A comparison of passive seismic monitoring of fracture stimulation from water and C O2 injection

Geophysics ◽  
2010 ◽  
Vol 75 (3) ◽  
pp. MA1-MA7 ◽  
Author(s):  
James P. Verdon ◽  
J.-Michael Kendall ◽  
Shawn C. Maxwell
Keyword(s):  
Hydraulic Fracturing ◽  
Shear Wave ◽  
Carbon Capture ◽  
Water Injection ◽  
Carbon Capture And Storage ◽  
Shear Wave Splitting ◽  
Data Set ◽  
Wave Splitting ◽  
Passive Seismic ◽  
Injection Depth

Hydraulic fracturing is used to create pathways for fluid migration and to stimulate production. Usually, water is the injected fluid, although alternative fluids such as carbon dioxide [Formula: see text] have been used recently. The amount of fracturing that [Formula: see text] can induce is also of interest for the security of carbon capture and storage. Hydraulic fracturing is usually monitored using passive seismic arrays, detecting microseismic events generated by the fracturing. It is of interest to compare the amount of seismicity that [Formula: see text] injection can generate in comparison with water. With this in mind, we have analyzed a passive seismic data set monitoring the injection of water and supercritical [Formula: see text] under very similar conditions, allowing us to make a direct comparison be-tween the fluids. We examined event locations and event magnitudes, and we used shear-wave splitting to image the fractures that are generated. For both fluids,the event locations map the formation of fractures moving away from the injection well with normals parallel to the minimum principal stress. The events during water injection are limited to the injection depth, while during [Formula: see text] injection, activity migrates above the injection depth. Event magnitudes are similar in both cases, and larger event magnitudes appear to correlate with higher injection pressures. Shear-wave splitting suggests that water injection generates more fractures, though the data quality is not good enough to make a robust conclusion about this. The comparability between water and [Formula: see text] injection means that lessons can be learned from the abundant experience of conventional water injection.

Linear‐transform techniques for processing shear‐wave anisotropy in four‐component seismic data

Geophysics ◽  
1993 ◽  
Vol 58 (2) ◽  
pp. 240-256 ◽  
Author(s):  
Xiang‐Yang Li ◽  
Stuart Crampin
Keyword(s):  
Time Series ◽  
Shear Wave ◽  
Seismic Data ◽  
Shear Waves ◽  
Shear Wave Splitting ◽  
Data Set ◽  
Reflection Data ◽  
Wave Splitting ◽  
Linear Transform ◽  
Zero Offset

Most published techniques for analyzing shear‐wave splitting tend to be computing intensive, and make assumptions, such as the orthogonality of the two split shear waves, which are not necessarily correct. We present a fast linear‐transform technique for analyzing shear‐wave splitting in four‐component (two sources/ two receivers) seismic data, which is flexible and widely applicable. We transform the four‐component data by simple linear transforms so that the complicated shear‐wave motion is linearized in a wide variety of circumstances. This allows various attributes to be measured, including the polarizations of faster split shear waves and the time delays between faster and slower split shear waves, as well as allowing the time series of the faster and slower split shear waves to be separated deterministically. In addition, with minimal assumptions, the geophone orientations can be estimated for zero‐offset verticle seismic profiles (VSPs), and the polarizations of the slower split shear waves can be measured for offset VSPs. The time series of the split shear‐waves can be separated before stack for reflection surveys. The technique has been successfully applied to a number of field VSPs and reflection data sets. Applications to a zero‐offset VSP, an offset VSP, and a reflection data set will be presented to illustrate the technique.

scholarly journals Automatic Shear Wave Splitting Measurements at Mt. Ruapehu Volcano, New Zealand

2021 ◽  
Author(s):  
◽  
Andreas Wessel
Keyword(s):  
New Zealand ◽  
Shear Wave ◽  
Automatic Measurement ◽  
Automatic Monitoring ◽  
Shear Wave Splitting ◽  
Measurement Tool ◽  
Data Set ◽  
The North ◽  
Wave Splitting ◽  
Ruapehu Volcano

<p>This thesis presents an automatic shear wave splitting measurement tool and the results from its application to data recorded in the vicinity of Mt. Ruapehu volcano on the North Island of New Zealand. The best methodology and parameters for routine automatic monitoring are determined and approximately 10,000 events are processed. About 50% of all S-phases lead to measurements of acceptable quality. Results obtained with this technique are reproducible and objective, but more scattered than results from manual measurements. The newly developed automatic measurement tool is used to measure shear wave splitting for previously analysed data and for new data recorded in 2003-2007. In contrast to previous studies at Mt. Ruapehu, we have a larger and continuous data set from numerous three-component seismic stations. No major temporal changes are found within the new data, but results vary for di erent station locations. I</p>

Inferring rock fracture evolution during reservoir stimulation from seismic anisotropy

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. WC157-WC166 ◽  
Author(s):  
Andreas Wuestefeld ◽  
James P. Verdon ◽  
J-Michael Kendall ◽  
James Rutledge ◽  
Huw Clarke ◽  
...  
Keyword(s):  
Rock Mass ◽  
Shear Wave ◽  
Hydraulic Fracture ◽  
Seismic Anisotropy ◽  
Rock Fracture ◽  
Shear Wave Splitting ◽  
Data Set ◽  
Tight Gas Reservoir ◽  
Wave Splitting ◽  
Microseismic Events

We have analyzed seismic anisotropy using shear-wave-splitting measurements made on microseismic events recorded during a hydraulic fracture experiment in a tight gas reservoir in Carthage, east Texas. Microseismic events were recorded on two downhole arrays of three-component sensors, the geometry of which provided good ray coverage for anisotropy analysis. A total of 16,633 seismograms from 888 located events yielded 1545 well-constrained shear-wave-splitting measurements. Manual analysis of splitting from a subset of this data set reveals temporal changes in splitting during fracturing. Inversion using the full data set allows the identification of fracture strike and density, which is observed to vary during fracturing. The recovered fracture strike in the rock mass is parallel to directions of regional borehole breakout, but oblique to the hydraulic fracture corridor as mapped by the microseismic event. We relate this to en-echelon fracturing of preexisting cracks. The magnitude of shear-wave splitting shows a clear temporal increase during each pumping stage, indicating the generation of cracks and fissures in a halo around the fracture corridor, which thus increase the overall permeability of the rock mass. Our results show that shear-wave-splitting analysis can provide a useful tool for monitoring spatial and temporal variations in fracture networks generated by hydraulic stimulation.

scholarly journals Automatic Shear Wave Splitting Measurements at Mt. Ruapehu Volcano, New Zealand

2021 ◽  
Author(s):  
◽  
Andreas Wessel
Keyword(s):  
New Zealand ◽  
Shear Wave ◽  
Automatic Measurement ◽  
Automatic Monitoring ◽  
Shear Wave Splitting ◽  
Measurement Tool ◽  
Data Set ◽  
The North ◽  
Wave Splitting ◽  
Ruapehu Volcano

<p>This thesis presents an automatic shear wave splitting measurement tool and the results from its application to data recorded in the vicinity of Mt. Ruapehu volcano on the North Island of New Zealand. The best methodology and parameters for routine automatic monitoring are determined and approximately 10,000 events are processed. About 50% of all S-phases lead to measurements of acceptable quality. Results obtained with this technique are reproducible and objective, but more scattered than results from manual measurements. The newly developed automatic measurement tool is used to measure shear wave splitting for previously analysed data and for new data recorded in 2003-2007. In contrast to previous studies at Mt. Ruapehu, we have a larger and continuous data set from numerous three-component seismic stations. No major temporal changes are found within the new data, but results vary for di erent station locations. I</p>

Upper mantle anisotropy beneath Sudetes from shear wave splitting - passive seismic experiment AniMaLS

2020 ◽  
Author(s):  
Julia Rewers ◽  
Piotr Środa ◽  
AniMaLS Working Group
Keyword(s):  
Shear Wave ◽  
Bohemian Massif ◽  
Upper Mantle ◽  
Shear Wave Splitting ◽  
Upper Mantle Anisotropy ◽  
Seismic Experiment ◽  
Wave Splitting ◽  
Passive Seismic ◽  
Mantle Anisotropy ◽  
Passive Seismic Experiment

&lt;p&gt;The passive seismic experiment AniMaLS was organized in 2017 in the Sudetes in Poland. One of the objectives was to study the anisotropy of the sub-crustal lithosphere and asthenosphere beneath the NE termination of the Bohemian Massif. Temporary seismic network of 23 broadband stations was operating in the area of Sudetes mountains and Fore-Sudetic Block, covering a ~200 x 100 km large area, with ~30 km spacing between stations. Obtained recordings were supplemented with data from permanent stations of Czech and Polish seismological networks located in the study area.&lt;/p&gt;&lt;p&gt;The Sudetes belong to internal zone of Variscan Orogen and are located in the NE part of the Bohemian Massif, between the Elbe Fault in SW and the Odra Fault in NE. The sudetic lithosphere represents a complex mosaic of several units with distinct histories of tectonic evolution and with consolidation ages ranging from the upper Proterozoic to the Quaternary. The aim of the project is to study seismic structure and anisotropy of the lithosphere-asthenosphere system based on broadband seismograms of local, regional and teleseismic events. The obtained data will be analysed using several interpretation methods. The poster presents the results of analysis by shear wave splitting method.&lt;/p&gt;&lt;p&gt;The analysis was done based on SKS and SKKS phases recorded during a ~2 years observation period. For analysis, three single-station methods were used: cross-correlation, eigenvalue minimization and transverse energy minimization. The dependence of resulting splitting parameters on the backazimuth of the event was also analysed. The results show that time delays between slow and fast S-wave components are typically in the range of ~0.5-1.6 sec, with average 1.2 sec. The splitting is interpreted as a result of lattice-preferred orientation (LPO) of mantle olivine. The azimuths of fast velocity axis are mostly consistent and showed largely WNW-ESE direction. They correlate well with trends of tectonic units observed at the surface and with strike directions of major fault zones. This suggests vertically coherent deformation throughout the lithosphere and frozen-in LPO, reflecting last tectonic episode which shaped Sudetic area. Obtained results were also compared with previous seismic studies of the upper mantle anisotropy in the neighboring areas by various methods.&lt;/p&gt;

Estimating interval shear-wave splitting from multicomponent virtual shear check shots

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. A39-A43 ◽  
Author(s):  
Andrey Bakulin ◽  
Albena Mateeva
Keyword(s):  
Shear Wave ◽  
Shear Wave Splitting ◽  
Azimuthal Anisotropy ◽  
Data Set ◽  
Vertical Seismic Profiling ◽  
Wave Splitting ◽  
Vsp Data ◽  
Classic Approach ◽  
A New Technique

Measuring shear-wave splitting from vertical seismic profiling (VSP) data can benefit fracture and stress characterization as well as seismic processing and interpretation. The classic approach to measuring azimuthal anisotropy at depth involves layer stripping. Its inherent weakness is the need to measure and undo overburden effects before arriving at an anisotropy estimate at depth. That task is challenging when the overburden is complex and varies quickly with depth. Moreover, VSP receivers are rarely present all the way from the surface to the target. That necessitates the use of simplistic assumptions about the uninstrumented part of the overburden that limit the quality of the result. We propose a new technique for measuring shear-wave splitting at depth that does not require any knowledge of the overburden. It is based on a multicomponent version of the virtual source method in which each two-component (2-C) VSP receiver is turned into a 2-C shear source and recorded at deeper geophones. The resulting virtual data set is affected only by the properties of the medium between the receivers. A simple Alford rotation transforms the data set into fast and slow shear virtual check shots from which shear-wave splitting can be measured easily and accurately under arbitrarily complex overburden.

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