Damage Analysis of High-Temperature Rocks Subjected to LN2 Thermal Shock

Wu, Xiaoguang; Huang, Zhongwei; Zhang, Shikun; Cheng, Zhen‐Qiang; Li, Ran; Song, Hengyu; Wen, Haitao; Huang, Pengpeng

doi:10.1007/s00603-018-1711-y

Cited by 119 publications

(22 citation statements)

References 38 publications

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“…The result shows that the mineral composition of bituminous coal mainly was kaolinite (60.8%), pyrite (16.2%), quartz (14.4%), and calcite (8.6%). A larger discrepancy in the thermal expansion coefficients between different minerals can induce more severe damage . The thermal expansion coefficient of quartz is 16.6‐24.3 × 10 −6 /°C, which is significantly higher than that of other minerals, as shown in Table .…”

Section: Macroscopic Fracture Evolution Before and After Ln2 Treatmentmentioning

confidence: 92%

Experimental study on the seepage characteristics of bituminous coal under the conditions of liquid nitrogen fracturing

Chen

Zhang

et al. 2019

Energy Science & Engineering

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In coalbed methane (CBM) exploitation, liquid nitrogen (LN2) fracturing has attracted much attention as a promising and effective means to enhance coal seam permeability. Considering the bituminous coal in the Xutuan coal mine of Anhui Province, China, the permeability characteristics of coal samples under different pressure and stress conditions, and a single LN2 treatment and cyclic fracturing conditions were studied. Additionally, an evaluation of the macroscopic cracking behavior of coal was carried out. LN2 treatment can be very effective in promoting the generation of macroscopic fissures in the coal, and the degree of damage increases with the number of fracturing cycles. The results of a single LN2 treatment showed that under a constant confining pressure, the permeability increased exponentially with the increase in gas pressure. The cyclic LN2 treatment showed that permeability first decreased and then increased with increasing gas pressure, which is consistent with the quadratic function distribution. The permeability of the coal sample increases exponentially with the number of cycles, but the growth rate gradually slows down. For the same absolute fracturing time, cyclic fracturing had a better fracturing effect than a single cycle, and the ratio of the permeability increment is 126.3%‐213.8%. The research results provide some guidance for the development of the LN2 freeze fracturing technology.

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Section: Macroscopic Fracture Evolution Before and After Ln2 Treatmentmentioning

confidence: 92%

Experimental study on the seepage characteristics of bituminous coal under the conditions of liquid nitrogen fracturing

Chen

Zhang

et al. 2019

Energy Science & Engineering

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“…Generally, the geothermal energy is mainly stored in a hot granite reservoir, which is distributed at the depth of 2-6 km with a temperature above 150 °C [6]. Due to the low permeability of reservoir matrices, the permeability enhancement technologies are often suggested to improve the thermodynamic efficiency and productivity of the enhanced geothermal system [7,8]. Liquid nitrogen (LN 2 ) cryogenic fracturing has been proven to be an efficient stimulation method, which has a great potential in establishing pathways with high permeability [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…Shao et al [18,19] found that rapid cooling would instigate more thermal cracking within the granite, leading to more pronounced deterioration of mechanical properties. Subsequently, they considered the potential causes of the thermal sensitivity discrepancy among the three rocks based on the result of scanning electron microscope (SEM) and X-ray diffraction (XRD) [8]. However, Wu et al [20] indicated that the uniaxial compressive strength (UCS) of granites cooled in water did not drop a lot until the rock temperature reached to 400 °C.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Mechanical and Permeability Evolution Effects of High-Temperature Granite Exposed to a Rapid Cooling Shock with Liquid Nitrogen

Wang

Xue

et al. 2021

Geofluids

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Liquid nitrogen (LN2), which can greatly improve the efficiency of hot dry rock (HDR) mining, is commonly used as a cooling material in the enhanced geothermal system (EGS). Physical property, triaxial compression, and permeability tests were undertaken on treated granite samples, for a better scientific understanding of the effect of the LN2 cooling method on the mechanical and permeability properties of the rocks after heat treatment. The experimental results indicated that the physical properties of the treated granite change significantly, such as the density and wave velocity are substantially reduced. Meanwhile, with the increase of treatment temperature, the macroscopic cracks on its surface are gradually generated and the volume is expanded clearly. In addition, the surface wettability of granite gradually increases with increasing temperature. Compared with the air/water cooling methods, under LN2 cooling condition, the mechanical properties decrease markedly. When the temperature exceeds 600°C, the granite strength decreases significantly to only 56.16% of the reference value. The deformation properties also change significantly, with a final strain of about 3% at failure for a sample at 800°C, showing an obvious ductile deformation characteristic. Further, an appreciable correlation also exists between the initial permeability of granite and temperature. Once the temperature exceeds 200°C, the increase in temperature contributes to the increase in initial permeability. In addition to the effect of temperature, the increase in load also leads to a change in the permeability coefficient. When the temperature reaches 600°C, the permeability of granite first decreases and then increases with the increases in axial stress. The results of this paper are valuable in understanding the effect of thermal shock by LN2 on the fracturing efficiency and permeability characteristics of dry hot rocks.

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“…The feasibility of cryogenic fracturing in reservoir stimulation was proved by a well-known field test using LN 2 as the fracturing fluid in 1998 [5]. Thereafter, various studies were carried out to investigate the cryogenic fracturing [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…Energies 2020, 13, x FOR PEER REVIEW 2 of 21 fluid in 1998 [5]. Thereafter, various studies were carried out to investigate the cryogenic fracturing [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Most of these investigations are based on experimental results, which mainly focused on the mechanical changes of the reservoir stratum (evolution of permeability, initiation and propagation of cracks, alteration of mechanical properties, etc.)…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Displacement of Water by Sub-Zero N-Hexanol in a Straight Channel

Huang

Wang

2020

Energies

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Series of displacement tests of water by cold n-hexanol (below 0 °C) in a straight tube were conducted to investigate the freezing-accompanied displacement process, which occurs during the cryogenic fracturing process. The interrelationship between water freezing and displacement flow was studied. It was found that the displacement flow could significantly affect the water distribution in the flow channel. Along with the displacement proceeding, the n-hexanol overtook the water in the flow direction gradually, and the water in the center of the channel was driven to the edge area. Moreover, the initially integrated water phase split into several parts during the displacement process. Once the water freezing occurred, two typical ice blockage patterns, i.e., complete ice blockage and incomplete ice blockage, were observed. In incomplete ice blockage pattern, the channel cross-section was partly occupied by the ice phase, which mainly affected the rate of subsequent fluid flow. In complete ice blockage pattern, the channel cross-section was fully occupied by the ice phase, which cut off the fluid flow in the original direction. Based on the test results, the influences of the initial water temperature, initial water column length and flow rate of n-hexanol on the formation of different ice blockage patterns are discussed. The decrease of the initial water temperature and the increase of the initial water column length are preferred to induce the occurrence of complete ice blockage. However, changing n-hexanol flow rate could lead to the occurrence of both incomplete ice blockage and complete ice blockage, which depends on the actual situations.

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Damage Analysis of High-Temperature Rocks Subjected to LN2 Thermal Shock

Cited by 119 publications

References 38 publications

Experimental study on the seepage characteristics of bituminous coal under the conditions of liquid nitrogen fracturing

Experimental study on the seepage characteristics of bituminous coal under the conditions of liquid nitrogen fracturing

Investigation of the Mechanical and Permeability Evolution Effects of High-Temperature Granite Exposed to a Rapid Cooling Shock with Liquid Nitrogen

Experimental Study on Displacement of Water by Sub-Zero N-Hexanol in a Straight Channel

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