The CO₂SINK (CO₂ Storage by Injection into a Natural saline aquifer at Ketzin) integrated project aims to advance the understanding of the science and practical processes involved in underground storage of CO₂ to reduce emissions of greenhouse gases to the atmosphere. The consortium running this EU project consists of 18 partners from universities, research institutes and industry out of 9 European countries.

It is the first demonstration project for large scale on-shore CO₂ storage in Europe. The storage site near the town of Ketzin, close to Berlin in Germany, includes industrial land and infrastructure which make it suitable as a testing site for underground injection of CO₂ into a deep saline aquifer.

The operation of the CO₂ underground storage is regulated under German law according to the legislation of mining from the state of Brandenburg. From March to September 2007 one injection well and two observation wells were drilled to a depth of 750 m to 800 m at a distance of 50 m to 112 m from each other.

The reservoir characterization was done by cutting and core analysis from the three wells, petrophysical well logs and 3D-seismics. The Triassic Stuttgart formation consists of siltstones and sandstones interbedded by mudstones deposited in a fluvial environment. The target formation in 600 m to 700 m depth is 80 m thick with sand channels measuring up to 20 m.

Temperature of the formation is around 35 °C. Hydraulic tests revealed formation productivities of around 0.04 m³ day^-1 kPa^-1 and 0.06 m³ day^-1 kPa^-1, respectively. Based on the thickness of the permeable zones of the formation this calculates to permeabilities between 40∙10^-15 m² and 80∙10^-15 m².

CO₂ from an industrial gas supplier will be used for the first injection phase at the Ketzin site. The injection of CO₂ is scheduled for spring 2008 and is intended to last up to two years. A maximum of about 60,000 t CO2 will be injected. The total amount is going to be adjusted during storage according to scientific and site specific requirements.

Spreading of the CO₂ plume will be monitored by a broad range of geophysical and geochemical techniques: The wells are completed as “smart” wells containing a Distributed Temperature Sensing (DTS) and Vertical Electrical Resistivity Array (ERT) behind the casing. A gas membrane sensor will be used for the continuous analysis of gases. Before and during injection downhole sampling of fluids for geochemical and microbiological analysis will be done. Injection of CO₂ will be interrupted at times for repeated downhole seismic (VSP, MSP) and cross-hole seismic experiments.

Numerical models and risk assessment strategies are going to be benchmarked via the monitoring results. At the End of 2008 results from half a year of storage operation will be available. The geological and the numerical models will be updated accordingly after compilation and interpretation of the monitoring data.