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Andrews J.,Applied Seismology Consultants Ltd. | Reyes-Montes J.M.,Applied Seismology Consultants Ltd. | Young R.P.,University of Toronto
Transactions - Geothermal Resources Council | Year: 2011

Using continuous microseismic records is a novel technique for better monitoring and understanding the mechanics of fracture network evolution during reservoir stimulation, and to provide a tool for diagnostic evaluation of recorded microseismic data. Hydrofracture stimulations are widely used to optimize production volumes and extraction rates in enhanced geothermal systems, petroleum reservoirs and block-caving mines. Microseismic monitoring is now becoming a standard tool for evaluating the position and evolution of a given treatment, principally by source locating microseismic hypocenters and visualizing these with respect to the treatment volume and infrastructure. The continuous microseismic amplitude record includes the full history of the seismic energy response of the rock mass recorded at a given geophone. We present case studies illustrating the use of this technique for supplementing microseismic locations to better understand the evolution of fracture treatments, and to diagnose the condition of a given data set, so as to design criteria for more effective processing of the discrete microseismic events.

Pettitt W.S.,Itasca Consulting Group Inc. | Pierce M.,Itasca Consulting Group Inc. | Damjanac B.,Itasca Consulting Group Inc. | Hazzard J.,Itasca Consulting Group Inc. | And 7 more authors.
46th US Rock Mechanics / Geomechanics Symposium 2012 | Year: 2012

Fracture Network Engineering (FNE) is the engineering design of rock mass disturbance through the use of advanced techniques to model fractured rock masses numerically, and then correlate field observations with simulated fractures generated within the models. Microseismic (MS) monitoring is a standard tool for evaluating the geometry and evolution of the fracture network induced during a hydraulic treatment, principally by source locating MS hypocenters and visualizing these with respect to the treatment volume and infrastructure (Figure 1). The integrated use of Synthetic Rock Mass (SRM) modeling of the hydraulic fracturing with Enhanced Microseismic Analysis (EMA) provides a feedback loop where the SRM is constrained by the information provided by the MS data, and the in-situ behavior of the fracture network is better understood, which leads to informed decisions on future field operations. This paper discusses the technologies used in FNE and some of the developmental challenges we face in order to provide a more efficient and robust application of the approach. Copyright 2012 ARMA, American Rock Mechanics Association.

King M.S.,Imperial College London | Pettitt W.S.,Itasca Consulting Group Inc. | Haycox J.R.,Applied Seismology Consultants Ltd. | Young R.P.,University of Toronto
Geophysical Prospecting | Year: 2012

A polyaxial (true-triaxial) stress-loading system, developed originally for determining all nine components of P- and S-wave velocities and attenuation and fluid permeability for 50.8 mm-side cubic rock specimens tested to failure, has been modified to permit the measurement of acoustic emission events associated with the failure process. Results are reported for Crosland Hill sandstone tested to failure under loading conditions leading to the formation of sets of aligned microcracks, achieved by maintaining the minor principal stress at a low value while increasing the two other principal stresses until failure of the rock. An ultrasonic survey associated with the test has been employed to map the transversely-isotropic velocity structure created by through-going parallel fractures resulting from the sets of aligned microcracks. This velocity structure has then been employed to locate acoustic emission events recorded during the test by four acoustic emission sensors located in each of the six specimen loading platens. A selection of acoustic emission events associated with one of the fractures has been processed for moment tensor analysis information, in order to determine the source type and orientation of microcracking as the fracture grows. The mechanisms indicate tensile behaviour during initial fracture propagation. Shear failure, however, appears to dominate as the fracture finally approaches the opposite face of the cubic specimen. The work presented here has, in part, led to the development of new rock testing systems and geophysical monitoring and processing technologies that will enable laboratory study of rock behaviour under conditions better resembling those experienced in situ. © 2011 European Association of Geoscientists & Engineers.

Milkereit B.M.,University of Toronto | Saleh R.,University of Toronto | Huang J.W.,Applied Seismology Consultants Ltd. | Valley B.V.,ETH Zurich
76th EAGE Conference and Exhibition 2014, Workshops | Year: 2014

Currently, only rnicroseismicity is used as a proxy for stress near deep mines. However, most of the physical properties of crystalline rocks are highly stress dependent. As such, the nonlinear and anisotropic variability of the in situ P-and S-wave velocities can potentially be linked directly to changes in the stress field. At an in-mine seismic laboratory, multi-component sensor arrays are deployed in multiple locations (3D) allowing for both controlled source and passive recordings. Previous in-mine seismic observatories have experienced a number of challenges with regards to sensitivity and longevity. Hence, the geothermally cool but highly stressed Sudbury mining camp offers a favourable setting for fundamental research in to time-lapse monitoring of seismicity, stress, and stress dependent physical properties at a deep mine.

Zhao X.P.,Applied Seismology Consultants Ltd. | Reyes-Montes J.M.,Applied Seismology Consultants Ltd. | Young R.P.,University of Toronto
46th US Rock Mechanics / Geomechanics Symposium 2012 | Year: 2012

Hydraulic fracturing methods for reservoir treatment are applied to increasingly complex environments including naturally or previously fractured reservoirs. The potential interaction with the in-situ fracture network or with fracturing induced in previous treatments plays a crucial role in the outcome of the stimulation, controlling the extent and geometry of the paths of enhanced fluid migration. Passive microseismic (MS) monitoring can provide an imaging of the effect of hydraulic treatments and an indication of the relative role of pre-existing fractures in the development of the fracture network. Further insights into the mechanisms of the induced fracturing is provided by the use of Synthetic Rock Mass (SRM) numerical models that reproduce the nature of the rock and the stress conditions imposed by the engineering. The rock mass is reproduced by an assembly of bonded particles with an embedded Discrete Fracture Network (DFN) to represent joints, faults or other pre-existing fractures. This study presents the analysis of the microseismicity induced during the treatment of a pre-fractured reservoir. The observations are compared with the results from tests on SRM samples that are subjected to the same fluid disturbance applied in the field, with a suite of DFN to reproduce potential in-situ fracturing scenarios. The combination of microseismic observations with the suite of SRM models will allow an interpretation of the fracture mechanism and its relation with the reservoir pre-existing fracturing. This combined approach provides field engineers with a unique tool for the design, monitoring and optimization of reservoir treatments. Copyright 2012 ARMA, American Rock Mechanics Association.

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