Effects of cyclic heating and LN2-cooling on the physical and mechanical properties of granite

Wu, Xiaoguang; Huang, Zhongwei; Cheng, Zhen‐Qiang; Zhang, Shikun; Song, Hengyu; Zhao, Xin

doi:10.1016/j.applthermaleng.2019.04.046

Cited by 120 publications

(31 citation statements)

References 35 publications

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“…is indicated that the rock structure was damaged by LN and the temperature gradient was an important factor. Wu et al [32,33] conducted a set of experiments to investigate variations of physical and mechanical properties of granite, including density, wave velocity, strength, and elastic modulus. According to the experimental results, they pointed out that the destruction of granite is aggravated with the number of heating and cooling cycles increasing.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation into the Distributions of Temperature and Stress around Wellbore during the Injection of Cryogenic Liquid Nitrogen into Hot Dry Rock Reservoir

Ren

Cai

2021

Mathematical Problems in Engineering

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Cryogenic liquid nitrogen fracturing is expected to provide an effective stimulation method for hot dry rock reservoirs to increase heat production. This paper establishes a three-dimensional model to calculate the distributions of temperature and stress of the reservoir rock when liquid nitrogen is injected into the wellbore. The sensitivity of different parameters and water fracturing to the stress state is studied. The results indicate that when liquid nitrogen is injected into the bottom of well, a huge heat exchange occurs on the rock surface, which generates great thermal stress on the fluid-solid interface, and the value of thermal stress exceeds the tensile strength of rock. For the effect of parameters, the primitive temperature of the rock has a significant impact on the value of maximum principal stress. The pressure drop and ambient pressure affect the thermal stress slightly. At the same time, a series of experiments are conducted to validate the effect of thermal stress induced by liquid nitrogen injection on the rock fracture. As the temperature rises, the shale samples are broken more severely at the action of thermal stress. Thus, the study of liquid nitrogen fracturing provides a scientific and effective method for geothermal exploitation.

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Section: Introductionmentioning

confidence: 99%

Numerical Investigation into the Distributions of Temperature and Stress around Wellbore during the Injection of Cryogenic Liquid Nitrogen into Hot Dry Rock Reservoir

Ren

Cai

2021

Mathematical Problems in Engineering

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“…As heating temperature increases, reductions in strength, elastic modulus, and P-wave velocities become more pronounced [17]. Heating and cooling cycles accelerate the mechanical deterioration of granite and augment permeability, which mainly occur during the initial few cycles, and elevating the heating temperature in cycles increases the damage rate of granite [18]. Compared to an abrasive water jet, an abrasive LN jet, which creates a larger and more irregular cavity with lower threshold pressure, exhibits better performance in perforation [19,20].…”

Section: Introductionmentioning

confidence: 99%

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

et al. 2021

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In cryogenic fracturing, a rock surface exposed to cryogenic fluids undergoes a large thermal gradient, and the resultant local tensile stress overcomes rock strength and initiates fractures. This study investigates the development of cracks generated from the cryogenic treatment of a borehole under no external confining stress on specimens. The experiments were performed on transparent PMMA specimens to observe fracture proliferation around boreholes. Liquid nitrogen was flowed through the boreholes to cool the borehole surface. The results show that initial fracture growth is characterized by abrupt starts and stops, and as the fracture propagates outward, the growth appears more continuous. In an early stage, horizontal/radial fractures and vertical fractures are the defining patterns. Horizontal fractures tend to be separated by a specific exclusion distance (i.e., spacing between cracks). While distinct horizontal/vertical fractures and exclusion distance manifest themselves at an early stage, fractures resulting from fracture interactions and curvatures can develop into complex shapes at later stages. Cryogenic thermal loading induces distinctively curved fractures. The tendency of curvature may prevent greater penetration. An increase in the borehole pressure during liquid nitrogen flow, however, can lessen fracture tortuosity and facilitate radial propagation. A high flow pressure and rate are also advantageous in that they accelerate cooling and fracture propagation.

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“…It is estimated that the energy content of HDR is 300 times of fossil fuel resources. Liquid nitrogen (LN 2 ) fracturing is an excellent method to produce geothermal energy (Wu et al 2019, Wu et al 2020, Yang et al 2021, and it is possible to form a large-scale fracture network with a good underground conductivity (Cha et al 2014). LN 2 is a cryogenic uid with a boiling temperature of − 195.8°C, at atmospheric pressure.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Compressive Strength and AE Characteristics of High-temperature Treated and LN2 Cooled Sandstone

Ding

Sun

Jia

et al. 2021

Preprint

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Liquid nitrogen (LN2) fracturing is beneficial to the development and utilization of geothermal energy. In this paper, the red sandstone was heated from room temperature to different temperatures (25°C-800°C) and then cooled with LN2. After attaining the room temperature, NMR, uniaxial compression, and acoustic emission (AE) tests were conducted, and results were compared for different samples. The results showed that with the increase in quenching temperature difference, the volume of micropores decreased gradually, while the volume of fine pores, mesopores, macropores and total porosity increased, resulting in the reduction of the compressive strength. Higher quenching temperature difference also reduced the sample’s total time to fail, and the failure mode was transformed from single inclined shear failure to conical failure. This is because the thermal stress (caused by the rapid cooling of LN2) expanded the original cracks of the sandstone, leading to high porosity and low compressive strength of the heat-treated and quenched samples.

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Effects of cyclic heating and LN2-cooling on the physical and mechanical properties of granite

Cited by 120 publications

References 35 publications

Numerical Investigation into the Distributions of Temperature and Stress around Wellbore during the Injection of Cryogenic Liquid Nitrogen into Hot Dry Rock Reservoir

Numerical Investigation into the Distributions of Temperature and Stress around Wellbore during the Injection of Cryogenic Liquid Nitrogen into Hot Dry Rock Reservoir

Propagation of Cryogenic Thermal Fractures from Unconfined PMMA Boreholes

Experimental Study on the Compressive Strength and AE Characteristics of High-temperature Treated and LN2 Cooled Sandstone

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