Showing papers by "Herbert H. Einstein published in 2020"
TL;DR: In this paper, the authors evaluate the radiated seismic energy normalized by external work for hydraulic fracturing, beam bending, and uniaxial compression experiments conducted on Opalinus clayshale and Barre granite specimens.
Abstract: We evaluate the radiated seismic energy normalized by external work for hydraulic fracturing, beam bending, and uniaxial compression experiments conducted on Opalinus clayshale and Barre granite specimens. Results suggest that normalized radiated seismic energy is highest for the beam bending, followed by uniaxial compression, and, finally, that the hydraulic fracturing experiments radiate the least seismic energy when normalized by external work. We also find that the normalized radiated energy during tests on Opalinus clayshale is 3% to 22% of that in Barre granite across multiple loading mechanisms.
7 citations
TL;DR: In this paper, the effect of penetration and non-penetrating fluids on hydraulic fracturing has been extensively studied, both theoretically and experimentally, and the results confirm that fluid penetration lowers breakdown pressure, does not affect the fracturing pattern, and influences the difference between fracture initiation and breakdown.
6 citations
TL;DR: In this paper, an in-house numerical code has been developed to simulate the viscoelastic deformation of rough fracture surfaces by systematically changing the surface roughness parameters: the Hurst exponent, mismatch length, and root mean square roughness.
Abstract: In many rock engineering projects such as hydrocarbon extraction and geothermal energy utilization, the hydraulic and mechanical behavior of rock fractures significantly affects the safety and profitability of the project. In field conditions, the hydraulic and mechanical behavior of rock fractures changes with time (the rock fractures creep), and this creep is not negligible even under dry conditions. In addition, creep is strongly affected by the rock fracture surface geometry. However, there is not much literature systematically studying the effect of surface geometry on rock fracture creep under dry conditions. This paper presents the results of a numerical study considering the effect of surface geometry on rough fracture viscoelastic deformations. An in-house numerical code has been developed to simulate the viscoelastic deformation of rough fractures. In addition, another numerical code has been developed to generate synthetic rough fracture surfaces by systematically changing the surface roughness parameters: the Hurst exponent, mismatch length, and root mean square roughness. The results indicate that by increasing the Hurst exponent or decreasing the mismatch length or decreasing the root mean square roughness, the fracture mean aperture decreases, and the contact ratio (number of contacting cells/total number of cells) increases faster with time.
2 citations