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Resistor Grid as a Tool in Resistivity Modelling
Stratil, Matěj ; Vilhelm, Jan (advisor) ; Klanica, Radek (referee)
The main aim of this thesis is a concise overview of geoelectrical resistivity methods and modelling in these methods. In the first part of the thesis the theoretical basis of resistivity methods is presented together with a brief description of particular examples of realization of field survey, namely the resistivity profiling, vertical electrical sounding and multielectrode resistivity method. The second part of the thesis is dedicated to description of forward and inverse problems in resistivity methods. The last chapter is focused on the resistor network model and contains several examples of practical calculations of this model. Key words - electrical resistivity method, resistor network, Kirchhoff's law
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Determination of mechanical parameters of rocks by analyzing full wave acoustic well logging record
Chalupa, František ; Procházka, Martin (advisor) ; Vilhelm, Jan (referee)
In this diploma thesis is at first a revision of field used process of interpretation of full acoustic well logging record in WellCAD program. This program uses an algorithm based on velocity analysis which uses semblance principle. Furthermore an independent interpretation of same data has been done in MATLAB program. In this one, individual steps of the process are verified using analysis of complex seismic trace - in particular by using instantaneous frequency. Both processes of interpretation were applied on wide spectrum of Bohemian Massif rocks with very different mechanic properties, so their robustness has been tested. The results of both interpretation processes have been compared and there haven't been found any fundamental differences, just minor, which can't be systematically eliminated with regard to WellCAD's capabilities. Interpreted values of Poisson's ratio and velocities of longitudinal and transversal have been used for comparison. As the credibility of mechanic parameters' values determined by interpretation processes mentioned above has been proven, other reasons of difference between mechanic parameters' values determined seismically and using static methods were searched for. At first a comparison of basic aspects in which the measuring methods differ (e.g. sample size,...
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New Methods in Sesimic Survey
Alexa, Martin ; Vilhelm, Jan (advisor) ; Valenta, Jan (referee)
The objective of this thesis is seismic survey, namely brief summary of a few selected new methods and technological modifications used in seismic survey of hydrocarbon deposits. The work focuses on a cable-free land seismic system, using optical fibre as acoustic sensors, technical improvements of vibrating units in Vibroseis technology and ocean bottom seismic while using VectorSeis Ocean technology. In the beginning concise historical outline and technical overview of progress from earthquake seismology to seismic survey is performed. Keywords: Seismology, seismic survey, hydrocarbons
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Effect of water reservoirs to seismicity
Beránek, Roman ; Vilhelm, Jan (advisor) ; Růžek, Bohuslav (referee)
The appearance of seismic activity after construction and filling of a water reservoir has been observed in many places around the world, including localities considered to be formerly aseismic. Occurrence and intensity of these earthquakes are determined by water reservo- irs' parameters, filling and discharging states and by local geological conditions and regional tectonic stress. The thesis firstly deals with two of the world's known significant hydroseis- micity examples and described is also seismicity in Nový Kostel area. The different types of hydroseismicity are thoroughly described along with all the major differences from ordinary earthquakes. The thesis further explains how water reservoirs may affect conditions important for earthquake occurrence such as hydrostatic pressure increase, pore pressure increase, and groundwater flow. These influences are related to water level fluctuations and therefore are described methods to analyze the relationship between earthquake occurrence and water level changes. Classical methods of crosscorrelation and frequency analysis are explained as well as not so common method of SSA (Singular Spectral Analysis). In the last section are all of these methods listed above applied to seismic data from the Nový Kostel area and water level measurements from...
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Construction of velocity sections in seismic prospection
Mokrá, Zuzana ; Vilhelm, Jan (advisor) ; Valenta, Jan (referee)
Aim of this thesis was to compare four different methods of construction of velocity sections in seismic prospection: t0 method, general inversion method, method based on presumption of linear velocity gradient medium and tomography. Each method assumes medium with different characteristics, calculations solve both direct and inverse problems, various types of seismic waves are utilised in calculations. It was determined, under which conditions any of afore mentioned methods can be used in common 2D seismic survey. Further on the thesis examines alternative source of seismic energy - set for dynamic penetration testing, which is commonly used in engineering geology. This source is compared to standard seismic hammer source. The thesis evaluated possibility of use this alternative source in seismic survey.
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Seismic monitoring of fluid contacts from horizontal wells
Janská, Eva ; Vilhelm, Jan (advisor) ; Fischer, Tomáš (referee)
When producing oil from a thin layer with a gas cap, gas is generally unwanted since the reservoir looses pressure. The pressure loss might cause the fluid vertical migration and therefore a misplacement of the horizontal production well. This is the main reason why the oil production is held back when a gas breakthrough occurs. The well is chocked, or run on lower production rates, until the oil column is recovered, but it is not known how long this will take. If the gas-oil contact could be monitored over time, then the gas breakthrough could be better prevented by reducing production from a particular well branch or even by blinding a specific part of the branch. The aim of this research is to test if monitoring of the gas-oil contact by a seismic acquisition inside the horizontal well is feasible. This could be done much cheaper, more often and with better repeatability than classical 4D seismic. The feasibility was investigated on 2D Troll subsurface models, using finitedifference acoustic modelling. Receivers are planned in the horizontal part of the production well and suggesting the best source position was one of objectives. The influence of variations in geological settings was also investigated. The most accurate information about the gas-oil contact shape and its distance from the well is...
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Earthquake Activity and San Andreas Fault
Voroňáková, Jana ; Vilhelm, Jan (advisor) ; Jakoubková, Hana (referee)
SUMMARY: This work deals with the San Andreas fault as a tectonically active area. It includes basic information about the fracture, its origins and history. The work shows, as scientists are now trying to combat the risk of impending earthquakes. Project of San Andreas Fault Observatory at Depth and individual predictions of the next earthquake rupture are described.
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Characterization of migmatite fracturing using ultrasonic methods
Petružálek, Matěj ; Vilhelm, Jan (advisor) ; Vavryčuk, Václav (referee) ; Koktavý, Pavel (referee)
Submitted PHD thesis is focused on fracturing process of migmatite, which is a low porosity anisotropic rock. Migmatite, from a locality Skalka, was chosen as a suitable experimental material, namely due to its macroscopically visible, plane-parallel structure (foliation). The fracturing was studied by means of uniaxial loading experiments on cylindrical samples with different dip of migmatite foliation: 13ř (subhorizontal), 81ř (subvertical) and oblique (47ř and 67ř). The net of eight piezoceramic transducers was employed for ultrasonic sounding (US) measurement and acoustic emission (AE) monitoring during the loading experiments. Realized study of migmatite fracturing is based on the interpretation of both mentioned ultrasonic methods. Part of this work was a software development, including its testing for processing and interpretation of measured AE and US data. Methodical part of the thesis consists of: development and testing of algorithms for automatic P wave arrival detection; introduction of anisotropic velocity model to describe magnitude and orientation of velocity anisotropy, as well as to localize AE events in anisotropic velocity field; determination of crack initiation stress using first arrival amplitude of US. Based on the interpretation of AE and US data, there was found a...
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