Anisotropy Study

All rock masses are seismically anisotropic, but most often, we ignore the anisotropy and apply isotropic methods even in the anisotropic formations. Ignoring anisotropy can lead to poor seismic imaging, mispositioning of the seismic reflectors, inaccurate well-ties, and incorrect interpretation of seismic amplitude for lithology and fluid content.

In order to overcome this problem, PPZG offers prediction of rock anisotropy using rock physics principles to better interpret seismic data, even with incomplete and uncertain information about rock anisotropy.

We consider three important geological origins of elastic anisotropy in sedimentary rocks:

  • Anisotropy due to shale
  • Anisotropy due to stress and fractures
  • Anisotropy due to fine laminations

Additionally, we explore the effect of fluids in modifying the anisotropy resulting from these causes.

Anisotropic model building using surface seismic data is a well-known under-determined and nonlinear problem

Detail map of AVAZ intensity and strike indicating the relative fracture density and strike at this location in the reservoir

Fracture direction and magnitude displayed for a carbonate reservoir

Left Variation with azimuth of the amplitude of the transverse horizontal component recorded High amplitude is red. Low amplitude is blue

AVAZ analysis on the Mississippian horizon shows zones of higher crack density indicated by hot colours and lower crack density indicated by cold colours