Detection and Analysis of Naturally Fractured Gas Reservoirs: Multiazimuth seismic surveys in the Wind River Basin, Wyoming

RE Grimm, HB Lynn, Charles Richard Bates, R Phillips, KM Simon, W Beckham

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)

Abstract

Multiazimuth binning of 3-D P-wave reflection data is a relatively simple but robust way of characterizing the spatial distribution of gas-producing natural fractures. In our survey, data were divided into two volumes by ray azimuth (approximately perpendicular and parallel (+/-45 degrees) to the dominant fracture strike) and separately processed. Azimuthal differences or ratios of attributes provided a rough measure of anisotropy. Improved imaging was also attained in the more coherent fracture-parallel volume. A neural network using azimuthally dependent velocity, reflectivity, and frequency attributes identified commercial gas wells with greater than 85% success. Furthermore, we were able to interpret the physical mechanisms of most of these correlations and so better generalize the approach. The apparent velocity anisotropy was compared to that derived from other P- and S-wave methods in an inset three-component survey. Prestack determination of the azimuthal moveout ellipse will best quantify velocity anisotropy, but simple two- or four-azimuth poststack analysis can adequately identify regions of high fracture density and gas yield.

Original languageEnglish
Pages (from-to)1277-1292
Number of pages16
JournalGeophysics
Volume64
Issue number4
Publication statusPublished - Jul 1999

Keywords

  • AZIMUTHAL ANISOTROPY
  • ELASTIC-ANISOTROPY
  • WAVE-PROPAGATION
  • MEDIA
  • ATTENUATION
  • DIRECTIONS
  • CONSTANTS
  • EQUATIONS
  • MOVEOUT
  • CRACKS

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