P-wave anisotropy in shales from crosswell data
- Stanford Univ., CA (United States)
- Univ. of Utrecht (Netherlands)
A crosswell dataset, collected at Conoco`s Borehold Test Facility in Oklahoma, was first processed using a tomography algorithm based on an isotropic velocity model. The resulting 2-D velocity tomogram was found to have huge artifacts believed to be caused by nonuniform ray coverage and possibly anisotropy. A comparison of the zero offset crosswell velocities (Horizontal Path Log) with the log-derived sonic velocities (Vertical Path Log) indicated nearly 25% P-wave anisotropy in some formations. Despite the artifacts, a good interpretation of the 2-D isotropic tomogram was made with the help of synthetic data. The data were then inverted using an algorithm that incorporates a model of elliptical transverse isotropy. This anisotropy model produced an unambiguous image for two components of velocity that simultaneously match the sonic log and the crosswell data. Both inversions support a final interpretation of 1-D vertical stratification of layers, some of which exhibit significant P-wave anisotropy. This interpretation is consistent with the sonic logs, crosswell data, and available geological information.
- OSTI ID:
- 89720
- Report Number(s):
- CONF-941015--
- Country of Publication:
- United States
- Language:
- English
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