Everyone active in the field of CCS knows the In Salah project in Algeria. The only full-scale CCS demonstration in a developing country, it is broadly known that the project has injected CO2 successfully in the briny layer bordering the gas reservoir. The extensive monitoring and verification programme, in collaboration with independent research institutions in Europe, has shown that the CO2 has remained in the storage complex. For those interested in the technicalities: soil gas sampling and surface flux, wellhead fluid sampling, shallow aquifer and microbiology monitoring have noted no anomalies except for a very minor short term seepage from an old well drilled in 1980 which has now been fully remediated.
Overview of the In Salah project.
This is a major result in itself. But there is much more that resulted from the In Salah project. Operational and monitoring techniques have been trialled to identify the most cost-effective and reliable methods, particularly in the areas of geomechanical and geochemical modelling and prediction. This has led to a picture of optimal injection rates as well as how the behaviour of CO2 matches predictions and models – at least, for this particular reservoir.
But as a first-of-a-kind, In Salah also had a lot to learn. So what should every CCS operator know? There are some outcomes that are already obvious by the absence of major irregularities: the In Salah project has confirmed that storage can be done safely and that site selection needs to be done in a careful manner. In addition, there are three lessons in particular that bear relevance to the projects that are being planned and started now.
First of all, the importance of high-quality baseline data of the reservoir cannot be underestimated. CO2 storage projects require the integration of a wider scope of datasets over a greater spatial extent compared to hydrocarbon developments. Although the monitoring technologies can comprise existing standard oilfield techniques and practices, specialist technologies and modelling of coupled processes are needed. CO2 plume development is not homogeneous, requiring high-resolution data.
The second finding is that monitoring cannot be deterministic for all reservoirs. Also when leakage risks are compared among sites (the Top-3 generally identified risks are legacy well-bore integrity, cap-rock integrity and CO2-plume migration direction) it is apparent that sites are just too different to apply a cookie-cutter monitoring program. Technologies for monitoring stored CO2 at one site may not work at all for others, so there cannot be a “one size fits all” monitoring programme. The costs of deploying different technologies can be quantified, but the benefits are more subjective. We found that some low-cost technologies can be very effective.
Lastly, after such rigorous testing and research, we feel that we can conclude that the In Salah CO2 storage project would retrospectively comply with most provisions in the EU CCS Directive and the draft requirements of the UNFCCC Clean Development Mechanism. We can also conclude that we know much more now about monitoring and modelling of CCS than a few years ago. At this point, most the regulation of CO2 storage projects is under development. Our project demonstrates that regulatory frameworks for CO2 storage should not be technology-specific. They should allow for the technological advances during the life-time of the project that will certainly be achieved.
Allan S. Mathieson
ISG JIP Programme Manager
Allan S. Mathieson is Programme Manager for the In Salah Gas Joint industry Programme at Krechba. He is a Petroleum Geologist by background but has over 36 years worldwide experience in mainly Petroleum Engineering, Production Operations and Field Developments. He has worked in exploration, field development, reserves evaluations, economics and planning and asset management. For the past 6 years he has been deeply involved with managing and co-ordinating all aspects of the Monitoring and Verification programme at the In Salah Gas (Krechba) CO2 storage project in central Algeria.