Adsorption behavior and shear degradation of ultrahigh-molecular-weight hydrolyzed polyacrylamide in a capillary flow

摘要

Ultrahigh-molecular-weight partially hydrolyzed polyacrylamides (HPAMs) are commonly used in polymer flooding to enhance oil recovery. However, the viscosity of the HPAM solution is susceptible to shear action. Viscosity change affects sweep range and displacement efficiency of the displacement fluid. Here, a macromolecular adsorption model in microcapillary is proposed to reveal the shear variation mechanism at low flow rates. The rheological behaviors of HPAMs with three different molecular weights are investigated using a stainless steel capillary. The shear rate distributions near contraction and within capillary are compared by numerical calculation using the laminar flow model. Experimental and numerical results show that the polymer solution was mechanically degraded at low flow rates, which is in agreement with the results predicted by the adsorption theory model. A new calculation method for the thickness of polymer adsorption layer at lower flow rates is proposed based on the adsorption model proposed in this study. It is found that the viscosity and adsorption of HPAM were changed with flow rate, and their changes are closely related to the displacement efficiency in the micropores of reservoirs. This study provides new perspectives for the selection of polymer injection flow rates and the water shutoff in reservoirs. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48270.