Smart thermoviscosifying polymer for improving drag reduction in slick-water hydrofracking

Abstract

Water-soluble polymers have been used as drag reducer in slick-water hydrofracking for unconventional hydrocarbons, however, the fatal “thermothinning” behavior and weak salt tolerance significantly impedes their practical use in more hostile environment. To alleviate these issues, here we present the first attempt to use a polyether-based thermoviscosifying polymer (TVP) as the drag reducer. Comparative studies on rheological behaviors and drag reduction performance were performed using TVP and currently-used partially hydrolyzed polyacrylamide (HPAM) with similar molecular weight. It is found that TVP solutions show thermothickening ability even at concentration as low as 200 mg⋅L−1, whereas HPAM solution only exhibits thermothinning behavior. The drag reduction of TVP is 73.47% while that of HPAM is 64.29% in 5.0 × 104 mg⋅L−1 NaCl saline water. More significantly, TVP provides improving drag reduction performance at elevated temperature. A higher drag reduction of 79.77% can be attained by TVP at 65 °C as compared to 70.18% for HPAM. The TVP displays a high drag reduction retention rate (94.57–97.77%) after shearing for 1 h at temperature range of 35–65 °C. These findings offer new possibilities for developing drag reducers for slick-water hydrofracking under harsh conditions.