Injection operation and operational pressure-temperature monitoring at the CO2 storage pilot site Ketzin, Germany-Design, results, recommendations

The Ketzin pilot site for geological storage of CO2 in the German Federal State of Brandenburg about 25 km west of Berlin is the only German CO2 storage site and has been the first European pilot site for on-shore storage of CO2 in saline aquifers. Continuous injection of CO2 started on June 30th, 2008, and a total of 61,396 t of CO2 have been injected by September 2012. The injected CO2 was predominantly food-grade with a purity >99.9%, only from May to June 2011, 1515 t CO2 from the Schwarze Pumpe oxyfuel pilot plant with a purity of >99.7% have been injected. The injection is accompanied by a comprehensive operational monitoring program. The program includes continuous measurements of flow rate, fill levels of intermediate storage tanks 1 and 2, outlet pressure and temperature for the injection plant, wellhead pressures (WHP) and casing pressures 1 and 2 for all wells, bottom hole pressure (BHP), bottom hole temperature (BHT) and distributed temperature sensing (DTS) along the injection tubing for the injection well Ktzi 201, BHP for the two observation wells Ktzi 202 (from March 2010 to October 2011) and Ktzi 200 (since October 2011), and above-zone pressure monitoring in shallow observation well P300. This operational pressure-temperature monitoring successfully ensured and proved a safe, smooth and reliable injection operation. A vital part of the operational P-T data comes from the downhole P-T measurements, which are recommended for any CO2 storage site. Without this downhole information, it would not have been possible to provide the complete picture of CO2 injection. The recommended downhole installation design of P-T tools distinguishes CO2 storage from the operational engineering of underground storage of natural gas, where BHP monitoring can be done via WHP recording. The DTS safety monitoring along the injection tubing supported typical operational processes as conditioning of the CO2 and improvement of injection rate and injection temperature and will be beneficial to any CO2 storage project. The above-zone pressure monitoring gives no hints to any hydraulic connection or CO2 leakage through or failure of the cap rock. (c) 2013 Elsevier Ltd. All rights reserved.