Seismic Inversion, as well as Simulated Annealing Inversion (SA) and Coloured Inversion converts seismic reflectivity data into acoustic impedance. It is a technique used the world over in multiple sites, and has become steadily more popular throughout the years as times change, and clients expect more and more information from their prospects. Geologists and Geophysicists may use seismic inversion for many differing purposes, though most use it to estimate properties from within the earth’s subsurface via reflected seismic waves.
How does it work?
Seismic inversion, as stated above, sorts reflected seismic waves into layered sets in order to indicate differing rock formations, which of course contain differing properties. Comparing these formations to formations on record allows for a pretty good indication of what exactly lies below us, as well as their properties. Seismic inversion is a process which is well known to have varying methods of which this data can be categorised – two of which are known as coloured inversion and simulated annealing inversion respectively.
What is Coloured Inversion?
Coloured inversion is generally considered a fast and lightweight way to quickly generate pseudo-relative impedance data. While indeed the process of coloured inversion is known as a quite quick solution, the application of additional modules to IHS or Petrel software such as Equipoise Software’s InSeis allows the interpreter to make the process far more definitive with the ability to calibrate logs, analyse impedance log spectra as well as match to log trends in a far more accurate manner than what coloured inversion normally permits.
What is Simulated Annealing Inversion?
This is considered a much more definitive way of estimating properties. Simulated Annealing Inversion is often called upon when coloured inversion shows disparities, and it is a way to achieve absolute and relative acoustic impedance by applying a model directly via the method of forward modelling. Simulated Annealing Inversion generally does this via computing the seismic response of many references of multiple impedance models and applies these known parameters (extracted from seismic data within the model – or externally depending on user preference).
Why are these techniques popular now?
Generally, seismic inversion has always held a back seat due to the relevance of depth conversion, and has taken a more complimentary role. However, recent advances in seismic inversion, such as the advent of Equipoise Software’s InSeis seismic inversion suite has allowed what began as a complimentary process to turn into a science of it’s own right – and the source of valuable information regarding the world below us.