Online Journal for E&P Geoscientists

Paton, Gaynor ¹; Bisset, Adrien ^*1; McArdle, Nick ¹
(1) ffA, Aberdeen, United Kingdom.

Frequency decomposition is now an accepted technique for identifying structural and stratigraphic variations within seismic reflectivity data. It is an extremely useful technique for identifying both channel systems and carbonate features especially when the expression is subtle and hard to interpret. Conventional frequency decomposition techniques use bandlimiting, which requires large vertical windows to analyse the frequency content of an event. This results in uncertainty over the vertical positioning of geological events and resultant smearing makes it difficult for the interpreter to understand the correct vertical localisation of closely stacked elements. Development of a new High Definition technique based on an adapted Matching Pursuit algorithm has resulted in the ability to define the individual components of a stacked system, in both carbonate and clastic environments. We present a comparison between the new technique and conventional frequency decomposition, illustrating the improvements in vertical resolution that are apparent within carbonate data and also a clastic environment off the western coast of Australia.

The carbonate data set example contains complex stratification within the reservoir units. Standard frequency decomposition gives valuable insight into the frequency content within the succession, however using High Definition frequency decomposition we have been able to identify pinch-outs which were not visible within either from the reflectivity data or by using standard techniques.

In clastic environments stacked channel systems are hard to interpret and it is almost impossible to get an accurate understanding of the evolution of the system. With High Definition Frequency Decomposition accurate vertical localisation is achieved so the evolution of the system can be visualised without the vertical averaging and inaccurate displacement of channel features. Results from a complex channel system from the Exmouth sub basin, Western Australia show the delineation of individual channels which are barely visible in the seismic data due to their thin nature.