Velocity Modeling

Velocity modeling for tomography, seismic modeling, illumination, and migration

Velocity models are key components of seismic imaging, and consequently, to reservoir description and geomechanical analysis, (Note: on this page 'velocity' or 'property' denotes not only compressional- and shear-wave velocities, but also anisotropic parameters).

The greater the subsurface complexity (e.g., strong velocity or anisotropic parameter variations or complex geological formations such as salt and basalt structures, heavily faulted zones, anisotropic environments due to sedimentation or fracturing, overthrusts, shallow gas, and others) the more advanced the migration algorithm used for imaging needs to be and the more velocity model accuracy and resolution is required.

Building accurate, high-resolution velocity models involves an iterative process of structural interpretation and modeling, velocity and anisotropic parameter analysis and modeling, and velocity updates.

WesternGeco velocity modeling is performed using i2i applications and includes automatic structural modeling and layer definition based on geological rules and property population (velocity and anisotropic parameters), again using geological conformance when needed and specific resolution for each property and each layer. Structural and velocity information is described in one compact velocity model that is directly ray traceable by our ray tracing-based applications: CIP tomography, seismic forward modeling, illumination studies and Kirchhoff prestack depth migration.

Recent enhancements to i2i applications have improved capabilities in the handling of extremely complex structural models (containing rough surfaces and multiple overhangs) that are now indispensable for accurate subsalt imaging. i2i also has the ability to import salt bodies as Gocad meshes.