ControllEd sourCE ElECtromAgnEtiC rEsonAnCE 19
The methodology for monitoring such procedures capture and storage (CCS) purposes, monitoring and
therefore already exists but can always be improved and control is required.
refined. Currently, arrays of underground multi-component,
receivers strategically placed in nearby monitoring wells
Low noise, high sensitivity
are used to capture microseismic events or geophysical
As previously emphasised the need for downhole tools changes taking place in the zones of interest.
with low noise and high sensitivity is crucial to identify These ‘cross-well’ configuration procedures require
the low amplitude, high frequency seismics. Microseismic careful planning, highly sensitive and accurate recording
tools are now developing which embody the combined and expert data manipulation and interpretation.
components of very low electronic noise and high gain Pre and post seismic studies using a non-destructive
digitisers with multiple omni directional geophones high energy, high frequency, down-hole seismic source
arranged within a sensor pack in order to achieve high is also expected to play a major role in all these types of
sensitivity. operations (Fig 1).
Such downhole systems are evolving from dedicated
VSP arrays into genuine multi-purpose systems with a
Confidence is high
large bandwidth of ~1600Hz, very low electronic noise There is a considerable amount of money and effort
levels and extremely high sensitivity, which is ideal for currently being invested into all procedural phases of the
hydraulic fracture surveys. enhanced oil recovery and carbon capture and storage
In order to keep survey/drilling costs down, even and confidence is high that such operations will benefit
slimmer tools are required, these will need to withstand from successful, accurate and safe techniques ensuring,
increasingly higher temperatures and pressures for longer where appropriate, commercial and/or environmental
periods of time. In certain large long duration projects, benefits. l
deployment of permanent sensor instrumentation in
monitoring wells may potentially be a more optimum Enter 19 or ✔ at www.engineerlive.com/ihss
solution.
Whatever commercial or environmental methods are William Wills is Geotechnical Support Engineer with Avalon
used involving pumping fluids deep into the subsurface Sciences Ltd, Somerton, Somerset, UK.
‘traps’ for enhanced hydrocarbon recovery or carbon www.avalonsciences.com
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Circle 19A or ✔ at www.engineerlive.com/ihss
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