Simple expressions for normal‐incidence reflection coefficients from an interface between fluid‐saturated porous materials

Gurevich, Boris; Číž, Radim; Denneman, A.I.M.

doi:10.1190/1.1836811

Cited by 43 publications

(25 citation statements)

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“…This is an indication that, at least for the range used here, the frequency of investigation hardly promotes large differences in the magnitudes of elastic and poroelastic reflection coefficients. For frequencies investigations of the order of ultrasonic frequencies the obtained results between elastic and poroelastic backgrounds is noticeably different as shown in literature (Gurevich et al, 2004). However for purposes of conventional seismic acquisition are not used the frequencies of investigation of the order of kHz (Yilmaz, 2001; Figure 7 -Absolute differences between the elastic and poroelastic P-wave reflection coefficients, i.e., R elast P P − R poro P P…”

Section: Resultsmentioning

confidence: 87%

“…Their work showed the complexity in the treatment of the reflection coefficient problem for poroelastic media in the case of a frequency-dependent investigation. Similarly, considering two isotropic poroelastic layers separated by a discontinuity interface, Gurevich et al (2004) defined reflection and transmission coefficients for a normal incidence P-wave. In this instance, the reflection coefficients for fast and slow compressional waves are presented in simple forms supporting the limitation of near offsets.…”

Section: Introductionmentioning

confidence: 99%

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Insights on Pp and Ps Reflection Coefficients at Poroelastic Seismic Horizons

Oliveira¹,

Martins²

2016

Rev. Bras. Geof.

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ABSTRACT. In oil and gas exploration, the seismic reflection method aims at obtaining information from subsurface and generating geological models based on travel times and amplitudes of recorded seismograms. In this context the poroelasticity theory is generally used as a good approximation for studying the seismic response of oil and gas reservoirs. As the reflection coefficients in poroelastic media have a very complex mathematical formulation, the dependence of such coefficients on fundamental poroelastic and petrophysical parameters remains poorly investigated. In this paper, we study the dependence of poroelastic reflection coefficients on petrophysical (i.e., the physical properties of the media) and data acquisition (i.e., the frequency of investigation and the angle of incidence) parameters. In order to investigate such a dependence, we use geologic models having a descontinuity interface between a clastic reservoir overlying a calcareous rock. We then construct 3D plots displaying the magnitudes of fast P-wave (R P P ) and converted S-wave (R P S ) reflection coefficients in saturated poroelastic media as a function of two specific variables. As the main petrophysical property, we considered the reservoir porosity φ varying from 5 to 30%. By assuming the angle of incidence θ as one of the variables of the dependence (i.e., 0 • ≤ θ ≤ 40 • ), we indirectly investigate the influence of the source-to-receiver distance on the reflection coefficients.As for the frequency of investigation presumably carried by the seismic source, we selected the following interval: from 10 to 200 Hz. Absolute differences between the correspondent poroelastic and purely elastic reflection coefficients provided a way to select the most important poroelastic parameters which similarly affect the elastic coefficients. The reservoir porosity showed to be the most important dependence parameter in the variation of the reflection coefficients, either in poroelastic or in purely elastic media.Keywords: reflection coefficients, poroelasticity, porosity, frequency investigation, incidence angle. RESUMO. Naárea de exploração de petróleo e gás, o método de reflexão sísmica visa a obtenção de informações de subsuperfície e a construção de modelos geológicos com base no tempo de percurso e nas amplitudes dos sismogramas. Neste contexto, a teoria da poroelasticidadeé geralmente usada como uma boa aproximação para o estudo da resposta sísmica de reservatórios de petróleo e gás. Como os coeficientes de reflexão em meios poroelásticos possuem uma formulação matemática muito complexa, a dependência de tais coeficientes sobre parâmetros poroelásticos e petrofísicos fundamentais permanece pouco estudada. Neste trabalho, estudamos a dependência dos coeficientes de reflexão poroelásticos sobre parâmetros petrofísicos (i.e., propriedades físicas dos meios) e de aquisição de dados (i.e., a frequência de investigação e oângulo de incidência). A fim de investigar a tal dependência, usamos modelos geológicos com uma interface de descontinuidade entre um...

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Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Insights on Pp and Ps Reflection Coefficients at Poroelastic Seismic Horizons

Oliveira¹,

Martins²

2016

Rev. Bras. Geof.

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“…Wei et al [10] used Biot's theory to study the problem of the reflection and refraction of elastic waves at an interface between a single phase elastic medium and a transversely isotropic liquid-saturated porous medium. Gurevich et al [11] studied simple analytical expressions for normal incidence reflection coefficients from an interface between fluid-saturated porous materials. Lin et al [12] studied the surface displacements, the surface strain, the rotation (rocking), and the energy partitioning during the reflection of plane waves in an inviscid fluid-saturated poroelastic half-space by Biot's theory.…”

Section: Introductionmentioning

confidence: 99%

Reflection and refraction of attenuated waves at boundary of elastic solid and porous solid saturated with two immiscible viscous fluids

Kumar

Saini

2012

Appl. Math. Mech.-Engl. Ed.

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The propagation of elastic waves is studied in a porous solid saturated with two immiscible viscous fluids. The propagation of three longitudinal waves is represented through three scalar potential functions. The lone transverse wave is presented by a vector potential function. The displacements of particles in different phases of the aggregate are defined in terms of these potential functions. It is shown that there exist three longitudinal waves and one transverse wave. The phenomena of reflection and refraction due to longitudinal and transverse waves at a plane interface between an elastic solid half-space and a porous solid half-space saturated with two immiscible viscous fluids are investigated. For the presence of viscosity in pore-fluids, the waves refracted to the porous medium attenuate in the direction normal to the interface. The ratios of the amplitudes of the reflected and refracted waves to that of the incident wave are calculated as a nonsingular system of linear algebraic equations. These amplitude ratios are used to further calculate the shares of different scattered waves in the energy of the incident wave. The modulus of the amplitude and the energy ratios with the angle of incidence are computed for a particular numerical model. The conservation of the energy across the interface is verified. The effects of variations in non-wet saturation of pores and frequencies on the energy partition are depicted graphically and discussed.

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“…Its predicted wave attenuation and dispersion only become significant at frequencies comparable to the so-called Biot's characteristic frequency, which is usually 0.1 MHz or higher (Gurevich, 2004). The relative fluid movement at low frequencies is negligible and the rock behaves like an elastic solid with the equivalent elastic moduli given by Gassmann's (1951) equation . In practice, fractures may have a significant impact on the flow properties of the reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Frequency-dependent seismic reflection coefficient for discriminating gas reservoirs

Xu¹,

Wang²,

Gan³

et al. 2011

J. Geophys. Eng.

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The asymptotic equation of wave propagation in fluid-saturated porous media is available for calculating the normal reflection coefficient within seismic frequency band. This frequency-dependent reflection coefficient is expressed in terms of a dimensionless parameter  , which is the product of the reservoir fluid mobility (i.e. inverse viscosity), fluid density, and the frequency of the signal. In this paper, we apply this expression to Xinchang gas-field, China, where reservoirs are super tight sands with very low permeability. We demonstrate that the variation in reflection coefficient at gas/water contacts is observable within seismic frequency band. Then we conduct seismic inversion to generate attributes which first indicate the existence of fluid (either gas or water), and then discriminate a gas reservoir from a water reservoir.

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Simple expressions for normal‐incidence reflection coefficients from an interface between fluid‐saturated porous materials

Cited by 43 publications

References 10 publications

Insights on Pp and Ps Reflection Coefficients at Poroelastic Seismic Horizons

Insights on Pp and Ps Reflection Coefficients at Poroelastic Seismic Horizons

Reflection and refraction of attenuated waves at boundary of elastic solid and porous solid saturated with two immiscible viscous fluids

Frequency-dependent seismic reflection coefficient for discriminating gas reservoirs

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