Real-Time Process Twin for CCS Offers Risk Management, Operational Insights

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 225871, “Real-Time Process Twin for CCS: A Critical Tool for Risk Management and Operational Insights,” by Nayad A. Wadia, SPE, Ramnath Easwar, and Greg Metcalf, John Wood Group. The paper has not been peer-reviewed.

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This paper details the importance and value derived from a real-time process-twin model for one of the world’s largest operating carbon dioxide sequestration projects.

This paper details the importance and value derived from a real-time process twin model for one of the world’s largest operating CO2-sequestration projects. The model provides real-time monitoring and forecasting of key flow-assurance parameters, including pressures, temperatures, densities, and impurity concentrations throughout the CO2 system. The process twin serves as a vital operational tool, guiding operators to mitigate risks associated with water dropout and rapid corrosion during shut-in conditions. The operators potentially can extend the time to react to an unplanned shut down or trip, saving significant daily operational costs.

CO2-Process Modeling

The process twin requires the physical pipelines and wells to be modeled both laterally, for pressure and flow dynamics, and radially, for heat-transfer effects. The pipeline and well-elevation profiles are to be discretized into smaller pipe segments such that the angles are maintained as close to reality for accurate hydrodynamic modeling, particularly pressure drop, while preserving model stability and speed.

Heat transfer is modeled by building wall layers with material density, conductivity, heat capacity, and thickness. Because CO2 systems are highly sensitive to pressure and temperature, the model incorporates ambient factors, such as wind speed, soil temperature, air temperature, and soil moisture. The internal and external heat-transfer coefficient are important input factors that require engineering judgement and knowledge of the ambient conditions to model effectively.

Steady-state and transient field data are used to tune the heat-transfer coefficients once the system is in operation. The key process boundary conditions to the model are the inlet flow rate, inlet temperature, fluid composition, valve positions, and outlet pressure. In this model, the boundary conditions are measured in the field with instrumentation and read into the model using an OPC connection from the process historian in real time.