Comparison of Rock Toughness Measurement Methods for Hydraulic Fracturing: A Research Note

Wang Xiaoming

Wang Xiaoming Independent Researcher

Keywords: Rock, Rock Toughness, Scratch Test, Straight-notched Brazilian Test, Semi-circular Bend Test

Abstract

One important rock property is toughness, which is the ability of a rock to resist further deformation or fracturing. Three modes used to quantify this property are: the opening mode (mode I), the shearing mode (mode II), and the tearing mode (mode III). In order to successfully fracture a rock, an estimation of rock toughness must be calculated for the formation. Three tests developed to quench that need are the scratch test, straight-notched Brazilian disc specimen test, and the semicircular bend test. The objective of this paper is to present the procedure, governing equation, and results for each test. Moreover, analysis of the results obtained from each test produced important correlations between rock toughness and shale properties. A comprehensive comparison is conducted on the tests presenting three primary differences, which are convenience, variables, and accuracy. In all three tests, the method used to induce fractures was a common limitation that restricted their applicability. This indicates the need to conduct more study and research in the field of fracture toughness measurement.

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