The SPE IOR-EOR Terminology Review Committee has released its recommendations for the use of improved oil recovery (IOR) and enhanced oil recovery (EOR) terminology in SPE’s latest technical report. The report comes after years of broad and active discussion within the SPE community around the terms and a month-long period for public comments in August.
Terry Palisch, 2024 SPE President, SPE Technical Director of Reservoir, Rodolfo Camacho, and SPE Technical Director of Production, Hamad Marri, formed a committee of SPE industry experts to review and make a formal recommendation to the SPE community. The committee aimed to clarify the relationships between IOR, EOR, and the newly introduced term, assisted oil recovery (AOR), positioning IOR as the overarching category.
The committee's goals were to provide recommendations on the following:
1. The relationship of IOR to EOR
2. The initial baseline for both IOR and EOR
3. The relationship of terms primary, secondary, and tertiary to other recovery terms
4. Refine the classification of recovery technologies that have characteristics that allow them to fall into multiple terms
5. Provide guidance on how to classify current and future technologies that increase recovery
AOR was proposed to categorize methods that support oil production but do not fall under secondary recovery or EOR. This move, while potentially contentious, was seen as necessary for clarity and future consistency.
IOR, AOR, and EOR Terminology Clarifications and Recommendations
Upon reflection, the authors recognized that secondary oil recovery, EOR, and the methodologies included in the newly defined term AOR all improve oil recovery through various distinct methods. Thus, they recommended continuing the use of IOR as an umbrella or overarching term that represents all efforts that result in increased recovery beyond that expected from unassisted primary oil recovery. With this in mind, they proposed the following definitions:
Primary Oil Recovery: The oil recovered by means of unassisted natural depletion-drive mechanisms using conventional vertical wells and completions. Mechanisms include solution-gas drive, fluid expansion, aquifer drive, gas-cap expansion, and/or rock compaction.
IOR: The oil recovered by means of all or any processes and techniques beyond the mechanisms defined in primary oil recovery and includes secondary oil recovery, AOR, and EOR.
Secondary Oil Recovery: The oil recovered by means of the injection of water into the aquifer/reservoir and/or the injection of produced gas into the gas cap/reservoir for the purpose of pressure maintenance and oil displacement.
AOR: The oil recovered by means of techniques and/or operations designed to assist the principal recovery process whether primary, secondary, or EOR. These techniques and/or operational changes do not materially alter the principal recovery mechanisms driving the oil production.
EOR: The oil recovered by means of the injection of fluids, materials, biological components, and/or the addition of energy not normally present in the reservoir that are designed to alter the physical and/or chemical properties of the rock and/or resident fluids to enhance oil production.