The Earth Study 360 Imaging System “An Insight into the Interpretation Realm” by Dr.Raanan Dafni, Emerson-Paradigm
Mumbai Chapter of Society of Petroleum Geophysicist (SPG) had organized a technical presentation on, The Earth Study 360 Imaging System “An Insight into the Interpretation Realm” by Dr. Raanan Dafni, Emerson-Paradigm on 7th Nov 2019, at NBP Green Heights, ONGC, BKC, Mumbai. In his interactive and well appreciated presentation, Dr. Raanan highlighted the (a) overview of ES360 Imaging System, (b) benefits of full-azimuth angle-domain imaging, (c) case studies from both Indian and global data and (d) pre-stack interpretative engine, i.e. supplementary information from directional image gathers.
The EarthStudy 360® Imager (ES360 Imager) is a versatile cluster-based depthmigration that simultaneously uses the full recorded wave field within acontrolled aperture to generate amplitude preserved, multi-dimensional, subsurface angle gathers which are 3D full azimuth, directional and reflection angle gathers. The Imager provides fast, target-oriented solutions for local analysis, and can also be used for imaging ona regional scale.It supports isotropic and anisotropic models, and all types of land and marine datasets, including narrow and wide azimuth streamer acquisitions and OBC data. Recently, ES360 migration included converted rays (P to S) also.
Unlike conventional ray-based imaging methods (e.g. Kirchhoff migration), EarthStudy 360 uses a point-diffractor operator to shoot rays from subsurface grid points up towards the surface, forming an accurate system for mapping the recorded surface seismic data into the subsurface Local Angle Domain (LAD) at each image point. This procedure ensures maximum illumination of the image points from all subsurface directions and surface source-receiver locations; all arrivals are taken into account and amplitudes and phases are preserved.
Earth Study 360 directional angle gathers enable specular and diffractionimaging, resulting in simultaneous emphasis on continuous structural surfacesand discontinuous objects such as faults or small-scale fractures, karst features. Structuralattributes at each subsurface image point (e.g. dip, azimuth and specularity)can be derived directly from the directional angle gathers.The ES360 directional angle gathers from Narrow azimuth surveys are suitable for diffraction imaging of discontinuities like faults and fractures as they are directly related to migration aperture and not sensitive to acquisition geometry unlike the reflection angle gathers. The diffraction imaging results are a better way of delineating the discontinuities than traditional ways like coherence cube.
Earth Study 360 reflection angle gathers display reflectivity as a function ofopening angle and opening azimuth and are most meaningful in the vicinity ofactual local reflecting surfaces, where the reflection angles are measured withrespect to the derived background specular direction. They are used forautomatic picking of full-azimuth, angle domain residual moveouts, which together with the derived background orientations of the subsurfacereflection horizons, provide a complete set of data for anisotropic velocity modeldetermination, azimuthally-dependent analysis of residual velocity (VVAZ) or amplitude versus angle/azimuth (AVAZ), using full azimuth angle domain seismic data, in order to determine fractureintensity (strength) and orientation (direction). These fractures derived from the seismic were verified with production data, FMI logs and available micro-seismics.
Regarding the future roadmap of ES360,Dr. Raanan demonstrated the applicability of Deep Learning (DL) to automatically obtaining different types of high resolution subsurface geometrical objects. The Deep Learning method is applied to spatial windows of overlapping full-azimuth directional image gathers. The application of Principle Component Analysis (PCA) on covariance matrices applied to these data windows significantly reduces the data, where only the principle (informative) directivity components are considered. The back propagation of these classified principle components to the image domain shows clear differentiation between structural reflectors, faults and point diffractors, even in areas heavily masked by ambient and coherent noise such as acquisition footprints. This approach shows great promise in identifying subsurface structural features with high accuracy which would be highly beneficial to the interpreters.
Mr. SK Sharma, (GGM-GP), HGS-Mumbai felicitated Dr. Raanan for his fantastic presentation. Mr. CPS Rana, (GGM-GP), Vice-President, SPG, Mumbai Chapter sum up the whole presentation, mentioning the international recognition of activities of SPIC, WOB on ES360 imaging system. Enthusiastic interpreters had made a valuable interaction with Dr. Raanan about the pre-stack interpretative engine of ES360.