LAPSE:2023.36580
Published Article
LAPSE:2023.36580
Fracture Patterns of Rocks Observed under Cryogenic Conditions Using Cryo-Scanning Electron Microscopy
August 3, 2023
Cryogenic fracturing, which uses liquid nitrogen (LN2) as a fracturing fluid, is a waterless fracturing method. However, previous attempts to investigate the fracture morphology of rocks after LN2 quenching have been mainly based on standard scanning electron microscopy (SEM) analysis at room temperature. This can be problematic since thermally-induced fractures created by temperature difference tend to close as a sample warms and thermal stress relaxes. To address this issue, we established a novel approach employing Cryo-scanning electron microscopy (Cryo-SEM) to investigate the fracture patterns induced by liquid nitrogen quenching under cryogenic conditions. This method can achieve in-situ visualization of fractures and pores with a nano-scale resolution at −190 °C. X-ray computed tomography (CT) is also employed to illustrate the fracture distribution inside samples. Cryo-SEM and standard SEM are compared, and statistical assessments are conducted to quantify fracture aperture size and closure scale. The results demonstrate that Cryo-SEM can more accurately preserve native fracture morphology and provide a more accurate means of evaluating fracture scales generated during LN2 quenching, particularly at higher temperature differences between rock and liquid nitrogen. Distinct fracture patterns and fracture width are observed for various rock types (i.e., coal, sandstone, shale, granite) by using these methods. More prominently, the maximum fracture width of coal, sandstone, shale and granite were 89.17 µm, 1.29 µm, 0.028 µm and 2.12 µm when the temperature difference between LN2 and rock samples were 296 °C. LN2 is shown to exhibit superior fracturing efficiency on coal and granite, characterized by complex fracture networks with branched fractures. This research contributes to our understanding of liquid nitrogen fracturing mechanisms and may offer effective approaches for unconventional reservoirs stimulation.
Keywords
cryo-scanning electron microscopy, cryogenic fracturing, fracture morphology, reservoir stimulation, thermal shock, unconventional reservoirs
Subject
Suggested Citation
An Q, Hong C, Wen H. Fracture Patterns of Rocks Observed under Cryogenic Conditions Using Cryo-Scanning Electron Microscopy. (2023). LAPSE:2023.36580
Author Affiliations
An Q: China United Coalbed Methane Corporation Ltd., Beijing 100015, China; Provincial Center of Technology Innovation for Coal Measure Gas Co-Production, Taiyuan 030082, China
Hong C: National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum, Beijing 102249, China [ORCID]
Wen H: National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum, Beijing 102249, China [ORCID]
Journal Name
Processes
Volume
11
Issue
7
First Page
2038
Year
2023
Publication Date
2023-07-07
Published Version
ISSN
2227-9717
Version Comments
Original Submission
Other Meta
PII: pr11072038, Publication Type: Journal Article
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LAPSE:2023.36580
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doi:10.3390/pr11072038
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Aug 3, 2023
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CC BY 4.0
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[v1] (Original Submission)
Aug 3, 2023
 
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Aug 3, 2023
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Calvin Tsay
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