f The Effects of Porosity on the Angle Dependent Reflectivity

Forward modeling of the Amplitude Versus Offset or Angle (AVO/AVA) response can provide useful information for petroleum or natural gas exploration. In this study, the seismic reflection amplitudes with variation of incidence angle over a horizontal interface have been calculated by Zoeppritz Equations. Angle dependent reflectivity of shale layer, which can be considered a trap for petroleum and natural gas environment over a limestone or sandstone have been studied with various porosity ratios for natural gas, petroleum and brine saturated reservoir rocks. Reflection amplitude values of reflected P waves (Rpp) for high porous reservoir rocks are around -0.2, -0.3 and -0.4 for brine, petroleum and natural gas saturated respectively. Saturation of natural gas or petroleum in an environment with high porosity is more sensitive to incidence angle than brine saturated case. This anomaly in reflection amplitudes is more significant in reflected S waves (Rps). Accordingly, reflection amplitudes for a salt trap over high porosity limestone or sandstone reservoir rock reaches up to 0.3.