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1

Simulation of seismic wave propagation in poroelastic media using vectorized Biot’s equations: an application to a CO2 sequestration monitoring case

Anthony Emmanuel, Vedanti Nimisha

Acta Geophysica

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2020

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Vol. 68, no. 2

435--444

EN

Wave propagation through porous media allows us to understand the response and interaction that occur between the elastic rock matrix and the fuid. This interaction has been described by Biot in his theory of poroelasticity. Seismic wave simulation using Biot’s formulations is computationally expensive when compared with the acoustic and elastic cases. This computational burden can be reduced by reformulating the numerical derivative operators to improve the efciency. To achieve this, we used a staggered-grid fnite diference operator to discretize 2D velocity stress equations as given by Biot’s theory. A vectorized derivative is applied on the staggered grid by shifting the coordinates. The reformulated equations were applied to compute the seismic response of a reservoir, where CO2 is being injected and the efect of injected CO2 in the formation is clearly seen in the synthetic data generated. The algorithm was coded in Python and to test its efciency, the simulation run-time was compared for both serial and vectorized equations, and the speed-up ratio was calculated. Our results show a decrease in the simulation run-time for the vectorized execution with over a factor of a hundred percent (100%). We further observed that the amplitudes of the events increase with an increase in CO2 saturation in the formation. This matches well with the real data.

2

Time reversal seismic source imaging using peak average power ratio (PAPR) parameter

Franczyk A., Leśniak A., Gwiżdż D.

Acta Geophysica

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2017

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Vol. 65, no. 2

299--308

EN

The time reversal method has become a standard technique for the location of seismic sources. It has been used both for acoustic and elastic numerical modelling and for 2D and 3D propagation models. Although there are many studies concerning its application to point sources, little so far has been done to generalise the time reversal method to the study of sequences of seismic events. The need to describe such processes better motivates the analysis presented in this paper. The synthetic time reversal imaging experiments presented in this work were conducted for sources with the same origin time as well as for the sources with a slight delay in origin time. For efficient visualisation of the seismic wave propagation and interference, a new coefficient—peak average power ratio—was introduced. The paper also presents a comparison of visualisation based on the proposed coefficient against a commonly used visualisation based on a maximum value.

3

Wyznaczanie współczynnika Poisson’a na podstawie pomiaru prędkości fal akustycznych

Markowska-Lech K., Sas W., Gabryś K., Lech M., Soból E.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

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2016

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z. 63, nr 1/II

99--108

PL

Współczynnik Poisson’a określany na podstawie prędkości fali podłużnej i poprzecznej jest stosowany w geofizyce jako jeden z parametrów charakteryzujących odkształcenie materiału. W laboratoriach geotechnicznych również prowadzone są badania z wykorzystaniem prędkości fal sejsmicznych, dlatego Autorzy podjęli próbę przeniesienia zależności znanych z teorii sprężystości na ośrodki gruntowe w celu wyznaczenia współczynnika Poisson’a. Praca zawiera wartości współczynnika Poisson’a otrzymane z badań naturalnych gruntów spoistych dwiema różnymi technikami: w aparacie trójosiowym wyposażonym w piezoelementy typu bender oraz w kolumnie rezonansowej.

EN

Poisson’s ratio as one of the parameters characterizing the material deformation is widely used in geophysics and it is based on shear and compressional wave velocities. On the other hand, in the geotechnical laboratories a lot of tests using mechanical waves velocities on soils are performed, so Authors have attempted to transfer the elasticity theory on soils and determine the Poisson's ratio. The paper presents the values of Poisson's ratio obtained for natural cohesive soils with two different techniques: the triaxial tests using bender elements (BE) and resonant column (RC).

4

On the interpretation of seismic cone penetration test (SCPT) results

Bagińska I., Janecki W., Sobótka M.

Studia Geotechnica et Mechanica

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2013

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Vol. 35, nr 4

3--11

EN

The paper deals with the methodology of performing and interpretation of seismic cone penetration test (SCPT). This type of test is used to determine velocity of the seismic wave in the soil medium. This study is focused on shear wave. The wave is triggered on the ground surface by hitting an anvil with a sledgehammer. Then, vibrations induced at different depths are measured. Based on recorded measurements wave velocity (Vs) and thus also small strain shear modulus Gmax may be calculated. An interpretation of exemplary seismic test results is presented. Crossover and cross-correlation methods are discussed and another, more adequate one is featured and then applied in the interpretation example. Conditions for correct test performance and interpretation are discussed.

5

Źródło generacji fali sejsmicznej w sondowaniach SCPT

Bajda M.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2009

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Vol. 18, No. 4

57--66

PL

W artykule przedstawiono problematykę doboru odpowiedniego źródła generacji fal sejsmicznych na potrzeby sondowań sejsmicznych SCPT. Podczas badań przetestowano różne źródła generacji fali sejsmicznej. Pomysły tych źródeł zostały zaczerpnięte z literatury oraz z informacji ośrodków naukowych zajmujących się podobnymi badaniami. Po scharakteryzowaniu techniki sondowań in situ opisany został obiekt doświadczalny Stegny, na którym przeprowadzono badania. Artykuł zawiera opis metodyki badań oraz wyniki badań terenowych, których analiza wykazała przydatność zaprojektowanego źródła do generacji fal sejsmicznych.

EN

The paper presents examples of seismic sources which has been developed to the generation of shear wave impulses during SCPT soundings. In situ measurements of seismic wave velocity performed at Stegny site were described. Geological description of test site, test procedure and analysis of obtained results were shown in this paper. An analysis of seismic cone penetration tests results indicates that new seismic source, made for SCPT tests, provides accurate and reproducible signal for measurements of the shear wave velocity Vs - a basic input parameter for seismic analyses.

6

Estimation of frequency dependent coda wave attenuation structure at the vicinity of Cairo Metropolitan Area

El-Haidy S., Adel M., Adel M., Adel M., Abu-El-Ata A., Sayed M.

Acta Geophysica

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2006

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Vol. 54, no. 2

177-186

EN

Estimation of seismic wave attenuation in the shallow crust in terms of coda wave Q structure previously investigated in the vicinity of Cairo Metropolitan Area was improved using seismograms of local earthquakes recorded by the Egyptian National Seismic Network. The seismic wave attenuation was measured from the time decay of coda wave amplitudes on narrow bandpass filtered seismograms based on the single scattering theory. The frequency bands of interest are from 1.5 to 18 Hz. In general, the values obtained for various events recorded at El-Fayoum and Wadi Hagul stations are very similar for all frequency bands. A regional attenuation law Qc = 85.66 f 0.79 was obtained.

7

Shear velocity inversion procedure for love waves

Zaman F. D., Masod K.

Journal of Technical Physics

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2003

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Vol. 44, no 3

295-301

EN

An inverse solution is presented to the seismic inverse problem for one-dimensional shear velocity variations. The Love waves, travelling in a layer overlying a half-space incident upon delta-function potential, are considered. The equation of motion for Love waves is transformed to the Schrodinger equation and then the potential is recovered by applying Gelfand-Levitan and Marchenko procedure.