I think you miss the point Thornynut. There are no proven...

I think you miss the point Thornynut. There are no proven reserves in ICN's case. Firstly , they have to be drilled , appraised and tested at Stanwells cost and risk.The most important thing here is risk.It is not certain that the ICN wells will produce or that the estimated reserves will be there. What you are trying to compare is the purchase of existing 2P reserves in Pures case compared to ICN's case where there are no 1P, 2P or 3P reserves in existence yet.
Secondly, there was no defined market for ICN's potential reserves, whereas there is for Pures.Stanwell has not only put up the money to prove up reserves but has provided a market, thereby adding the value that you have attributed to Pure. In other words the ICN gas is worthless if they cant sell it, so Stanwell has created the value.
You simply cant compare Pure to ICN .
I suggest you do a quick course , say reservior engineering 101, before you wade into discussions on reserve categories and calculations .
Occam