Research and analysis

Review of software used by the oil and gas industry to model hydraulic fracturing - summary

Published 22 October 2019

1. Chief Scientist’s Group research summary

This project reviews computer models that are used by the oil and gas industry to understand how subsurface hydraulic fracturing will progress. In the USA there are cases where fractures have extended further than intended and groundwater has been affected. However, the geological conditions there are very different from those in England.

As a relatively new area for the Environment Agency we needed to know what these models do, how they operate and what they can tell us to help assess environmental risk at individual sites.

1.1 Why was this project needed?

Computer models that simulate how rock fractures develop are a new topic for the Environment Agency. Factors such as the pressure at which fluids are injected are modelled with the aim of optimising the hydraulic fracturing. The results are included in the hydraulic fracture plan for a site. We needed to know:

• what models are used
• the physical parameters they take account of
• the assumptions and simplifications they incorporate.

This will help us to understand how operators might predict the development of hydraulic fractures. Also, model parameters are often calibrated against monitoring results as hydraulic fracturing progresses. This is particularly useful where there is no pre-existing data. The aim is that hydraulic fracturing can be adjusted using this procedure, to help ensure both fracture creation and compliance with permit conditions.

1.2 What did the project involve?

Commercially available software for hydraulic fracturing was identified and the main features were catalogued. A literature review was carried out in support of this and summary information was obtained from software providers. This included information on:

• computing requirements
• licensing options
• modelling methodology and input parameters
• the availability of guidance documents and training

1.3 What were the findings?

Seven modelling packages were identified as the most common. Each has different levels of sophistication and provide different results. Some are limited to simulating simple fractures, despite evidence that induced fractures are more complex, particularly where they interact with existing natural fractures. So the capacity to simulate any effects of induced fractures on existing fracture networks is important.

A reliance on hydraulic fracturing simulators alone as proof of compliance is not feasible, especially in new areas of exploration. Techniques such as geophysical monitoring would help to confirm simulations.

1.4 What is the next step?

In the absence of pre-existing calibrated models, regulators should consider whether the input parameters used in hydraulic fracturing proposals are reasonable for the formations, fluids and in situ stress conditions expected. Hydraulic fracturing activities should be monitored as they progress, and then models refined to improve their accuracy and as proof of compliance with permits.

A more comprehensive review should be carried out and input parameters (stress and rock properties) expected in UK shale gas fields should be quantified.

1.5 Publishing details

This summary relates to information from project SC170020 reported in detail in the following output:

Report:

SC170020

Title:

Review of software used by the oil and gas industry to model hydraulic fracturing

October 2019

Project manager:

Ian Davey, Research, Analysis and Evaluation

Research contractor:

British Geological Survey,
Environmental Science Centre,
Keyworth,
Nottingham
NG12 5GG

This project was funded by the Environment Agency’s Research, Analysis and Evaluation group, which provides scientific knowledge, tools and techniques to enable us to protect people and the environment.

Enquiries: [email protected]

© Environment Agency