CHALLENGES AND OPPORTUNITIES FROM MONITORING IN FLOWING WELLS (Invited Presentation)

Large Geologic Carbon Storage will need an adequate monitoring plan all along the project life. This will be requested for injection performances, site integrity, public acceptance or just because it will be made mandatory by the regulator.

Permanent borehole monitoring is possible from either pre-existing wells in depleted hydrocarbon fields, or dedicated monitoring wells drilled for the purpose of time lapse measurements. Putting sensors directly in the flowing wells (injectors or producers), in the annulus between casing and tubing is an attractive solution to be closer to the monitoring zone and to avoid expensive dedicated wells. However, the tubing deployed motion detector devices are contaminated by the flow noise in the vibrating pipe. New clamping systems avoiding this noise contamination are under development allowing such a solution in the near future.

The second aspect of monitoring from boreholes concerns the geophysical sensors. Two types exist. Those based on electronics solutions (geophones) and those based on optical fiber technologies (Distributed Acoustic Sensing DAS and Optical Point Sensors based on Fiber Bragg Grating (FBG)). These acoustic sensors will be used for both seismic imaging and induced microseismic detection and monitoring. However, other sensors could be considered like corrosion sensors, chemical sensors or Pressure and Temperature gauges (Distributed Temperature Sensing (DTS)). Each solution has limitations, temperature and life duration for geophones, fiber sensitivity and directivity for DAS cable. Hybrid solutions including DAS and OPS-FBG are probably the best hope for the future of long duration monitoring.

Having permanent (but retrievable) ultra-long multicomponent antennas deployed for the long term in CO2 storage sites will allow, at an optimized cost, 4D seismic imaging of the CO2 plume, as real time induced microseismic monitoring. Recording permanently seismic activity (active or passive) in the heart of the action area (injection zone) will allow a safe and efficient site monitoring.