I would imagine that infrastructure would be a lesser part of...

I would imagine that infrastructure would be a lesser part of the cost in comparison to the drilling/fracking and plant cost but still quite relevant. You could expect a main pipeline of about 450nb to cost around 1mil/km and at a glance its about 150km x 75km from one side of the play to the other, obviously this would be the backbone pipeline and depending on the field configuration there would be a number of tie in branches off it. If we assume a main pipeline 150km @1m/km and then 10 * 30km 200nb (about 0.5mil/km)sub branches reaching the outer limits we could assume that that infrastructure would come in at about $300mil, this would allow for connection of say 100 wells which would cost say $30mil a piece to complete (30mil*100=3.0billion). A separation, stabilisation, gas reinjection, oil pumping facility would also be required to process the collected gas prior to admission to TAPS, this I imagine would be in the vicinity of $0.5-1 billion giving a field development total of $4.3 billion (0.3+3.0+1.0). State incentive of 35% would bring this down to $2.8 billion which is still a lot of CAPEX

With 100 production wells each to produce 7.5mmbbls (assuming over 10 years) total production in this scenario would be 750mmbbls or at todays oil price(75mmbbl*$36) $27 billion or 2.7billion/pa

OPEX for north slop production appears to come in at around $20/bbl therefore in this scenario would be 75mmbbls * $20 =$1.5 billion leaving a profit of around $1.3 bllion p.a. If we then assume a field/plant life of 10 years the plant depreciation would be $280 million p.a leaving a profit of $1 billion p.a or about a 30% ROI before tax. With state tax (~25% with possible early concessions) included this will likely be roughly neutral at todays oil price the good news however is that under these assumptions each $1 increase in oil price equates to around $75 million increase in profit.

Disclaimer: My calculations are probably flawed