Study on the damage characteristics and damage model of organic rock oil shale under the temperature effect

Zhao, Guijie; Chen, Chen; Yan, Hao; Hao, Yinlong

doi:10.1007/s12517-021-07046-x

Cited by 6 publications

(4 citation statements)

References 27 publications

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“…The most basic task is selecting an appropriate damage variable to characterize the damage to the rock [21,22]. Based on the principles of residual strain [23], elastic modulus [24] and P-wave velocity [25], scholars have established expressions of damage variables. The attenuation of the elastic modulus and the accumulation of residual deformation are the external manifestations of damage; they cannot quantitatively reflect the degree of damage.…”

Section: Introductionmentioning

confidence: 99%

Energy Evolution and Damage Mechanism of Fractured Sandstone with Different Angles

Yao

Liu

et al. 2022

Energies

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To explore the influence of crack angle on the mechanical properties, energy evolution, and damage evolution of sandstone, uniaxial loading tests were conducted on sandstones with different crack angles. Through the stress–strain curve, the influence of the crack angle on the mechanical properties was analyzed. Based on energy theories and principles, the influence of crack angle on the energy conversion mechanism was analyzed. Based on crack angle and dissipated energy, a damage model considering the initial damage to the fractured sandstones was established. The following conclusions were drawn: (1) The strength and elastic modulus of sandstone decrease with an increase in crack angle, and Poisson’s ratio increases with an increase in crack angle; prefabricated cracks affect the crack initiation position, and accelerate the formation of fracture surfaces. (2) The stress–strain curve was divided into compaction stage, elastic stage, yield stage, and failure stage. The larger the crack angle, the longer the yield stage and the shorter the failure stage. (3) At the peak point, the elastic energy, dissipated energy, and input energy of fractured sandstone always decrease with an increase in crack angle; the energy consumption ratio increases with an increase in crack angle; and the energy storage ratio decreases with an increase in crack angle. (4) The damage variable shows a trend of slow accumulation–steady accumulation–rapid accumulation; the crack angle affects the initial damage of the specimen, and the dissipated energy affects the variation trend of the damage variable.

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Section: Introductionmentioning

confidence: 99%

Energy Evolution and Damage Mechanism of Fractured Sandstone with Different Angles

Yao

Liu

et al. 2022

Energies

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“…In recent years, researchers , have combined fractal theory with underground reservoirs to analyze the complex microscopic pore structure of the underground reservoirs. In addition, the pore structure of shale under heating and transformation conditions also has obvious fractal characteristics. , The larger the fractal dimension, the weaker the self-similarity and the higher the disorder and irregularity. Fractal theory is an important means to link the microstructure of the pore space roughness and pore surface roughness with the macroscopic quantitative characteristics.…”

Section: Resultsmentioning

confidence: 99%

Experimental Investigation on Composition and Pore Structure Evolution of Organic-Rich Shale via Supercritical Water

Meng,

Yao,

et al. 2023

Energy Fuels

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In in situ transformation of organic-rich shale, the evolution of shale composition and internal pore structure not only is directly related to the heat and mass transfer process but also affects the flow and migration of pyrolysis products in shale pores. In this study, the influence of high-temperature and high-pressure N 2 and supercritical water on shale pyrolysis process was compared. The results illustrated that the specific surface area of a shale under N 2 was lower than that under supercritical water. As a pyrolysis medium, supercritical water is more favorable to the development of pores in a shale. As the supercritical water temperature increased, the ratio of the micropores to mesoporous pores changed, leading to a significant increase in the average pore size. The expansion of the pores inside a shale and the development of effective pores are conducive to the formation of more seepage channels inside the shale, thus increasing the connectivity of the shale matrix. In addition, the porosity of the shale under supercritical water increased from 7.0182% at room temperature to 53.1124% at 450 °C, and the porosity increased by 7.6 times, which indicated that the supercritical water temperature could control the change of shale porosity. These phenomena highlight the potential of supercritical water application in in situ shale transformation.

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“…This can provide a basis for the mechanism of thermal crack, but it cannot be fully consistent with the actual fracture situation. In addition, some scholars have established some simplified solid-thermal coupling mathematical models to explore the temperature threshold of thermal crack and the conditions for different crack propagation paths in theory [26][27]. Based on the above analysis, it can be seen that there has been many research on rock thermal crack, but the main purpose of the research is to provide mechanism analysis for the variation of macroscopic physical and mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Study on Thermal Crack Characteristics of Granite in Shandong Province, China under Different Temperatures and Heating/Cooling Treatments

Zhang,

Li,

Zhang

et al. 2023

Preprint

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Understanding the thermal cracks of rock caused by high temperature is of great help to the development of underground engineering, such as geothermal mining, underground coal gasification. Although there has been many study on thermal cracking, it is not systematic and in-depth enough. In order to deeply study the thermal crack mechanism of rock, this paper conducted thermal cracking experiments on granite at different temperatures and heating/cooling paths, and qualitative and quantitative analysis was conducted on the crack initiation characteristics, propagation paths, and crack network morphology of rock thermal crack under different test conditions. The thermal crack mechanism was also analyzed from the perspectives of mineral petrology, fracture mechanics, thermodynamics, and other aspects. The research results show that there are two obvious mutation points in the study temperature range for samples with fast cooling paths (SF path: slow heating and fast cooling; FF path: fast heating and fast cooling), around 200-300 ℃ and 600 ℃, respectively, while for samples with slow cooling paths (SS path: slow heating and slow cooling; FS path: fast heating and slow cooling), there is only one mutation point around 600 ℃. The initiation positions of thermal cracking under all temperature paths are relatively similar, with intergranular crack located between particles at the edge of the sample or intercrystalline crack in the middle of feldspar or quartz aggregates. The initiation temperature of SF and FF path specimens is relatively low compared to SS and FS path specimens, and the number and size of cracks is small. The crack network structure formed by the SF path is the most complex, with the largest crack ratio and cumulative crack length; The crack network structure formed by the FF path is relatively complex, with a larger main crack size but relatively fewer secondary cracks; The FS and SS paths do not form a complex network with good connectivity. The process of thermal crack development can be divided into three stages: the development of small cracks, the joint development of main cracks and small cracks, and the connection of cracks into a network structure. The mechanism of thermal crack propagation is that the expansion and thermal conductivity between different crystals are different. The thermal stress caused by temperature gradient and the tension or shear stress caused by the inconsistent deformation of crystals form stress concentration in weak areas such as particles boundary, cleavage, and original cracks. Firstly, it causes some crystals with smaller strength or less rounded shape to crack, and when the combined stress is large, the cracks will gradually expand along the existing fine cracks. This also explains that the most main cracks of the SF and FF path specimens mainly surround some large mineral aggregates or between particles.

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Study on the damage characteristics and damage model of organic rock oil shale under the temperature effect

Cited by 6 publications

References 27 publications

Energy Evolution and Damage Mechanism of Fractured Sandstone with Different Angles

Energy Evolution and Damage Mechanism of Fractured Sandstone with Different Angles

Experimental Investigation on Composition and Pore Structure Evolution of Organic-Rich Shale via Supercritical Water

Study on Thermal Crack Characteristics of Granite in Shandong Province, China under Different Temperatures and Heating/Cooling Treatments

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