CoP and Petronas paid on a 3P basis because it was recognised...

CoP and Petronas paid on a 3P basis because it was recognised there was still significant scope for reserves upgrades and the then-current 3P was a better reflection of the ultimate 2P figure. That's why when you convert it to a 2P figure the number looks extremely high - because the 2P figure was nowhere near complete.

I normally use a value of about $1M per PJ of 2P in my calculations, but it really depends on three big factors - extraction cost, transport cost and sales price. The reason Kipper is valued at over $2M per PJ is because it's a fairly low cost field, in close proximity to a major market that's short of gas. That's a pretty unusual set of parameters these days.

CTP's existing gas is fairly low cost and selling into essentially the same market, but the key difference is in pipeline tariffs. Kipper gas only has to get to Melbourne, Mereenie gas has much further to go and these tariffs put a bigger dent in the DCF than some might realise, because those tariffs come entirely off your profit margin.