Offshore Pipeline Design for CCUS

09.09.2021

Offshore

By: Hans Brugman – Offshore Independents B.V.
Pieter Swart – Offshore Independents B.V.

Introduction

As concerns about climate change increase while global demand for energy continues to grow, we are committed to ensure a sustainable future by reducing and ultimately eliminating anthropogenic (caused by humans) Carbon Dioxide emissions in the atmosphere.

Carbon Capture, Utilization and Storage (CCUS) is one of the methods to reduce carbon dioxide emissions required to reach the goals of the Paris Climate Agreement.
Captured CO2 from a variety of sources (power plants, refineries, chemical plants), can either be used for industrial products, for greenhouses or can be transported for long-term storage in geological formations e.g. depleted gas reservoirs or saline formations.

However, large CO2 emitters (Power Stations or Industry) are typically located nearby populated (sub-) urban areas. The routing of CO2 pipelines and storage of CO2 near densely populated areas proved to be problematic. For example, in the last 10 years in the Netherlands, onshore CC(U)S projects in Barendrecht and various locations in Groningen and Noord Holland have been cancelled after protests from citizens and municipalities, who consider CO2 storage in their area an unacceptable risk. Main risk is reservoir seepage and leakage through legacy wells, but CO2 leakage from the transport pipeline is a risk. Also, increasing pressure in the reservoir may induce seismicity, a sensitive topic in The Netherlands.

An offshore storage location enhances acceptance of these risks. In Europe the Snøhvit pipeline in Norway is one of the few offshore CO2 pipelines to date, but currently various CO2 studies and projects in Norway (Northern Lights), the UK and NL are underway based on offshore storage with associated offshore pipelines.

The PORTHOS consortium (Port of Rotterdam CO2 Transport Hub & Offshore Storage) have initiated a plan to collect CO2 from the industrial area of the port of Rotterdam and transport it to an abandoned gas field offshore for storage.

Offshore Independents B.V. has performed an initial feasibility study and developed the Concept Selection/Pre-FEED study for the offshore pipeline part of this project. Some aspects of this study and some general observations are outlined below.

The project involves CO2 capture, transport and storage in the depleted P18-A gas field approximately 25 km from the onshore compressor station located on the Maasvlakte. A 30 km 42-inch onshore gathering pipeline transports the gaseous CO2 at 35 barg to the compressor station where the CO2 is compressed to 130 barg and dehydrated for transport to a former gas production platform via a 25 km 16-inch subsea pipeline. The CO2 is then injected via existing wells into a sealed reservoir of porous sandstone 3 km beneath the North Sea.

A similar project is being developed by ATHOS (Amsterdam-IJmuiden CO2 Transport Hub & Offshore Storage)

CO2 Pipeline Design

Design and construction of CO2 pipelines are similar to natural gas transmission pipelines. However, there are important differences as listed below:

  1. thermodynamic modelling (especially when dealing with impurities present in CO2),
  2. blow down modelling (low temperature control), specifying the maximum water content (corrosion control and fatigue behaviour),
  3. pipeline fracture propagation control (brittle fracture),
  4. use of elastomer materials and
  5. performing a QRA (Quantitative Risk Assessment, mainly related to release modelling and defining the allowable exposure limits).

These factors require special attention for CO2 pipelines, when compared with natural gas.

Read the full article here.

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