A physical model investigation of P and S wave azimuthal anisotropy on transmission

Khaled Al Dulaijan, Gary Margrave, and Joe Wong

ABSTRACT

Information related to fracture orientation and intensity is vital for the development of unconventional hydrocarbons, such as tight sand gas and shale gas. Numerical modeling provides a valuable tool for geophysicists to test and validate their methodologies that provide them with information about reservoirs. Fractures make numerical modeling more complicated and introduce complexities that might even require geophysicists to validate their numerical models before using them to test and validate their methodologies. Alternatively, physical modeling provides a unique opportunity to test, validate, and develop methods for characterizing fractured reservoirs. This report utilizes seismic physical modeling for fracture characterization, is a continuation to previous work conducted within CREWES, and is an in-progress work.

A two-layer model was built using vertically laminated Phenolic overlaid by Plexiglas to represent a fractured reservoir overlaid by an isotropic overburden. Three 9-component common-receiver gathers were acquired over that model in the laboratory. For each gather, 90 shot locations are distributed along a circle of radii 250 m, 500 m, or 1000 m and separated by 4o to cover all azimuths. P-wave first-arrival times were analyzed on all three gathers and fracture orientation was predicted. S-wave analysis suggests an error in the polarization direction of the horizontal transducers. An Alford rotation was applied to the four horizontal components and successfully minimized energy on components other than those two that have fast S wave and slow S wave.

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