Amplitude Analysis and Inversion for Prediction of Lithology and Hydrocarbons

By

A. Abdou¹, F. Yossef¹, M. Nessim², E. Shady², T. Nafie², S. Volterrani²

(1) Khalda Petroleum Company, Cairo, Egypt (2) WesternGeco, Cairo Center, Cairo, Egypt

 Information about the subsurface lithology and rock properties is encoded in the amplitudes of the seismic reflection data. This information can be decoded by using the appropriate technology. Reflection amplitude analysis and inversion techniques are advanced investigation tools that aim to provide rock physical properties from pre- and post- stack seismic data, which conceal valuable information about amplitude variations, and represent an ideal complementary use to the conventional subsurface structural imaging through the identification of different lithologies and fluid saturation.

It is known that, the amplitude of a seismic reflection is an angle- dependent function. Consequently, it varies with the offset distance between the source and the receiver. In certain depositional and reservoir settings, the variations of amplitudes with offset or with angle can provide useful clues to the presence or to the extent of a hydrocarbon zone. On the other hand, although the reservoir structure can be mapped from conventional stacked data, the post stack seismic inversion techniques are useful in the estimation of the acoustic impedance from reflection amplitudes. The estimated impedance can be further used to predict lithology and petrophysical properties away from well control.

Success of any of these techniques depends, mainly, on data quality and signal to noise ratio. With good 3D data quality that characterized by high signal to noise ratio and broad frequency spectrum, testing of these techniques can be proposed. Khalda had considered a study of the inversion technique, and in phase to consider testing amplitude variations with offset and angle techniques.