A study of arbitration method for determination of shale brittleness index
The ambiguous definitions of both brittleness and compressibility have led to longstanding debate on the characterization of shale brittleness. To resolve this, this study proposes a standardized shale brittleness index (SBI), defined as propensity of shale to breaking with minimal plastic deformati...
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| Format: | Article |
| Language: | English |
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AIP Publishing LLC
2025-05-01
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| Series: | AIP Advances |
| Online Access: | http://dx.doi.org/10.1063/5.0272122 |
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| author | Jian Min Jian Yang Fei Liu Ze Li Yuntao Liu Jun Su Wende Yan |
| author_facet | Jian Min Jian Yang Fei Liu Ze Li Yuntao Liu Jun Su Wende Yan |
| author_sort | Jian Min |
| collection | DOAJ |
| description | The ambiguous definitions of both brittleness and compressibility have led to longstanding debate on the characterization of shale brittleness. To resolve this, this study proposes a standardized shale brittleness index (SBI), defined as propensity of shale to breaking with minimal plastic deformation under tensile, shear, and compressive loads under standard conditions (20 °C, 101.325 kPa), clarifying its distinction from compressibility. Building upon material brittleness concepts and fracture mechanics, an arbitration method for SBI determination was developed by integrating three normalized components—peak stress-to-elastic modulus ratio, Young’s modulus, and peak strain—to quantify susceptibility to fracture and plastic strain. With this method, we analyzed the mechanical properties and mineral compositions of 25 downhole core samples from 17 shale gas wells across five formations in the Sichuan Basin. Our results revealed that the proposed method (B3) achieves correlation coefficients of 0.6443 and 0.6438 with conventional elastic strain ratio (B1) and mineral-weighted (B6) methods, respectively. B3 outperforms oversimplified approaches such as quartz content (B5) and Rickman’s modulus–Poisson’s ratio (B4) methods. The method enables cost-effective SBI evaluation using standard triaxial test data without complex stress-unloading experiments. It provides a robust basis for optimizing hydraulic fracturing stage placement—particularly in high-quartz (>70%), low-clay (<15%) intervals (e.g., Longmaxi 11 Formation) where B3 values exceed 80. This work establishes a five-tier classification framework (mechanism/definition/empirical levels) to resolve methodological inconsistencies across 45 existing indices, advancing standardized brittleness evaluation for shale reservoir stimulation. |
| format | Article |
| id | doaj-art-9d52eb958721445b80eb024d338d5bd5 |
| institution | OA Journals |
| issn | 2158-3226 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | AIP Advances |
| spelling | doaj-art-9d52eb958721445b80eb024d338d5bd52025-08-20T01:58:28ZengAIP Publishing LLCAIP Advances2158-32262025-05-01155055121055121-1310.1063/5.0272122A study of arbitration method for determination of shale brittleness indexJian Min0Jian Yang1Fei Liu2Ze Li3Yuntao Liu4Jun Su5Wende Yan6Engineering Technology Research Institute, Southwest Oil and Gas Field Company, Chengdu, ChinaEngineering Technology Research Institute, Southwest Oil and Gas Field Company, Chengdu, ChinaEngineering Technology Research Institute, Southwest Oil and Gas Field Company, Chengdu, ChinaEngineering Technology Research Institute, Southwest Oil and Gas Field Company, Chengdu, ChinaEngineering Technology Research Institute, Southwest Oil and Gas Field Company, Chengdu, ChinaEngineering Technology Research Institute, Southwest Oil and Gas Field Company, Chengdu, ChinaSchool of Petroleum and Natural Gas Engineering, Chongqing University of Science and Technology, Chongqing, ChinaThe ambiguous definitions of both brittleness and compressibility have led to longstanding debate on the characterization of shale brittleness. To resolve this, this study proposes a standardized shale brittleness index (SBI), defined as propensity of shale to breaking with minimal plastic deformation under tensile, shear, and compressive loads under standard conditions (20 °C, 101.325 kPa), clarifying its distinction from compressibility. Building upon material brittleness concepts and fracture mechanics, an arbitration method for SBI determination was developed by integrating three normalized components—peak stress-to-elastic modulus ratio, Young’s modulus, and peak strain—to quantify susceptibility to fracture and plastic strain. With this method, we analyzed the mechanical properties and mineral compositions of 25 downhole core samples from 17 shale gas wells across five formations in the Sichuan Basin. Our results revealed that the proposed method (B3) achieves correlation coefficients of 0.6443 and 0.6438 with conventional elastic strain ratio (B1) and mineral-weighted (B6) methods, respectively. B3 outperforms oversimplified approaches such as quartz content (B5) and Rickman’s modulus–Poisson’s ratio (B4) methods. The method enables cost-effective SBI evaluation using standard triaxial test data without complex stress-unloading experiments. It provides a robust basis for optimizing hydraulic fracturing stage placement—particularly in high-quartz (>70%), low-clay (<15%) intervals (e.g., Longmaxi 11 Formation) where B3 values exceed 80. This work establishes a five-tier classification framework (mechanism/definition/empirical levels) to resolve methodological inconsistencies across 45 existing indices, advancing standardized brittleness evaluation for shale reservoir stimulation.http://dx.doi.org/10.1063/5.0272122 |
| spellingShingle | Jian Min Jian Yang Fei Liu Ze Li Yuntao Liu Jun Su Wende Yan A study of arbitration method for determination of shale brittleness index AIP Advances |
| title | A study of arbitration method for determination of shale brittleness index |
| title_full | A study of arbitration method for determination of shale brittleness index |
| title_fullStr | A study of arbitration method for determination of shale brittleness index |
| title_full_unstemmed | A study of arbitration method for determination of shale brittleness index |
| title_short | A study of arbitration method for determination of shale brittleness index |
| title_sort | study of arbitration method for determination of shale brittleness index |
| url | http://dx.doi.org/10.1063/5.0272122 |
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