Quantifying the Matching Relationship of Sizes Between Partially Hydrolyzed Polyacrylamides and Regular Nuclepores

ABSTRACT Water‐soluble polymers have been extensively utilized for enhanced oil recovery (EOR) due to their strong thickening power to aqueous displacement fluids. However, the typical EOR polymer, high‐molecular‐weight (MW) partially hydrolyzed polyacrylamide (HPAM), often encounters injectivity challenges, particularly in low permeability reservoirs, which is attributed to the lack of a quantitative matching relationship of sizes between polymer and porous media. In this study, the radius of gyration ( R g ) and the hydrodynamic radius ( R h ) of five HPAMs with various MW ranging from 4.8 × 10 6 to 15.4 × 10 6  g·mol −1 were determined via light scattering. Subsequently, by employing polycarbonate nuclepore membranes to mimic regular micro‐ and nano‐pore throats, the flow and matching relationship of these HPAM solutions in porous media were investigated. It was found that the R g of HPAM gradually magnifies from 89 to 161 nm with an increase in polymer MW, while R h ranges from 53 to 92 nm. The matching relationship between R g / R h and nuclepore size ( R p ) can be described as follows: when R p / R g < 2.01 or R p / R h < 3.7, injection difficulties emerge for HPAM solution; conversely, when R p / R g > 2.48 or R p / R h > 4.77, there is no blockage caused by the HPAM solution.