Abstract

Heavy oil reservoirs in western Canada with viscosities ranging from 1,000 cp to 10,000 cp are being exploited using chemical enhanced oil recovery techniques. The most widely used polymer in enhanced oil recovery applications is hydrolyzed polyacrylamide (HPAM). The primary reason for its vast use is its higher viscosity in an aqueous solution and resistance to bio-degradation however is very prone to alkaline conditions as it hydrolyzes very rapidly under such environment.

To overcome this shortfall of conventional HPAM, a new co-polymer P(AAc-st-VP) was synthesized using Acrylic Acid (AA) and N-vinyl-2-pyrrolidinone (NVP) and proper initiator, that can offer stability against alkali. In the research presented herein, currently available conventional HPAM polymers were examined against new synthesized P(AAc-st-VP) co-polymer with improved properties by including different weight percent of N-vinyl-2-pyrrolidinone monomer for use with a focus on highly alkaline environment. Rheological properties were compared in terms of viscosity and elasticity under various NaOH concentrations and aging time, for typical alkali-polymer flood operations. The core flooding experiments of alkali-polymer (AP) flooding was conducted for oil samples collected from a heavy oil reservoir in Alberta. The results were analyzed for tertiary heavy oil recovery performance, residual resistance factor, and residual oil distribution. No significant change in rheological properties of P(AAc-st-VP) co-polymer was observed in presence of alkali even for longer aging times while the conventional HPAM showed much higher viscosity loss, becoming less effective for AP or ASP heavy oil recovery operations. Due to stable rheological characteristic under alkali condition, the new synthesised P(AAc-st-VP) co-polymer showed improved performance over conventional HPAM polymer in terms of injectivity and residual resistance factor. Analysis of the results indicates that AP flooding using P(AAc-st-VP) co-polymer could effectively overcome the drawbacks of conventional HPAM polymer and improve the recovery efficiency for the heavy oil with higher injectivity.

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