No abstract

SynopsisExperimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near &conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by an increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.

The flow behavior of dilute polymer solutions through porous medii has been investigated by use of a homologous series of polyacrylamide (PAAm) samples with a wide range of molecular weights and with nearly the same molecular weight distribution. Resistance to lamlnar porous medEa flow of dilute PAAm solutions increased markedly above the Newtonian value for the solvent after a critical flow rate was exceeded (onset). The investigations have been focused on the dependence on molecular parameters such as molecular weight, coil volume, and thermodynamic qualii of various solvents. Resistance coeff iclent/Reynolds number plots were determined experimentally and examined with respect to the onset, steepness, and maximum behavior. The results were interpreted with extensional flow equations, derived by Bkd et al. and extended by Durst and Haas. Based on the investigated solution structure of PAAm, one can correlate the measured onset Reynolds number (Re,) with a theoretically predicted Re,,*. Especially when pseudo-ideal (6) solvents with different solvent vlscosities are used, the onset Reynolds numbers are quite different, whereas the observed maximum reslstance increase is the same in both solvents.

No abstract

No abstract