The 3-C Struggle: Good News From the Trenches

The title of this luncheon presentation seems to imply that some sort of "trench warfare" is going on with three-component seismic data. Those who have had hands-on experience with 3-C data may know just how close to the truth this term sometimes is, but it is not meant to turn you away. The choice of title is meant to imply that progress in the area of 3-C technology has not been easy to come by, but progress is being made and that there are some really promising events to report on at this time.

When you consider that experiments with shear-wave exploration have been going on in one form or another since the 1950's, and that almost all acquisition crews, processors and interpreters still consider 3-C data to be an oddity. The word "struggle" seems appropriate for describing its lack of acceptance in the exploration community. After all, 3-C has been hailed as being "the next wave" of exploration for decades by advocates of this technology. So just how long do we have to wait for this wave to arrive?

Well, perhaps not too much longer. In fact, maybe it is already arriving. Not only have many 2-D, 3-C seismic lines been shot recently by many different companies, but 3D, 3-C surveys have been acquired by independent oil companies as well. Many examples now exist, both published and unpublished, that shear-wave data is able to provide valuable, and sometimes crucial, information that P-wave data alone is not able to provide about lithology and rock propel1ies. Perhaps the best evidence that 3-C technology is actually gaining acceptance is the fact that the people who actually find oil and gas are starting to use this technology to their advantage, whereas it has been almost exclusively in the realm of universities and research departments up until recent years.

A case history will be shown in this talk that illustrates one oil company's progression from (I) an initial idea that 3-C data might be able to help distinguish between sand and shale lithologies where P-wave data alone is insufficient, to (2) the acquisition, processing and successful interpretation of a 2-D, 3-C seismic line, to (3) the design, acquisition, processing and interpretation of a 3-D, 3-C survey from which a drilling location has been picked based on 3-D Vp/Vs maps.

Processing issues will also be discussed in this talk in order to give the flavour of how the multiple components of these datasets are processed concurrently. Topics will cover issues such as 3-C surface-consistent processing, statics and noise, shear-wave splitting and layer-stripping, resolution, and the shearwave versus converted-wave debate.