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VNG are trying to identify were there are oil and gas. And this requires alot of work to deside were to drill.
There are five main elements
The present of a source rock, normaly it si «skifer».
The second thing is the layer were the oil and gas are «created» and since the hydrocarbons have a less density than water, it flotes upwards until it hits a trap, trapping the oil and gas from moving all the way up.
In norway we have maps over the entire sea-ground. Then we need to look for bright areas and then try to find areas with larger amplitute and then find areas that are dimmed from the other areas. Then we use computer programs to find the area.
The computer program creates a 3d area.
Then they create a table based on depth instead of time.
In order to find what they are looking for the need to look for an area with just a simple oil rig nearby that is used for analyzing the area. So it is just like looking in the dark. (The are can be many kilometers away from the area).
After VNG has completed all their geological studies, they decide wether or not it is economically to be drilling there. It is all based about how many hydrocarbons they think it is in the oil rig. The oil gets smaller denser, while the gas expands.
Then they create a graph with the maximal and minimal volume of oil and gas they can find. Then they look at the likelyhood for finding oil in the reservoar and that gives them a change of succes. Something under 10% is very risky, 20% – 30% is mid-risky and 40% and above is normal.