The Kaiser effect in rocks: principles and stress estimation techniques

Lavrov, Alexandre

doi:10.1016/s1365-1609(02)00138-7

Cited by 281 publications

(150 citation statements)

References 58 publications

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“…The roughness of the fracture faces thus carries information about the stress history. This is in a way similar to other stress-memory effects in rocks, such as the Kaiser effect in acoustic emission, a phenomenon well known in rock mechanics (Becker et al 2010;Lavrov 2003).…”

Section: Discussionsupporting

confidence: 72%

Fracture permeability under normal stress: a fully computational approach

Lavrov

2016

J Petrol Explor Prod Technol

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Fractures contribute significantly to the overall permeability of naturally or hydraulically fractured reservoirs. In the cap rock, fractures may provide unwanted pathways for reservoir or stimulation fluids. Predicting fluid flow in naturally fractured rocks under production or fluid injection requires that permeability of a single, rough-walled fracture be well understood and accurately described as a function of the effective stress. The lack of information about the properties of fractures at depth calls for a numerical approach that would enable predicting the fracture permeability as a function of the effective normal stress. Such fully computational approach is developed in this study. The fracture deformation is calculated by solving the contact problem using the finite-element method. At each deformation step, the steady-state fluid flow in the fracture is computed in two orthogonal directions using the lubrication theory approximation, in order to evaluate the permeability and the hydraulic aperture of the fracture. The computational approach is tested on two examples: a 'brittle rock' (linear elastic) and a 'ductile rock' (linear elastic perfectly plastic). Both mechanical and hydraulic behaviours of the fracture under cyclic normal loading are found to be in qualitative agreement with the results obtained in a number of published experimental studies. The computational approach provides an insight into the actual mechanics of the fracture deformation under stress, and the effect of the latter on the permeability. In particular, hysteresis in the fracture roughness is obtained with the 'ductile rock', suggesting that (at least some) fractured rocks may retain 'memory' about their loading history imprinted in the fracture landscapes.

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Section: Discussionsupporting

confidence: 72%

Fracture permeability under normal stress: a fully computational approach

Lavrov

2016

J Petrol Explor Prod Technol

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“…As this memorized stress is reached, the AE activity increases. This phenomenon is known as Kaiser Effect (Lavrov 2003). The Kaiser effect may mask the micro-crack initiation threshold of rocks (Diederichs et al, 2004).…”

Section: Discussionmentioning

confidence: 99%

Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

2015

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Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating these parameters (e.g. hits and energy) to stress-strain plots of rocks let us detect cracking levels, properly. The number of AE hits is related to the number of cracks, and the AE energy is related to magnitude of the cracking event. For a full understanding of the fracture process in brittle rocks, prismatic specimens of granite containing pre-existing flaws have been tested in uniaxial compression tests, and their cracking process was monitored with both AE and high-speed video imaging. In this paper the characteristics of the AE parameters and the evolution of cracking sequences are analyzed for every cracking level. Based on micro-and macro-crack damage, a classification of cracking levels is introduced. This classification contains eight stages 1) crack closure, 2) linear elastic deformation, 3) micro-crack initiation (white patch initiation), 4) micro-crack growth (stable crack growth), 5) micro-crack coalescence (macro-crack initiation), 6) macro-crack growth (unstable crack growth), 7) macro-crack coalescence and 8) failure.

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“…Acoustic emissions (AE) are defined as transient elastic waves generated by the rapid release of energy within a material (Lockner et al 1992;Lavrov 2003;Antonaci et al 2012). They result from the generation, propagation of (micro-), nucleation or coalescence of cracks (Kendrick et al 2013).…”

Section: Crack Development and Measurementmentioning

confidence: 99%

“…The Kaiser effect is a well-known phenomenon in metallurgy (Kaiser 1950) but also in rock mechanics (Lockner 1993;Holcomb 1993;Lavrov 2003). It states that if a sample is subjected to a cyclic stress history, no acoustic emission occurs over a cycle until the applied stress exceeds the maximum previously applied stress.…”

Section: Kaiser Effectmentioning

confidence: 99%