Polymer rheology in porous media
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In this chapter, the important aspects of the rheology of non-Newtonian polymeric solutions as they flow through porous media will be described. This is sometimes referred to as the in-situ rheology of polymers, and one of the objectives here will be to compare and contrast this behaviour with the rheology of the bulk polymer solutions described in Chapter 3. It was noted in Chapter 3 that the bulk rheological behaviour of xanthan and HPAM is related to the molecular structures of these polymers. That is, the more rigid rod-type xanthan structure gave a purely pseudoplastic, inelastic solution at lower concentrations, whereas the flexible coil molecular structure of HPAM leads to solutions which show elastic behaviour even when fairly dilute. Again, as might be expected, the molecular structure plays an important role in determining the in-situ rheological behaviour. Another important factor is the microscopic structure and geometry of the porous medium itself. Clearly, the flows through a porous medium will be much more tortuous and complex than those found in rheometers where flows are well-defined (e.g. in capillaries, Couette flow, constant shear cone and plate flow, etc.). Thus, some aspects of the structure of porous media and how it may be represented by different mathematical approaches will be discussed. Prominent in the history of representing porous media is the simple idea of the capillary bundle (Dullien, 1979).
KeywordsPorous Medium Shear Rate Apparent Viscosity Effective Viscosity Deborah Number
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