Baseline studies for assessing risks to groundwater from onshore oil and gas and other deep subsurface activities - summary
Published 17 December 2021
Applies to England
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1. Chief Scientist’s Group report summary
This project investigated the typical ‘baseline’ range of concentrations of substances that could be associated with onshore oil and gas and other deep subsurface activities in 3 aquifers. It also developed a rapid assessment method to understand likely baseline chemistry conditions in other aquifers that have not been the subject of detailed investigation
1.1 Background
Baseline groundwater chemistry data tell us the quality of groundwater before new activities that could impact the aquifer take place and can be used to identify changes to groundwater quality once an activity has started. Baselines can be carried out at specific locations (for example, oil and gas sites), or can provide more general information about water quality across a wider area. Baselines are an important tool for monitoring change and protecting groundwater resources from new activities.
1.2 Approach
The project investigated baselines for 3 aquifers in England – the Sherwood Sandstone of the East Midlands and South Yorkshire, Lower Greensand aquifer of south-east England and the Pennine Coal Measures of the East Midlands and South Yorkshire.
New groundwater quality samples were collected and these were supplemented with data from the Environment Agency’s Water Quality Archive (WIMs). Substances of interest include: indicators of salinity, redox conditions (whether the groundwater is reducing or oxidising, which can indicate the likelihood of certain chemicals occurring), organic compounds, including volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), dissolved gases (carbon dioxide and methane) and Naturally Occurring Radioactive Material (NORM).
Factors that could influence the baseline chemistry were assessed, including land use, geology, climate and previous oil and gas activities. These factors were used to develop a method for assessing likely baseline concentrations in other aquifers.
2. Findings
The project found that baseline groundwater quality varied across the 3 aquifers and was influenced by both natural conditions and human activity.
Geological factors that have a big influence on the baseline groundwater chemistry include whether or not there are overlying superficial sediments that are rich in organic material, and aquifer rock type (for example, the presence of coal measures). Surface activities, including mining legacy, agriculture, industrial land use and urban environment can also have a big influence. The depth of the aquifer and whether or not it is confined by low permeability rocks can have a medium influence on baseline groundwater chemistry. The presence of nearby oil and gas activities appeared to have a low influence on these baselines.
3. Conclusions
The project identified the natural and human factors that influence baseline groundwater chemistry. The method presented can be used as a rapid assessment for understanding likely baseline chemistry conditions in the aquifers before onshore oil and gas (and other deep subsurface) activities take place.
4. Publication details
This summary relates to information from project SC170015, reported in detail in the following outputs:
- Report: SC170015/R
- R1: Baseline studies for assessing risks to groundwater from onshore oil and gas and other deep subsurface activities: synthesis report.
- R2: Baseline groundwater chemistry: the Sherwood Sandstone aquifer of the East Midlands and South Yorkshire.
- R3: Baseline groundwater chemistry: the Pennine Coal Measures of the East Midlands and South Yorkshire.
- R4: Baseline groundwater chemistry: the Lower Greensand aquifer of south-east England.
Project managers: Danielle Ashton and Sian Loveless, Chief Scientist’s Group.
Research partners: Pauline Smedley, Daniel Mallin Martin and Rachel Bell, British Geological Survey.
The Environment Agency’s Chief Scientist’s Group provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible. This project was delivered in partnership with the British Geological Survey.
Enquiries: [email protected].
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