Depth Conversion is an iterative process which is designed to serve as a rather important one. It is the process of forming an important step in the seismic reflection method, which is generally the act of measuring acoustic wave travel times to the actual depth of a marked asset. Sound confusing? It can be.
Sound confusing? It can be.
Essentially, the earth isn’t a flat piece of rock. If you’ve ever taken a walk to the beach before, you’ll have likely noticed that rocks seem to have multiple layers and lines upon them. This is the layers of what they are, and how they were formed. Imagine this on a much grander scale. The earth in itself is made of multiple components and multiple layers of differing forms of rock, which of course varies in thickness and forms. You might notice that some rocks are porous, and some are thick and solid. That is because they are two different types of rock.
Within the earth, there are thousands of different types, which means digging down and not quite knowing what you’re up against can be expensive, and very dangerous.
At this point, you might be wondering what this has to do with depth conversion. Essentially, the way of which depth is calculated is to use sound. Have you ever shouted in a cavern or a cave? You’ll no doubt have noticed the echoes of your voice rebounding back to you. Of course, the deeper the cave, the more you’re going to hear the echo of your voice.
(Almost) the same principle applies to depth conversion. Geoscientists bounce acoustics off rocks and use the way that the waves come back in order to determine what sort of rock they are dealing with below the earth. Of course, a porous rock will require far different equipment to drill through than a less porous one – though of course all kinds of other factors apply, and depth conversion is not simply just about this.
Of course, the deeper you’re going to go, and the more rock types you’re going to see. If you imagine a vertical slice of the earth, you’ll likely imagine seeing a picture (at least once!) of layers upon layers of multi coloured lines. Essentially, these colours are used to code the varying types of rock beneath the surface.
Depth conversion and Depth conversion software is designed in order to ascertain factors such as the type of rock and depth from the wavelengths of the acoustics which are bounced back and can gather all types of information about the subsurface.
A geoscientist or a petrophysicist will interpret this information and use depth conversion software such as Petrel or IHS Kingdom in order to create a three-dimensional model, called a velocity model.
While indeed the process is not exact, there are a number of tools out there such as Velit, a depth conversion plugin by Equipoise Software, which is designed to eliminate error and vastly reduce uncertainty.