Experimental Study on the Failure Mechanisms in Brittle Shales
Daobing Wang1, Xiaoqiong Wang2, Hongkui Ge2
1Department of Oil & Gas Storage and Transportation Engineering, Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development, Beijing Institute of Petrochemical Technology, Beijing 102617, People's Republic of China.
ACS Omega
|May 20, 2020
Summary
This study investigates brittle failure in Chengkou shale using triaxial tests and ultrasound. Shear wave velocity is sensitive to crack damage, and the Hoek-Brown criterion better predicts failure than Mohr-Coulomb.
Area of Science:
- Geotechnical Engineering
- Rock Mechanics
- Petroleum Engineering
Background:
- Brittle failure of shale formations is a significant challenge in hydrocarbon exploration and development.
- Understanding crack initiation, propagation, and coalescence is crucial for safe and efficient operations.
Purpose of the Study:
- To investigate the failure mechanisms of Chengkou shale.
- To analyze the mechanical behavior and crack evolution under various stress levels.
- To provide guidance for optimizing drilling and hydraulic fracturing operations.
Main Methods:
- Laboratory experiments using servo-controlled triaxial cells.
- Ultrasound monitoring to track wave velocity evolution.
- Analysis of stress-strain curves and failure criteria (Hoek-Brown and Mohr-Coulomb).
Main Results:
- Key mechanical parameters (peak stress, dilation onset stress, peak strain) show linear relationships with confining pressure.
- Wave velocity evolution accurately reflects stress-strain behavior; shear wave velocity is more sensitive to damage than compressional wave velocity.
- The Hoek-Brown criterion demonstrates a higher correlation coefficient (r²) compared to the Mohr-Coulomb criterion.
Conclusions:
- Wing crack damage models explain mixed tensile and shear failure mechanisms in Chengkou shale.
- Experimental findings offer valuable insights for optimizing drilling, well completion, and hydraulic fracturing in brittle shales.
- The study enhances understanding of shale mechanical behavior for improved resource extraction.
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