Fractured reservoir rock becoming important study recently, it is due to the high de-
mand of oil and gas. Some of fractured reservoir are basement rock, carbonate as well
as vulcanic rock. They have two kinds of porosity, primary and secondary porosity. The
primary porosity is caused by matrix and frame, and it is much smaller compared to
secondary porosity that caused by fractured zone. Elastic isotropy is assumed in most
cases of seismic analysis, processing and interpretation. Anisotropic especially trans-
verse isotropic behavior of seismic velocity, however, is found to exist in most crustal
and subsurface media especially in fractured reservoir rock. In this research, some
studies are done to investigate the effect of saturation on three types of fracture: iso-
tropic, vertical transverse isotropic and horizontal transverse isotropic rock. They are
studied using analytical model through extended Gassmann modeling and seismic
core physics laboratory. The analytical model of fractured zone is derived by extending
Gassmann equation for anisotropic model, it is known as Brown-Korringa equation.
This equation model the effect of fluid saturation in anisotropic fractured reservoir
rock. The samples of fractured rock are built from fractured sandstone in several condi-
tions, such as: isotropic, vertical transverse isotropic and horizontal transverse iso-
tropic. Then, they are measured in high pressured laboratory with several types scenar-
ios, such as variation of both overburden and pore pressure, several types of satura-
tion: SWIRR (saturated water irreducible), full water saturated and light oil saturated.
The results of numerical modeling show that in traverse isotropic media, both of P and
SV wave increase due to the fluid inclusion. The SH wave velocity is unaffected by fluid
inclusion. These results are different compared to isotropic Gassmann equation’s as-
sumption that S wave velocity is not sensitive to fluid substitution. Experimental studies
confirmed the results. In isotropic sample, P wave velocity increase around 25% to
52% with water inclusions, and 12% to 41% due to light oil inclusions. On vertical trav-
erse isotropic (VTI) media, P wave increase up to 34% due to water saturation, and in
horizontal traverse isotropic (HTI) media increase around 13% to 17%. Several types of
AVO responses due to the fluid inclusion in fractured reservoir rocks are also presented
also in this paper.