Recent Advances in Polymer Flooding in China.

Area of Science:

• Petroleum Engineering
• Enhanced Oil Recovery
• Polymer Science

Background:

• Polymer flooding is a mature enhanced oil recovery (EOR) technique, with significant applications in China's Daqing oilfield.
• Laboratory studies suggest polymer viscoelasticity enhances displacement efficiency and reduces residual oil saturation (ROS).
• Discrepancies exist between laboratory findings and recent field test results regarding high-concentration, high-molecular-weight (HCHMW) polymer effectiveness.

Purpose of the Study:

• To systematically summarize polymer flooding mechanisms and field applications in China.
• To critically review the viscoelasticity effect of polymers on ROS reduction.
• To clarify the reasons behind the limited application of HCHMW polymers despite promising laboratory results.

Main Methods:

• Critical review of existing literature on polymer flooding mechanisms and viscoelasticity effects.
• Analysis of laboratory core flooding data and field test results from China.
• Discussion of alternative polymer flooding mechanisms, including wettability alteration and gravity stability.

Main Results:

• HCHMW polymer application is limited due to a lack of understanding of polymer flooding mechanisms and potential reservoir issues.
• Salt-resistance polymers (SRPs) utilizing produced water show economic and environmental promise.
• Formation blockage and injectivity issues have been reported due to misinterpretations of polymer behavior.

Conclusions:

• The effectiveness of polymer flooding depends on a nuanced understanding of polymer properties and reservoir interactions.
• HCHMW polymer injection is not recommended for medium-to-high viscosity oils, especially in older wells.
• Further research and careful implementation are needed to optimize polymer flooding strategies, including the use of SRPs.