Measurement of Molecular Weight Distribution of Polyacrylamides in Core Effluents

Abstract

Summary A procedure to measure the molecular-weight (MW) and size distributions of polymers in core effluents by size-exclusion chromatography (SEC) and low-angle laser-light scattering (LALLS) was used to analyze Berea core effluent samples containing either a hydrolyzed or unhydrolyzed Polyacrylamide (PAAM). The average MW's of the PAAM's were measured with a precision better than ±5% at a 95% confidence level. For both PAAM's, the polymer in an early effluent sample after breakthrough had a narrower MW distribution and fewer low-MW molecules than the injected polymer. This led to a higher weight-averaged MW, Mw, for the early effluent than for the injected polymer. The effluent Mw decreased with increasing PV of polymer solution injected and approached the injected polymer's Mw after a large throughput. The results of the MW distribution measurements, which suggested a relatively large inaccessible PV for larger polymer molecules, are discussed in terms of steric-exclusion effects and dependence of retention rate on polymer size.