Presented by: Elive Menyoli, Emerson E&P Software Business Development Manager Geoscience Services
Domain: Reservoir Characterization
™, EarthStudy 360
The three most common uses for common image gathers are velocity analysis for imaging purposes, fracture characterization, and analysis of amplitude variation with angle (AVA) or offset (AVO) as direct hydrocarbon indicators. In a strongly deformed and faulted geologic terrain or in the presence of shallow velocity inversion where ray fields become multi-pathed, the assumptions made for imaging data in the offset domain could be violated (single path assumption). This will certainly lead to artifacts affecting offset domain CIGs, consequently making it difficult to perform meaningful AVO analysis.
Angle-domain common image gathers from Emerson’s EarthStudy 360 or Common Reflection Angle Migration (CRAM) technology uniquely define ray couples for each point in the subsurface, therefore resolving the typical multi-pathing problem. The result is more stable artifact-free angle gathers, regularly sampled in all dimensions, required for amplitude-versus-angle analysis.
The migration procedure is based on a specially designed point diffractor operator that ensures maximum illumination from all subsurface directions and all surface source-receiver locations, where all arrivals are taken into account and amplitude and phase are preserved. Each event in the data is associated with only one subsurface location. The amplitude preservation qualities of CRAM, combined with the organization of the amplitudes in the angle domain, make it ideal for reservoir characterization using AVA inversion.
This presentation features a case study contrasting AVO inversion and AVA inversion on an Eagle Ford Shale dataset. The results show that, compared with angle gathers transformed from post- migration offset gathers, angle gathers from CRAM have three critical advantages: more accurate incident angle computation, a robust and reliable amplitude versus angle (AVA) variation, and higher resolution inversion results.
Elive Menyoli is Emerson's E&P Software Business Development Manager for Geoscience Services. He has 15+ years of experience in the oil and gas industry. Prior to joining Paradigm, he worked at Marathon Oil and Total E&P USA, in deep water projects. Dr. Menyoli holds a MSc degree in Physics from the University of Goettingen, Germany and a PhD in Geophysics from the University of Hamburg, Germany. He has authored numerous publications in seismic imaging and interpretation, with a recent emphasis on shale resource plays.