Michael P. Warmack, Nicholas A. Azzolina, Wesley D. Peck, David V. Nakles, Bethany A. Kurz, John A. Hamling, Energy & Environmental Research Center University of North Dakota
The Plains CO₂ Reduction (PCOR) Partnership investigated the scale-up challenge in the commercial deployment of pipelines for the transport of captured CO₂ to the geologic storage site through three hypothetical pipelines. Each pipeline targeted the delivery of CO₂ to either enhanced oil recovery projects or for geologic storage in a saline reservoir. The results of the investigations confirmed that several factors can affect the cost of the pipeline—both in terms of installed cost and future operational costs associated with the pipeline, and a better understanding of the magnitude of these impacts emerged. The properties investigated in the hypothetical routes include the following:
- Pipe sizing (16, 20, 24, 30, 36, or 42 inch)
- Change in elevation
- Pipeline length
- Number of booster pumps (up to three)
- Pipeline operating pressure (2190 or 2700 psig)
Properties 2 through 5 impact the sizing of the pipe necessary to deliver a targeted amount of CO₂ on each pipeline system and must be considered in concert to determine the most cost-effective option. This study on the pipeline systems revealed challenges that a pipeline system will face:
- a. Pipeline cost estimates and cost drivers
- b. Cost and hydraulics optimization
- c. Temperature effects on the pipeline capacity and maximum injection pressure at an injection well.
For a given base volume of CO₂ to be transported through the pipeline, the major cost drivers for a pipeline system were determined by the volume of CO₂ being transported, length and elevation changes throughout the pipeline route, the initial and final conditions of the CO₂ stream being transported, and the price of steel. To minimize the cost of the pipeline system while optimizing the hydraulics of the system, the addition of pump stations should be considered. With the installation of pump stations, the pipeline diameter may be reduced, which would save on the capital cost of the pipeline system. However, the cost of the pump stations and their corresponding operating cost should be considered over the life of the project to determine the best overall options for the pipeline system. Since the exit temperature of the CO₂ stream from the pipeline may not reach the ground temperature at the terminus of the pipeline, especially during the heat of the summer, additional consideration should be given to how the exiting conditions of the CO₂ stream may impact the downstream operations such as injectivity into the injection wells. The addition of pump stations further compounds the possibility of hotter exiting temperature of the CO₂ stream as pumps will add heat back into the pipeline from the pressurization process of the pumps. Based on this study, the design of a CO₂ transport pipeline requires the balancing of many factors affecting the pipeline system. In this way, the overall cost and operational expenses associated with the pipeline system will yield the most cost-effective solution.