£85/MWh oil and gas Oil and Gas Authority regional growth Spending Review 2015 climate change UNFCCC North Sea energy intensive industries CCS Costs CCS competition CO2-EOR Joint Industry Project infrastructure CCS Strategy industrial strategy cost-competitive CCS CCS Clusters Phase 2 COP21 CCUS energy demand Delivering CCS Paris Agreement fifth carbon budget hydrogen Clean Growth Strategy CO2MultiStore CCUS Cost Challenge Taskforce Cost Challenge Taskforce CCS Technology CCS Lessons Learned low-carbon heat Cost Reduction carbon Industrial CCS CCS CCSA SCCS Energy Bill 2015