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Abstract: Previous HitAVONext Hit and Previous HitAnisotropyNext Hit from Logs and Walkaways

Scott W. Leaney, William E. Borland

Previous HitAVONext Hit (amplitude versus offset) is the seismic technique used for mapping lithology, and modeling is an important step for successful Previous HitAVONext Hit interpretations. Shear velocity measurements are essential, since Previous HitAVONext Hit attempts to exploit the elastic (as opposed to acoustic) nature of seismic wave propagation. A property of seismic wave propagation not often considered is Previous HitanisotropyNext Hit. This is probably because the magnitude of the Previous HitanisotropyNext Hit has been difficult to measure, and its Previous HiteffectNext Hit on Previous HitAVONext Hit is not widely known.

New technology is helping to improve Previous HitAVONext Hit modeling. Dipole source shear logging tools can now measure very slow shear velocities, increasing the range of applicability of Previous HitAVONext Hit, and new borehole seismic techniques can measure Previous HitanisotropyNext Hit. When integrated, these new measurements provide more detailed information about the elastic moduli that govern wave propagation, and bring the possibility for greater reliability in Previous HitAVONext Hit interpretation.

Two examples of ray-trace Previous HitAVONext Hit synthetics are shown to illustrate typical Previous HitAVONext Hit responses and the importance of shear velocity information. An overview of Previous HitanisotropyNext Hit is given and a new technique to estimate Previous HitanisotropyNext Hit from walkaway surveys (multi-offset VSPs) is described. The log and walkaway measurements are then integrated to study the impact of Previous HitanisotropyNext Hit on Previous HitAVONext Hit. First, the Previous HiteffectNext Hit of Previous HitanisotropyNext Hit on Ostrander's shale-sand model is investigated, and second, isotropic and anisotropic ray-trace synthetics are compared.

The Previous HiteffectNext Hit of Previous HitanisotropyNext Hit on Previous HitAVONext Hit is found to be significant and may be lead to misinterpretations of Previous HitAVOTop anomalies.

AAPG Search and Discovery Article #90982©1994 AAPG International Conference and Exhibition, Kuala Lumpur, Malaysia, August 21-24, 1994