MTA ME Research Group of Geoengineering

Hungary

MTA ME Research Group of Geoengineering

Hungary
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Kovacs A.,Geological and Geophysical Institute of Hungary | Kovacs A.,MTA ME Research Group of Geoengineering | Perrochet P.,University of Neuchatel | Darabos E.,MTA ME Research Group of Geoengineering | And 4 more authors.
Journal of Hydrology | Year: 2015

The present paper introduces new well hydrograph analytical tools for parameter estimation in karst aquifers. The analytical formulae provided in this study link aquifer properties with hydrograph recession coefficients, and provide quantitative characterisation of the spatial and temporal variations of the water table. Generally, spring hydrograph analytical techniques provide information on the characteristic hydraulic parameters and conduit spacing in a karstic catchment, while well hydrograph analysis provides information on local hydraulic and geometric properties of individual matrix blocks and in certain cases on the deep unkarstified aquifer zone.The combination of the spring and well hydrograph analytical methods represents a useful tool for understanding the structure and hydraulic behaviour of karst systems.A new well hydrograph analytical approach is presented, which makes the estimation of conduit spacing and catchment geometries possible. In most cases well hydrograph peaks can be decomposed into three exponential segments. Exponential segments in shallow systems do not correspond to different types of storage, but in most cases originate from the emptying of fissured matrix blocks.The proposed parameter estimation method is demonstrated through the application of field data. The test site is located in the Bükk Mountains, Hungary. Analytical methods were applied on two adjacent karstic catchments feeding the Szinva and Garadna springs. Hydrograph analysis of both springs and three well hydrographs were performed to investigate the hydraulic behaviour of the karst system and to estimate the spatial geometry of karst conduits. According to hydrograph analytical results, both spring and well hydrographs indicated similar matrix block geometries. Hydrograph analysis revealed the change of flow scale indicated by a significant drop of the value of recession coefficient.The investigation method introduced in this study provides important information for water resource assessment, contamination risk assessment, vulnerability assessment, flood prediction, geotechnical and speleological studies. © 2015.


Szegedi H.,University of Miskolc | Dobroka M.,University of Miskolc | Somogyi Molnar J.,MTA ME Research Group of Geoengineering
Near Surface Geoscience 2014 - 20th European Meeting of Environmental and Engineering Geophysics | Year: 2014

The Fourier-transform (FT) often results noisy Fourier spectrum because this operation is linear and contaminate noise in time domain dataset appear in the frequency domain also. Especially, in case of non- Gaussian nature of the noise distribution (for example outliers in the data sets) can cause appreciable distortions in the Fourier spectra. If we treat the FT as an over-determined inverse problem, the noise effect on the Fourier spectrum can be greatly reduced. The geophysical series inversion was used for the discretization. The scaled Hermite functions - note that they are eigen-functions of the FT - were chosen as basis function. During the inversion process by using the Steiner-weights we get a highly robust inversional FT method. Numerical tests show the significant noise rejection capability of the new inversion based FT algorithm.


Somogyi Molnar J.,MTA ME Research Group of Geoengineering | Kiss A.,University of Miskolc | Dobroka M.,University of Miskolc
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

Pressure strongly influences the mechanical, transport and elastic properties of rocks, such as acoustic velocity, porosity and elastic moduli. Seismic and borehole logging techniques measure these rock properties in order to infer subsurface information. To relate changes in seismic attributes to reservoir conditions, a thorough understanding of pressure effects on rock properties is essential. Therefore it is important to develop a petrophysical model based on simple physical assumptions which describes the relationship between Lamé constants as well as acoustic velocities and pressure. In this paper we present a rock physical model based on the idea that the pore volume of a rock is decreasing with increasing pressure to describe the pressure dependence of P and S wave velocities thereby the Lamé constants. Laboratory measured acoustic P and S wave velocities as a function of pressure -published in literature -are inverted to prove the applicability of the model and to obtain that of parameters. The quality checked joint inversion results showed that the calculated data matched accurately with measured data and also proved that the suggested petrophysical model performs well in practice.


Molnar J.S.,MTA ME Research Group of Geoengineering | Kiss A.,University of Miskolc | Dobroka M.,University of Miskolc
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

Acoustic velocity in rocks is strongly depends on pressure, indicating that wave propagation is very nonlinear and the quasistatic elastic properties of rocks are hysteretic. Characterization of hysteretic behavior is important for a mechanical understanding of reservoirs during depletion. Therefore a quantitative model -which provides the physical explanation -of the mechanism of pressure dependence is required. In this paper a petrophysical model is presented which describes the connection between the propagation velocity of acoustic wave and rock pressure both in case of pressurization and depressurization cycles as well as explains the mechanism of acoustic hysteresis. The developed model is based on the idea that the pores in rocks close during pressurization and reopen during depressurization. It is valid also for S wave velocities since the basis of the model is the change of pore volume. The model was applied to acoustic P and S wave velocity data sets. The parameters of the petrophysical model were determined by a linearized inversion method. The calculated data matched accurately with measured data proving that the new rock physical model describing acoustic hysteresis applies well in practice.


Somogyine Molnar J.,University of Miskolc | Somogyine Molnar J.,MTA ME Research Group of Geoengineering | Kiss A.,University of Miskolc | Dobroka M.,University of Miskolc | Dobroka M.,MTA ME Research Group of Geoengineering
Acta Geodaetica et Geophysica | Year: 2015

Understanding the relationship between pressure and rock physical parameters, such as acoustic velocities, elastic moduli, porosity is essential for exploring and exploiting of natural reserves. In this study we introduce petrophysical models which describe the relationship between acoustic P, S wave velocities as well as quality factors and pressure. The models are based on the idea that the pore volume of a rock is decreasing with increasing pressure. On the basis of the models the pressure dependent Lamé coefficients and loss angles were deduced. Laboratory measured acoustic P and S wave velocities and quality factors as a function of pressure were inverted to prove the applicability of the models and to obtain that of parameters. The quality checked joint inversion results showed that the calculated and measured data matched accurately and also proved that the suggested petrophysical models perform well in practice. © 2014, Akadémiai Kiadó.


Kovacs F.,MTA ME Research Group of Geoengineering | Turai E.,MTA ME Research Group of Geoengineering
Idojaras | Year: 2015

The cycle properties of the annual average, absolute maximum, and absolute minimum precipitation values have been calculated from precipitation data the Matra and Bukk regions. The cycle parameters of annual average and annual absolute maximum precipitation values have been determined using the data of a shorter 34-year (19702006) and a longer 53-year (1960-2012) period (38 precipitation measurement stations) through the determination of the parameters of frequency, amplitude, and phase with an analytic version of the discrete Fourier transform (DFT), and the values obtained on the basis of the two periods have been compared. Using prognosis parameters, a prognosis until 2025 has been made. Then, the regression function of the variation in time of average and absolute maximum precipitation values has been determined on the basis of actual and prognosticated data for the whole period (1960-2025). © 2015, Hungarian Meteorological Service. All rights reserved.

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