Knowledge about the presence and orientation of fractures and stress is fundamental to shale operators. From a seismic point of view, P-wave seismic energy propagating across fractures can be influenced and decelerated because of microscopic opening and closing of fractures as the P-wave propagates. Stress also affects seismic velocities. A phenomenon known as “strain hardening” occurs when applying stress to materials; they strengthen in different directions, and their seismic velocity changes. Therefore, the seismic velocity will be different, depending on the azimuthal orientation of the seismic wave.
We can measure these azimuthal velocity changes using azimuthally diverse prestack seismic data. In this presentation, we show how we develop 3D spatial estimates of horizontal anisotropy caused by fractures and stress on an Eagle Ford example (from Seitel) using AVAZ and VVAZ technology. These estimates enable the engineer to allocate the finite completion budget to the rock mostly likely to develop complex, richly-connected fracture networks. This reduces the costly occurrence of large numbers of stimulated but ultimately non-productive intervals, for significant economic savings. While AVAZ and VVAZ will function on conventional source-receiver sectored azimuthal gathers, optimal results can be expected on full-azimuth reflection angle gathers generated by EarthStudy 360.
is a Geophysical Technical Advisor at Paradigm. He has a BS Degree in Geosciences from Brown University, and an MS in Geophysics and MBA from the University of Houston. He has a thirty-year history in the geophysical industry, having also served at Schlumberger as a Principal Geophysicist, Product Champion, and Workflow Champion, and Amoco Production Company (now BP) as a Senior Petroleum Geophysicist onshore USA Gulf Coast and Gabon.