AVO analysis and modeling applied to fracture detection in coalbed methane reservoirs, Cedar Hill Field, San Juan basin, New Mexico
- Petrobras, Rio de Janeiro (Brazil)
- Colorado School of Mines, Golden, CO (United States)
The Cedar Hill Field in the San Juan Basin, New Mexico, produces methane from fractured coalbed of the Fruitland Formation. The presence of fracturing is critical to methane production due to the absence of matrix permeability in the coals. To help characterize this coalbed reservoir a three-dimensional, multicomponent seismic survey was acquired in this field. Prestack P-wave amplitude data are used to delineate zones of larger Poisson`s ratio contrasts (or higher crack densities) in coalbed methane reservoir, while source-receiver azimuth sorting is used to detect preferential directions of azimuthal anisotropy. Two modeling techniques (using ray tracing and reflectivity methods) predict the effects of fractured coal-seam zones on non-normal P-wave reflectivity. Synthetic CMP gathers are generated for a horizontally layered earth model, which uses elastic parameters derived from sonic and density log measurements. Fracture density variations in the coalbeds are simulated by anisotropic modeling. The large acoustic impedance contrasts associated with the sandstone/coal interfaces dominate the P-wave reflectivity response. They far outweigh the effects of contrasts in anisotropy parameters, for the computed models. Seismic AVO analysis of nine macrobins obtained from the 3-D volume confirms model predictions. Areas with large AVO productions identify coal zones with large Poisson`s ratio contrast, therefore high fracture density.
- OSTI ID:
- 80200
- Report Number(s):
- CONF-941015-; TRN: IM9532%%327
- Resource Relation:
- Conference: 64. annual meeting of the Society of Exploration Geophysicists and international exposition, Los Angeles, CA (United States), 23-27 Oct 1994; Other Information: PBD: 1994; Related Information: Is Part Of SEG international exposition and sixty-fourth annual meeting -- 1994 Technical program: Expanded abstracts with authors` biographies; PB: 1736 p.
- Country of Publication:
- United States
- Language:
- English
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