Diffraction imaging in fractured carbonates and unconventional shales

Abstract

Diffraction imaging is recognized as a new approach to image small-scale fractures in shale and carbonate reservoirs. By identifying the areas with increased natural fracture density, reservoir engineers can design an optimal well placement program that targets the sweet spots (areas with increased production), and minimizes the total number of wells used for a prospective area. High-resolution imaging of the small-scale fractures in shale reservoirs such as Eagle Ford, Bakken, Utica, and Woodbine in the US, and Horn River, Montney, and Utica in Canada improves the prospect characterization and predrill assessment of the geologic conditions, improves the production and recovery efficiency, reduces field development cost, and decreases the environmental impact of developing the field by using fewer wells to optimally produce the reservoir. We evaluated several field data examples using a method of obtaining images of diffractors using specularity filtering that could be performed in depth and time migration. Provided that a good migration velocity was available, we used the deviation of ray scattering from Snell's law to attenuate reflection energy in the migrated image. The resulting diffraction images reveal much of the structural detail that was previously obscured by reflection energy.

Seismic Diffraction Response from Boreholes

“…Diffraction imaging is an emerging technology for high-resolution imaging of small-scale subsurface structural details, and has found many applications, e.g. in reservoir imaging and fracture detection (Sturzu et al 2015, where further references are found). Borehole geometries are characterized by ultra-small diameters compared to the seismic wavelength, but extension in depth range of up to thousands of meters.…”

Separation of diffracted waves via SVD filter

“…Therefore, the seismic response characteristics of geological heterogeneous bodies (such as breakpoints, pinch-outs, karsts and collapse columns) often appear as diffracted waves (Bansal and Imhof 2005;Fomel et al 2007;Decker et al 2015). The diffracted waves are seismic responses caused by uneven geological bodies in the strata, which carry high-resolution, potentially even super-highresolution, geological information (Neidell 1997;Khaidukov et al 2004;Rad et al 2005;Sturzu et al 2015). Therefore, diffracted waves are one type of wave field used to effectively identify and track geologically heterogeneous bodies or zones.…”

“…Since the early 1950s, researchers recognized the potential of using diffracted waves to identify geological heterogeneous zones and began using diffracted waves to detect small faults (e.g., Krey 1952;Angona 1960;Harper 1965;Kovalevsky 1971;Landa and Maximov 1980;Landa et al 1987; Kanasewich and Phadks 1988), characterize karst edges (e.g., Decker et al 2015) and identify fractures (e.g., Popovici et al 2014;Sturzu et al 2014Sturzu et al , 2015 and uneven geological bodies (e.g., Landa and Keydar 1998). The research results of Sturzu et al (2014Sturzu et al ( , 2015 show that the single diffracted wave imaging results can effectively depict fractures in carbonate reservoirs. Decker et al (2015) believed that diffracted wave imaging results can effectively improve the horizontal resolution of a single karst cave and effectively identify heterogeneous regions below the reflection resolution.…”