The amplitude versus offset technology (AVO) has been more and more effectively used as direct hydrocarbon indicator in the seismic exploration in the Nile Delta and East Mediterranean areas. AVO techniques, inverted Lamé’s parameters, and fluid factor traces are applied to delineate the fluid content and rock properties of the clastic sedimentary rocks in the study area. In the present work, analysis of the amplitude versus offset AVO parameters (intercept A, gradient B and products A*B) as well as the reflection coefficient difference (Rp-Rs) are carried out using compressional (P-wave) and shear wave (S-wave) velocities and density measurements. The data necessary for the creation of AVO models, preferably come from dipole sonic tools and density logs, are obtained from several wells drilled in the study area. Several relationships are constructed between shear and compressional wave velocities, as well as some models relating the calculated elastic moduli in one hand and petrophysical parameters on the other hand were analyzed to observe the trends between elastic parameters and reservoir rock properties. The AVO inverted Lamé’s parameters, shear modulus () and Lamé’s modulus (incompressibility), are used to discriminate the gas-bearing zones from the brine ones. The combination of Lamé’s rock parameters with the rock density lambda*rho (and mu*rho (is used as an effective tool to improve the detection of reservoir lithology and fluids, as they provide additional information on the nature and content of the rocks and fluids from which they arise.
The ‘fluid factor’ technique is also used in this study to detect the gas-bearing zones. F-impedance logs and the fluid factor trace are constructed. High amplitude fluid factor reflections are indicated at the top and base of the gas sandstone reservoirs. A number of interpreted seismic sections are inverted to fluid factor ones to clarify the gas-bearing anomalies. These inverted sections together with the inverted gamma ray and fluid factor maps assist not only in the definition of several lithologic facies, fluid content and the straight forward structure, but also in the identification of the possible extension of the hydrocarbon reservoirs. This work proved that the study of amplitude versus offset technique, Lamé’s parameters and fluid factor amplitudes is very sensitive in the differentiation between the different rock and fluid contents constituting the gas-bearing reservoirs.
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