4.5 Injection scheme
We assume that the CO2 has already been separated from the raw gas stream on the production platform before the methane is exported. The separation process in most cases4 produces a stream of more than 75% CO2 (see Table 7 for actual concentrations). For offshore discoveries, the injection gas is compressed on a dedicated un-manned platform and then transported to the storage site for injection into the subsurface. We assume un-manned injection platforms to host the injection wells. The injection site is 10 km from the gas discovery. A schematic diagram of the process is shown in Figure 9. For onshore discoveries we assume that the storage site is also onshore, sited 10 km from production facility.
Figure 9 – Process schematic of a representative development with CCS