ISO 25206-1:2026

• Abstract:

  This document defines fundamental definitions for enhanced oil recovery (EOR) concepts and core methodologies, specifically addressing thermal recovery, gas flooding, chemical flooding, and microbial enhanced oil recovery technologies.

• Status: Published
• Publication Date: 08-Sep-2026
• ICS: 01.040.75 - Petroleum and related technologies (Vocabularies)
• ICS: 75.180.20 - Processing equipment
• Technical Committee: SC 10 - ISO/TC 67/SC 10
• Drafting Committee: SC 10 - ISO/TC 67/SC 10
• Current Stage: 6060 - International Standard published
• Start Date: 09-Sep-2026
• Due Date: 14-Aug-2027
• Completion Date: 09-Sep-2026

ISO 25206-1:2026 is an ISO International Standard from the oil and gas industries including lower carbon energy. It sets the general vocabulary for enhanced oil recovery (EOR), covering the core concepts used in thermal recovery, gas flooding, chemical flooding and microbial enhanced oil recovery. Engineers, project teams and standards writers use it to describe EOR methods with the same terms across reports, specifications and technical discussions.

What does ISO 25206-1:2026 specify?

ISO 25206-1:2026 defines the fundamental terms for EOR and the main method families used in the field. It is a terminology standard, so its role is to fix meaning and avoid ambiguity, not to prescribe operating procedures.

The document is organized into:

• Clause 1 - Scope
• Clause 2 - Normative references
• Clause 3 - Terms and definitions, with five subgroups:
  • Basic concepts
  • Terms related to thermal recovery methods
  • Terms related to gas flooding methods
  • Terms related to chemical flooding methods
  • Terms related to microbial enhanced oil recovery methods
• Bibliography
• Index

Clause 1 limits the vocabulary to EOR concepts and core methodologies and excludes specialized terminology from reservoir engineering, production engineering and surface engineering, as well as applications outside petroleum exploration and production. In practice, that means the standard is meant for shared EOR language, not for detailed discipline-specific design terms.

What are the key requirements of ISO 25206-1:2026?

ISO 25206-1:2026 is centered on definitions, and its main value is that it organizes EOR into a clear set of named concepts and method families. The terms are grouped so users can classify a project, a process or a report using the same vocabulary.

Basic concepts in Clause 3.1

• Enhanced oil recovery (EOR) is defined as injecting materials not normally present in the reservoir to improve recovery. In practice, this gives a broad umbrella term for tertiary recovery and for comparing different recovery routes.
• Oil recovery factor, sweep efficiency and displacement efficiency are defined together. This helps users separate how much of the reservoir is contacted from how well oil is displaced from that contacted rock.
• These basic terms provide the common language used in calculations, reporting and project comparisons.

Thermal recovery terms in Clause 3.2

ISO 25206-1:2026 covers thermal recovery and its main variants: hot water flooding, steam huff and puff, steam flooding, steam assisted gravity drainage (SAGD), fire flooding, also called in-situ combustion, and multi-component thermal flooding. In practice, the standard lets users distinguish cyclic steam treatment, continuous steam injection, in-situ burning and combined thermal approaches.

Gas flooding terms in Clause 3.3

ISO 25206-1:2026 defines gas flooding as a family that includes hydrocarbon gas, carbon dioxide, nitrogen, reduced oxygen air and flue gas flooding, plus foam flooding. This matters because the injection gas or displacement medium changes the project description, operating concept and technical comparison.

Chemical flooding terms in Clause 3.4

ISO 25206-1:2026 defines chemical flooding and the main subtypes polymer flooding, alkaline flooding, surfactant flooding, binary combination flooding and alkali-surfactant-polymer (ASP) flooding. For users, this creates a consistent way to name water-based chemical displacement methods and mixed-chemical systems.

Microbial enhanced oil recovery terms in Clause 3.5

ISO 25206-1:2026 defines microbial enhanced oil recovery (MEOR) and separates it into in-situ MEOR and ex-situ MEOR. This helps users state whether microorganisms are activated in the reservoir or introduced as prepared inoculum or metabolites.

What terms does ISO 25206-1:2026 define?

• EOR - enhanced oil recovery, a reservoir process that injects materials not normally present in the reservoir to increase oil recovery.
• Oil recovery factor - the recovered oil divided by the original oil in place.
• Sweep efficiency - the share of reservoir volume contacted by the displacement medium.
• Displacement efficiency - how effectively oil is displaced from the pore space that the medium contacts.
• SAGD - steam assisted gravity drainage, a steam-based method using paired wells and gravity-assisted production.
• ASP flooding - alkali-surfactant-polymer flooding, a chemical flooding method using an aqueous solution of alkali, surfactant and polymer.
• MEOR - microbial enhanced oil recovery, a method that uses microorganisms and their metabolites to improve recovery.

Who uses ISO 25206-1:2026?

ISO 25206-1:2026 is used by reservoir and production teams, EOR project engineers, technical writers, standards developers and organizations working in the oil and gas industries including lower carbon energy. It is especially useful when people need to classify an EOR project, write a technical report, compare recovery options or align terminology across companies and countries.

What does the ISO 25206-1:2026 document contain?

ISO 25206-1:2026 is a terminology document, so its main content is a structured vocabulary rather than procedures, test methods or design calculations. Clause 3 is the core of the standard and gives grouped definitions for basic EOR concepts and the main thermal, gas, chemical and microbial recovery methods.

The document also includes an index, which makes the definitions easier to locate by full term or abbreviation. The bibliography cites ISO/TS 3250:2021 as a source linked to the EOR definition. This format is useful for drafting specifications, reports, training material and other standards where precise wording matters.

International
Standard
ISO 25206-1
First edition
Oil and gas industries including
2026-09
lower carbon energy —
Enhanced oil recovery terms and
definitions —
Part 1:
General vocabulary
Industries du pétrole et du gaz, y compris les énergies à
faible teneur en carbone — Termes et définitions relatifs à la
récupération améliorée des hydrocarbures —
Partie 1: Vocabulaire général
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3  Terms and definitions . 1
3.1 Basic concepts .1
3.2 Terms related to thermal recovery methods .2
3.3 Terms related to gas flooding methods .2
3.4 Terms related to chemical flooding methods .3
3.5 Terms related to microbial enhanced oil recovery methods .3
Bibliography . 5
Index . 6

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 67, Oil and gas industries including lower carbon
energy, Subcommittee SC 10, Enhanced oil recovery.
A list of all parts in the ISO 25206 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv
Introduction
As enhanced oil recovery (EOR) technologies continue to advance and international collaborative projects
increase in number, there is a growing global demand for international standardization in this field. As a
universal technical language, terminology standards play a foundational role in international collaboration
by clearly defining the scope of the field and delineating boundaries with related disciplines.
To maintain terminological coherence across international EOR standards and to prevent conflicts in
application arising from ambiguous or contradictory definitions, coordinated efforts in standardization are
essential. The ISO 25206 series is being developed to establish a coherent framework of mutually reinforcing
definitions, ensuring conceptual alignment across all relevant international standards. This systematic
approach guarantees that precisely defined common terminology forms the essential basis for both the
understanding and implementation of EOR standards worldwide.
Based on the displacement medium and underlying mechanism, EOR is generally classified into the following
main types:
— thermal recovery;
— gas flooding;
— chemical flooding;
— microbial enhanced oil recovery.
This document provides general terms and definitions related to EOR, including fundamental concepts
covering the field and its subdivisions, as well as terms describing the major EOR technologies and their
associated processes. More specialized terminology for each specific category is defined in other parts of
the ISO 25206 series.
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