The OGA published analysis in May 2020, comparing the carbon intensity of United Kingdom Continental Shelf (UKCS) gas with imported liquified natural gas (LNG) and pipelined gas.
This analysis shows that gas extracted from the UKCS has an average emission intensity of 22 kgCO2e/boe; whereas imported LNG has a significantly higher average intensity of 59 kgCO2e/boe. The process of liquefaction, combined with the emissions produced by the transportation and regasification of the LNG once in the UK, are responsible for the considerably higher emissions intensity.
Importing gas via by pipeline, particularly from Norway, produces an even lower average of 18 kgCO2e/boe, which suggests there is still potential for the UKCS to continue to improve its operations and lower emissions further.
The publication/factsheet can be viewed here