Polymer flow resistance factors

An 18-20% hydrolyzed polyacrylamide was used in all tests. In all 300 ppm polymer solutions a radioactive C14 tagged polyacrylamide was used. At higher polymer concentrations (600 and 1200 ppm) a commercial product called Calgon Polymer 454 was added to the base 300 ppm radioactive solution. A special study was conducted to develop a radioactive polymer which has properties identical to the commercial product. Several experiments were run on both polymers to check these properties such as, viscosity measurements, friction reduction flow tests, and flow tests in porous media. These special studies showed that performance of the radioactive product was equivalent to that of the commercial product. A typical result of these tests is shown in Figure 1. The small differences in the polymer flow resistance factors are due to small differences in the textures of different sandpacks, rather than to differences in the chemical structures of the polymers. Friction reduction, viscosity, and retention experiments showed even closer agreements between properties of the radioactive and commercial product. 

Polymer flow resistance factors were computed from the equation below ... 

Figure 10 shows the polymer flow and residual resistance factor curve related to the experiments described in Figure 8. As can be seen, the polymer flow resistance factors stabilized at both 100% water saturation, and at residual oil saturation. The small differences in polymer flow resistance factors in these two experiments are probably due to small differences in pore structure from one pack to another.

The unsteady-state polymer flow resistance factors for any moment and distance can be determined from laboratory experiments, provided that the pressures are measured at an adequate number of locations. Combining these experiments with the determination of the flowing polymer concentration at difierent locations, the value of C it. or the absolute quantities of retained polymer can be determined for any location and for any time. 

The polymer flow resistance factor vs flow rate curve has a minimum in many cases [10]. It was also shown earlier [11] that over a critical flow rate an unsteady-state polymer flow can develop. In such a case, only the first value of the measured resistance factor will be on the resistance factor versus flow rate curve on its imaginary section (Figure 33). 

The polymer flow resistance factor shows a characteristic distribution as a function of distance in steady-state flow. This uniform distribution is due to the first invasion... 

Steady-state and unsteady-state polymer flow resistance factors at different distances from the injection face as a function of time. 

However, the exact values of the polymer flow resistance factors for any given distance coordinate can be determined if the pressure drops are measured in at least three segments of the porous body. The analytical solution of this problem is given in Appendix C. 

The average excess polymer flow resistance factor between 0—1 distance can be expressed as follows ... 

Figure 31 illustrates the obtained resistance factors as a function of time in the experiments described in the Procedure section. In the first pack, the resistance factor buildup is much faster than in the second pack. The first stop in flow resulted in a significant recovery in permeability to polymer solution. After resuming the injection, several hours were required to regain the maximum polymer flow resistance... 

Crosslinked polymer-like bulk gel used in water shut-off has very poor flowability the viscosity is very high (>10,000 mPa s). Uncrosslinked polymer is used to increase water viscosity. A movable gel is used in between it has the intermediate viscosity, and more importantly, it can flow under some pressure gradient. Colloidal dispersion gel (CDG) is a typical gel used in these situations. The mechanisms of a movable gel are (1) it has high viscosity to improve mobility ratio like an uncrosslinked polymer solution (2) it has a high resistance factor and high residual permeability reduction factor and (3) it has viscoelasticity so that the remaining oil in the rocks can be further reduced. 

Resistance is related to mobility, which includes the effects of both permeability reduction and viscosity increase. Obviously, the viscosity effect is not included in the residual resistance factor defined in Eq. 5.41 because water viscosity is used before and after polymer flow. Such a name convention is confusing. Therefore, we suggest the terms permeability reduction factor and residual permeability reduction factor be used. If the process were considered reversible, there would be no need for the term of residual permeability reduction factor. To include both permeability reduction and viscosity increase, we define another parameter, resistance factor (F,) ... 

September 23, 1994, followed by 0.327 PV ASP flood, and 0.273 PV polymer drive and water drive. The ASP solution viscosity was 16 mPa s. During water preflush, the oil recovery before ASP was 31.63% from the SII1.3 layer. The response to ASP injection was observed in November 1994 (after 0.0693 PV of injection). The average water cut in the entire pilot area decreased from 82.7% to a low of 59.7%, and the daily oil production increased from 37 mVd toapeakof91.5 mVd. The water injectivity decreased from 1.75 mV(md-MPa), stabilized at about 1.42 mV(m-d-MPa), and then dropped to 1.19 mV(m d-MPa). In general, after an ASP slug is injected, flow resistance increases, and water injectivity decreases. The simulation prediction showed about 20% incremental oil recovery factor over waterflood. The early performance matched very well with the simulation prediction. In this pilot test, the simulator used was GCOMP. 

From the pressure gradients determined for two flooding rates we are able to deduce the resistance factor RF, which serves as a measure of the flow resistance of the polymer solution in the pore space, as well as the residual resistance factor RRF. The factor RRF serves as a measure of the permeability reduction due to polymer material absorbed and retained in the pores. The values obtained for the VS/VA/AM-copolymers are particularly good. 

Fig. 1. A comparison of resistance factors during polymer flow developed by the radioactive and...

It was earlier pointed out that after the first invasion of a porous body with a polymer solution, the retained polymer shows a characteristic distribution. If, for the first invasion the flow parameters are chosen in such a manner that finally a steady-state flow is attained, this characteristic distribution of retained polymer will not change with time. This function determines a distribution of resistance factors. Then, if the flow rate is increased to a value above the critical velocity, the initial distribution of the resistance factors at this increased velocity shows also a characteristic distribution. Further analysis of the initial resistance factor distribution during unsteady-state flow is given in Appendix B. 

Fig. 10. The effect of residual oil saturation on polymer flow and residual resistance factors.

Abstract. This article describes a hydrodynamic model of collaborative flnids (oil, water) flow in porons media for enhanced oil recovery, which takes into account the influence of temperature, polymer and surfactant concentration changes on water and oil viscosity. For the mathematical description of oil displacement process by polymer and surfactant injection in a porous medium, we used the balance equations for the oil and water phase, the transport equation of the polymer/surfactant/salt and heat transfer equation. Also, consider the change of permeabihty for an aqueous phase, depending on the polymer adsorption and residual resistance factor. Results of the numerical investigation on three-dimensional domain are presented in this article and distributions of pressure, saturation, concentrations of poly mer/surfactant/salt and temperature are determined. The results of polymer/surfactant flooding are verified by comparing with the results obtained from ECLIPSE 100 (Black Oil). The aim of this work is to study the mathematical model of non-isothermal oil displacement by polymer/surfactant flooding, and to show the efficiency of the combined method for oil-recovery. 

They studied solutions of polyethylene oxide (a flexible coil, water-soluble polymer similar physically to HPAM) flowing through porous beds of different grain sizes and reported the onset of elastic behaviour at maximum stretch rate to be of the order 100 s and shear rates of the order 1000 s" More recently, Durst and Haas have made an extensive study of the flow of viscoelastic polymers in porous media (Durst et al, 1981, 1982. Haas et al, 1981a, b). They characterised the onset of high resistances by using a product of a resistance factor / and the Reynolds number Re, defined as ... 

The water mobility, may be further affected by the pore-blocking behaviour of the adsorbed polymer. This resistance to flow is thought only to affect the aqueous phase (White etal, 1973). It is related to a residual resistance factor (Jennings etal, 1971), RRF, corresponding to a final adsorbed level of polymer, Qf. The resistance factor, R, corresponding to a given adsorption level, Cg, may be given by a semi-empirical equation such as that used by Bondor etal (1972) ... 

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