Overview

The Porthos project is located offshore the Netherlands and represents the first large-scale CO₂ storage initiative in the Dutch North Sea. It targets storage in two depleted gas fields within block P18 and is expected to play a key role in reducing industrial CO₂ emissions from the port of Rotterdam industrial cluster.
Within SAFE-C, Porthos serves as a primary case study for developing and testing seismic monitoring strategies under baseline and operational conditions, with a strong focus on real-time data integration and analysis.

Site Characteristics

  • Location: Offshore Netherlands, North Sea, approx. 20 km from Rotterdam 
  • Storage type: Depleted gas fields
  • Geological setting: Sandstone reservoir (Main Buntsandstein Subgroup of Lower Germanic Trias Group)
  • Operational status: CO₂ injection planned (expected no sooner than second half of 2027)

Due to the short distance to the shore, the Dutch seismic monitoring system operated by KNMI is able to detect seismic events in the area of Porthos. Due to the limitations in accuracy of both magnitude and location detection, Porthos supports the development of improved offshore monitoring solutions under real-world conditions.

Monitoring Approach

SAFE-C supports the development of a comprehensive monitoring system tailored to the needs of an operational CO₂ storage site.
Key elements include:

  • Development and deployment of new offshore sensor systems, including posthole seismometers 
  • Integration of in-well Distributed Acoustic Sensing (DAS) data for dense spatial coverage 
  • Combination of offshore and onshore data streams into a unified monitoring framework 
  • Implementation of near real-time data processing and analysis workflows 

This approach aims to significantly improve detection capability and reduce uncertainties in offshore seismic monitoring.

Role within SAFE-C

The Porthos test site plays a central role in advancing monitoring from development to operational application, with relation to:

  • Evaluating the performance of new sensor technologies offshore 
  • Testing offshore real-time monitoring systems under realistic conditions
  • Integrating multiple data types into a coherent monitoring workflow 
  • Supporting the development of operational monitoring strategies for offshore CO₂ storage 

The site provides a crucial link between methodological development and practical implementation.

Why Porthos Matters

Porthos represents a large-scale, industry-driven CO₂ storage project in the vicinity (≈ 20 km offshore) of a densely industrialised region. Insights related to passive seismic monitoring gained here are amongst others particularly relevant for:

  • Designing monitoring systems for operational CCS sites 
  • Demonstrating the feasibility of real-time offshore seismic monitoring 
  • Reducing uncertainties in seismic event detection and interpretation 
  • Supporting safe and efficient operation at commercial scale 
  • Enhance public trust in the operational safety of the offshore CO2 storage sites 

The results contribute directly to improving monitoring strategies for future CO₂ storage projects in Europe and beyond.

Learn more about Porthos

 
Location of Porthos case study site.

Porthos project map: the Porthos project is located offshore Rotterdam. Onshore CO2 transport through a ~30 km long pipeline (violet line), offshore transport through a ~22 km long pipeline (black line) to the platform P18-A in the North Sea. The compressor site is situated at Maasvlakte and brings the CO2 pressure to a maximum of 130 bar. Source: Porthos webpage

Schematic overview of Porthos project.

Porthos project schematic overview: Left: The CO2 from the pipeline will be injected into the depleted gas field under P18-A via a well. Right: The former gas production platform P18-A is repurposed for CCS, injecting the captured carbon into the former reservoir more than 3 km below the seabed in the pores of the reservoir sandstone. The storage is monitored by seismometers on the seafloor and a DAS cable inside the injection well. Source: Porthos webpage

Links to Other Case Study Sites

SAFE-C combines insights from Porthos with results from other sites to cover a range of monitoring scenarios.