Fatigue Behavior of Granite Subjected to Cyclic Hydraulic Fracturing and Observations on Pressure for Fracture Growth

Grain-scale analysis of fracture paths from high-cycle hydraulic fatigue experiments in granites and sandstone

“…Previous studies have pointed out that the injection duration and the interval may influence the total number of cycles required to breakdown the specimen. 10,32,33 However, this influence was not investigated in the present study.…”

“…31 GG is composed of 50.2% plagioclase, 21.4% quartz, 13.4% biotite, and 9.4% orthoclase as well as other minor minerals, such as hornblende. 32 The fraction of biotite is higher compared with that in Pocheon granite, and biotite in GG is either platy or nondescript in terms of grain shape. The average grain size of GG is ~ 0.9 mm and 1.5 mm measured in the short-and the long-axis, respectively, which is approximately half the average grain size in PG.…”

A critical review of the experimental and theoretical research on cyclic hydraulic fracturing for geothermal reservoir stimulation

“…In this scope, many rounds of CHF with CPUC schemes using different upper limits would be carried out. When the specimens fail within 100 cycles, this upper limit value is considered a reasonable value in practical engineering (Jung et al 2021;Zhuang et al 2019;Zhuang et al 2016). The lower limit of CPUC is usually determined according to the performance of the equipment and experiences, such as setting the lower limit as 1 MPa to expel the air in the pipe (Ji et al 2021), so this lower limit threshold may not be a definite value.…”

“…Increasing the number of cycles can lead to the accumulation of fatigue damage, resulting in induced rock failure during the loading process (Jung et al 2021). Tariq et al (2020) studied the relationship between the BP during CHF and THF and the number of cycles.…”

Special Issue on Rock Fracturing and Fault Activation: Experiments and Models

“…They observed a brittle-ductile transition between low-to high-confining pressures and propose that the failure might be controlled by a mechanical coupling between water-invaded zone and dry zone. Jung et al (2021) analysed in laboratory hydraulic fracturing experiments the fatigue behaviour of cylindrical granite samples subject to different continuous and cyclic injection schemes. They found that the number of cycles to failure increases exponentially with decreasing maximum pressure and that cyclic injection led to more acoustic emissions, lower seismic energy and higher Gutenberg-Richter b values as compared to the continuous injection cases.…”