This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., April 22–24, 1974. 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 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. 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.
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:
a slow increase in mobility reduction during a long-duration flood;
a sudden drop in this value and no change in retention when flow resumes after a stoppage;
a reversible increase in retention in relation to a rate increase;
a considerable spreading out and often dissymmetry of polymer concentration curves;
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:
the extreme dispersion of local flowrates inside the porous structure;
the effect of elastic stresses on the flow of such solutions in pores;
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
Evaluating the performance of a polymer flood in a given field requires an understanding not only of the rheological behavior of solution under reservoir conditions, i.e. the mobility and permeability reductions of the aqueous phase, but permeability reductions of the aqueous phase, but also of their interactions with the reservoir rock, i.e. mainly retention but likewise any change in the solution during contact with the porous medium. Yet the rheological behavior depends to a great extent on the phenomenon of overall retention, whether due to adsorption or to flow dynamics. Adsorption is related to the surface properties of the porous medium. So it depends on the equilibrium between the fluids and the rock.