**4.2 Offshore CO2-EOR facilities**

*Enhanced Oil Recovery Processes - New Technologies*

3.Three phase test separators per ten wells

Surface facilities in CO2-EOR requires recovery of CO2 and reinjecting it back to the well, with which CO2 release to the atmosphere can be minimized as well as purchasing cost of additional CO2 can be reduced. Typical surface facilities for CO2- EOR are gas separation. Water treatment of CO2 compression and injection and also

Dehydration column removes the moisture content of the gas stream by using the contact with lean glycol in the upper part of the 14 tray column and the gas must be cooled first by the air cooler. Rich glycol is extracted from the bottom of the

2.A pump from separator system

dehydration can be seen in **Figure 7**.

*4.1.5 Separation process*

**134**

**Figure 7.**

**Figure 6.**

*Typical surface facilities for CO2-EOR [21].*

*Modifications on CO2 production well head [5].*

The majority of CO2-EOR projects are all similar in terms of facilities to those in the offshore. The following sections discuss the various equipment and facilities required at different phases of a typical offshore CO2 injection project.

### *4.2.1 Pig launcher and steel pipeline*

Depending on the CO2 stream composition, weight, temperature, and pressure, the outline of pig launcher ought to be in certain standards and suitable measures (e.g., DNV OSF-101). Pigging is usually used for dispatching new or re-appointing existing pipelines. A reconditioned or new pipeline needs to be hydrotested to guarantee pressure integrity. Frequent inspection for any degradation and verification of the effects of dry CO2 stream on the pipeline must be done. In any case, since the CO2 will be exceptionally dry, it is likely that future pigging operations will be less successive due to subsea situation. Normally, the pig traps are not fitted; thus, portable pig traps can be considered in the design [40].

Piping diameters and thickness are the main concern in designing the facilities in which for the purpose of CO2-EOR the pipeline could have two diverse design requirements. If the storage complex is already pressurized over the required level to keep the CO2 as fluid in injection wells, then the project may pick to utilize high-pressure liquid pipe. In other cases, for instance, the Hewitt Field model [11], the pressure inside the field would bit by bit be expanded using gaseous CO2 in the transport system until the field pressure can maintain liquid CO2 in the injection wells. During that time, the transport system would be changed over to a higher pressure fluid pipeline.

The pipeline system in onshore system is typically below 120 atm (1740.45 psi) and logically the pressure in the offshore CO2 pipeline is higher. In offshore frameworks, the CO2 is being pumped under long distances; thus, there is much pressure loss due to friction. With trunkline pressure between 150 and 250 atm, the CO2 may be injected into geological formation without further boosting of pressure. The pressure will be affected by the distance of onshore facilities and offshore storage complexes, which may affect the wall thickness and pipeline diameters [21, 41].

Due to the danger of transporting high-pressure liquid CO2, the transportation will be done in liquid and subsupercritical. To diminish the risk in onshore pipelines, it is likely that these will be at pressure lower than the required for offshore transport and ought to be expanded at a coastal booster station before going to offshore [42–44]. Besides, offshore pressure booster may be required if there is excessive pressure drop between onshore booster station and offshore storage complexes or if the pressure is inadequate to inject directly into reservoir [45].


### **Table 1.**

*Operation conditions of injection facilities in Nagaoka, Japan [42].*

To avoid two-phase flow that leads to critical damage and cavitation, the pressure downstream of an offshore booster pump should be over bubble point [46].
