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Polymer Flooding: The Essential Elements for Laboratory Evaluation
G. Chauveteau (Institut Francais du Petrole) | N. Kohler (Institut Francais du Petrole)
Abstract
Laboratory studies of Pusher and Kelzan solution behavior were carried out in a shaly sand containing a viscous oil and a low salinity brine, in order to prepare a polymer flood in a given field.
So, highly accurate reconstitutions of fluids and porous media were used. Long-duration floods through long sandpacks with stoppages followed by flow resumptions and rate variations, showed the complex rheological behavior of polymer solutions in porous media. Results of polymer solutions in porous media. Results of this investigation are: (1) a slow increase in mobility reduction during a long-duration flood; (2) a sudden drop in this value and no change in retention when flow resumes after a stoppage; (3) a reversible increase in retention in relation to a rate increase; (4) a considerable spreading out and often dissymmetry of polymer concentration curves; (5) for polymer-solution flow an effective pore volume less than that for brine.
An interpretation is proposed for all these observations taking the following factors into account: (1) the extreme dispersion of local flowrates inside the porous structure; (2) the effect of elastic stresses on the flow of such solutions in pores; (3) the effect of diffusion.
This analysis of the importance of dynamic retention was completed by a study of retention by adsorption. Injecting a slightly acid solution strongly affects adsorption and produces a very sharp increase in mobility reduction.
Then porous media and fluids from a field were used to analyze degradation processes and especially the problems encountered with some additives, oxygen and bacteria. Well-defined experimental conditions must be carefully respected to obtain a meaningful prediction of polymer performance inside a reservoir. polymer performance inside a reservoir