Effect of Injection Rate on Micro-seismicity Due to the Hydraulic Fracturing of Granite

Document Type

Conference Proceeding

Publication Date

1-1-2018

Abstract

Enhanced Geothermal Systems (EGS) utilize the heat of the earth to produce electricity or to heat buildings. In EGS, a crystalline rock, usually granite, is hydraulically-fractured to produce a network of fractures through which the water is circulated. While several pilot projects have proven that this technology can be successful, the strong seismicity caused during the hydraulic fracturing stage is limiting its widespread use. Therefore, the causes of this micro-seismicity need to be better understood. This research evaluated the effect of the rate of water injected in granite specimens on the magnitude and number of micro-seismic events produced during recently-conducted hydraulic fracturing tests. In these tests, granite specimens subjected to two different vertical loads (0 and 5 MPa) were hydraulically-fractured while visual and micro-seismic monitoring was performed. The objectives of this paper were to examine the relationship between the number and amplitudes of the first P-wave arrivals of micro-seismic hits, and the rates of water injected used in the tests. It was found that in pressure increments closer to failure, more AE (Acoustic Emission) hits occur after the highest injection rates. This delayed seismic response may be due to the release of stresses accumulated during the high injection-rate stages of the tests. The study also showed that considerable energy is released throughout the tests as hits with relatively high P-wave amplitudes are observed before the visible fractures propagate

Identifier

85197862548 (Scopus)

ISBN

[9789811301124]

Publication Title

Proceedings of Geoshanghai 2018 International Conference Rock Mechanics and Rock Engineering

External Full Text Location

https://doi.org/10.1007/978-981-13-0113-1_16

First Page

137

Last Page

144

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