Seismic Attenuation Workflow for Lithology and Fluid Interpretation

Abstract

Abstract

A seismic interpretation workflow was developed by using well log information, rock physics modeling and seismic attenuation analysis. From the well log information, rock physics modeling was performed to calculate the seismic attenuation within the lithological facies of interest. The workflow starts by using rock physics diagnostic and template tools in order to establish the theoretical model that best represent the lithological facies. Moreover, the Dutta-Odé (1979) patchy saturation model is used to determine the attenuation values by changing the gas saturation. From this, with an equivalent viscoelastic standard model (Zener, 1965) and by the knowledge of the high and low frequency limits of the complex modulus, a constant Q (quality factor) can be obtained (Dvorkin-Mavko, 2006). The rock physics templates address the seismic relations of velocities, acoustic impedance and attenuation with respect to diagenesis, compaction and saturation trends. These elements constrain the seismic properties to guide for prospective hydrocarbon areas.

The attenuation estimations from rock physics modeling were used to generate synthetic seismograms to assess the attenuation impact in the seismic response for interpreting the field seismic information. Few methods for calculating attenuation were tested in the controlled synthetic seismograms to find out which method could be the most stable in the real seismic data. For instance, in the seismic modeling, the bandwidth was varied to see the impact that high and low frequencies might generate on the seismogram and understand how that could affect the method for calculating attenuation in real seismic information. Seismic models with different scenarios were created to analyze what to expect when calculating attenuation, e.g. ranging below 1 Hz. The results of the estimated attenuation in real seismic traces around the well were compared to those modeled by rock physics and seismic modeling.

Application of the workflow for a gas reservoir in the Gulf of Mexico is discussed.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016