Optimizing Polymer Costs and Efficiency in Alkali-Polymer Oilfield Applications.

Area of Science:

• Petroleum Engineering
• Polymer Science
• Enhanced Oil Recovery

Background:

• Conventional polymer flooding faces challenges with polymer retention and high costs.
• Optimizing polymer performance in reservoirs is crucial for economic viability.

Purpose of the Study:

• To evaluate alkali-polymer (AP) flooding as a cost-effective enhanced oil recovery (EOR) method.
• To investigate the effects of polymer aging in alkaline conditions on viscosity and performance.
• To reduce polymer consumption and improve overall project economics.

Main Methods:

• Laboratory experiments involving polymer solutions aged in high pH conditions.
• Micromodel experiments in two-layer chips to simulate reservoir heterogeneity.
• Measurement of polymer adsorption on real rock and Berea sandstone.
• Interfacial tension (IFT) measurements for AP and alkali systems.

Main Results:

• Polymer aging at high pH increased viscosity by 60%, enhancing displacement efficiency.
• Polymer retention was reduced by approximately 50% in AP floods compared to conventional methods.
• AP floods achieved 80% recovery in high-permeability zones and 15% in low-permeability zones.
• IFT values reached as low as 0.006 mN/m with AP, significantly lower than alkali alone.
• Reduced polymer concentration in aged solutions maintained displacement efficiency, decreasing the equivalent utility factor (EqUF) by 40%.

Conclusions:

• Alkali-polymer flooding offers significant cost savings through reduced polymer usage and improved economics.
• The 'aging' of polymers in situ at high pH is a key mechanism for enhancing viscosity and reducing retention.
• AP flooding presents a viable and economical alternative for enhanced oil recovery.