Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions

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 charged dumbbell model for dilute polyelectrolyte solutions in strong flows

“…These results are in qualitative agreement with data on drag reduction in turbulent flow [8] and pressure drop vs. flow rate data in porous media flow [6]. These data for dilute solutions show an order of magnitude departure from Newtonian behavior at a critical flow rate which depends on salt concentration or charge density in a way consistent with the present model.…”

“…salt concentration is high) the extensional flow property being measured typically shows a sharp increase or onset at a critical magnitude of the velocity gradient, and this is similar to flexible nonionic polymers 1). If charge repulsion is strong, the critical onset point typically disappears and departures from near-equilibrium values of the flow property are evident at all shear rates [6]. This latter behavior is also typical of fiber suspensions or solutions of rigid macromolecules [8].…”

“…These cases correspond to larger values of the effective charge in the model. In flows involving some degree of extensional motion such as porous media flow [6], or orifice flow [7], or even turbulent pipe flow [8], the changes in equilibrium conformation due to the addition of salts can lead to qualitative changes in the behavior of dilute solutions. In particular, if charge repulsion is weak (i.e.…”

Extensional flow resistance of dilute polyacrylamide and surfactant solutions

“…F o r the polymer solutions at least, it is generally agreed that the reduction of wall shear stress is related to the high extensional resistance of these fluids and to the inhibiting effect of this resistance on the bursting motion near the wall in turbulent flow. This elongational resistance has also been observed in laminar flows where there is significant extensional motion, namely in entrance or orifice flow [1,2], converging channel flow [3,4], or flow in a porous medium [5,6]. In both the laminar and turbulent flows, the relevant motion is not simply extensional but is a mixture of shear and extension.…”

Rheological properties of aqueous polyacrylamide solutions

“…polymers. PAA is obtained by free-radical polyChauveteau 1 and Durst et al 2 reported signifimerization of acrylamide. It is widely used in modcant pressure drops in porous media flows of PAA ern technology as a thickening agent, suspending solutions compared to Newtonian liquids.…”