Investigation on the Fracture-Pore Evolution and Percolation Characteristics of Oil Shale under Different Temperatures

Haibo Tang, Yangsheng Zhao, Zhiqin Kang, Zhaoxing Lv, Dong Yang and Kun Wang
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Haibo Tang: College of Mining Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Yangsheng Zhao: Key Laboratory of In Situ Property Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China
Zhiqin Kang: Key Laboratory of In Situ Property Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China
Zhaoxing Lv: Key Laboratory of In Situ Property Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China
Dong Yang: Key Laboratory of In Situ Property Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China
Kun Wang: Shanxi Xinxin Composite Technology Co., Ltd., Taiyuan 030100, China

Energies, 2022, vol. 15, issue 10, 1-14

Abstract: It is well known that underground in situ pyrolysis technology for oil shale production is a promising field. In the in situ modification mining process, the permeability property of a shale matrix has a great effect on the transport capacity of pyrolytic products. For oil shale undergoing pyrolysis, the changes of internal structure (fracture and pore space) have a considerable influence on the permeability network which further affects the migration of hydrocarbon products. In this study, based on an oil shale retorting experiment performed under different temperatures (20 °C, 100 °C, 200 °C, 300 °C, 325 °C, 350 °C, 375 °C, 400 °C, 425 °C, 450 °C, 475 °C, 500 °C, 525 °C, 550 °C, 575 °C, 600 °C), an investigation on the distribution characteristics of the fractures was conducted using micro-CT technology. Meanwhile, mercury injection porosimetry was used to characterize the pore structure of the oil shale samples under different temperatures. Finally, a fracture-pore dual medium model was constructed to calculate the percolation probability to quantitatively describe the permeability variation of oil shale with temperature. The test results indicated that the higher the temperature, the larger were the pore spaces. The increase in pore volume due to pyrolysis temperatures mainly affected the pores ranging from 10 nm to 100 nm and occurred in the specific temperature range (400 °C to 425 °C). Additionally, CT images show that the fracture morphology varied with increasing temperature and the number and length of fractures at different temperatures were in great accordance with the fractal law statistically. On the other hand, simulation of the percolation probabilities discovered that in a single pore media model over the whole range of tested temperatures they were too low to exceed the threshold. In contrast, in the dual medium model, the theoretical threshold of 31.16% was exceeded when the temperature reached 350 °C. Moreover, the results demonstrated that fractures dominated the seepage channel and had more significant effects on the permeability of oil shale. What has been done in this study will provide some guidance for the in situ fluidization mining of oil shale.

Keywords: oil shale; pyrolysis; pore structure; fracture distribution; fracture-pore dual medium; percolation characteristics (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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