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Injection-induced seismicity: statistic and energetic analysis
Vlček, Josef ; Fischer, Tomáš (advisor) ; Horálek, Josef (referee)
Fluid injection into the rock formations represents a valuable analog to study the role of high-pressurized fluids in the seismogenic process. It is carried out in depths up to first thousands of meters in order to increase the permeability of rock formation for better exploitation of hydrocarbons and geothermal energy. The increased fluid pressure results in decrease of the strength of fractures and faults which causes their brittle failure that is observed in the form of microearthquakes and enables imaging of the stimulated rock volume. Besides this positive role, seismicity sometimes increases to the level that can be felt by the population, which can cause concerns about the seismic risk of these industrial operations. Thus, one of the main interests focused by recent studies deals with the maximum earthquake that can be triggered by hydraulic stimulations. I introduce the ratio between the hydraulic energy and released seismic energy, the seismic efficiency of injection, to assess the effect of fluid injection to the seismicity. This parameter is applied to data from two geothermal reservoirs (Gross Schönebeck and Soultz-sous-Forets) and one gas reservoirs (East Texas). We find that for different data sets, the seismic efficiency encompasses a broad range of magnitudes; from about 10-6 to...
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Magnitude calibration of seismic network WEBNET
Kolář, Dominik ; Fischer, Tomáš (advisor) ; Jakoubková, Hana (referee)
This thesis deals with determination of seismic magnitudes of West-Bohemian earthquakes. The first part summarizes basic information from the field of seismology and also about the earthquake swarms in the area of interest. The second part deals with calibration of magnitudes, i.e. determination of coefficient that corrects for attenuation and station corrections. Seismic data from the WEBNET network from 2012 were used to this purpose. In order to suppress tradeoff among the studied parameters the data were filtered and also usage of a fixed hypocenter depth was tested. The results show that the optimum attenuation correction is smaller than that used so far magnitude determination. It turns out that a deeper analysis is needed in order to find an optimum formula for magnitude determination at the West-Bohemia WEBNET network.
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Natural CO2 outburst and their relation to tectonic processes
Balák, František ; Fischer, Tomáš (advisor) ; Kolínský, Petr (referee)
This thesis is deals with the running geodynamic activity of NW Bohemia, where frequent earthquake swarms and natural CO2 emanations occur as a possible fade-out of the Tertiary rift activity. The first part summarizes the nature of these geological phenomena with a focus on CO2 escapes and its characteristics. These escapes are viewed from the viewpoint of geology and chemical and isotopic composition along with the effect of earth tides, barometric pressure and seismic activity. In the second part I analyse the records of two CO2 monitoring stations in terms of atmospheric pressure and ambient temperature.
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Joint interpretations of geophysical measurements as the key to understand landscape evolution
Tábořík, Petr ; Fischer, Tomáš (advisor) ; Kněz, Jaroslav (referee) ; Putiška, René (referee)
Užitá geofyzika představuje rychlý, efektivní a nedestruktivní způsob získávání informací o složení a stavu horninového prostředí, jakož i o studovaných geologických či geomorfologických procesech. Kombinování různých metod geofyzikálního průzkumu přináší ve srovnání s použitím pouze jedné geofyzikální metody výrazně širší rozsah měřených fyzikálních parametrů, což umožňuje získání mnohem podrobnějších informací o zkoumaném geologickém prostředí. K interpretacím geofyzikálních dat je vždy potřeba přistupovat obezřetně, protože jde mnohdy jen o jedno z pravděpodobných, nikoli však jediných možných řešení. Předkládaná disertační práce na několika vybraných případech ilustruje, jak snadno může dojít k nepřesné, nebo dokonce mylné interpretaci. V řadě případů přitom nemusí jít o problém kvality dat nebo chybného nastavení parametrů výpočetního modelu. Problém nastává při interpretaci výsledků, kdy dochází k přiřazení určité geologické kvality ke konkrétní měřené nebo modelované hodnotě nebo pozorované anomálii. Sdružené interpretace geofyzikálních metod (ideálně doplněné informacemi "negeofyzikálního" charakteru) mohou nejen přinést zásadní informace o studovaných geologických či geomorfologických fenoménech, ale také přispět metodickými poznatky, a to jak k metodám jednotlivým, tak zejména k jejich...
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Hydraulic fracturing
Mazáček, Michal ; Mls, Jiří (advisor) ; Fischer, Tomáš (referee)
This bachelor thesis deals with the process of hydraulic fracturing. Hydraulic fracturing (also called fracking or fracjob) is a method used for the stimulation of the oil or gas reservoirs. The point of the method is to inject the liquid under high pressure into the formation. The injection cause widening of existing fractures or making new ones. The goal of this thesis was to describe basic knowledge that are necessary to successful treatment. There were basics of rock mechanics described such as linear elasticity, plasticity etc. The main chapter describes the parameters of the fracture such as fracture wide, fracture height, fluid flow and fluid loss. Furthermore, the kinds of liquids were discussed in one chapter. In the end, the fracturation which had been done in Texas(USA) were shown and the spreading of the fractures were discussed.
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Use of borehole seismometers for the study of seismic wave attenuation
Konrádová, Diana ; Fischer, Tomáš (advisor) ; Hrubcová, Pavla (referee)
Nowadays, the seismic activity is most often recorded by seismic stations on the surface of the Earth. Nevertheless, in the recent years, Czech Republic started installing the borehole seismometeres. In Hartoušov in West Bohemia and Litoměřice, new monitoring seismic boreholes were built and borehole seismometers were installed. On data gathered by the seismometers in these areas, I have applied the spectral ratio method, in order to fully understand and further specify the influence of the near-surface layer. The data stemmed from various levels of depths and distinctive geological environments. Through the analysis of amplitudes, I defined their intensification on the surface and through the definition of the signal and noise ratio I showed what the significance of the use of borehole seismometers is in terms of improving the sensitivity of monitoring. The following spectral analysis served not only as a comparison with the theoretical outcomes, but also to determine the quality factor Q in the near-surface layer in Litoměřice and Hartoušov. Lastly, I evaluated the value of Q on the scale of 5 to 30 Hz, the influence of the local effects and geology.
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Earthquake swarms in West Bohemia - their onset and fade
Khodjaev, Alisher ; Fischer, Tomáš (advisor) ; Boušková, Alena (referee)
During the last 30 years, the activity of various earthquake swarms has been instrumentally recorded in the West Bohemian earthquake region. This work is studying the spatiotemporal evolution of seismicity preceding and following selected swarms from 1992 to 2020. The introductory part contains a brief description of the area of interest. The research part acquaints the reader with the necessary basics of seismology. In the next, phenomenon of earthquake swarms is described - their typical activity, possible mechanisms of origin, examples from the world and from the West Bohemia. In the practical part, using seismic catalogs, seismic activity preceding and following selected swarms is visualized. The aim is to find some regularities in the spatiotemporal evolution of the West Bohemian earthquake swarms. Using the visualization of the activity of selected swarms and the author's own interpretation, no regularities were found. For a more relevant conclusion a quantitative analysis should be carried out.
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Automatic processing of microseismic data and their relation to the hydraulic injection
Vlček, Josef ; Fischer, Tomáš (advisor) ; Plicka, Vladimír (referee) ; Růžek, Bohuslav (referee)
Microseismic monitoring is an integral part of scientific experiments or industrial operations associated with the hydraulic fracturing of bedrock, which is an effort to increase the permeability of rocks in the area and improve the exploitation, whether of heat, oil or natural gas. Monitoring of such newly formed or growing original fractures, usually followed by seismic events, is very important for observation and describing the hydraulic fracturing itself and its progress over time. Since the number of such events recorded is usually very high, classical methods of earthquake processing, where the arrival times of seismic waves are determined manually, seem to be very inappropriate. For this reason, automatic methods are used to process such datasets, which do not require manual determination of the arrival times of the seismic waves. In our case, the data were recorded by a dense network of surface receivers arranged in the shape of a ten-arm star. It was a total of more than nine hundred groups of vertical geophones, of which more than a quarter were also supplemented by a three-component seismic sensor. We then created an automatic procedure for the described network, the result of which is the determination of the location and the source mechanism for each seismic event. The recorded...
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