Study on the effects of water content and layer orientation on mechanical properties and failure mechanism of shale

Chenyu Wang, Shujian Li, Dongming Zhang, Beichen Yu and Xiaolei Wang

Energy, 2023, vol. 271, issue C

Abstract: In hydraulic fracturing, the drilling direction and hydraulic pressure can be simulated by the layer orientation (θ) and water content (ω) of the Brazilian splitting test. In this study, Brazilian splitting and acoustic emission tests of shale were carried out. The results show that the development characteristics of primary and secondary cracks are dominated by layer orientation(θ) and water content(ω), respectively. When θ = 60°, the layer shear slips significantly aggravate the crack rapid propagation. The cumulative AE count, tensile strength (σtm), tensile elastic modulus (Et) and brittleness index (BIt) are negatively correlated with water content (ω), and the average decreasing rates are 35.4%, 22.3%, 28.1% and 26.7%, respectively. Meanwhile, these parameters are minimum near θ = 60°. The fractal dimension (Df) of AE signal is positively correlated with the shale fracture complexity. As the layer orientation(θ) and water content(ω) significantly affects crack propagation and conductivity in shale, the drilling angle of 77° and the pressure of 10 MPa are selected in hydraulic fracturing to ensure the crack expansion capacity and avoid crack closure. The study can serve as a reference for hydraulic fracturing and shale gas extraction.

Keywords: Hydraulic fracturing; Layer orientation; Water content; Brazilian splitting; Shale; Acoustic emission (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:271:y:2023:i:c:s0360544223004449

DOI: 10.1016/j.energy.2023.127050

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