Three-phase oil/water and gas/water experiments were performed to investigate the dependence of relative permeability on wettability. Quantitative fluid saturations were determined with an X-ray computer-aided tomography (CT) scanner. Oil, water, and gas distributions generated in 3D were found, in some cases, to be highly nonuniform and dependent on experimental conditions. Results indicate that some traditional thinking about measuring relative permeability may be in error and merits further investigation.
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.
This paper was prepared for presentation at the 1999 SPE Mid-Continent Operations Symposium held in Oklahoma City, Oklahoma, 28-31 March 1999.
Ths paper wee selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(a). Contenta of the paper, as presented, have not bean reviewed by the Society of Petroleum Engineers and are aubjacf to sorraction by the autho@). The material, as presented, does not necessarily reflect any positionof the S@ety of Petroleum Engineers, ils offtc4rrs, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Permieaion to wpy is raatriotadto an abstrati of not mora than S00 words. Muatrationamay notbe copied. The abstract shouldoontainoonapicuouaacknowledgmentof where and by whom the papar is praaantad. Writs Publications Manager, SPE, P.O. Box 8S38S6, R!chardaon, TX 750SS-SS2S.Telex, 720SS9 SPEDAL. ASSTRACT boiling point (FBP) less than 538°C (lOOO°F). A Simulated distillation by gas chromatography isproposed extension for analyzi ng oi1 with FBP useful for determining compositional changes in greater than 538°C (8) has not been officially accepted due to the indirect method in which the crude oi1s undergoing enhanced oil recovery. Area noneluted fraction of the oi1 is estimated. This counts generated by simulated disti1lation are method involves adding an internal standard (ISTD) shown to correspond to weight rather than volume fractions by comparing simulated distillation mixture to the oil and calculating the noneluted oil fraction by comparing the ratio of ISTO and oil results to true boiling point results for three to their associated GC responses. Although this oils.Recent applications of simulated distillation are discussed including light end enrichment procedure does not involve a direct measurement of the noneluted material, simulated distillation of crude oil in a CO pilot, determination of visianalysis of whole oils has proven useful and cracking in thermal ?aboratory studies, and contamination of heavy oils.The use of an internal reasonably accurate for a wide variety of applications. standard to calculate the noneluted, heavy~rac~iOff of the oil has proven useful and reasonably accurate for a wide variety of applications. HETWHI OF ANALYSISThe experimental procedure for simulated distilla- INTROOUCTION tion is outlined in ASTM D2887-84.Analysis was Table 1 occurs. Distillation analysis is useful for determining performed on a Hewlett Packard 5840 gas chromatography equipped with a flame ionization detector compositional changes in crude oils undergoing en-(FID) and automatic liquid sampler. Operating conhanced recovery where mass transfer between phases ditions for the chromatographyare listed in True boiling point distillation as desand have been described previously by Chorn (6). cribed by ASTM method D2892 (1) is an effective means of characterizing the boiling distribution ofApproximately one microliter of a diluted oil a crude oil.Unfortunately, conventional distillation is time consuming and requires a large oil sample is injected into the chromat...
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