In offshore operations, marine risers serves as the conduit through which captured CO2 is conveyed from the topside facility or platform, in some cases from a CO2 carrier ship to the injection wellhead. CO2 is mostly injected in dense phase, near the supercritical region or in liquefied form. The flow of CO2 through marine risers is characterized by transients and variations in the fluid pressure, temperature and velocity. The pressure and temperature variations have huge effect on the density and transport properties of the flowing CO2. This book presents a concise study of the injection process and insight needed to plan and operate effectively CO2 injection process as parameters such as the injection rate, required injection pump pressure and temperature can be determined for a given operation.