Seismic Inversion can seem like a very confusing topic, much like Depth Conversion is, however, it is a very simple procedure. Seismic Inversion uses two things – original reflectivity data and impedance.
Original reflectivity data is recorded routinely over a period of time by putting essentially small microphones across the Earth’s surface in a grid-like format. It is then that a source transmits a sound from one end, through the grid of microphones to a reflector which bounces the sound waves back to the original source. These sound waves are used to measure depth.
Impedance is the rock property. This is measured by using the multiplication of sonic velocity (how hard or soft a rock is) and bulk density.
Geologists and Geophysicists may use seismic inversion for many different purposes, however, they are more commonly used to estimate properties within the earth’s subsurface with the use of reflective soundwaves.
Seismic inversion sorts these reflective soundwaves into layered sets in order to determine different rock formations, all with differing properties. Comparing these formations with others will give a pretty good indicator of what actually lies below the surface before going ahead to drill down.
More recently, coloured inversion has played a key role in determining what’s underneath the earth’s surface. Coloured inversion is a fast and lightweight tool which can be used in addition to IHS and Petrel software and gives the ability to calibrate logs, analyse impedance as well as match trends quickly. It’s with easy-to-use software packages like this which make seismic inversion easier to understand.
Seismic inversion though has always taken a backseat due to the relevance of depth conversion, however, recent advances such as relevant inversion software which is now available has turned the process into its own science. Not to mention, some very valuable information about the ground below us.
