Although WIT Inc. itself is fairly new, its operations are based on the WavePak processing system, which has a history going back to 1984. WavePak was created to support research on algorithms for seismic data processing. It was intended to provide a friendly environment for developers and was also intended to be easy to maintain and to port to new computer systems. Portability meant that good software no longer was lost when companies moved to new hardware and operating system environments. WavePak succeeded and lives today largely because the industry moved to the "Unix" type operating systems that were reasonably consistent over a variety of hardware platforms.

Initially WavePak simply executed a sequence of programs. Later it was realized that there were many cases in which a sequence of seismic operations could act on a single seismic gather without having to write to disk after each operation. This required that the WavePak system tie the seismic operations together under a main program which would pass the seismic gather from one operation to another. This action is called "piping" of data. The "piping" in WavePak is not implemented using operating system pipes but is programmed directly into the WavePak system - important for support of automatic parallelism as mentioned below.

In the early 1990's the industry was in the middle of a move to parallel processing. There were parallel algorithms that depended on the availability of shared memory across many compute nodes and what was called a "symmetric multi-processor operating system." Another scheme for parallel processing was the "distributed" viewpoint in which each machine was viewed as a separate compute unit that communicated with other compute units via the network. Data was moved between the machines by the use of message passing schemes. One of the first of these schemes to gain wide use was the "Parallel Virtual Machine" software (PVM) which was created at the University of Tennessee and Oak Ridge National Laboratory. This software was free and as development continued through the 1990's, it became very stable. The first implementations of another popular message passing scheme called MPI were made on top of PVM.

WavePak exploits PVM to implement "automatic parallelism" for a certain class of algorithms that used the WavePak system piping. There are two important features of the parallel processing supported by the WavePak system. The first is that it does not inherently use any disk space on the slave nodes - use of local disk is optional. The second and most important feature of the parallelism in WavePak is that it supports fault tolerance and load balancing in cases where the number of units of data to be processed is large compared to the number of compute nodes in use.

WavePak contains many of the standard algorithms used in processing seismic data as well as a number of wave-equation algorithms for imaging seismic data. One of the most important imaging algorithm available is a PSPI algorithm that will perform 2D or 3D shot record migration. This algorithm will operate over rough topography which also enables it to perform imaging of 3D VSP data. The algorithm is also able to image at angles other than vertical. This enables imaging of very steep reflectors or even overturned reflectors by imaging from an angle at which these reflectors appear to dip at angles less than 80 degrees. This algorithm also works in the presence of a laterally varying VTI anisotropic medium.

A key use of our Shot Record Migration algorithm is the generation of "time-shift gathers", which are used in our patent-pending Migration Velocity Focusing Analysis to generate velocity information directly from the time-shift gathers.

Another very important algorithm in the system is the 3D acoustic modeling algorithm that will simulate in either a constant density medium or a variable density medium. This algorithm has been used to simulate full 3D seismic surveys in cases where the target of interest was less than 5000 meters deep. In this case a billion seismic traces were simulated over a variable velocity and density medium. Another use of the simulation software is in the design of an offset VSP survey in the presence of salt. There are many cases in the Gulf of Mexico and elsewhere that have so much high velocity salt present that the first arrival at the well from an offset source may be from a headwave traveling in salt. In the presence of widespread salt it is important to simulate the survey to be sure that the first arrivals will come through the sediments.