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Shear-wave amplitude variation with offset (AVO) analysis can be used to map changes in density, shearwave velocity, and fracturing at reservoir scale by allowing the influence of each factor to be separately extracted from the observed seismic response. Weighted least-squares inversion of the anisotropic reflection coefficients was implemented to find the shear-wave splitting coefficient and velocity-contrast parameters. A timelapse nine-component, 4-D seismic survey acquired over Vacuum field in Lea County, New Mexico, was used to test our methodology of shear-wave AVO analysis and to compare the results with well production and azimuthal P-wave AVO analysis. Weighted least-squares shear-wave AVO stacks of the splitting parameter were found to be excellent predictors of well fluid-production performance, implying a strong link between seismically inferred fracturing and reservoir-scale permeability of the San Andres dolomites at Vacuum field. Analysis of the shear-wave velocity contrast indicated the presence of a second set of open fractures to the south of a carbon dioxide injector well where a 4-D anomaly associated with injection had been observed.

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Pseudo S-wave broadband response of C-waves after domain change T ransforming multicomponent data from one domain to another has long been an important tool for interpretation, V P /V S analysis and joint amplitude versus offset/angle AVO/AVA inversion. Recent interest in the dynamics of these domain changes has led to investigations in wavelet distortion and correction methods for improved inversion and bandwidth for well ties (Bansal and Matheney, 2010;Gaiser, 2011;and Ursenbach et al., 2012). In this article, we derive corrections for converted P-to S-waves (C-waves), to match their effective wavelengths with the physical wavelengths of S-waves, in P-wave time or depth. We call this a pseudo S-wave response. Although bandwidth is broadened, these corrections do not completely retrieve the resolution benefits of shorter wavelength S-waves.Implementation of these corrections has several key elements similar to Bansal and Matheney (2010): estimation of an interval V P /V S function, performing zero phase corrections and applying wavelet corrections using nonstationary wavelet filters (Margrave, 1998). Application of our technique to a 3D multicomponent data set acquired over the Marcellus shale provides broader bandwidth C-waves that match P-wave data and reveal improved well ties in the reservoir.