Applied Seismology Consultants

United Kingdom

Applied Seismology Consultants

United Kingdom

Time filter

Source Type

Mas Ivars D.,Itasca Consultants Sas | Pierce M.E.,Itasca Consulting Group Inc. | Darcel C.,Itasca Consultants Sas | Reyes-Montes J.,Applied Seismology Consultants | And 4 more authors.
International Journal of Rock Mechanics and Mining Sciences | Year: 2011

This paper describes synthetic rock mass (SRM) modeling, a new approach for simulating the mechanical behavior of jointed rock mass. This technique uses the bonded particle model for rock to represent intact material and the smooth-joint contact model (SJM) to represent the in situ joint network. The macroscopic behavior of an SRM sample depends on both the creation of new fractures through intact material and slip/opening of pre-existing joints. SRM samples containing thousands of non-persistent joints can be submitted to standard laboratory tests (UCS, triaxial loading, and direct tension tests) or tested under a non-trivial stress path representative of the stresses induced during the engineering activity under study.Output from the SRM methodology includes pre-peak properties (modulus, damage threshold, peak strength, etc.) and post-peak properties (brittleness, dilation angle, residual strength, fragmentation, etc.). Of particular interest is the ability to obtain predictions of rock mass scale effects, anisotropy, and brittleness, properties that cannot be obtained using empirical methods of property estimation. This paper presents the theoretical background of the SRM approach along with some example applications. © 2010 Elsevier Ltd.


Zhao X.,Applied Seismology Consultants | Young R.P.,University of Toronto
SEG Technical Program Expanded Abstracts | Year: 2011

In this paper, a numerical study using the distinct element method was initiated to validate understanding the relationship between fracture damage, fluid pressure and seismic velocity changes in a naturally fractured reservoir. The fracture damage zone and fluid permeable zone were successfully correlated with the time-lapse velocity changes extracted from the numerical model. The model offers the unique ability to examine directly the microprocesses leading to observed velocity changes. Validated models could be extended to quantitatively calibrate velocities required for microseismic locations over time, and predict the fracture propagation and fluid migration within a field-scale engineered reservoir. © 2011 Society of Exploration Geophysicists.


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

In this paper, in order to develop robust predictive models for engineering the reservoir and the induced or mobilized fracture network, a fully dynamic 2D Synthetic Rock Mass model is validated to simulate fluid injection in a geothermal reservoir by comparing modeling geometries of hydraulic fractures and induced seismicity with actual results. The numerical results qualitatively agree with field observations and reveal the possible interaction between new fractures and natural fractures indicated by recorded microseimic events. The model enables us to examine in detail the interaction between fluid pressure, rock deformation and slip on existing fractures for the different reservoir conditions. The validated numerical models can help provide insight on the relationship between seismicity, stress/damage and the fluid front in order to optimize the EGS reservoir stimulation for the project in hand or for future projects.


Timms N.E.,Curtin University Australia | Healy D.,Curtin University Australia | Healy D.,University of Aberdeen | Reyes-Montes J.M.,Applied Seismology Consultants | And 4 more authors.
Journal of Geophysical Research: Solid Earth | Year: 2010

[1] Transgranular microcracking is fundamental for the initiation and propagation of all fractures in rocks. The geometry of these microcracks is primarily controlled by the interaction of the imposed stress field with the mineral elastic properties. However, the effects of anisotropic elastic properties of minerals on brittle fracture are not well understood. This study examines the effects of elastic anisotropy of quartz on the geometry of brittle fracture and related acoustic emissions (AE) developed during indentation experiments on single crystals at ambient pressure and temperature. A Hertzian cone crack developed during blunt indentation of a single crystal of flawless Brazilian quartz parallel to the c axis shows geometric deviation away from predictions based on the isotropic case, consistent with trigonal symmetry. The visible cone crack penetration depth varies from 3 to 5 mm and apical angle from 53° to 40°. Electron backscatter diffraction (EBSD) mapping of the crack tip shows that fracturing initiates along a ∼40 μm wide process zone, comprising damage along overlapping en echelon high-index crystallographic planes, shown by discrete bands of reduced electron backscatter pattern (EBSP) quality (band contrast). Coalescence of these surfaces results in a stepped fracture morphology. Monitoring of AE during indentation reveals that the elastic anisotropy of quartz has a significant effect on AE location and focal mechanisms. Ninety-four AE events were recorded during indentation and show an increasing frequency with increasing load. They correspond to the development of subsidiary concentric cracks peripheral to the main cone crack. The strong and complex anisotropy in seismic velocity (∼28% Vp, ∼43% V s with trigonal symmetry) resulted in inaccurate and high uncertainty in AE locations using Geiger location routine with an isotropic velocity model. This problem was overcome by using a relative (master event) location algorithm that only requires a priori knowledge of the velocity structure within the source volume. The AE location results correlate reasonably well to the extent of the observed cone crack. Decomposition of AE source mechanisms of the Geiger relocated events shows dominantly end-member behavior between tensile and compressive vector dipole events, with some double-couple-dominated events and no purely tensile or compressive events. The same events located by the master event algorithm yield greater percentage of vector dipole components and no double-couple events, indicating that AE source mechanism solutions can depend on AE location accuracy, and therefore, relocation routine that is utilized. Calculations show that the crystallographic anisotropy of quartz causes apparent deviation of the moment tensors away from double-couple and pure tensile/compressive sources consistent with the observations. Preliminary modeling of calcite anisotropy shows a response distinct from quartz, indicating that the effects of anisotropy on interpreting AE are complex and require detailed further study. Copyright © 2010 by the American Geophysical Union.


Zhao X.P.,Applied Seismology Consultants | Reyes-Montes J.,Applied Seismology Consultants | Young R.P.,University of Toronto
75th European Association of Geoscientists and Engineers Conference and Exhibition 2013 Incorporating SPE EUROPEC 2013: Changing Frontiers | Year: 2013

The accuracy in the location of microseismic (MS) events relies, among other factors, on the use of a realistic velocity model in the forward calculation of travel times. During the hydraulic stimulation of deep rock reservoirs, the physical properties of the rock are altered and therefore the velocity structure is subject to changes along the treatment. In this paper, a numerical study using the distinct element method and the cross-correlation technique is carried out to measure velocities in a naturally fractured geothermal reservoir in order to better understand the relationship between induced microseismicity and fractures, fluid pressure and seismic velocity anisotropy. The fracture damage zone and fluid permeable zone were successfully correlated with the time-lapse velocity changes extracted from the numerical model. The model offers the unique ability to examine directly the microprocesses leading to macroscopic velocity changes. Validated models could be extended to quantitatively calibrate velocities required for microseismic locations over time, and predict the fracture propagation and fluid migration within a field-scale engineered reservoir. Copyright © (2012) by the European Association of Geoscientists & Engineers All rights reserved.


Zhao X.P.,Applied Seismology Consultants | Reyes-Montes J.R.,Applied Seismology Consultants | Young R.P.Y.,University of Toronto
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

Microseismic (MS) monitoring is extensively applied as a method for remotely imaging the effect of the treatment and the changes imposed on engineered reservoirs both in real time or post-treatment analysis. 3D microseismic locations could provide us the first-hand information of the geometry and extent of induced fracture network, but there are still many issues and problems waiting for us to understand the fundamental process along the fluid injection. One of the current challenges is to robustly solve the focal mechanism using sparse monitoring arrays. In this study, a synthetic rock mass model was developed to model typical source modes (shear and tensile) and 3-compoment waveforms were monitored using sets of linear particle arrays similar to the field operation. This tool is used to evaluate the robustness in the determination of source mechanisms against monitoring array configurations. The results show that with the optimal array orientation and aperture a consistent solution is reached using tools placed along a minimum of two monitoring wells. Further development of the tool can also be used to build a database that provides a tool to directly compare modelled and field data in order to probabilistically estimate a feasible focal mechanism for different receiver layouts.


Huang J.W.,Applied Seismology Consultants | Reyes-Montes J.M.,Applied Seismology Consultants | Young R.P.,University of Toronto
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

In a previous numerical study (Huang et al., 2013), we developed a new grid search algorithm to automatically locate microseismic (MS) events from streaming data recorded by surface monitoring survey. The symmetric nature of the semblance with respect to the origin time was used to identify the MS location. In this paper, we form a comprehensive workflow by extending this algorithm to include arrival time refinement using cross-correlation and nonlinear optimization similar to Geiger's method to update the location and origin time in order to minimize the residual between the observed and the theoretical arrivals. We demonstrate the efficiency of our workflow on seismograms continuously recorded by surface monitoring stations. We show that the automated grid search identified a significant amount of potential signals indicating the level of local seismic activities. The nonlinear optimization is applied to events with clear arrivals, and the vertical uncertainty due to the surface acquisition geometry and the coarse grid effect in the grid search are reduced. This algorithm can be directly applied to both natural earthquakes and reservoir stimulation monitoring.


Pettitt W.,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.
Leading Edge (Tulsa, OK) | Year: 2011

Fracture network engineering (FNE) involves the design, analysis, modeling, and monitoring of infield activities aimed at enhancing or minimizing rock mass disturbance. FNE relies specifically on advanced techniques to model fractured rock masses and correlate microseismic (MS) field observations with simulated microseismicity generated from these models. Hydrofracture stimulation is an example where FNE is playing a role, with hydraulic treatments now being widely used to optimize production volumes and extraction rates in petroleum reservoirs, enhanced geothermal systems, and preconditioning operations in caving mines. MS monitoring is now becoming a standard tool for evaluating the geometry and evolution of the fracture network induced during a given treatment, principally by source locating MS hypocenters and visualizing these with respect to the treatment volume and infrastructure. The integrated use of synthetic rock mass (SRM) modeling of the hydrofracturing with enhanced microseismic analysis (EMA) within FNE provides a feedback loop in which SRM is enhanced and constrained by the information provided by the MS data. This improves interpretation via direct observation of the micromechanics within the distinct element models used. Recent developments in both SRM and EMA technologies are described using case studies of the techniques applied to hydrofracture stimulations. We identify and discuss some future developmental challenges these technologies face, including their further integration and validation so as to provide more efficient and robust application of the FNE approach. © 2011 Society of Exploration Geophysicists.


Huang J.W.,Applied Seismology Consultants | Reyes-Montes J.M.,Applied Seismology Consultants | Zhao X.P.,Applied Seismology Consultants | D. Chu F.,BGP Inc. | Young R.P.,University of Toronto
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

Hydraulic fracturing stimulates reservoir and imposes stress changes in the surrounding rock that typically induce or trigger seismicity with a wide range of magnitudes. Seismic monitoring provides insight into the reservoir deformation and give critical feedback to the on-going stimulations. We have developed a passive seismic tomography technique adapted from earthquake seismology to jointly locate induced microseismic events and update the velocity of the reservoir illuminated by the microseismicity. We calculate travel-time based on the fast sweeping method to account for complex 3D distribution of velocity and use the adjoint method to transform the inverse problem to a forward problem which can also be solved by the fast sweeping method. In this paper, we apply our algorithm to a two-stage reservoir stimulation project and demonstrate the capability of the microseismic tomography in mapping the stimulated rock volume and in quantifying the reservoir degradation even in the absence of visible Pwaves.


Reyes-Montes J.M.,Applied Seismology Consultants | Zhao X.P.,Applied Seismology Consultants | Chu F.,China National Petroleum Corporation | Young R.P.,University of Toronto
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

Microseismic monitoring of hydrofracture treatments can result in a significant number of events displaying a high energy S-wave arrival but have a P-wave that is close to or below the ambient noise level. Traditional location methods, relying on P-wave polarization information to determine the source vector, would fail to determine a source location for events where only S-waves were observed. In order to overcome the lack of source vector information, the S-wave polarization can be investigated using similar methods as those used to analyze the P-wave polarization. Depending upon the nature of the S-wave polarization due to transmission effects, either the full source vector or the plane containing the source vector can be estimated. Based on two hydrofracture microseismic data sets, this paper analyses the robustness of MS event location using S-wave polarization information to obtain event source vectors, and demonstrates that the use of this additional information in the standard location algorithm is able to increase up to 7-fold the number of located events in field operations. The enhanced number of located events provides a more complete image of the induced fracture network, enabling a more robust interpretation of the effect of the hydraulic treatment.

Loading Applied Seismology Consultants collaborators
Loading Applied Seismology Consultants collaborators