Seimic Modeling of Geological Sequences and Fluid Filled
Asuaje, Ramon1, Evgeny Chesnokov1 (1)
Physical properties of rocks have different responses depending on the lithology and fluids in the formation. The Seismic response of a lithologic column will depend on the thickness, the fluid, and the vertical arrangement in which it was deposited. The fluid itself has a big influence in the seismic response and this can be studied through AVO and phase analysis of the wave. The idea of this study is to set a layer cake model which simulates a vertical arrangement similar to the fining upward and coarsening upward formations filled with gas or water presented in different depositional environmental systems. The Gassman equation was used to perform the fluid substitution in the different settings. The Hashin-Strikman bounds gave out the relationship between different grain size lithology formations and their elastic constants. To simulate the gradual grain size variation in the settings, we took from well logs velocity values for clean sandstones and shale, as well for different variation in the constitution of it. At the end a relationship between the lithologic settings and the fluid within it were described by an equation which relate velocity to sand percentage. AVO analysis was used to characterize and differentiate the fluid within the formation. The Hilbert transform was used to study the phase change of the wave in a CMP gather. At the end phase changes were appreciable at large offsets using the imaginary part of the Hilbert transform. Moreover, different window lengths were used to calculate the slope of the phase given by Hilbert equation and better identified the phase changes. The AVO analysis helped to characterize the fluids in the lithologic settings.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California