Low salinity water flooding has been recognized as prominent enhanced oil recovery technique, acting at microscopic scale by reducing residual oil saturation thanks to a combination of intertwined mechanisms. In the last ten years, several studies and applications have been performed by Academia and Oil Companies giving indication of the process potentialities to increase oil production both in clastic and carbonate reservoirs.

1. Low Salinity Water Injection: Eni’s Experience
Shrinath Ghadge
Chemical and Petroleum Engineering , University of Pittsburgh,
Pittsburgh, PA 15261
Rotondi, Marco, et al. "Low Salinity Water Injection: eni’s Experience." Abu Dhabi International
Petroleum Exhibition and Conference. Society of Petroleum Engineers, 2014.
PETE 2201

2. Outline
 Introduction - Low Salinity Water Injection
 Eni low salinity EOR workflow
 Filed case A : Low Salinity water injection
 Filed case B : Low Salinity water + Polymer injection
 Conclusions
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3. Why Low Salinity Water Injection?
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Conventional water flooding
• Lower production rate
• High energy input High operating cost
• Oil molecules are bound to clay particles by
bridges of divalent ions (Ca+2, Mg+2)
• In high sal. Water, bridges are compressed
to clay surface by electrical forces

4. Basic requirements for a low salinity water flooding
 Injected source water should have a salinity less than 6 g/l and optimal range is
1-2 g/l
 Formation rock should contain water sensitive minerals (clay) and should not be
strongly water-wet
 Formation brine should contain divalent ions
 Reservoir oil should contain polar components
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5. Eni Low Salinity EOR Workflow-Year 2006
After the effectiveness of the technique was proved by lab analyses and SWCTTs, an inter-
well pilot was performed.
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6. Single-Well Chemical Tracer Test (SWCTT)
Field was Selected in West Africa- Year 2013Eni’s Workflow
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7. Field Case (A)-Low Salinity Water Injection
Eni’s Workflow
Lowering the salinity of the injection water to different degrees can
change rock wettability and improve oil recovery.
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8. Field Case (B)-Low Salinity +Polymer Injection
Adding polymer to the water of water-flood

Increase in viscosity

Decrease in mobility ratio

Increase in volumetric sweep efficiency

Increase in oil recovery
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9. Single-Well Chemical Tracer Test (SWCTT)
https://www.youtube.com/watch?v=3s0p5C2WSpw
• Additional oil recovery in the range of 3-
4% for polymer injection
• The combination of low salinity and
polymer injection was found be the most
efficient chemical EOR process
Site selected: North Africa
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10. Conclusions
 Low salinity water flooding has been recognized as prominent enhanced oil
recovery technique
 Low salinity is considered by Eni a key EOR method due to low capital and
operational costs
 Low Salinity water + Polymer Injection = Highly efficient oil recovery
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Thank you