AVO, near and far - the end of the trend?
This paper gives a brief overview of the history of the well-known and famous ‘background trend’ in AVO theory, which also goes by the names ‘lithology trend’, ‘fluid line’ and sometimes ‘noise trend’. Whereas the discovery of the trend met with euphoria, stirring hopes that it would become much easier to detect hydrocarbons, this promise has hardly been fulfilled. One of the problems was (and is) that the trend is much steeper than what theory based on rock properties predicts. This paper explains why and how the trend can be so steep. It explains how a clear trend emerges regardless of lithology, hydrocarbons or even noise. Any contribution from lithology or pore fluid, if it exists, will be smaller and often completely drowned by what I call the ‘transformation trend’.