| Abstract |
Fracture Network Engineering (FNE) involves the design, analysis, modeling and monitoring of in-field activities aimed at enhancing or minimizing rock mass disturbance. FNE relies specifically on advanced techniques to model fractured rock masses and correlate microseismic field observations with simulated microseismicity generated from these models. FNE thus involves the integrated use of two main technologies, as described below. 1. A Synthetic Rock Mass (SRM) numerical model — SRM models combine Bonded Particle Modeling with Discrete Fracture Networks (describing the pre-existing network of joints, faults or other fractures) to represent the rock mass on a large scale (100 m or larger). SRM samples are subjected to the same mechanical or fluid disturbance expected in the field and produce synthetic seismicity that can be compared directly with microseismic data collected in the field. 2. Enhanced Microseismic Analyses (EMA) – EMA is used to map a disturbed or enlarging fracture network within a monitored rock volume using microseismic data acquisition, signal processing and interpretation. The feedback provides “first-order” information to engineers on fracture development in situ, and provides network statistics such as fracture orientations, connectivity and failure mechanisms. The integrated use of these technologies means the SRM is enhanced and updated by the information provided by the microseismic data, and allows the microseismic data to be better interpreted by direct observation of the micromechanics within the particle models used. The validation of the predictive models resulting from the SRM technique makes it possible to develop robust guidelines for engineering fracture networks based on insitu conditions, rock mass properties and operational controls. The combined SRM–EMA procedure has been used successfully in several practical applications, including design and control of very large surface and underground mining (massive caving) operations, evaluation of empirical rules for the effect of size on the strength of rock masses, monitoring of hydraulic fracturing in petroleum production and observation of micro-seismic activity around underground openings. This paper provides details of recent developments in both SRM and EMA technology and suggests research that will lead to the application of FNE for more effective stimulation of an Enhanced Geothermal System (EGS). |