Seismic imaging (migration) is potentially the single most important step in processing seismic data; it is usually the “final step” in processing and it has contributed to some of the most important finds in the petroleum industry.
Conventional wave equation migration (WEM) is proposed to image the Earth’s internal structure using by propagating data downward through a velocity model and is limited where the structure and velocity field generate more complex arrivals, such as turning and ‘prism’ waves. Prism waves are waves that undergo multiple primary reflections at scattering interfaces before propagating to the recording sensor array. Complex propagation paths give rise to arrivals that are seen as noise in the imaged data.
RTM is one of the latest migration methods that capable of handling the migration process in complex structures (limited wave illumination, high dip> 85 degrees, prism waves, etc.) – which previously could not be handled by conventional migration methods (Wave Equation Migration – WEM, Kirchhoff, etc.).
RTM propagates downward and upward events through Earth’s internal structure, clearly handling turning waves and all other complex propagation paths. In many cases this ability to use complex wave modes allows imaging of subsurface areas that have poor direct illumination. RTM can help to interpret discontinuous structures in complex geologic zones.
The advantage of RTM is because this method solves the wave equation in two directions (forward and reverse):
- Forward modeling of the wave source, so if we have a wave source on the earth’s surface, the modeling result will be downgoing waves.
- Reverse time modeling from the receiver with the reverse time.
- Cross Correlation of the results both forward modeling and reverse time modeling.
- The sum of the samples produced in order to obtain a seismic cube.
The migration results from the model data data below demonstrate that reverse-time migration (RTM) is more accurate in imaging steeply dipping faults than Kirchhoff.
