--> --> Abstract: Paradigms for Problem Stratigraphy: Interpolation, AVO, and Thin Gas Charged Viking Reservoirs in West Central Alberta, by Lee H. Hunt, Scott Hadley, Mark Hadley, Jon Downton, and John Zhang; #90078 (2008)
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Paradigms for Problem Stratigraphy: Interpolation, AVO, and Thin Gas Charged Viking Reservoirs in West Central Alberta

Lee H. Hunt1, Scott Hadley1, Mark Hadley1, Jon Downton2, and John Zhang2
1Fairborne Energy Trust, Calgary, AB, Canada
2CGGVeritas, Calgary, AB, Canada

Viking reservoirs represent attractive exploration targets. These reservoirs are comprised of shoreface Previous HitsandstoneNext Hit assemblages that occur at depths greater than 2800m that often retain 12-14 percent Previous HitporosityNext Hit over 0 to 7 meters thickness. The sandstones have low permeabilities but are commonly overpressured and gas bearing with typical recoverable resource of 8 Bcf and 300 Mbbls condensate per section. The structural setting for the area includes both extensional and compressional tectonic elements. The complex aerial extent of the reservoirs may be a result of structurally influenced erosion surfaces formed during basin wide transgressive events. In general, Previous HitreservoirNext Hit quality shoreface deposits are preserved in structural lows.

Even with 3D seismic, accurate Previous HitreservoirNext Hit prediction is very challenging. The productive Previous HitreservoirNext Hit is less than 1/15 of a wavelength in thickness, which contributes to a poor correlation between seismic amplitude and measures of Previous HitporosityNext Hit thickness. AVO modeling indicates the gas effect of this sand accentuates the discrimination of the Viking Previous HitreservoirNext Hit at far offsets. AVO was thus identified as having a theoretic advantage in Previous HitpredictingTop this thin target.

The 3D coverage in the area has coarse source and receiver line geometries which create irregularities in the offset and azimuthal distribution of the data. Upon prestack migration, these irregularities give rise to kinematic distortions which adversely distort the AVO analysis. To address this issue, an offset and azimuth preserving interpolation scheme was employed to regularize the data prior to migration. We show that the new interpolation method significantly improves the PSTM gathers, resulting in superior AVO results. This is validated by AVO attribute comparisons with over 30 well ties and the resultant maps which are consistent with the structural erosional model.


AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas