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K12-B, CO2 storage and enhanced gas recovery

The K12-B gas field will demonstrate the feasibility of CO2 injection and storage in depleted natural gas fields on the Dutch continental shelf, with the aim of building a permanent CO2 injection facility. Gaz de France Production Nederland B.V. and TNO are monitoring the CO2 injection and the test phase data are being assessed by European research institutes cooperating in several CO2 storage research programmes.

The K12-B gas field, located in the Dutch sector of the North Sea some 150 km northwest of Amsterdam, has been producing from the Upper Slochteren Member (Rotliegend) since 1987. The natural gas produced has a relatively high CO2 content (13%). Prior to transport to shore the CO2 is separated from the production stream gas. In the past the CO2 was vented into the atmosphere but now a large part is re-injected into the reservoir, at a depth of approximately 4000 m. K12-B is the first site in the world to inject CO2 into the same reservoir from which it originated. The CO2 injection started May 2004, coinciding with major measurement programmes dedicated to determining the potential for both CO2 storage and enhanced gas recovery (EGR) as well as the corrosion of the injection tubing caused by the CO2. To date some 50 kt of CO2 has been injected. The data are being interpreted in several research programmes, including MONK, CO2REMOVE, CATO, CASTOR and CO2GEONET.

The phases

The CO2 injection programme comprises two phases in different locations at the K12-B reservoir. In phase 1, CO2 was injected into a fully depleted, single well reservoir compartment from May 2004 until January 2005 while in phase 2, which began in February 2005, CO2 was injected into a nearly depleted reservoir compartment that is still under production. At the start of phase 2, two tracer chemicals were injected into the reservoir together with the flow of CO2. These tracer chemicals enable an accurate assessment of the flow behaviour in the reservoir and the associated sweep efficiency of the injected CO2. In phase 2 the following were also measured / monitored:

  • Pressure, temperature and flow at various locations (injector and producer wells):
    • At the compressor
    • At the wellhead
    • Along the well trajectory
    • At reservoir depth
  • Composition of the gas and water produced, including minute tracer concentrations
  • CO2 injection tubing integrity (Multifinger caliper and down-hole video logs)

Potential

Interpretation of the phase 1 measurements and assessment of the injectivity in the reservoir compartment confirmed the expected behaviour of CO2 and reservoir response during injection, validating existing correlations and reservoir simulation predictions. As for the more complicated phase 2 measurements, in January 2008 an increase of 5% CO2 was observed in the K12-B1production well. In April 2006 tracer chemicals were detected at the more distant K12-B5, the second production well in the compartment some 1000 m from the CO2 and tracer injection point. These observations are currently being investigated in order to assess the potential for enhanced gas recovery (EGR) and the tracer performance is being evaluated in CO2GEONET. The K12-B field has so far posed no major complications. The use of tracers has enhanced understanding of the reservoir and its behaviour and the K12-B field shows great potential for CO2 storage. EGR potential is still undergoing close investigation.

Drs. ing. Maurice Hanegraaf

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Drs. ing. Maurice Hanegraaf

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