Monitoring safe underground storage behaviour

Monitoring techniques for demonstrating site conformance

State of the art

Monitoring technologies are expected to be improved for reliable control of CO2 storage. Many of the tools and techniques in use at the existing sites, such as Sleipner, come from Oil&Gas sector. The costs for deploying such techniques however need to be optimized and other techniques coming from other sectors still need to be adapted and demonstrated for CO2 storage purposes. Geochemical monitoring through deep sampling is mainly performed with permanently installed Geochemical monitoring , which has been tested in key onshore CO2 storage sites such as Frio Brine (US), Otway (AUS), Ketzin (GER) and Hontomin (ES).

Some tools as the Distributed Acoustic Sensor (iDAS) already installed at Hontomin in well H-I has been utilised for VSP surveys (this tool was developed through deployment at Hontomin, Otway (AUS), Ketzin (GER), or AQUISTORE (CAN)) Regarding soil gas monitoring stations, both BGR and UNIROMA1 stations were tested at different pilot and naturally leaking sites.

The aim of this task is to test different technologies under real-life conditions, each measuring different useful parameters that, when integrated, will contribute to understand what is occurring in the reservoir and the overburden, which is key for the demonstration of safe and environmentally sound CO2 storage and for providing the needed information for risk management. 

Progress beyond the state of the art

Monitoring techniques for demonstrating site conformance using different monitoring techniques will be validated. For geochemical monitoring, a deep sampler will be tested at larger depths in the observation well (H-A) under harsh saline environments, supported by the knowledge acquired from the U-tube system at the injection well, H-I. Sampling fluids that are representative of in-situ conditions is still a challenge in particular for removable tools that can resist downhole pressure temperature and salinity. Improvement of active and passive seismic methods will be done, taking advantage of the existing settings in Hontomin, this will include testing the use of the Silixa IDAS cable for monitoring purposes other than VSP. This will allow acquiring precise data from the storage complex while validating monitoring techniques that can represent a cost effective solution when compared to well-known geophysical techniques common for Oil&Gas. In addition, different soil gas monitoring stations will be installed in Hontomin, pursuing a continuous control of the values in surface that will allow a TRL progress and a more complete monitoring plan at Hontomin. The combination of continuously measured soil gas composition data with CO2 flux surveys will allow interpreting thresholds representing an irregularity.