Summary
Experiments in both Berea sandstone and sandpacks have been conducted to measure dispersion and steady-state relative permeabilities. Measurements have been made on both high-tension brine/oil and a low-tension, three-phase, brine/oil/surfactant/alcohol mixture. One interesting aspect of these experiments is the amount of microemulsion phase trapping. The endpoint microemulsion saturations for both the oil/microemulsion and brine/microemulsion phase pairs were high even at 10–3 dyne/cm [10–3 mN/m] interfacial tension (IFT). The dispersion was measured for each phase with radioactive and chemical tracers. The dispersivity was found to be a strong function of phase, phase saturation, porous medium, and IFT. Values of the dispersivity varied by two orders of magnitude over conditions investigated to data. Extremely early breakthrough of the tracer used in the oil phase (carbon 14) at high tension is especially remarkable. The brine tracer (tritium) curves were similar to that for 100% brine saturation except for a shift caused by material balance reasons. The classical solution to the convection-diffusion equation for single-phase flow has been generalized to multiphase flow and was used to aid in interpreting these data. This combination of relative permeability and dispersion in each phase of the experiment with a high-concentration, three-phase-microemulsion sulfonate formulation is believed to be new, and more directly applicable to commercial surfactant flooding than previously reported experimental results.
Introduction
In this paper we report the initial results of a project1 to investigate the transport in porous media of several chemicals used in EOR. Specifically, we are studying the behavior of high-concentration, three-phase micellar formulations in beadpacks, sandpacks, and sandstone. The rheology, relative permeabilities, and dispersion coefficients have been the primary focus of this study to date. In this paper, we report on the last two parameters for a single polymer-free micellar formulation. These results are based on the theses of Delshad2 and MacAllister.3 The rheology of this and other EOR fluids is reported in Ref. 4. Oil recovery and history matching was done by Lin.5
A unique feature of this work was the way in which the relative permeabilities and dispersion experiments were combined into essentially the same experiment (see the section on procedures and materials). Since trapping has a profound effect on the efficiency of micellar/polymer flooding, another important feature is the measurement of microemulsion phase trapping at each relative permeability endpoint. These are believed to be the first direct measurement of this type.
Literature Review
No attempt will be made here to review the numerous high-tension relative permeability studies reported during the past several decades. Also, only a few of the classical single-phase flow dispersion studies will be mentioned.
Low-tension data are much less extensive. Leverett,6 Mungan,7 du Prey,8 Talash,9 Bardon,10 Batycky,11 Klaus,12 and Amaefule and Handy13 are among the few who have reported results as a function of IFT. All of these results were for two-phase fluids. Furthermore, apparently only Talash, Klaus, and Amaefule and Handy used fluids containing sulfonates such as we are primarily concerned with, and then only at very low sulfonate concentrations.
The general observations are that the relative permeability curves tend to increase and have less curvature as the IFT decreases or the capillary number increases. The residual saturations decrease simultaneously. Consistent with the capillary desaturation curves and theory reported by others,14–16 the nonwetting-phase saturation decreases first, then the residual wetting phase. It has been speculated for a long time that these curves will eventually become straight lines, but few if any of these experiments attained the ultralow IFT typical of optimal micellar fluids that would be necessary to test this idea.
A CUSTOMIZED QUASI THREE-PHASE DRAINAGE RELATIVE PERMEABILITY MODEL FOR SOME INDONESIAN WATER-WET SANDSTONES
