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