension

2018

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Tensile stresses likely occur in the rock masses around large or intricately shaped caverns. Hydraulic fracturing for oil, gas, or geothermal development requires a deep understanding of crack extensions under tensile stress. Computer simulation is helpful for the estimation of such deformation and failure of in-situ rocks and requires a mechanical model representing complex rock behaviors under tension. The authors' research group previously proposed the variable-compliance-type (VC) model for rocks and examined the model under compression. In this study, the applicability of the VC model was investigated under uniaxial tension. The close relation between the VC model and the microscopic failure mechanisms of crack extensions under uniaxial tension was clarified using the linear elastic fracture mechanics and the damage mechanics. Based on the relation, the VC model was modified to reproduce the deformation and failure under uniaxial tension. Then the model was validated by comparing the simulated and experimental results of complete stress-strain curves in both dry and wet conditions, loading-rate dependence, and creep deformation of various rocks under uniaxial tension. In addition, the applicability of the model to numerical simulation programs and the future subjects were discussed.

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Section: Comparison Between the Simulated And Experimental Resultssupporting

confidence: 83%

Section: Comparison Between the Simulated And Experimental Resultsmentioning

confidence: 70%

Modeling of Complete Stress-Strain Curves and Time-Dependent Behaviors of Rocks under Uniaxial Tension

2018

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“…Although the temperature of hot dry rock (HDR) geothermal reservoir is generally higher than 200°C, HDR with lower temperature still has value to be developed [46]. According to our experimental data, granite has an obviously lower strength at 150°C when the injected pore fluid is scCO 2 .…”

Section: Implications For Egs Projectsmentioning

confidence: 79%

Effects of Water and scCO₂ Injection on the Mechanical Properties of Granite at High Temperatures

Shen

Zhang

et al. 2020

Advances in Civil Engineering

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Geothermal energy is an important resource to substitute for traditional fossil fuels. The mechanical properties of reservoir rock under the conditions of water and scCO2 injection at different temperatures are crucial for the safety of Enhanced Geothermal Systems. However, the effects of working fluid on the mechanical properties of granite at in situ temperatures are still rarely reported. To reveal the impact mechanisms, conventional triaxial compression experiments were conducted on granite specimens with different confining pressures (2–20 MPa), different pore fluid (10 MPa water or CO2), and different temperatures (25–150°C) in the present study. SEM analyses were applied to the specimens to determine failure surface morphologies after the experiments. The experimental results show that the effective confining pressure, pore fluid, and temperature have significant effects on the strength of granite specimens. The strength of granite increases with the increase of effective confining pressure, with similar granite strength under the same effective confining pressure (dry, water, and CO2). Temperature strengthening of granite is limited by high confining pressure (∼15 MPa). Under the effective confining pressure of 5 MPa, temperature weakening occurs on granite specimens when temperature is higher than 90°C. There is fluid diffusion in the specimens during compression. The higher viscosity of water may cause a temporary decrease in effective confining pressure, which may increase the strength of granite. The growth or formation of cracks is mainly observed in quartz and feldspar grains without short-term chemical effects. More visible cracks are observed on the specimens and more volume of fluid is injected under CO2 injection conditions, which may be beneficial to increase the permeability of geothermal reservoir.

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“…The geothermal energy of hot dry rock (HDR) is an undeveloped, safe, and renewable energy that is abundant all around the world [1,2]. China has a large number of geothermal resources, with developmental potential, which are distributed primarily in Tengchong in the Yunnan province, Qiongbei in the Hainan province, Changbaishan in the Jilin province, Wudalianchi in the Heilongjiang province, and Yangbajing in Tibet [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Destruction Law of Borehole Surrounding Rock of Granite under Thermo-Hydro-Mechanical Coupling

Feng

Chen

et al. 2020

Geofluids

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The destruction of the rock that surrounds boreholes under thermo-hydro-mechanical coupling is an important factor for borehole stability in hot dry rock (HDR) geothermal energy extraction. Failure experiments for granite under triaxial stress ( σ 1 > σ 2 > σ 3 ) were conducted as 500°C superheated steam was transported through the borehole. High-temperature steam leads to large thermal cracks in the surrounding rock, which are randomly distributed around the borehole and gradually expand outwards. The randomly distributed thermally induced microcracks increase the complexity of the initial fracture morphology around the borehole and contribute to the appearance of multiple branch fractures. Fracture development is negligibly affected by ground stresses during the initial stages. However, fractures are deflected towards the maximum horizontal principal stress under ground stresses during later periods. During fracture propagation, high-temperature steam more easily penetrates the rock because its viscosity is lower than water. Towards the end of the crack expansion, the steam loses heat and liquefies, which increases the elongation resistance, and results in the arrest and intermittent expansion of the cracks.

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Prospect of HDR geothermal energy exploitation in Yangbajing, Tibet, China, and experimental investigation of granite under high temperature and high pressure

Cited by 31 publications

References 6 publications

Modeling of Complete Stress-Strain Curves and Time-Dependent Behaviors of Rocks under Uniaxial Tension

Modeling of Complete Stress-Strain Curves and Time-Dependent Behaviors of Rocks under Uniaxial Tension

Effects of Water and scCO₂ Injection on the Mechanical Properties of Granite at High Temperatures

Destruction Law of Borehole Surrounding Rock of Granite under Thermo-Hydro-Mechanical Coupling

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Prospect of HDR geothermal energy exploitation in Yangbajing, Tibet, China, and experimental investigation of granite under high temperature and high pressure

Cited by 31 publications

References 6 publications

Modeling of Complete Stress-Strain Curves and Time-Dependent Behaviors of Rocks under Uniaxial Tension

Modeling of Complete Stress-Strain Curves and Time-Dependent Behaviors of Rocks under Uniaxial Tension

Effects of Water and scCO2 Injection on the Mechanical Properties of Granite at High Temperatures

Destruction Law of Borehole Surrounding Rock of Granite under Thermo-Hydro-Mechanical Coupling

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Effects of Water and scCO₂ Injection on the Mechanical Properties of Granite at High Temperatures