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Foamy oil transport as a multiphase flow system. In some heavy and extra heavy oil production fields in Venezuela the oil production occurs due to the gas in solution, which tends to form a foam, consisting of a dispersion of gas and water in oil.

Foamy oil behavior at reservoir conditions and its transport process through porous media have been the focus of many multiphase flow researches. However, few studies have been developed at surface conditions, in which the oil viscosity increases considerably and the gas bubbles that are trapped in the foamy oil are expanded due to the change in pressure and temperature.

Transportation of foamy oil through pipelines is a challenge in Venezuelan fields due to the relatively high gas volumes produced with oil. Part of this gas is dispersed as foam and the rest flows as a separate phase generating different flow patterns in the pipelines.

This experimental study is focused on the behavior of a multiphase mixture composed by foamed emulsion, with high oil viscosity flowing through horizontal pipelines.

The evaluated conditions correspond to 8. Three different flow patterns were obtained: Foaminess and foam stability were found to be dependent on the operational conditions. Foamability increases with the increment of the gas and liquid flow rates, while foam stability tends to decrease when the liquid flow rate increases and the gas flow rate decreases. Las condiciones evaluadas en este estudio corresponden a un 8. Understanding the behavior of this foamy oil flowing through pipelines is necessary in order to develop more accurate models for the design and evaluation of the multiphase flow systems used to transport these heavy oils at surface conditions.

According to Shohamthe single-phase flow hydrodynamics systems are well understood, however, the simultaneous flow of two fluids is considerably more complex due to the presence of the gas and liquid phase. For two-phase flow, it is necessary to consider operational variables as: Ishii and Hibiki coincide with Shoham saying that developing the constitutive equations required to specify the thermodynamic, transport and chemical properties of the multiphase streams are considerably more complicated in comparison to single-phase flow due to the complex nature of two or more phases flowing together with a mobile and deformable interface, in which different flow patterns can be present.

For the case of gas-liquid systems, according to Shohamdifferent flow patterns can exist, in the case of segregated flow. It is possible to find stratified smooth or wavy flow at low gas and liquid flow rates, annular and annular wavy flow for very high gas flow rates, intermittent flow patterns, called slug flow or elongated bubbles, depending on whether there are gas bubbles dispersed in the slug body or not, and finally, the dispersed bubble flow which occurs at very high liquid flow rates.

In the case of oil dominated systems, which are the focus of this work, twelve flow patterns were identified and classified, depending on the gas-liquid spatial configuration and the oil-water configuration. Three-phase flow systems for high oil viscosity is a topic that has been calling the attention of the multiphase flow research community recently. This is due to the significant reserves of heavy and extra-heavy oil EHOand the imminent production of gas and water caused by water coning or channeling in reservoirs or to vapor injection as predominant enhanced oil recovery method for oil production.

InBannwart et al. They found that the increment in the total pressure drop is directly proportional to the superficial gas velocity in the pipeline and proposed a pressure drop model based on Lockhart-Martinelli model obtaining a good fitting.

They obtained experimental data of holdup in the pipe, pressure gradient and flow pattern which were compared against the unified model proposed by Zhang and Sarica They found significant discrepancies between the experimental results and the model predictions.

There is still a large controversy regarding the phenomenology of these foamy EHOs as it is not clear which the mechanisms that stabilize these non-aqueous foams are Belandria, According to SchmidtEdward et al. Another alternative is mutlifasico consider the effect of the high interfacial viscosity promoted by the presence of substances, liquid crystals deposited at the interface, and the low rates of drainage mlutifasico film inter-bubbles.


They found that there is an optimum concentration of water at which the stability of the foam increases, and small quantities of water and surfactants produce a drastic change in the foaminess ,ultifasico the oil.

In addition, Marcano et al. The hypothesis, presented by Marcano et al. They also suggested that gas bubbles are stabilized due to the rearrangement of water droplets dispersed in oil Figure 2surrounding the interface and increasing the superficial viscosity and elasticity associated to smaller droplet sizes in the emulsion.

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The studies of Adil and Mainisuggest that multitasico promote crude foamability. In contrast, Tang and Firozabadi and Sheng et al. Belandria studied the effect of solids in non-aqueous foam with mineral oil viscosity up to 0.

Above this value it was not possible to form foam under the studied conditions. Foamy oil at reservoir conditions exhibits a behavior typical of a non-Newtonian fluid, with lower viscosities than the oil and less resistance to flow. Foam is essentially an unstable thermodynamic system where the interactions are extremely complex and depends mainly on the following factors: The experimental facilities are composed by two horizontal flow loops with different diameters 0.

The sections in the flow loops are Figure 3: The liquid flow rate is measured with Coriolis flow meters. In this study, the liquid phase was water in oil emulsion.

The length diameter ratios for the different sections are as indicated in Table 1.

Around 56 experimental points were carried in the 0. The operational conditions used in this study are presented multifazico Table 2. Before starting the experiments, the tank was filled up with mineral oil, and was carefully mixed with 8. This surfactant is a fatty acid mixture of CC18 and its salts generated by the reaction with the Monoethanolamine MEA ; this simulates the natural surfactants present in most of the Venezuelans crude oils Marcano et al. After preparing the liquid phase, it was recirculated during 30 min at a fixed flow rate in order to obtain water in oil emulsion.

Once the emulsion was formed, it was mixed with air until meta-stable foam was produced. Table 3 presents the properties of the fluids used. For each experimental point the hydrodynamic parameters were kept constant with time, namely: Once the dynamic test multifaasico were achieved and one experimental point was obtained, the foam was separated by gravitational separation in the tank for 24 hours.

The emulsion viscosity was determined using a viscometer of concentric cylinders type HAAKE RC, while density and mass flow rate were quantified using a Coriolis flow meter. Foamability and foam stability were studied in two stages, one of them consisting of taking samples of each experimental point in 3 graduated cylinders, and the other one consisting of trapping a volume of the fluid in the pipe using quick closing valves, repeating each point three times.

Then, with the relation between multifaisco maximum foam height and the liquid height after total foam breakup, it was possible to determine the foamability.

Flujo Multifasico III : Flujo Vertical & Flujo Inclinado

The stability of each system was determined using the half-life time of the foam, which corresponds to the time at which the column height is half the original foam height.

During the experiments, it was observed that foam and a separate gas phase were flowing simultaneously in the pipe, forming different flow patterns similar to the case of gasliquid systems flowing in horizontal pipes. Foam samples were taken under dynamic conditions and foamability and foam stability were studied.

Three different flow patterns were obtained, namely annular flow, slug flow and stratified wavy flow, depending on the gas-liquid ratio used in the test. Figure 4 shows pictures of the flow patterns obtained in this study and Figure 5 the corresponding pressure response in pipeline.

It is possible to identify in the plots of pressure signal against time the significant instability effect in the slug flow due to the intermittency of this flow pattern, and a lesser instability in the pressure response for a foamy segregated flow pattern, as the gas phase and the foamy emulsion phase are separated in the case of stratified flow and annular flow. Similar results were presented by Bogdanovic et al.

However, in this study the non-oscillating pressure corresponds to the segregated flow pattern. Characteristics of the foam emulsion. In order to represent the characteristics of the Foamy Oil, a highly viscous mineral oil with a viscosity of 0. The liquid mixture contains a water cut of 8.

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The dispersion morphology was analyzed using optical microscopy. The foamability and foam stability studies of the system were conducted in two different ways: These figures show the foam evolution with time. The foam life and the behavior of the different stages of the foam: The coarsening process presented in Figures 8 b glujo 9b takes place when the bubbles morphology changes from spherical to polyhedral shape in which bubbles are separated by flat liquid films due to the liquid loss in the foam.

Then in Figures 8d and 9d the coarsening effect is no longer present, only the collapse effect was visualized. In these experiments, the drainage stage took less flhjo ten minutes Figure It was possible to observe how in the first ten seconds after taking the sample the entire graduated cylinder volume was occupied by foam with bubbles of small diameter less than 1 mm. The size of the bubbles increases as coalescence progresses, 15 minutes later the shape of the bubbles in the foam were mostly spherical, covered by a liquid film, with bubble size in the order of several millimeters and it was possible to differentiate two zones: This can be clearly seen with the drainage curve.

The first mechanism is dominated by gravitational drainage, which occurs in the first ten minutes.

This mechanism is characterized by the highest drainage velocity, as exhibited by the steep slope of the curve for this period. The second mechanism is dominated by capillary suction, occurring after the first 40 minutes. This mechanism results in a very slow drainage velocity, as kultifasico by the near flat drainage curve for this region.

There is an intermediate period of time between 10 minutes sec and 40 minutes secwhen both mechanisms are present. The foam formed in this study took around four hours to fully collapse.


In this study, the same assumptions as Iglesias et al. Foamability is represented through the non-dimensional foam height, that is, the ratio of the final liquid height in which no-foam is present in the graduated cylinder to the maximum foam height. Figure 11 shows how the foamability of both pipelines of 0. This effect was expected since higher flow rates translate into an increased mixing energy in the static mixers used to produce the foam.

Foam stability is quantified using the half-life time of the foam, Figure 12 shows how the foam stability tends to decrease when the liquid flow rate increases and the gas flow rate decreases. Based on visual observations it was possible to identify three differentiated flow patterns and their transition zones between the flow patterns characterized. These zones are identified in Figure And another zone where the flow pattern corresponding to each experimental point can be clearly identified, being whether foamy slug or foamy annular flow.

For the transitional flow pattern zone the reduction of the half-life time of the foam is faster than for the other zone. Similar results were obtained by Salagerwhen the disperse phase bubbles fraction increases in the foam, it produces an increment in the bubbles interactions which is translated into an increment in the collapse velocity and hence there is less foam stability.

The most relevant results of the experimental study were: These flow patterns were foamy stratified flow, foamy slug flow, and foamy annular flow, in which the denser phase was formed by the foamy emulsion and the lighter phase was air.

This differentiated trend on the pressure response could be used in the future to identify the dominant flow pattern in a particular pipeline section. Application of this signal behavior at an industrial scale could help enhance the performance of online, real time monitoring systems, and validate multiphase flow simulators prediction capability under producing scenarios with foamy oils like the Orinoco Belt case.

Flow patterns Three different flow patterns were obtained, namely annular flow, slug flow and stratified wavy flow, depending on the gas-liquid ratio used in the test. Characteristics of the foam emulsion In order to represent the characteristics of the Multiifasico Oil, a highly viscous mineral oil with a viscosity of 0. Multiphase Flow 18 3 ,