Since the early to mid-1980s, inversion has been in discussion. Inversion is defined by Sheriff in his dictionary of geophysics terms as “Deriving from field data a model to describe the subsurface that is consistent with the data”(Sheriff, 2002, p. 194). My first exposure was at Amoco when I heard this topic discussed by Roy Lindseth. An excellent history of the topic is given in Lindseth (1979). The term inversion has always seemed to mean different things to different people. It also seemed to evoke very strong comments based on individuals’ experiences on the topic. I was recently told that a “constrained sparse-spike inversion algorithm” was simply nothing more than a phase rotation of the seismic. When I mentioned the parameters that went into this type of algorithm, the individual did not want to discuss it because it did not support his argument against utilizing the process. I am forever amazed at how much confusion there still is and at how people can be so completely confused in their very definitive statements. In 2000, I wrote an article in the Society of Exploration Geophysicists’ The Leading Edge in an effort to present a guide to the interpreters who use inverted data (Latimer et al., 2000). A lot has happened since 2000, and it is time to update the interpreter community with added details and further explanations, which are featured in this chapter. I will expand the discussion from simply post-stack seismic-trace inversion to include pre-stack data and geostatistical inversion. I will provide a description of terminology and again a basis for comparison and usage of acoustic-impedance inversion products, and I will give the interpreter a methodology for quality control and interpretation of inverted data.
I still contend, as I did in 2000, that the first and foremost prerequisite in doing any type of inversion is to have the absolute best seismic processing completed prior to attempting an inversion. I will show, however, that a post-stack inverted data set may help you determine whether the data should be reprocessed, thereby indicating that it can sometimes also be used as a screening tool for further work.