This paper was prepared for the Society of Petroleum Engineers Symposium on Mechanics of Rheologically Complex Fluids, to be held in Houston, Tex., Dec. 15–16, 1966. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Introduction This communication presents an extension of an earlier study by Christopher and Middleman of the applicability of a non-Newtonian generalization of the Blake-Kozeny equation to the laminar flow of non-Newtonian polymer solutions through porous media. The earlier work, done with dilute aqueous solutions of carboxymethylcellulose, indicated that the model put forth correlated data with an average error of 18 per cent and a standard deviation of the friction factor of 0.21 over a range of three orders of magnitude in a modified Reynolds number. A survey of the literature available at that time indicated some evidence of viscoelastic effects, in contrast with the conclusions drawn by Christopher and Middleman it was decided to extend the earlier study by examining a more elastic fluid, polyisobutylene dissolved in toluene. In addition, data were obtained for tubes packed with sand, and for tubes packed with binary mixtures of glass spheres. We still fail to see viscoelastic effects. The basic experimental techniques, and the methods of reducing and correlating the data, are as described by Christopher and Middleman and in more detail by Christopher and by Gaitonde. Polyisobutylene [PIB L-100, Enjay Co.] solutions in toluene were run at 25.0 deg C. Power-law parameters were obtained from capillary viscometry performed over a range of shear rates corresponding to the shear rates achieved in the porous medium. Table 1 shows the solution properties, including the zero-shear viscosities of the solutions and the viscosity average molecular weight of PIB L-100. CORRELATION OF DATA Fig. 1 shows the friction factor-Reynolds number correlation of the data obtained using tubes packed with glass spheres of a narrow size range. The data are correlated with an average error of 9.8, per cent and a standard deviation of 0.14 by ........................................(1) where ........................................(2) and ........................................(3)

Abstract This work was undertaken to define the conditions under which the Deborah number characteristic of the flow process may become large enough to cause significant deviations from the usual drag coefficient-Reynolds number relationships for purely viscous fluids flowing through porous media under non-inertial conditions. The analysis suggests that major [order-of-magnitude] effects may be expected to occur at Deborah number levels in the range 0.1 to 1.0. Experimental studies using a porous medium, having a permeability of 46.4 × 10-0 sq cm. support this analysis and define the critical value of the Deborah number at which viscoelastic effects are first found to be measurable. Prior studies, in which no effects attributable to fluid elasticity were found, are seen to have been confined to lower Deborah number levels. The influences of a high Deborah number level upon the uniformity of the flow and upon the distribution of the fluid residence times in the porous medium are considered briefly. Introduction While the pragmatic significance of studies of flows through porous media requires no discussion, there is additionally a very strong motivation for such studies from a strictly theoretical point of view: flows in this geometry provide an excellent opportunity for a study of the behavior of viscoelastic 25 fluids at high levels of the Deborah number. This dimensionless group, representing a ratio of time scales of the material and the flow process, may be defined as: ........................................(1) in which f1 denotes the relation time of the fluid under the conditions of interest in the problem under consideration and IId represents the second invariant of the deformation rate tensor. This latter term depicts the intensity or the magnitude of the deformation rate process, and the dimensionless group defined by Eq. 1 may be considered to represent the ratio of the size interval required for that fluid to respond to a change in imposed conditions of deformation rate as compared to the time interval between such changes. It is thus an index of the extent to which the velocity field is unsteady from a Lagrangian viewpoint [i.e., from, the viewpoint of an observer moving with a given fluid element as it proceeds its course or trajectory in a process], using the relaxation time of the fluid as a wait of time. For perfectly steady flows (e.g., under laminar flow conditions in a very long tube the Deborah number is identically zero; for highly unsteady processes it may be large. It has been shown elsewhere that quantitative mathematical descriptions of the properties of viscoelastic fluids rather generally predict a fluid-like response to be exhibited whenever the Deborah number is sufficiently low, and that the same materials will exhibit an essentially solid-like response whenever the Deborah number becomes large. In the case of dilute polymeric solutions in steady laminar shearing flows [NDeb = 01], the fluid-like response is, of course, well known and requires no further discussion. That the same materials may behave as elastic solids when deformed suddenly enough [NDeb large] may be demonstrated dramatically by impacting a blunt object suddenly upon a pool of such a "fluid": in this case the material may deform appreciably [sheets 6 to 20 in. in diameter are readily formed], but it retracts elastically to its initial configuration, rather than flowing or splashing as a Newtonian fluid does.