The SPE CO2 Storage Resources Management System (SRMS), first published in 2017, is a system that aims to provide the carbon capture and storage (CCS) community with a standard for storage resources classification and categorization.
The SRMS provides a consistent approach to estimate Storable Quantities, evaluate the commerciality of projects, and present results in a comprehensive classification framework. It provides all stakeholders (governments, regulators, financial entities, etc.) a means for comparing and contrasting CO2 storage estimates based on project maturity and geologic certainty. It also provides context for an investment and tracking the performance of the investment.
The SRMS classification is aligned with that of the time-tested and widely used Petroleum Resources Management System (PRMS). The SRMS has been adopted by the industry (e.g., Santos, and the US Department of Energy) in CO2 storage management.
The 2025 SRMS Update was approved for publication by the SPE Board in January 2025 along with the endorsement of six sponsoring societies. The update involved a 2-year review process led by a CO2 Storage Resources Committee (CSRC) working group.
Like the original 2017 SRMS, the 2025 SRMS Update contains four major sections: Basic Principles and Definitions, Classification and Categorization Guidelines, Evaluation and Reporting Guidelines, and Estimating Storable Quantities, plus an Appendix covering the glossary of terms.
In preparing the update, the working group held multiple consultations and solicited input from interested parties, stakeholders and the public. Every comment received was carefully reviewed and addressed to ensure the updated document reflected the broad range of perspectives. The most significant distinction between the 2017 SRMS and the 2025 SRMS Update is that the former focused on pure geologic storage while the latter also incorporates CO2 EOR as a form of storage.
Basic Principles and Definitions
The SRMS is intended for use with application to geologic formations in the subsurface (excluding caverns) completely saturated with brine, depleted hydrocarbon fields, and CO2 EOR fields. The expanded scope of the updated SRMS states that the reference to CO2 EOR storage may extend to other enhanced petroleum recovery processes such as enhanced gas recovery.
When a CO2 storage resource assessment is conducted in conjunction with petroleum projects, the reported classification of uncertainty ranges of the storable resources (in SRMS) and petroleum quantities (in PRMS) must align.
The SRMS framework provides a “principles” view of classification that can represent the gross or entitlement share. A project may be defined at various levels and stages of maturity from notional to injecting. The term “notional” has been used in place of “future.”
Classification and Categorization Guidelines
In Determination of Discovery, it is more clearly stated that the assessment must include having confidence there will be containment of the injected CO2 over a period established by the project including post-injection through to site closure. A new subsection on Containment Assessment and Project Maturity has been added. The definition of Determination of Commerciality is revised to better align with that in the PRMS. A new subsection on Development Concepts has been added to clarify that the type of operation, such as brine extraction to manage pressure, should be addressed in the assessment.
Evaluation and Reporting Guidelines
Project-based storage resource evaluations are based on the estimates of future injection and associated cash flow schedules for each project as of an effective date. SRMS 2017 described two types of storage projects, a standalone storage project and an integrated storage project where the project is developed in direct combination of a larger revenue-generating and CO2-generating project. The evaluation of revenue and cash flow methods for the two types of projects were discussed.
The update clarifies that when the project is developed for corporate reasons or regulatory requirements, such as to meet CO2 emission targets or maintain the license to operate, the revenue should consider broader aspects, such as carbon pricing and valuation assigned internally. The economic evaluation should reflect the expenditure of developing and operating the storage site as a cost shared by the developing entity’s revenue-generating activity.
Estimating Storable Quantities
In the discussion of the volumetric estimation of storable quantities, clarification has been made regarding selection of reference volume and that the storage efficiency must be established with the chosen reference volume. For example, for saline aquifers within a geologic trap, the reference volume may be the pore volume within the structure or alternatively, the volume of mobile water within the structure. For a CO2 EOR operation, the reference volume may be the mobile volume of both oil and water within the reservoir at the start of the CO2 EOR project. The storage efficiency must be established for the chosen reference volume, which must be defined. The storage efficiency of a saline aquifer will not be equivalent to that of a depleted hydrocarbon reservoir. The storage efficiency should reflect the development concept contemplated by the project and should have been established from analog storage sites or by flow modeling representative of the storage type and storage mechanisms. A new subsection on Containment Assessment has been added to highlight the importance of its assessment and incorporation in resource quantification and uncertainty range.
Tables and Appendix
The glossary of terms used in storage resources evaluations has been reviewed and definitions have been updated as needed. The term Containment Area has been replaced with Storage Complex. New terms such as Effective Date, Economically Not Viable Contingent Storage Resources, Economically Viable Contingent Storage Resources, and Notional have been added.
The CO2 Storage Resources Committee (CSRC), under the SPE Carbon Dioxide Capture, Utilization, and Storage (CCUS) Technical Section, manages the SRMS and SRMS Guidelines. With the 2025 SRMS Update, all stakeholders can look forward to greater consistency and transparency for project assessments as the CCS industry continues to expand and develop. The CSRC Update subcommittee will focus next on updating the SRMS Guidelines.