In Salah CO2 Storage JIP: CO2 sequestration monitoring and verification technologies applied at Krechba, Algeria

Abstract

Abstract The In Salah project in Algeria is an industrial-scale CO 2 storage project in operation since 2004. Carbon dioxide from several gas fields with a CO 2 content of 1–10% is removed from the production stream to meet the export specification of 0.3% CO 2 . It is re-injected it into a 20 m thick fractured sandstone formation down-dip of the Krechba producing field at a depth of around 1850 m. There are currently three horizontal injectors at Krechba, injecting up to 50 mmscfd of CO 2 and drilled perpendicular to the dominant fracture orientation to maximize injection capacity. Over the life of the project it is planned to store up to 17 million tonnes of CO 2 –to date, just over 3 million tonnes of CO 2 have been injected. A Joint Industry Project (JIP) was set up in 2005 to monitor the CO 2 storage process using a variety of geochemical, geophysical and production techniques over a 5 year period. A pre-injection risk register was prepared as part of the initial assessment of the injection site which was used to design the original monitoring programme. Key risks identified included leakage from old wellbores and possible vertical leakage through the overburden. Four years after injection start up, a quantitative risk assessment was undertaken which identified wellbore integrity and potential migration of CO 2 out of the licensed storage area as the key risks which resulted in further changes to the forward monitoring programme. A data collection programme was initiated prior to the start of injection in August 2004. A number of monitoring technology reviews have been conducted over the last 5 years using detailed modeling and a Boston Square which has been invaluable in comparing the relative cost and value of quite diverse technologies. To date, with the exception of the CO 2 encountered in the old KB-5 appraisal well (now fully decommissioned), there has been no indication of any CO 2 moving out of the storage complex (comprising the injection zone and the immediate overburden). The suite of technologies to be deployed at any CO 2 storage site for monitoring and verification purposes is readily available and uses mainly standard oilfield techniques and practices. However, each site will require a site specific suite of cost effective and focused technologies to provide the maximum benefit–there is no “cookie cutter” approach when it comes to designing a Monitoring and Verification programme. Our experience at Krechba to date is only in the early phases of a programme which could extend for 20 years and our key conclusions from the first 5 years of monitoring will be presented.