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

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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.