Favorable Viscosity Research Articles

Effects of shear rate, viscosity ratio and liquid crystalline polymer content on morphological and mechanical properties of polycarbonate and LCP blends

AbstractStudies were conducted on the effects of shear rate, viscosity ratio and liquid crystalline polymer (LCP) content on the morphological and mechanical properties of polycarbonate (PC) and LCP blends. The LCP (LC5000) used was a thermotropic liquid crystalline polymer consisting of 80/20 of parahydroxybenzoic acid and poly(ethylene terephthalate) (PHB/PET). The viscosity ratio (viscosity of LCP: viscosity of matrix) was varied by using two processing temperatures. Due to the different sensitivity of materials to temperature, variation in the processing temperature will lead to varying viscosity of the components in the blends. Based on this principle, the processing temperature could be manipulated to provide a favourable viscosity ratio of below unity for fibre formation. To study the effect of shear rate, the flow rate of the blend and the mould thickness were varied. The shear rate has a significant effect on the fibrillation of the LCP phase. The effect was more prominent when the viscosity ratio was low and the matrix viscosity was high. At 5 wt% LCP, fibrillation did not occur even at low viscosity ratios and high shear rates. It was also observed that the LCP content must be sufficiently high to allow coalescence of the dispersed phase for subsequent fibrillation to occur.© 2002 Society of Chemical Industry

Effect of Bromination on the Properties of Ethylene-Propylene-Diene Rubber in the Presence of Divinylbenzene

Abstract The curing behavior and vulcanizate properties of EPDM and brominated EPDM (BEPDM) were compared using a dicumyl peroxide curing system. The BEPDM displayed lower torque and crosslink density, but better tensile properties than the EPDM. In the presence of divinylbenzene (DVB) coagent, all vulcanizates, i.e., EPDM, BEPDM, and their blends with natural rubber, had improved tensile properties. At low DVB concentration, the filler effect of DVB on the modulus enhancement was noticed. At high and comparable DVB concentration, both the BEPDM and NR/BEPDM blend showed significantly higher modulus (M100) and tensile strength than their EPDM counterparts. The BEPDM was also found to have higher crosslink density and storage modulus (E′) than the EPDM. This observation could be attributed to the better dispersion of DVB in the BEPDM and NR/BEPDM vulcanizates, as supported by TEM measurements. The TEM data is also consistent with the properties observed on the uncured mixes, in which the NK/BEPDM + DVB mix has favorable viscosity and die swell properties due to the more homogeneous DVB dispersion in the rubber phases. Thus, the bromination of EPDM has resulted in better processing and vulcanizate properties of the rubber and its blend with natural rubber.

In vitro comparison of soaking solutions for rigid gas-permeable contact lenses

The comfort of rigid gas-permeable contact lenses is influenced by multiple factors, including the composition of lens material and the presence of surface deposits and/or cleaning solution residues on the lens, as well as the direct effect of lens care solutions on the lens and eye. This study was designed to examine the comparative properties of several soaking solutions with respect to wettability, viscosity, and substantivity, which are essential to maintaining patient comfort. Solutions included in this trial were: OPTI-SOAK™ Conditioning Solution, Boston Advance ® Conditioning Solution, Boston ® Conditioning Solution, Barnes-Hind ® Wetting and Soaking Solution, Duracare™ Conditioning, and Total ® Cleaning, Wetting & Soaking Solution. Wettability, as indicated by mean wetting angle, was determined and OPTI-SOAK Conditioning Solution, followed by Boston Advance and Boston Conditioning solutions, respectively, yielded superior results. For viscosity, OPTI-SOAK Conditioning Solution again provided the most favorable (highest) viscosity, followed by Boston Conditioning and Barnes-Hind solutions. With regard to substantivity, a measure of sustained wettability, Boston Conditioning Solution achieved the highest measurement, followed by OPTI-SOAK and Boston Advance solutions. On the basis of this in vitro evaluation. OPTI-SOAK Conditioning Solution provided the highest potential for patient comfort based on a combination of wettability, viscosity, and substantivity.

On the Role of the Viscosity Ratio during Low-Capillary-Number Forced Imbibition in Porous Media

Abstract The role of the viscosity ratio κ during forced imbibition in porous media is investigated theoretically using a new simulator, and experimentally based on displacements in model pore networks. Both theory and experiment show that κ is an important parameter of microdisplacement in porous media, not only for intermediate and large capillary number values, but also for small values, say Ca -6 . In the latter region the residual nonwetting saturation S or is virtually independent of Ca for κ 1. The unexpected result is that, even for very small values of Ca, S or decreases appreciably as κ decreases, especially in the case of very good wettability. Simulations indicate that the effect of κ on S or for low Ca values is enhanced as the contact angle decreases. The phenomenon is attributed to a synergistic effect between capillary microfingering and localized viscous forces. It must be emphasized that the velocity gradients which are created locally by the advance of a single meniscus, or of a wetting film, are sufficiently large to make viscous stresses important, even when the Ca value of the macroscopic flow is very low (say, of order 10 -8 ). A favorable viscosity ratio reduces the extent of capillary microfingering and thus increases the efficiency of microdisplacement, despite the fact that for Ca -6 the viscous stresses are negligible on a macroscopic scale. Further work is needed to analyze the synergism between κ and θ e at low Ca values.

Use of Dispersion Relationships To Model Adverse-Mobility-Ratio Miscible Displacements

Summary Improved predictions of petroleum reservoir performance are needed to reduce the risks associated with field-scale miscible flooding. A major shortcoming of established prediction techniques is their failure to model accurately the effects of mobility ratio and viscous fingering on volumetric sweep and displacement efficiency. This paper establishes the feasibility of using physical dispersion relationships to account for fluid mixing associated with viscous fingering. The dispersion relationships use an additional parameter to incorporate a dependence on the local viscosity gradient. Adverse viscosity gradients increase mixing, while favorable viscosity gradients decrease mixing. The dispersion relationships reduce to the normal form when no viscosity gradients are present. The dispersion parameter needed is determined with published data for flow in a long, sandstone core system. Once established, the dispersion relationships are used to predict the performance of a much more complex displacement of reservoir oil by CO2. The simulations reproduce all the salient features observed experimentally and establish the validity of the approach. In particular, the effect of system length is modeled correctly.

Effect of adsorption on the optimal displacement of acidic crude oil by alkali

AbstractRecovery of acidic crude oil from porous media can be enhanced by injection of alkaline agents. For this process we have analyzed the detrimental effect of alkali adsorption on the mineral surface. The model, which is an extension of our earlier inert solid model, was formulated by conserving three independent species. The previous solution procedure is shown to fail and a new analysis of composition paths is necessary. By introducing the notion of critical point, a short‐cut procedure is developed.The predicted profiles and effluent histories are discussed. A new result is that adsorption on the solid surface could change the ultimate recovery even for an infinite slug of alkali due to the reduced influence of the optimal region in displacing oil. Further, the influence of a favorable viscosity ratio in displacing oil is also shown to be reduced by adsorption.

Some Surprises in the Transport of Miscible Fluids in the Presence of a Second Immiscible Phase

Abstract Displacements were conducted in Berea cores to gain insight into the mechanism of tertiary oil displacement and propagation by a micellar slug. Contrary to expectation, the first oil mobilized by micellar fluid was among the first oil (instead of the last oil) to be produced, giving the appearance of either viscous fingering or of unusually large dispersion. To eliminate the possibility of unfavorable mobility ratios caused by oil/water/surfactant interaction, we conducted several runs in which an injected hydrocarbon displaced another hydrocarbon, initially at residual saturation. In other experiments, water (the wetting phase) at irreducible saturation was displaced by a distinguishable injected aqueous phase. Injected hydrocarbon appeared in the produced fluids immediately after oil breakthrough, yielding behavior similar to the micellar-slug experiments. Even with a favorable viscosity ratio of less than 0.01, the apparent dispersion was huge. However, mixing zones in the wetting-phase displacements were quite normal and similar to those observed for single-phase flow Nonwetting-phase fronts (injected hydrocarbon displacing resident hydrocarbon) are smeared much more than wetting-phase fronts because the entrance of hydrocarbon into smaller water-filled pore throats is delayed until the capillary entrance pressure is overcome by differences in the flowing oil and water pressure gradients. Oil might not be displaced from the smaller pores until long after oil breakthrough. Nonwetting-phase dispersion, which occurs in many EOR processes, can be expected to be one or two orders of magnitude greater than dispersion measured in single-phase-flow experiments. Entrance of the wetting phase, however, is not delayed; hence, wetting-phase mixing zones are short.

A New Method To Simulate the Effects of Viscous Fingering on Miscible Displacement Processes in Porous Media

Abstract Dispersion and viscous fingering are important parameters in miscible displacement. Effects of dispersion on concentration profiles in porous media can be simulated when the viscosity ratio is favorable. The capability to simulate viscous fingering is limited. This paper presents a new method to simulate effects of viscous fingering on miscible displacement processes in porous media. The method is based on the numerical solution of a general form of the convection-dispersion equation. In this equation the convection term is represented by a fractional flow function. The fractional flow function is derived from Darcy’s law by using a concentration-dependent average viscosity and relative flow area to each fluid at any point in the bed. The method was extended to the description of a polymer flood by including retention and inaccessible PV. A Langmuir-type model for polymer retention in the rock was used. The resulting convection-dispersion equation for displacement by polymer was solved numerically by the use of a finite-element method with linear basis functions and Crank-Nicholson derivative approximation. History matches were performed on four sets of laboratory data to verify the model: (1) an unfavorable viscosity ratio displacement, (2) stable displacement of glycerol by polymer solution, (3) unstable displacement of brine by a slug of polymer solution, and (4) a favorable viscosity ratio displacement. In general, computed results from the model matched laboratory data closely. Good agreement of the model with experiments over a significant range of variables lends support to the analysis.

Rationalizing the Influence of Crude Wetting on Reservoir Fluid Flow With Electrical Resistivity Behavior

In laboratory tests designed to simulate a natural distribution of crude oil surfactants in porous rock, waterflood behavior may exhibit oil-wet characteristics, whereas electrical resistivity remains essentially the same as for water-wet systems. These observations agree with a hypothesis that considers the influence of pore-wall roughness on the contact angle in a rock/water/oil system. Introduction The literature confronts us with apparent contradictions when considering the wetting state of crude oil reservoirs. There abounds laboratory evidence that many reservoir systems behave in a neutral to oil-wet fashion in fluid flow tests. But data also have been reported showing that the electrical resistivity of highly oil-saturated rocks is extremely high. Electric logs of natural systems seldom find reservoir resistivities approaching the extreme. We also see little evidence of inverted saturation profiles we might expect in reservoirs if fluid profiles we might expect in reservoirs if fluid positions are reversed from the water-wet case. Thus, positions are reversed from the water-wet case. Thus, observed resistivity data appears to refute laboratory flow data that indicate some reservoirs to be oil-wet.Fluid flow behavior, comparing water-wet with oil-wet, is exhibited in two ways:the relative permeability to water is higher at any saturation in permeability to water is higher at any saturation in the more oil-wet case, resulting in an equal relative permeability to water and oil at lower water permeability to water and oil at lower water saturation when oil-wet, andin the oil-wet case, oil continues to drain from the rock during waterflood after water breakthrough whereas, in the water-wet case, at least for favorable viscosity ratios, oil production ceases shortly after water breakthrough. Experimenters have reported differences in electrical behavior in rock/water/oil systems of differing wettabilities. Their results can be summarized as follows. As oil saturation increases, the electrical resistivity increases far more dramatically in the more oil-wet systems than for water-wet systems. Some data have indicated that resistivity approaches infinity even at moderate water saturations. A common feature in these studies is that the oil-wet data were obtained on rocks or synthetic pore systems within which the entire internal surface had been coated with some surface active material, such as Dri-Film, to produce the oil-wet character. This results in an affinity of the total surface of the rock for oil. In other words, a complete reversal of fluid positions was achieved when compared to the water-wet case and, thus, resistivity became extremely high. But, if we consider the manner in which crude oil accumulates in a reservoir, it appears unlikely that the above process properly simulates how oil surfactants may deposit in real reservoir systems. Natural Crude Accumulation To describe the original distribution of fluids in an oil reservoir, two properties of the system must be explored. JPT P. 1459

Genesis of the melt rocks at Tenoumer Crater, Mauritania

A common problem encountered at probable meteorite impact craters is the occurrence of associated melt rocks, presumably produced by the impact event, that cannot be matched chemically to the target rocks. A similar situation is found at Tenoumer crater, Mauritania. Chemical analyses of 11 melt rocks range from felsic country rock values to much more mafic compositions in two well-defined chemical sequences. Only one of the melt rocks is essentially isochemical with the adjacent granodioritic country rock. This specimen consists of a heterogeneous glassy to cryptocrystalline groundmass commonly containing shocked country rock fragments and lechatelierite. It is clearly an impactite. Conversely, some of the more mafic melt rocks display reasonably normal igneous textures and may show no shock features whatsoever. Without the certain knowledge that all these rocks had a common genesis, some of these mafic rocks could be mistaken for products of endogenous magmatic activity. Neither meteoritic contamination nor vapor fractionation can explain the chemical sequences exhibited by these melt rocks. They most likely result from the combination of felsic country rocks with various amounts of an amphibolite vein that appears to strike through the center of the crater. The hypothesis is advanced that the amphibolite was preferentially incorporated in the impact-generated melt because of favorable kinetic and viscosity characteristics. Since mafic segregations are common in Precambrian metamorphic terrains, this mechanism may also explain other similar occurrences. The clear-cut evidence from Tenoumer makes it difficult to deny an impact origin for certain craters solely on the basis of associated melt rocks that are not isochemical with the country rocks.

Considerations in the Recovery of Bradford Crude by Composite Solvent Slugs

Abstract This investigation was made to evaluate the comparative effects of the viscosity and the phase behavior of the buffer fluid in the composite solvent displacement of Bradford crude from waterflooded sandstone cores. Buffer slugs of propane, naphtha and other refined hydrocarbons exhibiting increasingly favorable viscosity ratios and decreasing solubility relationships, respectively, with Bradford crude, were used in long Berea sandstone cores. The secondary slug was isopropyl alcohol. The results indicate that higher oil recoveries are obtained for increasingly favorable phase re lat ion-ships even when these are accompanied by unfavorable viscosity ratios within the range studied. Moreover, when propane is used as a buffer slug with an adverse viscosity ratio of 36, it gives higher oil recoveries than at a similar size slug of an amyl alcohol having a viscosity ratio of 1.09.The investigation was extended to the study of the effect of flooding rate on oil recovery. Residual Bradford crude was displaced from a 6 - ft Berea sandstone core at rates varying from 0.3 to 30 ft/ day. The results show that as flooding rates were increased above or decreased below a minimum range of 1 to 2 ft/day, displacement efficiency increased considerably. Introduction In recent years, the alcohol slug process as a means of tertiary recovery has been the subject of many investigations. Gatlin and Slobod showed the advantages of the combination solvent slugs over the previous single-slug process. The combination slugs require less total slug material to obtain similar oil recoveries. The basic combination process involves injecting a primary or buffer solvent which is preferentially oleophilic, followed in turn by a water-driven slug of isopropyl alcohol. This procedure ensures that the buffer slug, which is miscible only with the reservoir oil, displaces and replaces the oil and is in turn displaced, together with the water, by the isopropyl alcohol slug miscible with both fluids. Likewise, for those reservoir oils that show some degree of phase incompatibility with isopropyl alcohol, as does Bradford crude, a proper buffer solvent can artificially make the alcohol process technically feasible. From an economic standpoint, propane or LPG would be the most appropriate primary solvent to be used in the field; however, Taber, et al have indicated that the alcohol process becomes highly inefficient in the displacement of light hydrocarbons because of the entrapment of these hydrocarbons during the stabilized bank formation. Moreover, since materials such as propane have such low viscosities, adverse viscosity ratios with most reservoir oils would be generated, thereby possibly further reducing the efficiency of the buffer solvent. This paper presents the results of an experimental study of the comparative effects of viscosity ratio and phase relationships on the displacement efficiency of Bradford crude by means of dual solvents. The work was extended to include the effect of flooding rate on oil recovery. Rates within the range of field and laboratory values were used. EXPERIMENTAL PROCEDURE APPARATUS The porous media used in this study consisted of two 10-ft and one 6-ft Berea sandstone cores, 3-in. in diameter. These were cast in galvanized steel pipe of 3/12-in. ID and the annulus was filled with Armstrong cement. The 10-ft cores were assembled by connecting two 5-ft units, which were joined together by 8-in. steel flanges fitted to the pipe. Intimate contact between the two sections was obtained by inserting a thin disk of the same sandstone between the core faces. The outlet and inlet ends of the cores were covered with threaded pipe caps. The injected fluid was gravity fed to two variable-rate positive-displacement pumps. SPEJ P. 45ˆ

The Effects of Gravity Segregation in Laboratory Studies of Miscible Displacement in Vertical Unconsolidated Porous Media

Abstract This study of the effect of gravity segregation was carried out in a vertical core of unconsolidated sand, 4 ft long and 2 in. in diameter. Fluids of varying viscosity and density were injected into the top of the core and moved at constant rates of 25, 50 or 100 ft/day by use of a positive displacement pump. The composition of the efflux was analyzed by measurement of the refractive index. The main variables in this study were in viscosity ratio, the density difference between in-place and displacing phases, and the rate of flow. The experiments fell into four logical groups:favorable viscosity ratio and favorable density difference;favorable viscosity ratio and unfavorable density difference;unfavorable viscosity ratio and favorable density difference; andunfavorable viscosity ratio and unfavorable density difference. The behavior of these four systems at various rates of flow was determined by measuring the length of the mixing or transition zone which developed between the displaced and displacing phases. The data indicated that gravity segregation could act to shorten this mixing zone when the displacing material was the less dense phase, and lengthen the zone for unfavorable density differences. The magnitude of the effect was most marked at slow rates when sufficient residence time existed to allow significant flow to occur. The change in the length of the mixing zone with density difference, rate and viscosity ratio was plotted, and from these graphs it became evident that the length of the mixing zone was really dependent upon the ratio of the viscous forces to the gravity forces. If the ratio of these quantities is used as a parameter, we find that the plots of mixing zone length vs the dimensionless quantity V/Vc, yields a greatly simplified presentation of the data. Such plots confirm the importance of the ratio of the viscous forces to the gravity forces in analyzing the flow behavior in vertical systems. Introduction The idea of using miscible phase displacements to increase recovery of crude oil has been under active study for more than 15 years. Most of this work has been carried out in the research laboratories of the industry and in universities. In such studies a great deal of attention has been directed toward determining the amount of miscible material required to recover all of the oil from a porous medium. The nature and extent of the mixing zone which develops between the two miscible materials has also been observed for many situations, including those where the fluids used have different densities. In many of the cases where density differences exist, however, the effect of gravity segregation on the mixing zone has not been explicitly studied. It seems quite likely that serious errors might be present in such experimental work. That is, the literature presents certain data which suggest changes in efficiency of the process as a result of some explicit change in a variable, when it may well be that the change in the efficiency results from gravity effects. The objective of this study, therefore is to determine the effect of density differences of miscible fluids on the observed efficiency of the displacement process. Since such density differences cause selective movement of fluids within the porous medium, the study becomes vitally concerned with gravity segregation. Moreover, since the amount of gravity segregation which can occur for a given set of fluids depends upon residence time, the rate of flow in these experiments also becomes an important variable. Finally, since the actual distribution of the fluids within the system (fingers, etc.) also affects the results, the viscosity ratio is another pertinent variable. Hence, this study may be characterized as a determination of the nature of the mixing zone between miscible phases as a function of density differences, viscosity ratio, and rate of flow. Fortunately these variables are inter-related. SPEJ P. 1ˆ

Mathematical Model of an Unstable Miscible Displacement

DOUGHERTY, E.L., CALIFORNIA RESEARCH CORP., LA HABRA, CALIF. JUNIOR MEMBER AIME Abstract A phenomenological theory for a one-dimensional unstable miscible displacement similar in type to the Buckley-Leverett model but including the effects of mixing is proposed An equation giving the fractional flow of pure solvent through an oil phase containing dissolved solvent is derived including the effects of gravity and nonhomogeneities. Numerical integration of the resulting pair of nonlinear hyperbolic partial differential equations gives volumes of dissolved and undissolved solvent as functions of space and time. Parameters in the model which characterize mixing due to dispersion were determined from experimental data; the parameters correlated with viscosity ratio. The results indicate that the rate of dispersive mixing is proportional to volumetric flow rate Incorporated into our equations were Koval's heterogeneity factor H, which characterizes mixing due to channeling. This allowed satisfactory predictions of displacement behavior observed in horizontal floods in nonhomogeneous cores; but in most cases the values of H which we used were considerably larger than those used by Koval. Introduction It has been shown that for favorable viscosity ratios, the diffusion equation with convection satisfactorily describes the behavior of a miscible displacement in a porous media. Numerous attempts to develop a satisfactory mathematical description for the case of unfavorable viscosity ratio have been reported, but they have met with only partial success. These attempts, which are reviewed by Koval, have taken two approaches:development of a flow model akin to the Buckley-Leverett approach for immiscible displacement neglecting the effects of mixing andsimultaneous application of Darcy's Law for flow and the diffusion equation with a convection term for mass transfer. We set out to construct a mathematical model of Type 1 including, though, the effects of mixing. Based upon a set of hypotheses, we derived a pair of non-linear hyperbolic partial differential equations which describe in a one-dimensional system the combined effects of flow and mixing. To work with these equations it was necessary to develop a fractional flow formula. The combined system was integrated numerically using the method of characteristics.In our equations the mixing process is characterized by four parameters. Three of these, labeled beta, p and p, account for dispersive type mixing. The fourth is the heterogeneity factor H, proposed by Koval to account for channeling due to nonhomogeneities in the porous media. Values of the parameters which would cause agreement between theory and experiment were determined by trial-and-error for miscible floods conducted in horizontal cores of both homogeneous and heterogeneous materials. Calculations were also performed for vertical floods in homogeneous cores.The purpose of this paper isto present the details of the mathematical analysis,to present the results of the calculations,to consider what light the results shed on the mixing process in an unstable miscible displacement, andto provide a firmer foundation for the correlation technique developed by Koval for predicting the behavior of unstable miscible floods. STATEMENT OF PROBLEM The problem is to construct a mathematical model which describes in one dimension the observed behavior in an unstable miscible displacement. The approach is phenomenological in that the equations are based on assumptions which violate certain physical precepts known to apply to the displacement phenomenon. However, the assumptions do allow us to account mathematically for the more essential phenomena. The work is of value if we can quantitatively predict experimental results which heretofore could not be predicted, even though the synthetic nature of the model belies complete explanation of the observations.We assume that the system is comprised of two contiguous flowing phases. One phase, which we call free solvent, has the properties of pure solvent. We call the fraction of the pore volume occupied by this phase the solvent saturation, designated s. SPEJ P. 155^

Experiments on Mixing During Miscible Displacement in Porous Media

Abstract The paper describes experiments on miscible displacement in various porous media and the results of these experiments. Both glass bead packs and natural cores were used. Bead diameters varied from 0.044 to 0.47 mm, and pack lengths varied from 83 to 678 cm. Natural cores used were Berea and Torpedo sandstone. By taking samples as small as 0.5 cc and using refractive index for analysis, the data on break through curves could be plotted to within ± 0.5 per cent. To plot the data correctly on error function paper, a parameter (Vp - v)/vV was used which allowed for the predicted growth of the front as it moved past the observer. The change in the amount of mixing (length of mixed zone) was studied by varying velocity, length of travel, bead size, viscosity ratio and pack diameter. When the displaced material was less viscous than the displacing material (favorable viscosity ratio), these changes were adequately predicted by theory. When natural cores were used, rather than glass beads, the amount of mixing was greatly increased - also qualitatively predicted by theory. In experiments with favorable viscosity ratios in which the ratio was varied from 0. 175 to 0. 998, it was found that the rate of mixing was changed by a factor of 5. 7. Thus, the rate of mixing is strongly affected by viscosity ratio, even when the theoretical error function relationship for mixing is valid. Experiments using fluids with viscosity ratios near 1.0 showed that the instability effects of even a slightly unfavorable viscosity ratio (1.002) caused disproportionately more elongated breakthrough curves than found with a favorable viscosity ratio (.998). When the viscosity ratio was as high as 5.71 these instability effects were much more pronounced, as evidenced by the shape of the breakthrough curve. The displacements at viscosity ratios above 1.0 no longer followed the theoretical error function curve.

The Deterioration of Miscible Zones in Porous Media

Published in Petroleum Transactions, AIME, Volume 213, 1958, pages 228–235. Abstract Recent literature shows that pronounced increases in oil recovery can result from the use of miscible systems in recovery operations. This literature also points out certain problems associated with maintaining miscibility, e.g., compositional changes resulting from alterations in pressure and temperature or from zone dilution. The purpose of the work described in this paper was to study miscible zones for possible use in waterflooding operations and examine the manner in which these zones break down. The fluid system selected for study was oil - tertiary-butyl alcohol - water, which, because of its narrow range of miscibility, is ideally suited for investigation in short, linear systems. The laboratory-observed effects on oil recovery and zone stability of a number of variables are reported. Among the variables investigated were miscible zone size, viscosity ratio, length of travel, and interstitial water saturation. Results obtained with this system show that interstitial water adversely affects recoveries because of premature phase break. Salinity of the water further aggravates this situation. This effect, although pronounced for this system, would probably occur in any fluid system containing an alcohol. As expected, viscosity ratio has a decided influence on recovery efficiency and zone stability. The results also show that use of a sufficient zone size, even though the system has poor phase characteristics, yields higher oil recoveries than are obtained from straight water floods. Length-of-travel studies showed a square root relationship between zone growth and path length for favorable viscosity ratios. No such clear-cut dependence was observed under unfavorable viscosity conditions. Introduction As new oil reserves have become increasingly more difficult and expensive to find and develop, the oil industry has devoted more and more time and money to finding more efficient methods for exploiting known reserves. The increasing number of water floods is one manifestation of this attempt to improve oil recoveries from existing fields. Since considerable quantities of oil are by-passed by the waterflood process, it is only a partial answer to the problem. The search continues.