Seismic Fracture Characterization by QVOA Analysis Using Simulated Seismic Data by Physical Modeling

Vertical fractures cause azimuthal anisotropy in the wave-energy attenuation. To predict the fractures’ azimuth from seismic data, we develop a method of analysis of azimuthal variations in the attenuation. It is so-called QVOA analysis that means “Q Versus Offset and Azimuth”. Fractures’ network can be represented as an anisotropy model of a transversally isotropic medium with a horizontal axis of symmetry (HTI). As a sought-for parameter, we consider the fractures’ azimuth (φ0), which identifies the fracture strike. We develop our QVOA method to estimate the φ0-azimuth of fractures from seismic data simulated by physical modeling. The Q-data on the attenuation are estimated along three seismic lines with 3 azimuths of the source-receiver line, φ =  \(0^\circ\) , φ =  \(45^\circ\) , and φ =  \(90^\circ\) . To estimate the fracture-strike φ0-azimuth, we use the least squares method (LSM), namely, we minimize the functional of the difference between the theoretical function Q−1(θ, φ–φ0) and the real attenuation estimated from seismic data. We estimate the azimuth of the fracture strike (φ0) using our new Canonical equation of the Q−1(θ, φ–φ0)- function. The Canonical formula results in the smallest and the most stable absolute ∆φ0-angle error of \(0.26^\circ\) (compared to the older versions of QVOA-method). The maximal attenuation is obtained at the φ =  \(0^\circ\) the orthogonal direction to the fracture strike; and the minimal attenuation is at the φ0 =  \(90^\circ\) , which is the fracture-strike azimuth. Thus, the experiment fully confirms the theory.