Anisotropic velocities and offset vector tile prestack-migration processing of the Durham Ranch 3D, Northwest Colorado

Abstract

This article describes the anisotropic P-wave processing and resulting velocity attributes of the Durham Ranch 3D Firefly survey in the southern Sand Wash Basin of northwest Colorado (Figure 1). The goal of the seismic effort at Durham Ranch is to provide a clearer 3D image of the structures that may influence reservoir fracturing and capture anisotropy attributes that can be related to the local distribution of these fractures. With structural dip greater than 10° in portions of the reservoir, accurate imaging and properly positioned anisotropy information requires prestack migration. The high-density spatial coverage achieved in the Durham Ranch shoot afforded an opportunity to migrate in a domain that preserves a wide-azimuthal distribution of prestack data for anisotropy analysis. Improved imaging and positioning of the anisotropy attributes provides a clearer (perhaps causal) relationship between local deformation and fracturing, thus aiding in the selection of productive well locations and/or stimulation methods.