Flow behavior polyacrylamide, effect

Almost every biological solution of low viscosity [but also viscous biopolymers like xanthane and dilute solutions of long-chain polymers, e.g., carbox-ymethyl-cellulose (CMC), polyacrylamide (PAA), polyacrylnitrile (PAN), etc.] displays not only viscous but also viscoelastic flow behavior. These liquids are capable of storing a part of the deformation energy elastically and reversibly. They evade mechanical stress by contracting like rubber bands. This behavior causes a secondary flow that often runs contrary to the flow produced by mass forces (e.g., the liquid climbs the shaft of a stirrer, the so-called Weissenberg effect ). 

Lakatos., I., Lakatos-Szabo, J., Toth, J., 1979. Eactors influencing polyacrylamide adsorption in porous media and their effect on flow behavior, Paper presented at the Symposium on Surface Phenomena in EOR, Stockholm, August, Plenum. 

FACTORS INFLUENCING POLYACRYLAMIDE ADSORPTION IN POROUS MEDIA AND THEIR EFFECT ON FLOW BEHAVIOR... 

The adsorption or the lack of adsorption of the polyacrylamides influences strongly the flow behavior of the polymer solution and carrier phases in the porous systems. If no adsorption takes place in the porous media, an identical hydrodynamic effect with the system containing adsorbed film can be maintained by use of 3-6 times as much of the polymer. This fact unfavorably decreases in practice the effectiveness of the polymer flooding. 

Polymers that have been suggested for mobility control in oil reservoirs include polyacrylamides, hydroxy ethyl cellulose, and modified polysaccharides which are produced either by fermentation or by more conventional chemical processes. In this paper the solution properties of these polymers are presented and compared for tertiary oil recovery applications. Among the properties discussed are non-Newtonian character for different environmental conditions (electrolytes and temperature), filterability, and long term stability. The behavior of these water soluble polymers in solution can be correlated with the effective molecular size which can be measured by the intrinsic viscosity technique. A low-shear capillary viscometer with a high precision and a capability of covering low shear rates (such as 10 sec - - for a 10 cp fluid) has been designed to measure the viscosities. The measurement of viscosities at such slow flow conditions is necessitated... 

Investigatorsstudying partially hydrolyzed polyacrylamide solutions observed apparent viscosities 5 to 20 times the values measured in a conventional viscometer at the shear rates believed to exist in the porous media. These viscosity increases were not anticipated from the rheological behavior of the fluids. Pye introduced the concept of the resistance factor to quantify this effect. Burcik observed a decrease in the mobility of brine in a Berea sandstone disk that had been previously contacted with partially hydrolyzed polyacrylamide. The mobility reduction persisted even after 100 PV of brine had been flushed through the disk. Burcik concluded that polymer molecules retained in the pore structure by adsorption or mechanical entrapment were hydrophillic and restricted the flow of water. 

---