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ISO/TR 27923:2022 — Carbon Dioxide Capture, Transportation and Geological Storage — Injection Operations and Storage Site Management
Operational guidelines for safe and effective CO2 injection well management and storage site operations
1. Introduction to CO2 Injection Operations and ISO/TR 27923
Carbon capture and storage (CCS) is a critical technology for mitigating climate change by preventing CO2 emissions from industrial sources from reaching the atmosphere. While the capture and transportation components of the CCS chain have received substantial attention, the injection and storage phase is equally critical — it is the ultimate containment stage where CO2 must be securely retained in geological formations for centuries to millennia. ISO/TR 27923:2022 addresses this phase by providing comprehensive guidelines for injection operations and storage site management.
The standard was developed by ISO/TC 265 (Carbon dioxide capture, transportation, and geological storage) and provides a technical report that consolidates operational best practices for CO2 injection wells, storage site monitoring programs, corrective action planning, and site closure procedures. It is designed to complement the more prescriptive requirements of ISO 27914 (Geological storage) by providing deeper operational context and practical implementation guidance.
ISO/TR 27923:2022 addresses the operational reality that CO2 injection is not a static process — conditions in the storage formation evolve over time, and injection operations must adapt accordingly. The standard provides a risk-based framework for managing these dynamic conditions throughout the project lifecycle.
2. Injection Well Construction and Operations
2.1 Well Design Considerations for CO2 Service
CO2 injection wells face unique challenges compared to conventional oil and gas wells. The injected CO2 is typically in a dense or supercritical phase, which has high diffusivity and can react with formation water to form carbonic acid. ISO/TR 27923 provides detailed guidance on well materials selection, including the use of corrosion-resistant alloys for tubing and the design of cement formulations that remain chemically stable in CO2-rich environments over extended periods. The standard emphasizes the importance of multiple barrier verification — at least two independent barriers between the injected CO2 and the environment must be demonstrated at all times.
| Well Component | CO2 Service Requirement | Verification Method |
|---|---|---|
| Production casing | CO2-resistant material or corrosion allowance | Material certificate, NDE inspection |
| Tubing string | Corrosion-resistant alloy (13Cr, 22Cr, or higher) | PMI testing, dimensional inspection |
| Cement sheath | CO2-resistant formulation with low permeability | Bond log evaluation, mechanical integrity test |
| Packer | Elastomer rated for CO2 and temperature cycling | Factory acceptance test, installation verification |
| Wellhead and tree | CO2 service rated, 5,000+ psi working pressure | Hydrostatic test, function test of valves |
2.2 Injection Monitoring and Control
The standard specifies requirements for real-time monitoring of injection parameters at each well. Key parameters include injection pressure, temperature, flow rate, and cumulative volume. Pressure monitoring is particularly critical — injection pressure must be maintained below the formation fracture pressure to prevent creating unintended leakage pathways. The standard recommends bottom-hole pressure monitoring in addition to wellhead pressure, as bottom-hole conditions can differ significantly from surface readings due to the density and compressibility of the CO2 column. Automatic shut-in systems with appropriate set points are required to prevent overpressure events.
2.3 Well Integrity Management
A well integrity management program must be established and maintained throughout the injection period. The standard requires periodic mechanical integrity tests (MIT), including both Annulus Pressure Monitoring (APM) and a Pressure Fall-off Test (PFT) or similar evaluation. Corrosion monitoring through the use of corrosion coupons, caliper surveys, and ultrasonic wall thickness measurements is essential. The standard emphasizes that well integrity is not a one-time assessment but requires continuous surveillance and periodic re-evaluation.
Well integrity failure is one of the most significant risks in CO2 storage projects. ISO/TR 27923 emphasizes that a single failed barrier, if not detected and remediated promptly, can lead to uncontrolled CO2 migration. The standard’s recommended testing frequency may need to be increased for wells in challenging environments or those with a history of integrity issues.
3. Storage Site Monitoring Program
3.1 Monitoring Objectives and Strategies
ISO/TR 27923 defines a comprehensive monitoring framework with three primary objectives: verifying containment (confirming CO2 remains within the storage complex), tracking plume migration (mapping the spatial distribution of injected CO2), and detecting leakage (identifying any unintended CO2 release from the storage complex). The monitoring program must be risk-based and adaptive, meaning that monitoring strategies evolve as understanding of the storage complex improves and as the CO2 plume expands. Baseline monitoring (pre-injection) establishes reference conditions against which all future monitoring data is compared.
3.2 Monitoring Technologies
The standard reviews a wide range of monitoring technologies applicable to CO2 storage sites, organized by their measurement principle. Seismic methods (surface seismic, vertical seismic profiling, cross-well tomography) provide the primary means of plume imaging. Non-seismic geophysical methods include electrical resistivity tomography, gravity surveys, and electromagnetic surveys. Geochemical monitoring of groundwater and soil gas provides direct evidence of containment. Well-based monitoring includes pressure and temperature gauges, distributed temperature sensing (DTS) using fiber optics, and downhole fluid sampling. The standard provides guidance on technology selection based on site-specific conditions.
| Monitoring Method | Detection Capability | Spatial Coverage | Cost Level |
|---|---|---|---|
| 3D surface seismic | Plume geometry, facies changes | Full field (km scale) | High |
| Vertical seismic profiling (VSP) | Near-wellbore plume extent | Well-centric (100-500 m) | Medium |
| Downhole pressure/temperature | Formation response, pressure build-up | Point measurement | Low |
| Distributed temperature sensing (DTS) | Flow distribution, leak detection | Along wellbore profile | Medium |
| Groundwater geochemistry | Leakage detection (pH, alkalinity, TIC) | Local (wells and springs) | Medium |
| InSAR satellite monitoring | Surface deformation linked to pressure change | Full field (regional scale) | Medium |
3.3 Corrective Action Planning
An essential component of ISO/TR 27923 is its guidance on corrective action plans (CAP). The standard requires that operators develop CAPs during the planning phase, before injection begins. CAPs address potential leakage scenarios, well integrity failures, monitoring system malfunctions, and unanticipated migration. Each corrective action must specify triggering conditions, response procedures, responsible personnel, and verification criteria. The standard emphasizes that corrective action planning is not a one-time exercise — CAPs must be reviewed and updated as operational experience accumulates and as the understanding of storage complex behavior evolves through monitoring data.
From an engineering perspective, the most valuable contribution of ISO/TR 27923 is its integrated approach to injection management. Rather than treating well operations, monitoring, and corrective actions as separate activities, the standard weaves them into a continuous management cycle: plan-inject-monitor-evaluate-adjust. This closed-loop approach is essential for managing the long-term uncertainties inherent in geological storage.
4. Site Closure and Post-Closure Planning
The standard addresses site closure procedures, recognizing that closure is not a single event but a process. Closure qualification requires demonstrating that the CO2 plume has stabilized, formation pressures have declined to acceptable levels, and no leakage pathways exist. Post-closure planning covers long-term stewardship responsibilities, including periodic monitoring (at reduced frequency), records management, and financial planning for long-term obligations. The standard provides guidance on developing site-specific closure criteria that satisfy regulatory requirements while being technically achievable based on site conditions.
5. Frequently Asked Questions
Q1: What is the difference between ISO/TR 27923 and ISO 27914?
A: ISO 27914 provides normative requirements for geological storage of CO2, while ISO/TR 27923 is a Technical Report that provides operational guidance and best practices for implementing the requirements. The TR offers more detailed context on injection operations, monitoring technology selection, and corrective action planning.
A: ISO 27914 provides normative requirements for geological storage of CO2, while ISO/TR 27923 is a Technical Report that provides operational guidance and best practices for implementing the requirements. The TR offers more detailed context on injection operations, monitoring technology selection, and corrective action planning.
Q2: What monitoring frequency does the standard recommend?
A: The standard does not prescribe fixed monitoring frequencies — it advocates a risk-based approach where monitoring frequency is determined by site-specific risk assessment. Continuous monitoring (e.g., pressure and temperature) is required during injection, with periodic surveys (seismic, geochemical) conducted at intervals that may range from annually to every 5 years depending on site conditions and regulatory requirements.
A: The standard does not prescribe fixed monitoring frequencies — it advocates a risk-based approach where monitoring frequency is determined by site-specific risk assessment. Continuous monitoring (e.g., pressure and temperature) is required during injection, with periodic surveys (seismic, geochemical) conducted at intervals that may range from annually to every 5 years depending on site conditions and regulatory requirements.
Q3: How should a corrective action plan be structured?
A: The standard recommends that each corrective action include: specific triggering conditions (e.g., pressure above threshold), a clear description of the action, designation of responsible personnel, required resources, implementation timeline, and verification criteria to confirm effectiveness.
A: The standard recommends that each corrective action include: specific triggering conditions (e.g., pressure above threshold), a clear description of the action, designation of responsible personnel, required resources, implementation timeline, and verification criteria to confirm effectiveness.
Q4: Can ISO/TR 27923 be applied to CO2-EOR projects?
A: While primarily written for dedicated geological storage, the injection monitoring and well integrity management principles are applicable to CO2-EOR operations. However, CO2-EOR projects should also reference ISO 27916 for storage quantification and ISO 27914 for storage-specific requirements.
A: While primarily written for dedicated geological storage, the injection monitoring and well integrity management principles are applicable to CO2-EOR operations. However, CO2-EOR projects should also reference ISO 27916 for storage quantification and ISO 27914 for storage-specific requirements.
