High resolution diffraction imaging for reliable interpretation of fracture systems

Abstract

Small-scale subsurface features, such as natural fractures, act as scattering sources for seismic waves propagating through the subsurface. The wavefield generated by those source points is identified as diffraction energy. The amplitude of this type of energy is much smaller than the recorded events reflected from actual interfaces between different geological layers. Moreover, diffraction energy is normally suppressed by conventional processing and standard imaging algorithms, where summations and averaging processes are applied. The common objective in such processing workflows is to focus on the high specular amplitudes in order to enhance the continuity of seismic reflection events for improving the structural mapping of the subsurface. Our goal is to complement the traditional seismic interpretation workflow by integrating information relative to diffraction energy as another seismic attribute to be interpreted. The technique applied in this paper is based on a depth imaging algorithm that maps and bins the recorded surface information into multi-dimensional, local angle domain (LAD) common image gathers. The advantage of this system is its unique ability to decompose the wavefield into reflection and diffraction energy directly at the image locations. This paper provides a brief overview of the technology and illustrates its benefits when applied to the Eagle Ford and Barnett shale reservoirs, where seismic data can be of moderate quality, leading to accurate, high-resolution, and highcertainty seismic interpretation for risk-managed field development.