Correlations based primarily on theoretical models of polymer flow in porous media assume that the power-law index for polymer flow in porous media, <,> is identical to the power-law index determined from rheological measurements. This is not a good assumption, and tic for fio i porous media must be determined from analysis of experimental data. Several polymer/rock systems have been studied in which 26.27,38 en sufficient experimental data are taken, correlations may be developed relating polymer mobility to polymer and rock properties. Willhite and Uhl26 correlated and tic with k p for three xanthan concentrations with Eqs. 5.23a through 5.23g. Units for are [Pg.22]

The theoretical basis for spatially resolved rheological measurements rests with the traditional theory of viscometric flows [2, 5, 6]. Such flows are kinematically equivalent to unidirectional steady simple shearing flow between two parallel plates. For a general complex liquid, three functions are necessary to describe the properties of the material fully two normal stress functions, Nj and N2 and one shear stress function, a. All three of these depend upon the shear rate. In general, the functional form of this dependency is not known a priori. However, there are many accepted models that can be used to approximate the behavior, one of which is the power-law model described above. [Pg.387]

The correlations represented by Eqs. 5.26a through 5.26e can be extended to interpolate for polymer concentrations between 1,000 and 2,000 ppm by use of a correlation based on the modified Blake-Kozeny model for the flow of non-Newtonian fluids. 62 Eq. 5.27 is an expression for A bk derived from the Blake-Kozeny model. Note that all parameters are either properties of the porous medium or rheological measurements. Eq. 5.27 underestimates A/ by about 50%. However, Hejri et al. 6 were able to correlate pBK and A for the unconsolidated sandpack data with Eq. 5.28. Eqs. 5.27 and 5.28, along with Eq. 5.24, predict polymer mobility for polymer concentrations ranging from l.,000 to 2,000 ppm within about 7%. [Pg.22]

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