P‐wave attenuation anisotropy in fracture characterization: numerical modeling for reflection data

Abstract

In the frames of HTI model, we study the phenomenon of azimuthally varying P‐wave attenuation, or Q ‐anisotropy, caused by the presence of aligned saturated fractures. The magnitude of P‐wave attenuation along the principle anisotropy directions of HTI medium (perpendicular and parallel to the crack strike) is linked to the complex phase velocity associated with cracks. P‐wave attenuation in the direction perpendicular to the crack strike is always greater than that parallel to the crack strike. Q ‐anisotropy appears to be rather more distinctive than reflectivity anisotropy, on which AVOA analysis (azimuthal AVO) is based. The information on wave attenuation from wide‐azimuth reflection data would be used in fracture characterization. The behavior of P‐wave attenuation in a function of offset (or angle of wave incidence) and azimuth is studied (we termed it “QVOA analysis” by analogy with AVOA analysis). Azimuthal variation of attenuation becomes the strongest for large angles of incidence, which correspond to the maximum offsets.