In both land and marine settings, multiples (echoed reflections of seismic waves) must be addressed through attenuation. Three types of multiples are:
- Free surface multiples
- Peg-leg multiples
- Interbed multiples
Multiple Removal Techniques
ION has created several techniques to address multiples, some of which are statistical signal processing methods; others depend on velocity differences between the multiple and the signal; while others still are model based. Our techniques include model-based, deconvolution, and velocity-based approaches, as follows:
- 3D SRME (Surface Related Multiple Elimination) unique to data acquired in the Marine environment. It is a two-part processing sequence where the data is used to model the multiple, and that modeled multiple is then subtracted out from the data. This method is fully data driven, and the only input needed is the data to be modeled. The user need not identify the multiple generators. The SRME method requires a free surface to work, and as such, is a marine tool that can be used for water bottom multiples. WAZ and 3D concepts have been fully integrated throughout development of our 3D SRME toolkit.
- IMA (Interbed Multiple Attenuation) works with data acquired in both land and marine and is used for removing peg-leg multiples. IMA is an extension of the SRME methodology so that the module will work on interbed multiples. The model/subtraction methods are the same, yet the domain where the module works is expanded from marine only to land. Typically, the strongest multiples are removed by another method, and then the remaining interbed multiples are removed by IMA. This compute intensive technique combines our geophysical expertise with the latest technology efficiently on large surveys.
Deconvolution approaches use predictive deconvolution with an appropriate time lag so that multiples can be attenuated in a seismic section. For the method to work, an operator must be chosen that corresponds to the two-way travel-time of the multiple. Additional signal processing is often needed to optimize this approach to remove multiples.
Velocity-based approaches depend on the ability to differentiate the multiple from the primary based on differences in their move-out velocities. While these methods can work well, they are very data dependent and have largely been replaced by model-based multiple removal techniques. Regardless of the method used, whether it's deconvolution or velocity-based approaches, our staff has the expertise to combine these methods with 3D SRME and IMA to accurately remove the multiple and leave the signal.