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Compensating for migration stretch to improve the resolution of S-impedance and density inversion

Authors:

Abstract

Zoeppritz’s (1919) equations describe the partitioning of the P- and S-wave energy into transmitted and reflected components as a function of incident angle. The three-term approximation of the Zoeppritz’s equations developed by Aki and Richards (1980) show that P-impedance (ZP), S-impedance (ZS), and density (ρ) can be estimated from the “PP” reflected waves as a function of incident angle. At near angles the PP reflection is only sensitive to changes in ZP. At farther angles, the PP reflection is sensitive to changes in all three parameters, ZP, ZS, and ρ. Because no converted waves are measured, the loss in resolution for inverted ZS and ρ is due to migration stretch. Correction for migration stretch rather than conventional “stretch-mute” corrections provides three advantages: (1) preservation of far angles required for accurate ρ inversion, (2) improvement in the vertical resolution of ZS and ρ volumes, and (3) preservation of far angles that provide greater leverage against multiples. We apply our workflow to data acquired in the Ft Worth Basin and retain incident angles up to 42° at the Barnett Shale target. Comparing the spectrum of ZP, ZS, and ρ of the original gather and migration stretch compensated data, we find an insignificant improvement in ZP, but a moderate to significant improvement in resolution of ZS and ρ.

Presentation Date: Wednesday, September 18, 2019

Session Start Time: 1:50 PM

Presentation Time: 3:55 PM

Location: 217D

Presentation Type: Oral