Potential environmental impacts from techniques to enhance rock permeability: summary
Published 28 November 2022
Applies to England
© Crown copyright 2022
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1. Chief Scientist’s Group report summary
This project reviewed ways in which oil and gas or geothermal reservoirs in England could be engineered to enhance rock permeability and productivity. It considered the suitability of these techniques for different conditions and possible environmental impacts. The findings will help the Environment Agency regulate these techniques effectively.
1.1 Background
Techniques to enhance rock permeability are widely used in oil and gas and geothermal heat and power operations to achieve and maintain an adequate flow rate. Permeability can be enhanced when a rock is physically broken (fractured) by pumping fluids into the rock at high pressure, or chemically by injecting acid which dissolves part of the rock.
1.2 Approach
A shortlist of possible rock permeability enhancing techniques was identified. Techniques covered matrix acidising, acid fracturing, fluidic oscillation, energised fluids and foams, carbon dioxide fracturing, gelled propane/LPG fracturing, narrow diameter multilateral drilling, shock fracturing, propellant fracturing, low volume hydraulic fracturing, and enhanced geothermal systems.
A literature review and industry interviews were used to collate information and answer questions about the techniques. Questions considered the purpose of the technique, suitable rocks and conditions, commonly used chemicals, water volume, pressures applied and frequency of application, infrastructure and surface operations, technique limitations and potential environmental impacts.
1.3 Results
Techniques to enhance rock permeability are suited to different geological and environmental conditions. Physical and chemical techniques can be combined, and operational parameters designed to maximise effectiveness based on factors such as specific reservoir geology, existing flow pathways and pressure conditions.
Potential environmental impacts from these techniques include, but are not limited to, the use of chemicals, particularly the acids used in acid-based techniques and additives to improve effectiveness, and the handling of these chemicals and any waste produced, which could impact ground and surface water and be hazardous to human health.
1.4 Conclusions
This report summarises many of the ways that rock permeability can be increased. These techniques will have different impacts on the subsurface and environment and will be more or less suitable in certain conditions. This information will help the Environment Agency consider appropriate risk-based monitoring and management that could be used to enhance rock permeability.
1.5 Project details
This summary relates to information from the following project:
- Report: SC210002/R
- Title: Potential environmental impacts from techniques to enhance rock permeability
- Project manager: Sian Loveless, Chief Scientist’s Group
- Contractor: WSS Energy Consulting Ltd, Export House, Woking, GU21 6QX
This project was commissioned 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.
Enquiries: research@environment-agency.gov.uk
© Environment Agency