A low-frequency asymptotic model of seismic reflection from a high-permeability layer

Analysis of compression wave propagation through a high-permeability layer in a homogeneous poroelastic medium predicts a peak of reflection in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of the Biot's model of poroelasticity. A new physical interpretation of some coefficients of the classical poroelasticity is a result of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and the Darcy's law. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The latter is equal to the product of the kinematic reservoir fluid mobility, an imaginary unit, and the frequency of the signal. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). The practical implications of the theory developed here are seismic modeling, inversion, and attribute analysis

Advanced Reservoir Imaging Using Frequency-Dependent Seismic Attributes

Our report concerning advanced imaging and interpretation technology includes the development of theory, the implementation of laboratory experiments and the verification of results using field data. We investigated a reflectivity model for porous fluid-saturated reservoirs and demonstrated that the frequency-dependent component of the reflection coefficient is asymptotically proportional to the reservoir fluid mobility. We also analyzed seismic data using different azimuths and offsets over physical models of fractures filled with air and water. By comparing our physical model synthetics to numerical data we have identified several diagnostic indicators for quantifying the fractures. Finally, we developed reflectivity transforms for predicting pore fluid and lithology using rock-property statistics from 500 reservoirs in both the shelf and deep-water Gulf of Mexico. With these transforms and seismic AVO gathers across the prospect and its down-dip water-equivalent reservoir, fluid saturation can be estimated without a calibration well that ties the seismic. Our research provides the important additional mechanisms to recognize, delineate, and validate new hydrocarbon reserves and assist in the development of producing fields

A LOW-FREQUENCY ASYMPTOTIC MODEL OF SEISMIC REFLECTION FROM A HIGH-PERMEABILITY LAYER

Abstract. Analysis of compression wave propagation through a high-permeability layer in a homogeneous poroelastic medium predicts a peak of reflection in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of the Biot's model of poroelasticity. A new physical interpretation of some coefficients of the classical poroelasticity is a result of the derivation of the main equations from the Hooke's law, momentum and mass balance equations, and the Darcy's law. The velocity of wave propagation, the attenuation factor, and the wave number, are expressed in the form of power series with respect to a small dimensionless parameter. The latter is equal to the product of the kinematic reservoir fluid mobility, an imaginary unit, and the frequency of the signal. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly-permeable layer (a lens). The practical implications of the theory developed here are seismic modeling, inversion, and attribute analysis

Using frequency-dependent siesmic attributes in imaging of a fractured reservoir zone

Normal reflection from a fractured reservoir is analyzed using frequency-dependent seismic attributes. Processing of 3D low-frequency seismic data from a West-Siberian reservoir produced an accurate delineation of the fracturedhydrocarbon-bearing zones. P-wave propagation, reflection and transmission at an impermeable interface between elastic and dual-porosity poroelastic media is investigated. It is obtained that the reflection and transmission coefficients are functions of the frequency. At low frequencies, their frequency-dependent components are asymptotically proportional to the square root of the product of frequency reservoir fluid mobility and fluid density

An Asymptotic Model of Seismic Reflection from a Permeable Layer

Analysis of compression wave propagation in a poroelastic medium predicts a peak of reflection from a high-permeability layer in the low-frequency end of the spectrum. An explicit formula expresses the resonant frequency through the elastic moduli of the solid skeleton, the permeability of the reservoir rock, the fluid viscosity and compressibility, and the reservoir thickness. This result is obtained through a low-frequency asymptotic analysis of Biot’s model of poroelasticity. A review of the derivation of the main equations from the Hooke’s law, momentum and mass balance equations, and Darcy’s law suggests an alternative new physical interpretation of some coefficients of the classical poroelasticity. The velocity of wave propagation, the attenuation factor, and the wave number are expressed in the form of power series with respect to a small dimensionless parameter. The absolute value of this parameter is equal to the product of the kinematic reservoir fluid mobility and the wave frequency. Retaining only the leading terms of the series leads to explicit and relatively simple expressions for the reflection and transmission coefficients for a planar wave crossing an interface between two permeable media, as well as wave reflection from a thin highly permeable layer (a lens). Practical applications of the obtained asymptotic formulae are seismic modeling, inversion, and attribute analysis

Pressure diffusion waves in porous media

Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency