Attenuation estimates from VSP and log data

Abstract

VSP data and well log information from the Ross Lake oilfield, Saskatchewan (owned by Husky Energy Inc.) are used to estimate P-wave and S-wave attenuation (Qfactors). The VSP surveys used both vertical and horizontal vibrators as sources and a downhole five-level, threecomponent receiver. From the spectral ratio method applied to downgoing waves, results are obtained for QP as well as QS. We estimate an average QP, over an interval of 2001200m, to be 67 from the spectral ratio technique. We also use VSP-sonic drift curves to find a Qp of 40 over the same interval. QS estimates are 23 from the spectral ratio method and about 37 from “guesstimated” S-wave drift curves over the same interval.