Agile microseismic monitoring for geothermal

UK – Cornwall

Monitoring of a water injection on a geothermal well

Grassland – agricultural terrain

3 km radius around the injection well

Continuous passive seismic recording was performed using STRYDE Nodes™. Nodes were deployed 5 days prior to the start of injection to acquire baseline data. Recording continued during injection, and for a period of ~2 weeks post-injection.

The survey design aimed to optimise spatial sampling (azimuths and offsets) of the seismic wavefield around the injection well, and was largely driven by land access constraints due to the large number of landowners in the survey area. The nodes were deployed in various 1C and 3C arrangements, with station spacing varying from 50 m up to 1 km.

441 nodes for 28 days

For node deployment, 2 teams of 2-3 people deployed 441 nodes in 2.5 days, and for retrieval,  teams of 1-2 people retrieved 441 nodes in 1 day

28 days of continuous passive seismic data, in SEG-D format from 400+ receiver stations

Using the world’s smallest land seismic sensors to acquire this survey made conversations with private landowners easier. Stakeholders were amazed by how small the equipment was and happily granted permission to access and deploy instruments on their land, once they understood how non-intrusive the equipment and survey would be.

Providing access to STRYDE’s seismic sensors within 2 weeks ensured the team at Oxford was able to align with Eden Geothermal’ s operational plans for injection, and meant they were able to successfully capture the baseline data prior to injection and monitor the subsurface thereafter.

Given the tight project timeline, the deployment of the nodes needed to be extremely fast paced. The node’s compact weight and size, combined with stakeless deployment operations enabled by STRYDE’s Navigator Tablet and App, meant that even with a small deployment team 441 nodes could be deployed by foot in just 2.5 days.

It was important to have the nodes in the ground for as long as possible to effectively identify any seismic events that occurred pre, during and post-injection. STRYDE’s autonomous Nodes™ can reliably record continuous data 24 hours a day for 28 days. This enabled seismicity monitoring data to be recorded by the team at Oxford over the entire lifecycle of the geothermal well stimulation operations.

The STRYDE system has transformed the price point of land seismic equipment relative to the cost of conventional seismic instruments. Furthermore, the ability to deploy the miniature nodes quickly meant planning, preparation, and logistical overheads were greatly reduced, unlocking further cost savings and efficiency gains.

The simplicity of the STRYDE system means that it is extremely easy to use and is even accessible to people with no previous seismic experience. The Oxford team required only a couple of hours of virtual training to onboard them to the system prior to deployment operations commencing. This allowed the team to start up efficiently and effectively, as was required to comply with the tight operational schedule for fluid injection.