Fracture Density Estimation Using Spectral Analysis of Reservoir Reflections: A Numerical Modeling Approach

Abstract

We use a 3-D finite difference numerical model to generate synthetic seismograms from a simple fractured reservoir containing evenly spaced, discrete, vertical fractures. The fractures are represented using a single column of anisotropic grid points. Analysis of seismic amplitudes and spectral characteristics were carried out on the top and base reservoir reflections as well as scattered wave coda for models with fracture spacing ranging from 0.01 to 0.1 fractures/m. Results show that the bulk scattered wave energy contained in a common shot gather increases greatly when the fracture spacing is greater than about 1/4 wavelength. Wavenumber spectra for integrated amplitude versus offset from a time window containing the base reservoir reflector show spectral peaks corresponding to the fracture spacing.