Publication Abstract

not signed in
Log In
Title Microseismic Investigation of Rock Fracture and its Application in Rock and Petroleum Engineering

Authors R. P. Young and C. Baker

Publication Reference 2001, International Journal of Rock Mechanics News Journal, 7, 19 - 27

Abstract The principles employed by seismologists to study earthquake mechanics and the internal structure of the Earth have, for several years, been applied to engineering-scale problems. These techniques have provided information on the condition of a rock-mass and its response to various types of human intervention. As seismology has made significant advancements over the last decade or so, so the application of these techniques to engineering problems has become more powerful and versatile. In particular, significant advances in instrumentation and computing power have broadened the scope of these investigations, and high fidelity seismic data are now routinely collected as part of many studies. Advances in software have provided the opportunity for real time processing and visualisation such that the results can now be used to optimise the way in which the particular engineering activity is undertaken. Thus, microseismic monitoring has matured from a science of ‘hazard assessment’ to one of a useful and versatile engineering tool. One significant factor that has greatly increased the potential utility of microseismic monitoring as a diagnostic technique has been recent advances in numerical modelling methods. While the advances in processing described in the preceding paragraph have provided increasingly sophisticated analysis of seismic source mechanisms, rock properties and rock mass behaviour, the ability to interpret these results has remained often subjective and sometimes ambiguous. This arises because many of the data processing techniques employed in seismology rely on data-inversion methods that, by nature, provide non-unique solutions. The development of fully dynamic modelling codes (e.g. the Particle Flow Code developed by the Itasca Consulting Group) has allowed realistic simulations of rock behaviour to be made. Such studies have improved our understanding of the fundamental mechanics of seismic processes, and thus allowed more controlled interpretations of observed data to be made. An integrated approach, employing both acoustic monitoring in the laboratory and the field, combined with geomechanical numerical modelling provides a very powerful method of understanding in situ rock mass behaviour. The modelling allows predications of the rock response to be made based on the properties obtained from laboratory experiments. The microseismic data is then collected in the field to validate the model and appropriate refinements are made to provide a realistic interpretation of the true behaviour. This complementary approach is shown schematically in Figure 1 and represents the current state of the art for this approach. This work was carried out by a consortium of Itasca Consulting Group (Minneapolis) and the Applied Seismology Group at Liverpool University funded by Atomic Energy Canada Limited and Ontario Power Generation. This paper aims to provide an overview of the types of information that can be obtained from microseismic data, particularly when used in conjunction with modelling methods, and to highlight some applications relevant to the fields of rock and petroleum engineering. The methods are illustrated by examples from recent studies using state of the art methodologies.

Key Figure Key Figure
FIGURE 1: PFC2D modelling of the mine-by tunnel (URL) showing: (top left) view of the mine-by tunnel after excavation; (top right) microcracks that have formed in a very fine resolution PFC2D simulation after 2 months of stress corrosion --- i.e., time dependent degradation of rock strength; (bottom left) seismicity recorded during excavation of round 7; (bottom right) seismicity 'recorded' in a coarse resolution PFC2D simulation. (Work by AECL, OPG, Itasca and Liverpool University - Courtesy of Atomic Energy Canada Ltd.))



Return to publications list

< Return to the home page   ::  Contact Us
Applied Seismology Consultants