I've been modelling this one up and wondered if someone could...

I've been modelling this one up and wondered if someone could help me on some of my assumptions (not my field). With the two new wellls they are looking to drill at Mereenie, how should I think about cost/GJ.
Assumptions:
1. they will add T10TJ/day from the new wells,
2. current production is c25TJ/day
3. Current cost per GJ of $4 based on CTP accounts
4. Increasing throughput at the plant by 40% but plenty of capacity (54TJ/day)
5. $4m capex for CTP share of two new well costs

Is it reasonable to assume fixed cost to run the plant, therefore with higher volume, price per GJ for Mereenie comes down to $2.80 ?