Porthos: An Exciting Approach to Carbon Capture and Storage

Approach to Carbon Capture and Storage

Why moisture measurement is crucial to CCS

The P18 cluster of three gas fields sits approximately 3.5 km beneath the shallow waters of the North Sea, just off the coast of the Netherlands.  The first of these fields – P18-2 – was discovered in 1985 and came on-stream in 1997, with the smaller P18-4 and P18-6 gas fields beginning production in 1993 and 2003 respectively.  Although output from the P18 cluster peaked in 1998, gas continued to flow for another decade and, by 2018, 13.5 bcm of natural gas had been extracted. 

Although the fields are depleted and no longer commercially viable for gas production, they have now found a new life as reservoirs for carbon dioxide (CO2), which will be captured from industrial process plants around the port of Rotterdam. 

This exciting and imaginative idea is called Porthos, short for Port of Rotterdam Transport Hub and Offshore Storage.  Porthos is led by the Port of Rotterdam Authority, working with energy companies Gasunie and Energie Beheer Nederland (EBN), and is recognized by the European Commission as a vital infrastructure project.  Most importantly, it is playing a transformative role in the expansion of Carbon Capture and Storage (CCS) and Carbon Capture and Utilization (CCU) projects around the world, as part of the global drive to meet Net Zero. 

Carbon Capture and Storage starts in 2026 

If all goes according to plan, the process of injecting CO2 into the P18 fields will begin in 2026.  Porthos has contracted with four Joint Development Partners – Air Liquide, Air Products, ExxonMobil and Shell – to help them reduce their carbon emissions and meet their climate objectives while transitioning to cleaner energy forms of production.  In total, the four companies will capture 2.5 million metric tons of CO2 each year. 

CO2 in a gaseous form will be fed, at a pressure of 35 bar, into a new pipeline being laid through the Rotterdam port area.  It will then pass through a compressor station, where the pressure is increased to 130 bar, for subsequent transmission through an offshore pipeline to the P18-A platform; this was previously used as part of the natural-gas extraction process. 

From here, the CO2 will be injected into the reservoir via an existing metal-cased well, fitted with a new inner tube.  As CO2 pressure increases in the offshore pipeline during the early operation period, the fluid state may transition from vapor to supercritical dense phase, depending on temperature; the supercritical dense phase is optimal for efficiency as the CO2 will have the viscosity of a gas but the density of a liquid. 

The reservoir consists of porous sandstone rocks, from the Lower Triassic period and belonging to the Triassic Main Buntsandstein Subgroup.  These lay beneath a non-permeable layer of capstones, formed from siltstones, claystones, evaporites and dolostones.  This arrangement allows large volumes of CO2 to be stored within the porous rock, while the capstones prevent the gas escaping.  Once each field has reached capacity, it will be sealed and then continually monitored, with final reservoir pressure being close to that of the original natural-gas pressure. 

Maintaining quality, safety and efficiency

The Porthos project will capture CO2 from a variety of industrial processes, each of which will potentially introduce a range of contaminants that may affect the quality, safety and efficiency of the downstream Carbon Capture and Storage operation.  Contaminants may include hydrocarbons from petroleum refining, sulphur from flue gasses, amines from gas stripping and moisture from both process and transportation operations. 

Contaminants such as moisture can create a range of problems.  Water vapor can condense to a liquid, freeze to ice and react with CO2 and sulfur compounds to form aggressive acids.  The results will include corrosion of metal surfaces, pipeline blockages and damage to moving parts such as high-speed compressor blades. 

There is, therefore, a robust set of project specifications to control the quality of the CO2 gas.  For example, total sulphur compounds must be less than 20 ppm (micromol/mol), while the maximum moisture content can be no higher that 70 ppm, with the gas being free of all liquid content down to at least -10°C at a standardized analysis condition of 20 bara.  

To meet these criteria, it is essential that accurate and consistent measurement of contaminants is maintained throughout the process chain, from the point at which carbon is captured to final injection into the reservoir.  For example, advanced devices such as Michell Instruments’ Condumax II Dew-Point Analyzer can play a key role, providing a precise measurement of hydrocarbon dew point. 

Our latest instruments are based on proven sensor technologies, simple to set up and use, and installed as reference instruments by leading calibration laboratories around the world.  As such, they offer an ideal solution for organizations that want to exploit the potential of Carbon Capture and Storage, safely and efficiently.  

With over 40 years’ experience in the development of innovative precision instruments, we are the application experts in dew-point measurements for all Carbon Capture and Storage applications. If you would like to discuss your requirements, please contact our team today.  

The Porthos project is representative of the more than 250 Carbon Capture and Storage initiatives that are being planned or are in development worldwide.  It will play a crucial role in helping the Netherlands meet its climate objectives – to reduce national carbon emissions by 55 % by 2030, compared with the levels in 1990, and to be climate neutral by 2050. 

The Rotterdam port area accounts for 14 % of the country’s carbon emissions, with many of the large petrochemical and energy production operations being ideally suited to the process of carbon capture.  Although the bulk of the CO2 captured by the Porthos project will be stored in offshore reservoirs, there are also initiatives to explore ways in which CO2 can be used as a feedstock. A great example is Alco Energy, which captures CO2 from its ethanol plant and pipes this direct to greenhouses where it is used to promote the growth of tomatoes and peppers. 

Related Information

Statista: CCS projects 2023

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The Importance of Carbon Capture and Storage

Moisture Measurement and Carbon Capture

Using Electrolyzers for Industrial H2 Production

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Related Products

Portable Dew-Point Tester – Michell CDP301
Hydrocarbon Dew-Point Analyzer - Michell Condumax II
Turnkey Gas System for CO2 Quality Control – Carbo2Detek

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