Fibre-optic distributed Acoustic Sensor Technology for seismic Monitoring During shale gas Extraction (FAST-MoDE)

Lead Research Organisation: University of Bristol
Department Name: Earth Sciences


Microseismic monitoring during hydraulic stimulation allows operators to monitor the development of fractures as they propagate. They can then optimise their operations, while ensuring that they are conducted in an environmentally safe manner.
Presently, microseismicity is monitored either using geophones placed in dedicated monitoring boreholes, or dense sensor arrays at the surface. These methods are costly, and can pose logistical challenges. In certain settings, monitoring is also limited by the performance of geophones at high temperatures and pressures. As a result, microseismic monitoring arrays are typically deployed for less than 25% of fracturing operations in North America.
Improvements in microseismic monitoring systems are needed, allowing operators to deploy effective microseismic arrays at most (or all) hydraulic fracturing sites in an economically and logistically viable manner. This will enable them to optimise hydrocarbon extraction at these sites, while ensuring that they operate in an environmentally-responsible manner.
In-well deployment of fibre-optic cabling as a Distributed Acoustic Sensor (DAS) addresses the cost and logistical problems outlined above and has shown significant potential as a microseismic monitoring tool. The use of fibre-optic DAS in this context requires the development of novel data processing algorithms capable of handling this new type of data. This project will develop bespoke DAS instrumentation workflows, to be used by oil and gas companies and microseismic service companies.
Chevron, one of the world's largest multinational oil and gas companies, regularly conduct hydraulic stimulation activities and they are exploring the use of fibre-optic DAS as a microseismic monitoring tool. Use of the novel processing workflows developed during this project will enable Chevron to increase the uptake of fibre-optic as a microseismic monitoring tool amongst their operational divisions.
Shale gas operators must submit a Hydraulic Fracturing Plan (HFP) to the Environment Agency (EA) and Oil and Gas Authority (OGA) for approval before hydraulic fracturing can take place. The EA strongly recommends the use of microseismic monitoring to map the growth of fractures during stimulation. To ensure regulatory compliance, the EA must therefore develop the capacity to efficiently evaluate microseismic monitoring plans submitted to the agency. Since an HFP will include a proposal to monitor for seismic events, regulators require up-to-date knowledge in this rapidly developing field to assess material submitted to them by the operators. Through close collaboration, this project will allow the EA to determine whether proposed microseismic deployments, including fibre-optic monitoring, satisfy regulatory requirements.
The main project of objectives are to:
1. Develop processing workflows for fibre-optic DAS data through partnerships with the full supply chain from equipment supplier (Silixa), to data processing, to end-user (Chevron).
2. Develop tools and guidelines for regulators for the assessment of microseismic monitoring plans including DAS technology for hydraulic fracturing in the UK.
These objectives will be achieved by through three work packages.
1. Microseismic processing workflows currently used to treat geophone data will be adapted for application to DAS fibre-optic data.
2. The processing workflows will be optimised for use with large data volumes because any fit-for-purpose processing method must be capable of handling large data volumes.
3. Embed new knowledge in the regulators of the shale gas industry in the UK through a workshop, development of tools for inclusion in their processes and a short-term placement at the EA.
With the first UK shale gas sites due to begin hydraulic fracturing this year, this project is particularly timely and important for the future success of the UK shale gas industry, with significant potential worth to the UK's economy.

Planned Impact

The objective is to enable the routine use of fibre-optic Distributed Acoustic Sensor (DAS) systems for microseismic monitoring of hydraulic fracture stimulation (HFS) operations. To achieve this, the project will develop processing algorithms for DAS systems and contribute to guidelines for UK regulators for the assessment of Hydraulic Fracturing Plans (HFPs) that include DAS technology to monitor HFS.

The development of efficient and robust methods for analysis of fibre-optic DAS data will transform how microseismic data is acquired and processed, offering several advantages for operators:
- Cost effective microseismic monitoring, allowing monitoring to be conducted at more HFS sites while reducing costs.
- Improved quality of microseismic images, leading to a better understanding of hydraulic fracture systems, resulting in more opportunities to optimise extraction of unconventional hydrocarbon resources.
- Acceptance of appropriate and proportionate microseismic monitoring plans for hydraulic fracturing operations in the UK.

The tested workflows will deliver proof-of-concept that fibre-optic DAS technologies can be used to produce microseismic images during HFS. These workflows will be developed in conjunction with research geophysicists from the project's commercial partners, thus ensuring that they will be able to adopt the new processing methods into their in-house software and microseismic monitoring workflows. By doing so, fibre-optic DAS microseismic imaging can be used effectively in operational settings by the partners' commercial units.

DAS service providers will benefit from the ability to offer improved and expanded services, which will result in an increase in commercial opportunities.

The main impact for regulators will be:
- An improved understanding of current microseismic monitoring techniques, technologies and capabilities, thus allowing an informed assessment of proposed monitoring configurations.
- Improved efficiency of the HFP review and acceptance process by enabling regulators to assess technical detail presented by operators.
- Improved engagement and communication with industry operators on regulation compliance.
- Training materials, which also create the opportunity for self-sustaining competency in microseismic monitoring (e.g, in the Environment Agency).
Description Through this research we have developed machine learning based methods to identify microseismic events in DAS fibre optic data. Also submitted a number of papers on using DAS data to detect and locate microseismicity. Acquired DAS data for the first time in the Antarctic.
Exploitation Route Anyone who is interested in using fibre optic technology to detect or monitor seismic activity would be interested in these results. Example include petroleum companies, geothermal energy operators, and volcanology observatories.
Sectors Digital/Communication/Information Technologies (including Software),Energy

Description Oil companies are very interested in this technology and have expressed an interest in our research. Project has led to funding the ACT project called DigiMon, which looks at the use of DAS in monitoring subsurface injection of CO2. Technology has been applied (for the first time) in the Antarctic (2019/20 season) to image ice quakes and the properties of ice sheets.
First Year Of Impact 2018
Sector Energy,Environment
Impact Types Economic,Policy & public services