Types of Modeling There are many types of seismic modeling from simple well log synthetics, through complex 3-D raytrace modeling and on to full-elastic wave equation modeling. Accuracy, time and economic constraints must be considered in selecting the modeling type. Raytrace modeling simplifies sounds path by simulating one raypath
from source to receiver.
Raytracing is often a good choice for investigating seismic effects because:
- Visualization of raypaths, especially in 3-D, assist in analysis and understanding of imaging
- Acquisition geometry can be tested before deployment in field
- Results can be sorted into common-reflection-point (CRP) gathers to simulate 3-D PreSDM
- Raytrace amplitudes are good approximations when modeled correctly
- 2D and 3D raytrace software is proven and available
- When running extensive 3-D models on today's fast computers, cost in time and money are very reasonable
Above: East-west cross section of Ship Shoal South 3-D model showing common-reflection-point gather (CRP) raypaths for selected bins on a 4300m subsalt horizon. For clarity, only every 20th CRP is shown. Note that the CRP display is effective in indicating the imaging problems below the salt edge at 10,000m distance along the model. Wave Equation modeling, solves differential equations by approximating wave front
motion between small cells of model.
- Produces more realistic seismic response than raytracing, especially in complex areas
- Visualization of wavefronts in movie form illustrates complexity of sound traveling in earth
- Includes complex interaction of all types of waves and can include anisotropy
- Matches the modeling done in wave equation prestack migration
- Usually much slower than raytracing, so more expensive in time and cost
Above: 2-D acoustic finite difference model with wave field penetrating and reflecting from a salt body |