Refrigeration
Enhanced Oil Recovery & Gas Injection Compressor Lubricants
Enhanced oil recovery and gas injection compressor lubricants are selected for compressors raising CO₂, natural gas, hydrocarbon gas or nitrogen to the pressure required for reservoir injection.
The lubricant challenge changes with the injection gas. CO₂ can dissolve into the lubricant and reduce operating viscosity, hydrocarbon gases can cause significant oil dilution, while nitrogen and lean dry gas place greater emphasis on compressor design, cleanliness and long-term lubricant stability. Gas composition, pressure, temperature and whether the process gas contacts the lubricant therefore determine the correct chemistry.
NEXT Lubricants supplies PAO, PAG, water-soluble PAG, PEG and mineral compressor lubricants for EOR, gas reinjection, pressure-maintenance and reservoir-injection applications. Gas injection using CO₂, natural gas and nitrogen is an established EOR method, with the injected gas either displacing oil or dissolving into it to improve recovery.
Compression process
Enhanced Oil Recovery & Gas Injection: Process, Applications & Compressor Role
EOR and gas-injection systems compress CO₂, hydrocarbon gas or nitrogen for injection into an oil reservoir. Injection may maintain reservoir pressure, improve displacement or achieve miscibility between the injected gas and reservoir oil.
Injection compressors can be reciprocating, centrifugal or other process-gas designs depending on gas composition, flow and pressure. Where process gas contacts the lubricant, gas solubility and dilution become important; dry-sealed or separately lubricated compressors require a different lubricant-selection approach. Siemens Energy supplies reciprocating and centrifugal compression technologies specifically for CO₂ injection and EOR applications.
CO₂ Injection
CO₂ is compressed for miscible or immiscible reservoir injection, with lubricant selection influenced by CO₂/oil contact, pressure and operating viscosity.
Hydrocarbon Gas Injection & Reinjection
Natural gas, associated gas or enriched hydrocarbon gas can be recompressed and injected for pressure maintenance or enhanced recovery.
Nitrogen Injection
Nitrogen provides an alternative injection gas for reservoir pressure support and oil displacement where reservoir and project conditions suit it.
Water-Alternating-Gas (WAG)
WAG alternates periods of gas and water injection to improve reservoir sweep; the compressor handles the gas injection portion, while water is handled separately by injection pumps.
Lubrication Considerations
Gas Dilution & Operating Viscosity
Where injection gas directly contacts the lubricant, dissolved gas can reduce the oil's operating viscosity. The effect depends strongly on gas composition. CO₂ requires CO₂-specific solubility consideration, while rich hydrocarbon gas can cause severe dilution of conventional mineral or PAO lubricants. NEXT GPL PAG is specifically formulated to maintain viscosity where hydrocarbon gas dilution would significantly thin conventional oils.
Injection Pressure & Compressor Design
EOR compression can involve demanding high-pressure service, but high gas pressure does not automatically mean the bearing lubricant experiences reservoir injection pressure. Compressor architecture must therefore be established first. Siemens Energy uses reciprocating, integrally geared and centrifugal compressor technologies for CO₂ injection, including high-density centrifugal compressors for offshore CO₂ reinjection.
Injection Gas Composition
“Gas injection” does not define one lubricant duty. Lean natural gas, rich associated gas, recycled hydrocarbon gas, nitrogen and CO₂ behave differently with compressor lubricants. Where recycled produced gas is used, heavier hydrocarbons, moisture, CO₂ or H₂S can further change the lubricant requirement.
Miscible vs. Immiscible Injection
Miscibility primarily defines the reservoir displacement process and pressure target, rather than directly determining lubricant chemistry. CO₂ injection above the reservoir's minimum miscibility pressure can achieve miscible displacement, while operation below MMP remains immiscible. MMP itself depends on reservoir temperature and the properties of the oil and injected gas.
products
Recommended NEXT EOR & Gas Injection Compressor Lubricants
NEXT GPL PAG
Light–Medium Hydrocarbon Injection / Reinjection
Base Oil: PAG
ISO Range: 32 – 680
NEXT GPL PAG-WS
Rich / Heavy Hydrocarbon Reinjection
Base Oil: PAG-WS
ISO Range: 32 – 460
NEXT GPL PAG-EO
Severe-Dilution Heavy Hydrocarbon Injection
Base Oil: PEG
ISO Range: 32 – 220
Cross reference tool
Our technical team can help identify the right product.
Recommendation
Technical Support, Compatibility and Cross-Reference Documentation
Changing compressor lubricant brands requires confidence that the replacement lubricant is suitable for both the compressor and the existing oil in the system.
NEXT Lubricants provides technical support for lubricant conversions and replacement projects.
Over more than 10 years, we have built an internal database comparing the compatibility and performance of NEXT lubricants with many commonly used industrial compressor oils.
Frequently Asked question
What gases are used for enhanced oil recovery?
Gas-injection EOR commonly uses CO₂, natural gas or hydrocarbon gas, and nitrogen. The chosen gas and injection strategy depend on reservoir pressure, temperature, crude-oil properties, gas availability and project economics.
What is the difference between miscible and immiscible gas injection?
In miscible injection, the injected gas and reservoir oil develop miscibility under the required reservoir conditions, reducing interfacial effects and improving displacement. Below the minimum miscibility pressure, gas injection remains immiscible but can still improve recovery through mechanisms such as oil swelling, viscosity reduction and pressure support.
What is minimum miscibility pressure?
Minimum miscibility pressure, or MMP, is the pressure above which an injected gas and a specific reservoir oil can develop miscibility under the relevant reservoir conditions. It depends on factors including reservoir temperature, oil composition and injected-gas composition rather than being one fixed pressure for all EOR projects.
What is WAG injection?
Water-Alternating-Gas injection alternates slugs or periods of water and gas injection to improve reservoir sweep and control gas mobility. The gas compressor compresses the injection gas; it does not compress the water. Water injection uses a separate pumping system.
What lubricant is used for CO₂ EOR compression?
PAO lubricants can be suitable for CO₂ process compression, but the correct lubricant depends on compressor design, gas/oil contact, pressure, temperature and expected CO₂-driven viscosity reduction. NEXT currently positions NEXT PAO and GPL PAO for CO₂ process compression, including EOR-related service.
Why are PAG lubricants used for hydrocarbon gas reinjection?
Hydrocarbon gases can dissolve into mineral and PAO oils and reduce their operating viscosity. PAG chemistries generally have lower hydrocarbon dilution, allowing the lubricant to retain more of its viscosity under gas-contact conditions. NEXT GPL PAG is formulated specifically around this property.
When should NEXT GPL PAG-WS or PAG-EO be considered?
NEXT GPL PAG-WS becomes relevant as the injected or recycled hydrocarbon gas becomes richer and heavier. NEXT GPL PAG-EO is the specialty choice where very heavy hydrocarbons create severe dilution and maximum operating-viscosity retention is required.
Can the same lubricant be used for CO₂ and natural-gas injection?
Not automatically. CO₂, nitrogen, lean natural gas and rich hydrocarbon gas have different solubility and compatibility behavior. The compressor architecture and actual injection-gas composition should be evaluated before using one lubricant across multiple injection trains.
Related Applications
Explore Other Gas Compression Applications
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Natural Gas Gathering
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CO₂ Compression
Core CO₂/lubricant solubility and operating-viscosity selection for industrial process CO₂.