Investigation on the thermal cracking of shale under different cooling modes

Li, Xinlei; You, Lijun; Kang, Yili; Liu, Jiang; Chen, Mingjun; Zeng, Tao; Hao, Zhiwei

doi:10.1016/j.jngse.2021.104359

Cited by 10 publications

(4 citation statements)

References 56 publications

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“…The permeability was mainly controlled by the pyrolysis of organic matter and the thermal stress fracture of inorganic matter [19,20]. When the temperature exceeded the threshold temperature, the permeability increased rapidly to a value nearly 100 times the original [21]. The variation of shale permeability is slight when the heating temperature is lower than 200 degrees centigrade, and there is a process decreasing and then increasing the heating temperature to higher than 200 degrees centigrade [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Study on the Inner Mechanisms of Gas Transport in Matrix for Shale Gas Recovery with In Situ Heating Technology

Li,

Hu,

et al. 2024

Processes

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In order to improve the productivity of shale gas, in situ heating technology has been applied generally. However, this technology is limited by unknown properties in heated matrix, e.g., permeability. Therefore, a method for measuring the permeability of heated shale matrix particles was designed, and transport tests were conducted on the shale matrix at heating temperatures of 100~600 degrees centigrade. Through fitting the experimental data with numerical simulation results, pore structures and permeabilities at different heating temperature conditions were obtained and the corresponding transport properties were determined. The porosity and pore radius were positively correlated with the heating temperature, while the tortuosity was negatively correlated with the temperature of the heat treatment. Despite the weakening effect of Knudsen diffusion transport, slippage transport played a critical role in the transport function of the heated shale matrix, and the domination became stronger at higher heating temperatures. The study of gas transport in heated shale matrix provides a guarantee for the effective combination of in situ heating technology.

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Section: Introductionmentioning

confidence: 99%

Study on the Inner Mechanisms of Gas Transport in Matrix for Shale Gas Recovery with In Situ Heating Technology

Li,

Hu,

et al. 2024

Processes

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“…Guo et al (2020b) studied the physical and mechanical properties of shale with different bedding plane angles after air cooling at 25-300 C. The results show that a higher temperature can induce a more serious deterioration of rock properties. Li et al (2022) experimentally studied the thermal cracking behaviour in shale at 20-600 C under different cooling methods. The results show that water cooling has a stronger thermal shock than air cooling.…”

Section: Introductionmentioning

confidence: 99%

“…The results show that a higher temperature can induce a more serious deterioration of rock properties. Li et al. (2022) experimentally studied the thermal cracking behaviour in shale at 20–600°C under different cooling methods.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation on hydraulic fracture propagation in laminated shale based on thermo-hydro-mechanical-damage coupling model

Zhang

Guo

et al. 2023

International Journal of Damage Mechanics

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The temperature of a deep shale reservoir may reach more than 100°C, and the effect of thermal shock on shale hydraulic fracturing has rarely not been considered in previous studies. Based on mesoscopic damage mechanics and the finite element method, a thermo-hydro-mechanical-damage (THMD) coupling model considering temperature, seepage, stress, and damage fields was constructed to investigate the effects of reservoir temperature, convective heat transfer coefficient ( h), in-situ stress difference and bedding plane angle ( αθ) on shale hydraulic fracturing. The results show that multiple hydraulic fractures (HFs) can occur under thermal shock and that HFs control the distribution of seepage, temperature, and stress fields. Reservoir temperature, in-situ stress difference and αθ are primary factors affecting hydraulic fracturing, whereas h is a secondary factor. When the reservoir temperature rises from 50°C to 150°C, the initiation and breakdown pressures decrease by 65.5% and 16.7%, respectively. HFs cross the bedding plane more easily, and fracture complexity is obviously enhanced. A higher h is favourable for slightly reducing the initiation and breakdown pressures, but it has little influence on the fracture complexity. Once the in-situ stress difference is low, there is a high fracture complexity, but HFs are more easily captured by bedding planes to limit the propagation of fracture height. When the in-situ stress difference is high, HFs are more likely to form bi-wing fractures. Whether αθ is too large or small, it is not conducive to improving the fracture complexity. In this study, when αθ is 30°, HFs and bedding planes intersect to form a fracture network. Essentially, thermal shock plays a key role in reducing the initiation pressure and forming multiple HFs during the fracturing process, and fracture propagation mainly depends on the injection pressure. The results can serve as reasonable suggestions for the optimization of shale hydraulic fracturing.

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“…Heat treatment is another possible method to address the water-related damage in shale formation. , Jamaluddin et al first proposed heat treatment to eliminate the water block and clay swelling in the near-wellbore zone of water-sensitive sandstone formation. Experimental results showed that the bound and blocked water in sandstone core samples with 8–15% clay minerals can be removed after the heat treatment in a high-temperature oven, leading to permeability improvements of 51 and 764–988% in cores exposed to 600 and 800 °C, respectively.…”

Section: Introductionmentioning

confidence: 99%

Heating-Induced Enhancement of Shale Gas Transport and Its Application for Improving Hydraulic Fracturing Performance

et al. 2022

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Enhancing the gas transport capacity of shale is essential to obtain economical gas production. Thermal stimulation has been theoretically and experimentally proven as a feasible technology for improving shale gas extraction. In this work, Longmaxi organic-rich shale samples were heated at 200−1000 °C for 240 h to investigate the feasibility of heating-induced generation of additional gas transport pathways and improvement of gas transport capacity (diffusivity and permeability) within the shale matrix. Results show that the mass loss of shale samples is basically unchanged after 200 °C, while a significant mass loss ranging from 3.5 to 14.4% can be observed in the heat treatment at 400−1000 °C. Decomposition (e.g., organic matter, calcite, and dolomite) and clay dehydration are the primary causes of shale mass loss. The organic matter in the shale remained unchanged after 200 °C heat treatment but greatly reduced, until almost disappeared, after 400 and 600 °C heat treatments, and the content of carbonate minerals dropped sharply, until almost disappeared, after 600−1000 °C heat treatment. Nitrogen adsorption experiments and in situ scanning electron microscopy observations show a significant improvement of pore volume and pore size after 400−600 °C heat treatment. However, the mineral melt and recrystallization after the heat treatment at 800 and 1000 °C can cause pore destruction and densification, resulting in pore volume decrease, indicating that the best heating temperature in Longmaxi shale samples is around 600 °C to enhance the pore volume and connectivity in the shale matrix. The methane adsorption decreased by 63.0%, the effective diffusion coefficient in the macropore increased by 263 times after 600 °C, and the permeability increased by 212.8 times at 5 MPa confining pressure. The newly formed transport pathways derived from 600 °C heat treatment may also improve shale matrix permeability at a high effective stress ranging from 30 to 65 MPa, which is a typical stress condition in the shale formations 2000−4500 m in depth. Based on the experimental results in this study, we proposed the heat treatment to improve hydraulic fracturing performance by mitigating fracturing-induced formation damage (e.g., water blockage, clay swelling, and secondary precipitation) within the fracture−matrix interface. In situ combustion of shale gas in hydraulic fractures may be a possible method to heat the shale formations and generate heating-induced transport pathways on the wall surfaces of hydraulic fractures.

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Investigation on the thermal cracking of shale under different cooling modes

Cited by 10 publications

References 56 publications

Study on the Inner Mechanisms of Gas Transport in Matrix for Shale Gas Recovery with In Situ Heating Technology

Study on the Inner Mechanisms of Gas Transport in Matrix for Shale Gas Recovery with In Situ Heating Technology

Numerical simulation on hydraulic fracture propagation in laminated shale based on thermo-hydro-mechanical-damage coupling model

Heating-Induced Enhancement of Shale Gas Transport and Its Application for Improving Hydraulic Fracturing Performance

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