Thermoviscosifying Smart Polymers for Oil and Gas Production: State of the Art.

Water-soluble polymers have been extensively used in all sections of the oil and gas upstream industry, but their inherent thermothinning behaviour has limited their applications in harsh environments. To address this issue, thermoviscosifying (or "thermothickening") polymers (TVPs) whose aqueous solution viscosity automatically increases upon increasing the temperature were introduced in the early 1990s. This review first recalls the background for developing such smart materials, followed by demonstrating the mechanism of thermothickening. Next, three major TVPs including N-alkyl substituted acrylamide copolymers, grafted polyethers, and cellulose derivatives are summarized with respect to their structure-property relationship, then their practical trials or potential uses in oil and gas drilling fluids, cementing slurries, hydraulic fracturing, steam flooding, and enhanced oil recovery are discussed. Finally, the advantages and disadvantages of the current TVPs are commented and future prospects are discussed to close this review.