Extending CO₂ Transport Solution (ECOTS)

Background and project purpose ?
The operation of CO₂ transport and injection with CO₂ two-phase flow condition can lead to significant CAPEX reduction and increased operational window for the storage of CO₂ in low-pressure or depleted reservoir. The assessment of existing Flow Assurance tools indicates their technology gaps in basic models of hydrodynamic and transient processes for two-phase CO₂ flow. Significant progress has been made in the ongoing project 618052 Equinor «CO₂FACT». However, the validation of these Flow Assurance tools requires the data from large-scale test facilities such as in Porsgrunn or operational data from fields. There is little chance that operational data will be available in the near future.

What was the project objective ?
The project has three main goals:
• Upgrade the multiphase rig in Porsgrunn for experimental study with CO₂ fluid. This upgrade is necessary to be able to study different flow scenarios associated with CO₂ transport and storage.
• Execute experimental campaign for CO₂ pipeline flow: Steady-state and transient two-phase gas-liquid flow in a pipe close to horizontal inclinations
• Assess the scaling performance of the existing flow assurance tools and quantify the uncertainties of these tools.

What has the project done in terms of activities?
Four work packages were defined:
WP1. Modification of multiphase flow rig for CO₂ applications:
Necessary equipment adapted to CO₂ was installed, such as safety valves, instruments, detectors and a filling system for liquid CO₂.

WP2. Commissioning tests of multiphase flow rig:
The integrity of system, safety system, calibration of all instrumentation and operational procedure establishment will be performed.
WP3: Experimental study of CO₂ two-phase flow:
Five types of tests in the original project plan were carried out with pure CO₂:
• RFO (ready for operation): Displacement of N2 from system
• Two-phase flow tests under steady-state and liquid dominated flow conditions
• Two-phase flow test with slugging potential
• Depressurization tests
• Valve characteristics for choke valve
Additional tests were carried out after Shell joined the project as a late participant. These tests were:
• Repetition of some series in original tests for two-phase steady-state flow (pure CO₂)
• CO₂ two-phase steady-state flow with low liquid loading condition (pure CO₂);
• CO₂ two-phase steady-state flow with impurities (N2 & CH4)
• Depressurization tests with CO₂ with impurities (N2 & CH4)

WP4. Assessment of commercial Flow Assurance tools:
The existing flow assurance tools will be assessed by comparing the available experimental data (obtained in WP3, CO₂ FACT JIP, CARDICE JIP). The potential improvement needs will be identified, and the recommendation for the further improvement of the existing flow assurance tools will be proposed.

What has the project achieved ? Did the project achieve its objective ?
There were three main objectives in this project: facility upgrade, experimental study and data analysis.

The facility upgrade has been following the standard procedure of offshore facility development in Equinor. Zero HSE incident during the whole development period.

Extensive experiences of operation of existing facility and good preparation of the project team make effective execution of experimental program. Successful execution of all planned tests demonstrates that the upgraded facility has all functionalities as expected. Large amounts of experimental results with high quality have been obtained. Some selected results have been presented at TCCS-11 (June, 2021, Trondheim), and shared with Northern Lights project. Some important discoveries from the tests have been implemented in the Northern Lights project.

Assessment of the experimental data available (CARDICE, CO₂FACT and ECOTS) shows that some technology gaps exist in the existing commercial flow assurance tools. Additional efforts are needed to have more detailed analysis of the test results.

Future plans?
The experimental results need further detailed analysis, some results will be disseminated in corresponding conferences or journals. The experimental results are believed to be the key to benchmark the commercial flow assurance tools for CO₂ transport and injection in the future.