Anisotropic permeability in fractured reservoirs from frequency‐dependent seismic Amplitude Versus Angle and Azimuth data

Abstract

Attempts have previously been made to predict anisotropic permeability in fractured reservoirs from seismic Amplitude Versus Angle and Azimuth data on the basis of a consistent permeability‐stiffness model and the anisotropic Gassmann relations of Brown and Korringa. However, these attempts were not very successful, mainly because the effective stiffness tensor of a fractured porous medium under saturated (drained) conditions is much less sensitive to the aperture of the fractures than the corresponding permeability tensor. We here show that one can obtain information about the fracture aperture as well as the fracture density and orientation (which determines the effective permeability) from frequency‐dependent seismic Amplitude Versus Angle and Azimuth data. Our workflow is based on a unified stiffness‐permeability model, which takes into account seismic attenuation by wave‐induced fluid flow. Synthetic seismic Amplitude Versus Angle and Azimuth data are generated by using a combination of a dynamic effective medium theory with Rüger's approximations for PP reflection coefficients in Horizontally Transversely Isotropic media. A Monte Carlo method is used to perform a Bayesian inversion of these synthetic seismic Amplitude Versus Angle and Azimuth data with respect to the parameters of the fractures. An effective permeability model is then used to construct the corresponding probability density functions for the different components of the effective permeability constants. The results suggest that an improved characterization of fractured reservoirs can indeed be obtained from frequency‐dependent seismic Amplitude Versus Angle and Azimuth data, provided that a dynamic effective medium model is used in the inversion process and a priori information about the fracture length is available.

Fundamental controls on fluid flow in carbonates: current workflows to emerging technologies

“…Further research has highlighted the frequency-and scale-dependent nature of fracture compliance (Hobday & Worthington 2012), the use of scattered seismic energy to constrain fracture spacing and intensities (Vlastos et al 2007), and advanced numerical methods to simulate seismic-wave propagation in discrete representations of fracture populations (Hall & Wang 2012). Although by no means mature, improved approaches to predict anisotropic permeability have been explored through the analysis of frequencydependent seismic amplitude v. angle and azimuth data (Ali & Jakobsen 2013). Constraints on fracture apertures have been sought through joint seismic inversion combined with analysis of production data (Shahraini et al 2011).…”

Impact of poroelastic effects on the inversion of fracture properties from amplitude variation with offset and azimuth data in horizontal transversely isotropic media

“…This illustrates that, in the presence of WIFF, the anisotropic behavior of the medium also becomes frequency-dependent. The dependence of the mesoscopic WIFF mechanism on the rock physical properties, the fracture geometry, and the frequency makes the analysis of frequency-dependent seismic attributes a valuable source of information with regard to the mechanical and hydraulic properties (e.g., Al-Harrasi et al, 2011;Tillotson et al, 2011;Ali and Jakobsen, 2014).…”

Evaluation of resistivity anisotropy parameters in the Eastern Mitidja basin, Algeria, using azimuthal electrical resistivity tomography

“…). Indirectly, permeability anisotropy may be also seen through the anisotropy of other physical properties, such as seismic velocities (e.g., Ali and Jakobsen ; Collet and Gurevich ) or electrical conductivity (Kirkby and Heinson ). Seismic velocities are generally higher in the direction of higher permeability, especially if the latter is due to aligned fractures.…”