In the essay below I play a friendly devil's advocate on the subject of elastic seismic modeling. For four or five years, however, I was a task leader for the DOE SEG-Imaging project on elastic seismic modeling, and I championed the importance of elastic modeling and seismic mode conversions. I believe strongly that this project should continue, with both government and industry support -- and it is, for now.

If you have an interest in this project, I would be happy to give you contact information for the current project leaders. In the meantime, here's a link to the official project web site. Unfortunately, it is rarely up-to-date.

Forward modeling can be applied as part of any seismic imaging or interpretation project. Whatever the project, the purpose of using forward modeling is to arrive at a better interpretation of field seismic data by comparison to computational data. Wave equation modeling is useful for studying complex imaging problems, for processing and algorithm testing, and for AVO analysis.

Recent technological advances in the seismic industry have greatly increased the importance of understanding and using the full elastic wavefield generated during the course of seismic exploration. In a collaborative effort to study elastic phenomena, the National Laboratories could make obvious and significant contributions, given their expertise in elastic modeling and their extensive computing facilities.

In the mid-1990's, a numerical simulation effort known as the 3D SEG/EAGE modeling project was carried out through a cooperative effort between the U.S. National Laboratories and two professional societies of industry geophysicists. Various oil companies contributed the the time and expertise of their staff to define and construct a realistic geophysical model for subsequent computational modeling. Participants at several U.S. National Laboratories used this model and seismic simulation software to produce numerical data at their supercomputer facilities. The results of these simulations were subsequently distributed throughout industry for benchmark testing of new seismic imaging software.

In the time since the SEG/EAGE acoustic modeling project, the National Labs have tried to stimulate oil and gas industry interest in a collaborative 3D elastic modeling project. My experience in talking with various representatives of the oil and gas industry was that although they mostly agreed that a 3D elastic modeling consortium was a good idea, their response to specific proposals was ambivalent, and no one was willing to contribute their own time.

I believe the main factor behind the lukewarm support for this effort at this time is the current industry inexperience with issues related to processing and interpreting multicomponent seismic data. When the SEG/EAGE acoustic modeling project was initiated, the oil and gas industry was specifically interested in seismic exploration under salt. There was a clear need for a benchmark of acoustic prestack depth migration algorithms to judge their relative merits and performance for subsalt imaging.

I still believe that there will be a need for a similar industry-wide benchmark for multicomponent seismic data. Before that time arrives, however, our industry needs more experience working with multicomponent seismic data. Ocean bottom cable seismic acquisition is currently a proven technology only for undershooting gas chimneys. It is unlikely that this will be the only or main application for OBC seismic, but other applications still require more research and testing. The oil and gas industry will not be in a position to define a model for a computational modeling project until it has a better grasp of the environments in which this technology will be applicable, and the economic importance of its contribution.

In addition to needing more OBC acquisition experience to define an appropriate model, industry also needs more experience with multicomponent processing and interpretation so that it can define the study objectives underlying such a project. The seismic industry is not ready to define a benchmark dataset in part because the seismic research community is still in the early stages of defining appropriate uses for these data. There is currently a scarcity of commercial and contractor software available for processing and interpreting multicomponent seismic data, a testament to the immaturity of OBC seismology.

On the other hand, there have been some specific problems for which industry has been able to agree on elastic modeling for consortium-lead projects. The most notable to date is probably the SMAART consortium, where 2D elastic computational data were generated to serve as a benchmark for subsalt seismic multiple suppression. This dataset is now being used as a benchmark for computationally expensive (2D) wave scattering algorithms for multiple suppression and elimination. As acquisition practices continue to improve and computational costs continue to decrease, wave scattering and inversion methods will likely gain acceptance and popularity. As this occurs, there will be an inevitable progression from the use of 2D inverse wave scattering algorithms to the use of 3D algorithms. As this progression takes place, industry and government should be prepared to develop a three dimensional computational model utilizing the experience gained through the use of the 2D SMAART model. In this way, the 2D SMAART model and its 3D successor could serve roles in the development of inverse wave scattering methods that would be completely analogous to the roles that the Marmousi and SEG/EAGE salt model played in the development of 2D and 3D prestack depth migration.

An industry/government consortium to develop and generate a 3D computational dataset for seismic algorithm benchmarking is a proven concept. The SEG/EAGE salt model has demonstrated the value of a public resource of this nature in advancing technology in the oil and gas industry. In fact, it is doubtful that industry, without government involvement, could muster the resources necessary for a project of this scale. However, at the present time the oil and gas industry does not have the necessary experience with multicomponent and OBC seismic data to initiate a 3D elastic modeling consortium, even with National Laboratory involvement and support. Industry probably will be ready to initiate such a project within three years [more like eight years -- wpk, 2005]. At that time, the involvement of the National Laboratories will be crucial to the success of such an effort.