Two different CO₂ injection field tests are conducted in the nearly depleted K12-B gas field offshore the Netherlands in different compartments. The CO₂ is originating from the produced gas (the methane contains a fraction of 13% CO₂), is separated on the production platform, and reinjected into the reservoir. The first test, finished in 2004, consisted of CO₂ injection through a single well in a depleted reservoir compartment to test the injectivity. The second test is still ongoing in a nearly depleted reservoir compartment comprising two gas production wells and one CO₂ injection well. This chapter describes the simulation results based on a detailed geological model and history matching to the production data until December 2005. A highly accurate match has been obtained.

In March 2005, two tracers were added to the injected CO₂ so that injected CO₂ could be discriminated from resident CO₂. Breakthrough of the tracers has been observed for both producing wells after 130 days (in 2005) and 463 days (in 2006). For the first well, the simulation results for CO₂ breakthrough have been compared to the tracer time. Results were accurate within a few days. For the second well, the comparison could not be made yet because injection and production data are only available until the end of 2005.