P-SV Numerical modelling and AVO of the Cardium conglomerate in the Carrot Creek field of central Alberta, Canada

Ashraf Abdalla

ABSTRACT

This work implements the use of numerical seismic modelling to investigate mode-converted P- to SV-reflected wave traveltimes and the amplitude versus offset (AVO) response of reflectors from the Cardium Conglomerate in the Carrot Creek Field of central Alberta, Canada.

Field data represented by 12 km of 3-component reflection seismic collected over 2 lines and numerous well logs are provided as the data base for the area. Synthetic events that closely represent Cardium reflections based on kinematics were obtained and gave a good idea about the structure velocity of the area.Cardium reflections were studied in terms of AVO using the conventional processing parameters. Further analysis of AVO effects on Cardium boundaries were conducted by considering substantial differences in Poisson's ratio between the Cardium layer and the surrounding media.

All modelling results demonstrate the importance of considering Poisson's ratio in AVO studies. Poisson's ratio has a strong effect on changes in reflection coefficient as a function of the incident angle. With substantial differences of Poisson's ratio across the reflecting interface, polarity reverse may occur depending on the velocity contrast between the two media. In this specific area where the Cardium Conglomerate exists as thin interval, considerable difficulties are experienced in resolving independent formation boundaries. In investigating possible Poisson's ratios for one medium, it is found that the medium boundaries can have the same response for the different cases assumed. Event tuning is also shown to be a result of considering Poisson's ratio.

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