Wide Azimuth Processing (WAP)
Thanks to our vast experience onshore, offshore and in transition
zones, Geotrace is uniquely qualified to bring you the sophisticated
tools and expertise required to take on these tough challenges.
The process starts with the formation of Hybrid Gathers, a re-sorting of the data coming from a single intersecting line of sources and receivers. Offset Vector Tiles or OVTs are generated from Hybrid Gathers by selecting data in a range of offsets and azimuths. The resulting data sets “tile” the survey area and can be migrated.
The OVTs can then be migrated in time or depth and produce a remarkable new set of migrated gathers that essentially generalize our traditional “scalar” gathers into “vector” gathers called Offset Migrated Gathers or OMG.
OMGs in turn allow for a direct measurement of the difference between the “fast” and the “slow” travel times and the direction (azimuth) in which this propagation occurs.
This technique measures the azimuthal “moveout” and direction of minimum travel times (∆t,φ) in the OVG to extract the fracture density and orientation. The result is a visual image or “map” of fractured volumes.
Seismic waves propagate through the Earth at different velocities in different directions due to depositional layering and vertical fractures in the rock formations. These different velocities are described as Vertical and Horizontal Anisotropy (VTI and HTI) and are observed in wide azimuthal seismic data.
Fractures are everywhere in the Earth. Natural fractures and induced fractures by hydraulic fracturing process play a very important exploration and production role in conventional reservoirs such as sands and carbonates or unconventional reservoirs such as shales. Orthorhombic anisotropic prestack migration is the perfect technology to handle VTI and HTI simultaneously and provide flat gathers for AVO analysis and prestack inversion, RockRes®, for lithology and fluid prediction.
Fracture orientation and intensity, a 3D volume with vector fractures – orientation and intensity, are then computed from the velocity differences in different azimuthal angles derived from VTI and HTI parameters and Orthorhombic Migration using OVT technology. FracMapTM is extracted from the vector volume along a constant time or interpreted surface. The vectors represent the orientation of the fractures and the thickness of the vectors represents the fracture intensity or magnitude.
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