Investigation on the influence of sulfonic substitution in polyacrylamides for minimizing drag in turbulent flow of slickwater fluids

Abstract

The use of slickwater fluids for fracking is key for accessing unconventional shale/tight‐sand reservoirs. To mitigate the frictional losses observed during the injection, drag reducers like sulfonated polyacrylamides (SPAMs) are added to the slickwater fluids. The current study presents a unique controlled investigation that examines the impact of sulfonic group substitution, ranging from 5 to 25 wt%, in SPAMs. The molecular weight of the polymers is kept constant at ~7.5–7.8 million Daltons. The investigation is two‐pronged: first part is comprised of drag reduction (%DR) performance of the polymers in fluids of varying salinities on a laboratory flow‐loop. The results obtained indicated the inter‐dependence of fluid salinity and sulfonic substitution on the polymer performance; for example, %DR deterioration of SPAM with 5 wt% substitution was 24.7%; to the contrary, the deterioration was only 15.6% for SPAM with 25 wt% substitution with rise in fluid salinity from 150 ppm to 110 k ppm. The second part of study included in development of a physics‐based model where the polymer relaxation response (Weissenberg number) was improvised to accommodate the impact of governing parameters and then, successfully correlated with the %DR performance using phenomenological equations for the studied range of parameters.