ISIM - Interactive Seismic Imaging and Modeling

Flatness criteria of migrated gathers or focusing analyses are conventionally used for evaluating the quality of migration velocity models and further to compute updates on non-perfect velocities. In complex situations as, e.g., beneath salt bodies these approaches may fail due to too poor quality of the gathers or even invisible gathers. In such situations other methods need to be applied to finding a better velocity field. A currently acknowledged approach is the trial-and-error change of parts of the salt body geometry accompagnied by fast migration that directly shows the effect of the model change on the stacked image. Geologically plausible appearance of subsurface reflectors and dips or curvatures of reflectors are valid criteria for determining whether model changes have led to an improvement. Very fast migration tools are needed for such a strategy of interactive velocity model building. Ray-based schemes like Kirchhoff migration need to be modified to provide the extreme speed needed.

We are currently developing a tool for interactive migration that consists of very fast migration schemes and a GUI that is used for salt dome editing. The fast migration follows the line of extracting velocity independent parts of the summations to a pre-processing step that needs to be done once only while during the iterative migration work only the smaller rest needs to be repeated. Together with adapted degree of data decimation, the migration of the pre-computed slantstacks lead to a speed-up of several orders of magnitude.
 

Objectives

• Salt dome modeling in real-time
• Interactive migration
• Visualization and geobody surface editing

Method

• Application based data compression by slantstacking and event picking
• Fast and interactive ray / beam migration
• Triangulated salt dome surface
• Interactive velocity model editing
• Desktop solution for editing andb parametrization
• Cluster connection for migration, achieving high paralellization
• Modularized application interface

Interactivity

• Real-time working cycle
• Migration result reacting on salt dome changes
• Salt dome edges visible in velocity and in seismic representation
• Multiple object visualization

Beam-Stack Migration - Objectives

• Very fast migration tool
• Application for repeatable migration procedure
• Controlled accuracy
• Investigation of major subsurface reflectors in no time

Beam-Stack Migration - Method

• Pre-migration summation by local slantstacking
• Adjustable compromise between image quality and completeness versus speed
  and image sparseness
• Automated event selection by slantstacks
• Beam focussing and data compression
• Isotropic, VTI, and TTI models
• High level parallelization