Imagine a ray-based solution that maintains all of the flexibility of the Kirchhoff migration while inheriting the desirable properties of the full wave migrations. Paradigm has captured a new perspective on ray-based imaging and implemented it as a solution that can be applied to a broad range of exploration and development imaging objectives.

Referred to as the Common Reflection Angle Migration, this new pre-stack depth migration seeks a uniform illumination of the subsurface by performing a dense ray tracing from every image point up to the surface. These rays are traced in uniform angle increments and in all directions to ensure that all arrivals are taken into account and all amplitudes and phases are preserved. This “bottom up” ray tracing approach is performed in the “local angle domain” providing the engine and local reference system to map surface recorded seismic data to each image point.

With this new imaging perspective, the common reflection angle migration is able to use the entire wave field within a controlled aperture, making it ideal for both full-volume migrations and target-oriented migrations along specified exploration or development targets. More importantly, by formulating the migration in the local angle domain, the program is able to output true angle domain image gathers in depth, the natural domain for performing seismic inversion.

Improved Imaging
The common reflection angle migration is an anisotropic multi-arrival solution that uses the entire wave field, making it ideal for solving complex imaging objectives including overthrust and subsalt delineation.

Improved Amplitudes
The common reflection angle migration performs its imaging in the local angle domain to achieve uniform illumination of all image points, producing amplitude preserved angle-dependent gathers and reflectivities. These outputs are ideally suited for seismic reservoir characterization objectives.

Improved Flexibility
The common reflection angle is an output-driven migration with the ability to control and target its output along or at specific exploration or development targets.

New Opportunities
All of the properties of the common reflection angle migration make it ideally suited for field development projects that make use of time-lapsed (4D) acquisition surveys.

Increased Technical and Operational Complexity
Exploration and Development geoscientists are faced with generating subsurface images in areas of increasing technical and operational complexity. Imaging in the local angle domain provides a vehicle for dealing with this complexity. The common reflection angle migration is ideal for the following types of imaging challenges:

• Positioning of anisotropic overthrusts
• Qualifying subsalt reflectors
• Resolving stratigraphic or velocity detail
• Recovering reflectivities
• Predicting pre-drill pore pressure

Uniform Illumination
The common reflection angle migration constructs true angle gathers by summing all seismic events with the same reflection/diffraction angle. By performing a uniform illumination of the image point, all arrivals are included and all amplitudes and phases are preserved. Using the information provided by the specular rays and the corresponding Fresnel zones, a count of the number of reflections contributing to each image point and each reflection angle can be made. These illumination factors can be posted (see image at right) on the common image gather, an extremely useful diagnostic for understanding both amplitude behavior and the capacity of the recorded data to illuminate the subsurface.

Platform support
The Common Reflection Angle Migration is an add-on to Paradigm’s GeoDepth Velocity modeling and imaging solution. It is available on Linux clusters running 64-bit Linux Red Hat 3 or 4 operating systems.