Phenomenological study of unstable two-phase CO2 flow in a pipeline system

As the link between CO2 capture and the final storage, CO2 transportation by pipeline plays a major role in enabling a large-scale implementation of CO2 capture and storage (CCS) networks across Europe towards 2040. There is ample experience in transporting CO2 in the form of a liquid (e.g., Snøhvit CO2 project since 2008, Northern Lights Project development, CO2 transport for enhanced oil recovery in the USA). Existing CCS projects are based on storage in saline aquifers at hydrostatic pressure, and thus the well-known experience in transporting liquid CO2 can be applied. However, new potential storage in depleted natural gas fields, representing about 30% of the estimated total capacity, has been identified on the Norwegian Continental Shelf (NCS). These fields are characterized by relatively low reservoir pressures that may result in CO2 transport in two-phase flow conditions, i.e., in the form of a gas-liquid mixture. This is an uncharted area. The two-phase flow conditions can result in strongly unstable flow which may pose a risk to the integrity of the injection well and the rest of the transport system. This project focuses on establishing a fundamental understanding of the occurrence of two-phase flow instabilities and transient phenomena in CO2-pipeline systems. The success of this project will represent a major step forward for enabling cost-effective large-scale CO2 capture and storage infrastructure.

Potential CO2 storage locations in the Norwegian Continental Shelf, NCS, are in saline aquifers and in depleted fields. The latter represents about 30% of the potential storage capacity. Existing CCS projects are based on storage in saline aquifers at hydrostatic-pressure in which the well-known experience in transporting dense phase CO2 can be applied. However, due to the low pressure, the storage in depleted reservoirs may require transporting CO2 in a two-phase state, which is an uncharted area. In this context, there is an important lack of understanding related to potential flow instabilities during the transport of CO2 in pipelines at two-phase flow conditions. This causes serious concerns about the maturity of the computational models for designing, analysing and operating the future CO2 pipeline infrastructure. This project focuses on closing important knowledge gaps on two-phase flow instabilities and transient phenomena in CO2 pipeline systems. The success of this project is of great relevance for minimizing the risks related to CCS operations and new developments, in addition to enabling the access to the more than 30% of storage capacity represented by depleted fields and thus contributing to the Norwegian goal of cutting domestic emissions by 50-55 precent by 2030. The work proposed in this project will fill in the knowledge gap by generating benchmark data from three highly specialized experimental facilities in Norway. The unique data will enhance our understanding, the physics of instability phenomena related to CO2 systems, and significantly improve the quality of simulator models.