Research and analysis

Onshore oil and gas monitoring: a structured approach to quantifying whole-site methane emissions - summary

Published 21 October 2021

Applies to England

1. Chief Scientist’s Group research report summary

This project has investigated how to quantify the total amount of methane being emitted from an onshore oil and gas site. This quantification involves combining measurements of methane concentrations with, for example, wind speed and direction, and may also require computer modelling to calculate the methane emission rate.

The study considered how the methods for measuring methane can be chosen systematically so that, when combined with other data and techniques, they give estimates of whole-site emissions that are appropriate for different purposes.

1.1 Background

Methane is an important greenhouse gas that contributes much more global warming per tonne than carbon dioxide. Reducing methane emissions from the onshore oil and gas sector will help to address climate change: improved measurement systems for methane emissions can play an important role in achieving these reductions.

Within an onshore oil and gas site there may be a range of methane emission sources, including leaks and engineered releases during normal or non-routine operations. Whole-site methane emissions are the total emissions from a site combined from all the individual emission sources over a specific period.

1.2 Approach

The project was a desk-based scoping study that used expert knowledge and existing literature to investigate the purposes behind quantifying whole-site methane emissions, emission characteristics and site types, techniques for the quantification of methane emissions, and the selection of measurement techniques.

1.3 Results

The study highlighted the importance of understanding the purposes behind quantifying whole-site methane emissions and suggested three categories of monitoring purpose: scoping, routine, and research. The purpose of the monitoring will help determine the level of certainty needed in the methane emission rate. The certainty in the whole-site methane emission depends on the uncertainties in each element of the calculation. This can include uncertainties in measurements of methane concentrations in the air; wind speed and direction; and in any computer modelling.

Whole-site methane emissions can be quantified either by combining the measurement of each individual source or by measurements of the total methane plume from the whole site. The available techniques include fence-line monitoring, imaging, point concentration sampling, Differential Absorption Lidar (DIAL), tracer, and air quality towers. For each approach, an uncertainty level is suggested alongside the need for any computer modelling and any additional information needed to calculate an emission rate (for example wind speed and direction). Some of the approaches are suitable for continuous monitoring and some for measurement campaigns, with the tracer technique or DIAL having the potential to provide the highest level of certainty.

The study outlines how monitoring purpose, site type, and emission characteristics could be used in deciding on the most appropriate measurement technique.

1.4 Project details

This summary relates to information from the following project:

• Report: SC200002/R
• Title: Onshore oil and gas monitoring: a structured approach to quantifying whole-site methane emissions
• Project manager: Mark Bourn, Chief Scientist’s Group

This project was delivered by the Environment Agency’s Chief Scientist’s Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.

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