Acoustic emissions and source mechanisms observed in the hydraulic fracturing of gypsum considering fluid diffusivity

Document Type

Conference Proceeding

Publication Date

1-1-2021

Abstract

Hydraulic fracturing is used to create new fractures and propagate existent ones, thus enhancing the permeability of a rock reservoir. Four experiments were conducted at constant injection rates in molded gypsum (high porosity, low-stiffness): two at 20ml/min and two at 2 ml/min. Not only did the test setup allow one to monitor Acoustic Emissions (AE), it also allowed one to visually observe i) the behavior of the fracturing and fluid patterns for each test, and ii) the fluid to diffuse into the rock matrix, while pre-fabricated flaws were gradually pressurized until cracks developed. By evaluating the time-variation of the source mechanisms of the AE events produced, it was noted that the number of AE events were spread-out throughout the specimen rather than concentrated near the flaws. This is interpreted to be a result of pore pressures diffusing through a larger area of the specimen. Also, by evaluating the time evolution of the source mechanisms of the AE events, these were classified as tensile, compressive, shear and mixed-mode. Compressive and tensile mechanisms were the most and less predominant, respectively.

Identifier

85123050623 (Scopus)

ISBN

[9781713839125]

Publication Title

55th U S Rock Mechanics Geomechanics Symposium 2021

Volume

4

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