April 09th, 2026

Industry News

Evaluating Pipelines for Conversion to CO2 Service

by Brian Cooper, PE
Acuren Inspection, Inc.
Written for publication in the Michigan Oil & Gas News

As carbon capture, utilization, and storage (CCUS) projects continue to develop, pipeline operators are increasingly evaluating whether existing infrastructure can be converted to transport CO2. Reusing existing gathering and transmission assets has the potential to reduce costs, shorten project timelines, and minimize right-of-way impacts — but conversion to CO2 service requires careful technical evaluation.

With interest in carbon management growing — including potential applications tied to enhanced oil recovery (EOR) and long-term storage — the question is becoming more relevant for operators across regions with established infrastructure. However, converting a pipeline from natural gas or crude service to CO2 is not a straightforward process. CO2 introduces unique hydraulic behavior, phase considerations, and integrity risks that must be addressed through disciplined engineering.
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A successful feasibility evaluation typically focuses on three key areas: defining the CO2 stream and operating conditions, assessing material suitability and integrity risks, and completing a front-end engineering and design (FEED) level analysis that integrates technical, operational, and regulatory requirements.

Pipeline inspection and testing are critical steps in evaluating infrastructure for CO2 service conversion. -- Photo provided by Acuren Inspection, Inc.

Defining the CO2 Stream

CO2 composition and phase behavior drive nearly every aspect of pipeline design and operation. Under federal hazardous liquid regulations, CO2 is defined as a fluid consisting of more than 90% CO2 compressed to a supercritical state. In practice, however, captured CO2 streams often contain impurities such as water, nitrogen, oxygen, hydrocarbons, and sulfur compounds.
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These impurities influence corrosion risk, dehydration requirements, compression needs, and the location of phase changes within the system. Establishing a clear design basis — including composition ranges, pressure and temperature conditions, and expected flow rates — provides the foundation for determining whether a pipeline can operate safely and reliably in CO2 service.

Hydraulics and Operability

Unlike many natural gas systems, CO2 pipelines typically operate within a relatively narrow pressure and temperature range to maintain a stable phase. Variations in elevation, ambient conditions, or flow rates can cause phase changes that introduce operational challenges.
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Flow simulation is a critical tool for evaluating feasibility. By modeling the system under expected operating conditions, operators can determine capacity, identify pressure limits, and assess whether dense-phase operation can be maintained. These insights help define compression requirements, control strategies, and potential system constraints before any physical modifications are made.

Material Suitability and Integrity

CO2 service introduces integrity threats that differ from those encountered in natural gas or crude oil pipelines. Two key concerns are fracture propagation and internal corrosion. In certain conditions, fractures can propagate rapidly if the pipeline material does not have sufficient toughness, while the presence of water and impurities can accelerate corrosion.
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A material suitability assessment typically begins with a review of construction records to understand pipe grade, seam type, and material properties. Where records are incomplete, targeted testing may be required. These evaluations help determine whether the pipeline can safely operate under CO2 conditions or whether mitigation measures — such as crack arrestors or enhanced corrosion control — are necessary.

FEED Evaluation and Project Planning

Once operating conditions, hydraulics, and material suitability are understood, a FEED-level evaluation brings these elements together into a practical conversion plan. This process addresses key questions related to pipeline integrity, regulatory requirements, and constructability.

A baseline integrity assessment — often supported by in-line inspection (ILI) and data integration — helps identify existing threats and required repairs. At the same time, operators must establish a defensible maximum operating pressure based on the combined technical analysis.

Regulatory considerations also play a central role. Federal requirements call for a documented conversion procedure demonstrating that the pipeline is suitable for CO2 service, while state-level permitting and siting processes may also apply. In Michigan, for example, Act 16 provides a framework for CO2 pipeline siting under the Michigan Public Service Commission.
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The FEED process typically results in a defined scope of work, preliminary engineering plans, permitting requirements, and a cost estimate that supports investment decisions.

The Bottom Line

Converting existing pipelines to CO2 service can offer significant advantages, but only when supported by a thorough technical evaluation. By combining composition analysis, flow simulation, material assessment, and FEED-level planning, operators can determine whether a pipeline can be converted as-is, requires modification, or is not suitable for conversion.
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As interest in carbon capture continues to grow, the ability to leverage existing infrastructure could play a key role in advancing projects from concept to execution — particularly in regions with established oil and gas assets.