Operational flexibility of CO2 transport and storage

 One of the advantages of CCS as a means of CO₂ abatement is that several industrial processes, as well as fossil fuel power generation, can be captured and connected to a pipeline network. Multiple sources of CO₂ can then be transported to suitable geological reservoirs and injected to ensure secure storage. Many industrial operations, and power generation, can generate intermittent and variable amounts of CO₂with some impurities. These factors can affect pipeline transport and potentially storage conditions. IEAGHG commissioned a study to investigate the extent to which intermittent supply and transport might influence storage and EOR. Experience from the United States shows that large point sources CO₂ with a high level of purity (~99.7%) can be effectively and safely delivered using integrated pipeline networks. Moreover, these pipeline networks can act as a buffer by supplying CO₂ from several sources. CO₂ can also be temporarily compressed or 'packed' into pipelines as a short term measure.

Impurities particularly H2O and O2, can have negative impacts on pipelines including fracture propagation, corrosion, non-metallic component deterioration and the formation of hydrates and clathrates. The density and viscosity of fluids can also be affected. Non-condensables like N2, O2, Ar, CH₄ and H2 should be separately limited to <4% because their presence increases the amount of compression work. Compression and transport of CO₂ for CO₂-EOR use in the United States has shown that impurities are not likely to cause transport problems provided CO₂ stream composition standards are maintained and pressures are kept significantly over the critical point (≥10.3 MPa).

CO₂ storage in deep saline formations can be managed by using multiple wells and water pumping to control and releave excess pressure, and control plume geometry. The use of CO₂ for EOR relies on controlling pressure and flow rate conditions to optimise oil recovery. Restricted injection caused by wells being shut in can result in deleterious changes in reservoir pressure and oil miscibility.

Provided that adequate levels of purity can be achieved, and large point sources of CO₂ can be connected to a managed pipeline network, the evidence from this study shows that secure storage can be achieved and integrated with EOR.