Azimuthal velocity analysis of 3D seismic for fractures: Altoment-Bluebell field

Khaled Al Dulaijan, and Gary F. Margrave

ABSTRACT

The 3D seismic data was acquired within Bluebell Field, the eastern portion of Altamont-Bluebell field in northeastern Utah. Altamont-Bluebell field is within the Uinta Basin, and is considered an unconventional reservoir in the sense that natural fractures act as fluid storage and conduits in the tight sandstones and carbonates. Information related to fracture orientation and intensity is vital for the development of such reservoirs. Therefore, this paper utilizes Velocity Variations with Azimuth (VVAz) to estimate the direction and intensity of fractured-induced anisotropy within one of the reservoirs, Upper Green River formation.

VVAz inversion method is applied based on the non-hyperbolic NMO equation for TI media that was derived by Grechka and Tsvankin (1998). Our code has been tested on a 3D physical modeling dataset and results are shown in another report. Isotropic NMO velocities are used along with azimuthally variant time residuals to estimate fast and slow NMO velocities and their direction. Hampson-Russel VVAZ has also been implemented and results are compared in the report.

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