The In Salah CCS project in central Algeria is a world pioneering onshore CO₂ capture and storage project which has built up a wealth of experience highly relevant to CCS projects worldwide. Carbon dioxide from several gas fields is removed from the gas production stream in a central gas processing facility and then the CO₂ is compressed, transported and stored underground in the 1.9 km deep Carboniferous sandstone unit at the Krechba field.

Injection commenced in 2004 and since then over 3.8Mt of CO₂ has been stored in the subsurface. The storage performance has been monitored using a unique and diverse portfolio of geophysical and geochemical methods, including time-lapse seismic, micro-seismic, wellhead sampling using CO₂ gas tracers, down-hole logging and core analysis, surface gas monitoring, groundwater aquifer monitoring and satellite InSAR data. Routines and procedures for collecting and interpreting these data have been developed, and valuable insights into appropriate Monitoring, Modelling and Verification (MMV) approaches for CO₂ storage have been gained.

We summarize the key elements of the project life-cycle and identify the key lessons learned from this demonstration project that can be applied to other major CCS projects, notably:

• The need for detailed geological and geomechanical characterization of the reservoir and overburden;
• The importance of regular risk assessments based on the integration of multiple different datasets;
• The importance of flexibility in the design and operation of the capture, compression, and injection system.

The In Salah project thus provides an important case study for knowledge transfer to other major CCS projects in the planning and execution phases.