Effect of Fracture Geometry on Reflection Response

Abstract

Naturally fractured reservoirs are an important component of global hydrocarbon reserves and hence are gaining importance in case of earth resource exploration. This chapter deals with the study of the effect of fracture density on reflection response of the earth medium. The reflection coefficients due to the incident P-wave have been calculated for two types of models. In the first model, isotropic medium underlined by a horizontally fractured medium was considered which is equivalent to vertical transverse isotropic medium (VTI). In the second model, both the isotropic and anisotropic mediums are considered. The reflection coefficient for isotropic medium has been calculated using Ruger (Geophysics 62:713–722, 1997) equation and Graebner (Geophysics 57:1512–1519, 1992) equation was used for modeling VTI medium.

In the present work, the model of vertical transverse isotropic (VTI) gas hydrate layer overlain by an isotropic sedimentary layer has been considered. The reflection coefficients obtained from the isotropic and anisotropic models have been compared. The comparison shows that the reflection coefficient increases with increase in the fracture density due to fracture induced anisotropy. This study further shows that for small angle of incidence (<35°) the reflection coefficient obtained for VTI medium does not differ significantly from that of an isotropic case.