Fractured reservoirs have been encountered worldwide and in general they are profitably produced, however it is safe to say that none of them have been depleted efficiently. As the seismic industry focuses more on production and development it is becoming more important to recognize the presence of fractures for optimal reservoir management. Fractures can significantly influence the behavior of reservoir porosity and permeability, resulting in numerous dry wells and higher production costs. A key strategy for fractured reservoir management is a quantitative description of the geology, geophysics and petrophysical attributes.
3D seismic surveys, where compressional waves generate shear-wave reflections (PS-waves), can provide complimentary surface-seismic information to help identify fracture properties early in the production history of a reservoir. Based on measurements of azimuthal anisotropy attributes, PS-waves can indicate fracture density and strike, and because of their asymmetry they are also sensitive to fracture dip. Examples from both land and marine 3D PS-wave surveys demonstrate the potential of using these attributes to characterize subsurface stress variations that are important for open fracture development. These intermediate-scale seismic properties will be critical for solving specific production problems associated with different fractured reservoir types, and could improve reservoir modeling: production-history matching, and fluid-flow simulation. From an economic point of view, if PS-wave surveys prevent a small fraction of unproductive wells, then they are worth the expense.
AAPG: Application of Seismic Attribute Analysis to Reservoir and Exploration Studies