Experimental Investigation of the Anisotropic Evolution of Tensile Strength of Oil Shale Under Real-Time High-Temperature Conditions

Yang, Shengnan; Yang, Dinglong; Kang, Zhiqin

doi:10.1007/s11053-021-09848-y

Cited by 37 publications

(5 citation statements)

References 41 publications

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“…(3) The yield stage: In this stage, the stress–strain curve transitions to show nonlinear behavior; with increasing stress, the stress–strain curve begins to form a plateau. The reason for this phenomenon is that, when the internal loads within the oil shale exceed a certain limit, its internal fractures will expand, and mineral particles will become more distant, thus resulting in the continuous increase in the number and size of internal microfractures, a continuous breaking of internal stress balance, and a continuous consumption of accumulated energy [ 24 , 25 ].…”

Section: Resultsmentioning

confidence: 99%

Study on Pyrolysis–Mechanics–Seepage Behavior of Oil Shale in a Closed System Subject to Real-Time Temperature Variations

Wang

Huang

2022

Materials

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In situ mining is a practical and feasible technology for extracting oil shale. However, the extracted oil shale is subject to formation stress. This study systematically investigates the pyrolysis–mechanics–seepage problems of oil shale exploitation, which are subject to thermomechanical coupling using a thermal simulation experimental device representing a closed system, high-temperature rock mechanics testing system, and high-temperature triaxial permeability testing device. The results reveal the following. (i) The yield of gaseous hydrocarbon in the closed system increases throughout the pyrolysis reaction. Due to secondary cracking, the production of light and heavy hydrocarbon components first increases, and then decreases during the pyrolysis reaction. The parallel first-order reaction kinetic model shows a good fit with the pyrolysis and hydrocarbon generation processes of oil shale. With increasing temperature, the hydrocarbon generation conversion rate gradually increases, and the uniaxial compressive strength of oil shale was found to initially decrease and then increase. The compressive strength was the lowest at 400 °C, and the conversion rate of hydrocarbon formation gradually increased. The transformation of kaolinite into metakaolinite at high temperatures is the primary reason for the increase in compressive strength of oil shale at 400–600 °C. (ii) When the temperature is between 20 and 400 °C, the magnitude of oil shale permeability under stress is small (~10−2 md). When the temperature exceeds 400 °C, the permeability of the oil shale is large, and it decreases approximately linearly with increasing pore pressure, which is attributed to the joint action of the gas slippage effect, adsorption effect, and effective stress. The results of this research provide a basis for high efficiency in situ exploitation of oil shale.

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Section: Resultsmentioning

confidence: 99%

Study on Pyrolysis–Mechanics–Seepage Behavior of Oil Shale in a Closed System Subject to Real-Time Temperature Variations

Wang

Huang

2022

Materials

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“…Yang et al [10] conducted uniaxial compression tests on oil shale at real-time high temperatures and found that its compressive strength and elastic modulus first decrease and then increase as temperature increases. Yang et al [11] reported that the tensile strength of oil shale first decreases and then increases with temperature rising. However, real-time analyses of the shear properties of oil shale at high temperatures have not been reported.…”

Section: Introductionmentioning

confidence: 99%

Effect of real-time temperature and shear angle on the mechanical strength and energy evolution of oil shale

Ren¹,

Wang²,

Yang³

et al. 2022

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During in situ thermal injection in oil shale mining, the shear properties of oil shale at real-time high temperatures considerably affect the stability of injection and production wellbore as well as oil and gas production. The results of this study show that the shear strength and modulus of oil shale decrease with an increase in the shear angle at real-time high temperatures. With increasing temperature, the shear strength and modulus first decrease and then increase, reaching their lowest values at 400 °C. Thereafter, at temperatures above 400 °C, the energy accumulated in the elasticity and crack propagation stages is released and a large amount of energy is liberated during the instability failure. Finally, with rising temperature, the failure stage of oil shale changes from brittle to ductile, secondary fractures gradually increase and the failure characteristics step-by-step turn from through to nonthrough cracking characteristics.

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“…The increase in energy demand and low levels of oil resources have necessitated urgent research on alternative energy [1,2]. Oil shale, a finegrained sedimentary rock containing organic matter (kerogen) that can be converted into shale oil and gas, has attracted considerable attention as an auxiliary energy source owing to its abundant reserves and wide distribution [3][4][5][6]. Compared to directly burning oil shale as a powerplant fuel to generate electricity, aboveground retorting and in-situ pyrolysis of kerogen to yield oil and gas is currently more preva-lent [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…Compared to directly burning oil shale as a powerplant fuel to generate electricity, aboveground retorting and in-situ pyrolysis of kerogen to yield oil and gas is currently more preva-lent [6,7]. Among these extraction methods, in-situ retorting is the most promising technology for extracting liquid or gaseous hydrocarbons from wells by directly heating underground oil shale formations to avoid adverse environmental effects [4,[6][7].…”

Section: Introductionmentioning

confidence: 99%

Effects of composition and pore evolution on thermophysical properties of Huadian oil shale in retorting and oxidizing pyrolysis

Sun

Lü

et al. 2021

Fuel

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Experimental Investigation of the Anisotropic Evolution of Tensile Strength of Oil Shale Under Real-Time High-Temperature Conditions

Cited by 37 publications

References 41 publications

Study on Pyrolysis–Mechanics–Seepage Behavior of Oil Shale in a Closed System Subject to Real-Time Temperature Variations

Study on Pyrolysis–Mechanics–Seepage Behavior of Oil Shale in a Closed System Subject to Real-Time Temperature Variations

Effect of real-time temperature and shear angle on the mechanical strength and energy evolution of oil shale

Effects of composition and pore evolution on thermophysical properties of Huadian oil shale in retorting and oxidizing pyrolysis

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