We continuously recorded hydraulic and seismic data through this period.
#Well drawdown test series
The first stage of our well testing programme, between January and the end of March 2022, consisted of a series of injection tests. While we can’t entirely rule out the possibility of an event being felt or heard at surface, in such a case we can stop operations while we investigate the source of the event, and can change our operating conditions to reduce the likelihood of further felt events. In addition to being a useful analytical tool, monitoring the real-time data from our seismic network helps us to manage and control our operations, so that we maintain microseismicity within limits which don’t cause annoyance or disturbance to our neighbours. Microseismic monitoring data is a key tool during well testing because it provides us with essential information about the permeability of the formations around the well, and the spatial movement of water through the rock. But because our monitoring network is extremely sensitive, it can pick up and locate the minutest of movements, many kilometres below ground, which would otherwise go unnoticed. Usually, any such microseismic events are so tiny that they can’t be felt at surface. This was completed in early September 2022.Įven low levels of injection and production can lead to adjustment and settling of the natural fractures in the rock, so we expected that our seismic monitoring network, installed before drilling started, would detect some low-level seismicity (microseismicity) associated with well testing. To clean it out and restore permeability, we spot injected biodegradable organic acid into the well at the level of the plugged zone to dissolve the alkaline cement and calcium carbonate, with the acid being neutralised and broken down in the process.įollowing the well cleaning, we carried out a production test, and more injection testing.
#Well drawdown test install
The permeability had been good news, but its location had meant that we had to use limestone and cement to temporarily seal it off, so that we could install casing and drill to total depth without continually losing drilling fluid into the formation. During drilling, we’d encountered a permeable ‘loss zone’ at a depth of 3940m. In August 2022 we carried out some well cleaning operations. Testing was paused following a felt seismic event (1.7 magnitude, 1.56mm/s Peak Ground Velocity) on 9th March, and resumed a week later, being completed at the end of March without any further felt seismicity.
At Eden Geothermal, the first phase of injection testing started in January 2022.
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