The OGA have published a number of benchmarking reports about the UKCS which can be found at the links below.

Benchmarking of UKCS production efficiency and losses with interactive visuals

Analysis and benchmarking of Unit Operating Costs (UOC) and operating expenditure...

UKCS asset performance benchmarking using Recovery Factor data

Benchmarking of the flaring and venting of greenhouse gases on the UK Continental...

Statistics for a wide range of recent UKCS decommissioning activities