FR3098911A1 - Device and method for determining a value of interfacial tension between two fluids - Google Patents

Abstract

The present invention relates to an improved tensiometer for obtaining a measurement of interfacial tension at equilibrium, for surfactants characterized by a kinetics of diffusion and adsorption at the so-called slow interface, by means of an intermediate flow member ( B). The desired technical effect is the improvement of the precision of the observation of the interfacial tension and more precisely the possibility of measuring the interfacial tension at equilibrium between two fluids, at least one of which contains a so-called kinetic amphiphilic molecule. slow diffusion and / or adsorption. Figure 5 to publish

Description

Device and method for determining an interfacial tension value between two fluids

The present invention relates to a method for determining the interfacial tension between two fluids and a device for implementing this method.

When two immiscible fluids are brought into contact with each other, it is necessary to supply energy to increase their contact surface. This energy per unit area is called interfacial tension. If two fluids are put in concentric flow at the microfluidic scale and at low Reynolds, a competition between the interfacial energy and the viscous energy appears. The interfacial energy is reduced by minimizing the surface to volume ratio and tends to form spheres. Conversely, viscous energy tends to form a jet. Thus, when the viscous energy is low, the inner fluid will form drops within the outer fluid and when the viscous energy is high, the inner fluid will form a concentric jet within the outer fluid. The formation of drops is due to absolute instabilities and the formation of the jet to convected instabilities. Thanks to a model based on these instabilities, it is possible to calculate the interfacial tension between a drop regime and a jet regime. Knowledge of this interfacial tension value is of great importance in many technological sectors. Mention will thus be made, without limitation, of chemical processes, inkjet printing, spray atomization, emulsification processes, assisted hydrocarbon recovery processes (EOR for English enhanced oil recovery ).

Several methods are already known in the state of the art for determining the value of this interfacial tension. A first solution, called the weighed drop method, consists of collecting a determined number of drops in a container, from a capillary. By weighing the container, the average weight of each drop is then deduced, and the interfacial tension is then calculated, from the value of this weight, as well as from the radius of the capillary used. An alternative solution, called the rotating drop, consists of pouring a drop into a container, then rotating it under the effect of centrifugal force. From various parameters, such as in particular the shape adopted by the drop during its rotation, the value of the interfacial tension is deduced. However, these known solutions have certain drawbacks. Thus, they are often tedious to implement. In addition, each determination method is limited to a relatively narrow measurement range, a low temperature range and measurement at atmospheric pressure.

The realization of the interfacial tension measurement at equilibrium for the pairs of fluids whose diffusion and adsorption time of the surfactant is greater than the so-called microfluidic time, which is defined as being equal to the radius of the jet divided by the speed of the fluid, is particularly difficult to implement. These couples of fluids being numerous, it is essential to carry out an improvement of the system.

In the context of surfactant chemical assisted recovery, the surfactant formulations injected must be optimized in order to obtain an interface with the oil having an ultra-low interfacial tension under the pressure and temperature conditions of the reservoir, ie. less than 10 ^-2 mN/m. The optimization of these formulations is classically carried out using Huh's empirical method. This method is based on bringing the formulation to be tested into contact with the oil in a tube, cf. figure 1. This figure represents a salinity scan of a formulation containing Sodium Dodecylbenzenesulfonate (SDBS), isobutanol and different concentrations of sodium chloride. This formulation is brought into contact with decane. The tubes shown in the center (with a gray rectangle) highlight formulations leading to a Winsor III type microemulsion, which is an example of a sought-after system for EOR applications. For this type of formulation, the interfacial tension strongly depends on the salinity; in fact, at low salinity and at high salinity, systems of Winsor I type, respectively Winsor II are obtained and these biphasic systems have an interfacial tension greater than 10 ^-2 mN/m; the desired system is therefore the intermediate salinity system, of the Winsor III type, characterized by the appearance of a third intermediate phase and exhibiting an ultra-low interfacial tension, ie. less than 10 ^-2 mN/m. Thus, it is necessary to prepare many tubes in order to scan a wide range of salinity with a step of the order of a few grams per liter to determine the optimum salinity corresponding to the minimum interfacial tension. After their preparation, the tubes must be left to stand so that each system can reach its thermodynamic equilibrium. It may take a few days to a few weeks. Figure 1 schematically illustrates a salinity scan of a formulation containing SDBS, isobutanol and different concentrations of sodium chloride, after standing in tubes. In this figure, the water is shown in white, and the oil phase is shown in black. This formulation is brought into contact with decane. The tubes shown in the center (with a gray rectangle) highlight formulations leading to a Winsor III type microemulsion, which is an example of a sought-after system for EOR applications.

In view of the preparation and equilibration times, the costs generated by the volumes involved and the difficulty of working under pressure, a microfluidic tensiometer, named GammaDrop, has been developed, see document "Ultralow Interfacial Tension Measurement through Jetting/Dripping Transition ". This tensiometer, based on the work described in the documents FR2980576 and US2011/0197664A1, makes it possible to carry out high-throughput experiments at high pressures and temperatures using small volumes. Thus, the costs are reduced and the optimization of a formulation is carried out in one day. Nevertheless, the latter has a major drawback: measurements of interfacial tension at equilibrium are only obtained for systems containing so-called fast-kinetic surfactants, ie. having diffusion and adsorption kinetics at the interface faster than the time it takes for the interface to travel a distance equal to the radius of the jet produced by the tensiometer. However, in many industries such as the petroleum or even agri-food or cosmetics industries, the surfactants used are characterized by diffusion and adsorption kinetics at the so-called slow interface. In order to resolve this major drawback, it is essential to allow time for the surfactants to diffuse and be adsorbed on the interface before carrying out the measurement.

A general objective targeted by the invention is to provide an improvement of the tensiometer described in these documents, to obtain a measurement of interfacial tension at equilibrium, for surfactants characterized by diffusion and adsorption kinetics at the so-called interface. slow. In other words, the technical effect sought is the improvement of the precision of the observation of the interfacial tension and more precisely the possibility of measuring the interfacial tension at equilibrium between two fluids of which at least one contains an amphiphilic molecule said to have diffusion and/or slow adsorption kinetics.

The device and the method of the invention aim to remedy these various drawbacks. In particular, the invention aims to propose a device and a method making it possible to determine, in a reliable and simple manner, the value of interfacial tension between two fluids, even in the case of the use of a surfactant characterized by a kinetics of diffusion and adsorption at the so-called slow interface. It also aims to provide such a method, which can be implemented for a wide range of interfacial tensions, in an automated manner and with increased precision, at temperatures and pressures that can go up to 150 ° C and respectively 150 bar. More particularly, this invention aims to modify the current geometry of the Gammadrop tensiometer in order to create an internal fluid film on the external face of the internal capillary. The outer fluid flowing around this film, a pre-equilibration zone is created upstream or substantially at the location of the outlet nozzle of the inner capillary.

The present invention relates to a device for determining an interfacial tension value between two fluids comprising:

- an inner flow member and an outer flow member, preferably coaxial, the inner flow member opening into the internal volume of the outer flow member;
- an intermediate flow member,
- Means for supplying at least two fluids to the three flow members;
- Means for varying the flow rate of at least one of the fluids; And
- means for observing the nature of the flow downstream of the opening of the inner flow member into the outer flow member
characterized in that the intermediate flow member opens into the internal volume of the outer flow member, the intermediate flow member being configured to create a fluid flow film in contact with the periphery and the along the inner flow member.

According to one embodiment, said supply means supply the intermediate flow member and the inner flow member with the same fluid.

According to one embodiment, the intermediate flow member is coaxial with the inner flow member.

According to one embodiment, the intermediate flow member opens into a zone upstream or substantially at the location of the opening of the inner flow member into the outer flow member.

According to one embodiment, the external flow member is a tube based on fused silica coated with polyimide or microfluidic chip Pyrex® silicon or Pyrex® or fused silica.

According to one embodiment, the inner flow member is a tube made of stainless steel, glass, fused silica, Pyrex®, ceramic, quartz, sapphire or polymer resistant to pressure, temperature and chemical conditions.

According to one embodiment, the device comprises means for controlling the temperature and the pressure of at least one of the fluids.

According to one embodiment, the means for controlling the temperature and the pressure of at least one of the fluids are designed to bring at least the internal space of the external flow member under temperature and pressure conditions supercritical for at least one of the fluids or under conditions identical to the experimental process in question.

According to one embodiment, the means for observing the nature of the flow downstream of the opening of the inner flow member into the outer flow member comprises at least one optical sensor, at least one photodiode and laser barrier, preferably a camera, preferably a CCD camera.

According to one embodiment, the means for supplying two fluids comprise at least one syringe pump, preferably one syringe pump for each fluid.

According to one embodiment, the means for supplying two fluids are designed to apply flow rates between 2 μL/h and 336 mL/h, preferably between 2 μL/h and 8 mL/h.

According to one embodiment, the internal flow member has an internal radius ranging from 50 to 200 μm, preferably from 100 to 180 μm and a length from 1 to 80 cm, preferably from 5 to 20 cm.

According to one embodiment, the inner flow member, the outer flow member, the means for supplying fluids, the means for varying the flow rate of at least one of the fluids and the means for observing the nature of the flow are designed to allow the flow of fluids having a viscosity between 1 cP and 1000 cP and preferably from 1 to 300 cP.

According to one embodiment, the means for varying the flow rate of at least one of the fluids comprise a control PC containing software for analyzing images or an electrical signal connected to said observation means.

According to one embodiment, the device comprises additional means for supplying a fluid intended to be mixed with the external fluid or with the internal fluid, preferably in the form of syringe pumps.

According to one embodiment, the device comprises a microfluidic mixer, located between the supply means and the flow members.

Furthermore, the invention relates to a method for determining at least one interfacial tension value between two fluids, implementing the device according to one of the preceding claims, comprising the following steps:
- a first fluid, called inner fluid, is caused to flow into the inner flow member, as well as a second fluid, called outer fluid, into the outer flow member, as well as a third fluid, said intermediate fluid, in the intermediate flow member;
- we place ourselves first of all in conditions such that, downstream of the outlet of the inner flow member in the outer flow member, it forms,
. i) either drops of the interior fluid in a carrier phase formed by the exterior fluid,
. ii) either a continuous jet of the inner fluid into the outer fluid;
- The flow rate of at least one of the two fluids is varied;
- a pair of fluid flow rate values, called transition values, from which
. i) either a continuous jet of the interior fluid is now formed in the exterior fluid;
. ii) either drops of the interior fluid now form in the exterior fluid; And
- Said interfacial tension value between these two fluids is deduced therefrom.

According to one embodiment, the fluids are brought into contact for a time sufficient for the diffusion, absorption and rearrangement of the amphiphilic molecules and/or particles to take place and for the interface to have reached its equilibrium before the measurement, the contact time preferably being able to reach 500 seconds.

Other characteristics and advantages of the method according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the appended figures and described below.

List of Figures

Figure 1 illustrates the contacting of the formulation to be tested with the oil in a tube according to the prior art.

Figure 2 illustrates the implementation of the Gammadrop tensiometer.

Figure 3 illustrates different types of flow depending on the variation in fluid flow rates.

Figure 4 illustrates the evolution of the transition curve between a jet regime and a drop regime as a function of the interfacial tension γ.

Figure 5 illustrates the detail of an implementation of the invention according to one embodiment.

Figure 6 illustrates the fluidic connections connecting the supply means and the flow members.

The objective of this invention is to improve the tensiometer for determining an interfacial tension at equilibrium between two fluids, at least one of which contains an amphiphilic molecule having diffusion and/or adsorption kinetics at slow interfaces. By slow, we mean a diffusion and/or adsorption time (the “and” also taking into account the sum of diffusion and adsorption time) greater than the time at which the measurement is made.

The device according to the invention comprises an inner flow member, an intermediate flow member and an outer flow member. These flow members, also identified under the name of "capillaries" in the art of the technique, are preferably coaxial. In addition, they are arranged so that the inner flow member opens into the internal volume of the outer flow member.

According to the invention, the device comprises means for supplying at least two fluids to the three flow members. The means for supplying two fluids make it possible to produce the flows in the inner, intermediate and outer flow members. Preferably, the two fluids, called inner liquid and outer liquid, can be immiscible liquids or whose solubilization kinetics are slow enough to allow measurement, for example water and oil. Advantageously, one of the two fluids can comprise a surfactant.

In order to modify the operating conditions within the internal and external flow members, the device comprises means for varying the flow rate of at least one of the fluids. The flow variation means are linked on the one hand to the supply means and on the other hand to the internal, intermediate and external flow members.

In addition, the device according to the invention comprises means for observing the nature of the flow downstream of the opening of the inner flow member into the outer flow member. Thus, it is possible to analyze the nature of the flow (jet or drops) at the outlet of the inner flow member, in order to deduce the interfacial tension.

According to the invention, the intermediate flow member opens into the internal volume of the outer flow member, in a zone upstream or substantially at the location of the outlet of the inner flow member in the external flow organ. Additionally, the intermediate flow member is configured to create a film of fluid flow in contact with the periphery and along the inner flow member. In other words, the fluid flowing in the intermediate flow member passes through the intermediate flow member, and enters the outer flow member in an area where the outer fluid flows. The intermediate fluid then positions itself around the inner flow organ, due to the respective positioning of the flow organs and due to the interfacial tension between the fluids.

The creation of the fluid flow film in contact with the periphery and along the interior flow member makes it possible to create a progressive contact between the two fluids upstream or substantially at the location of the nozzle of the interior capillary in order to to allow time for the surfactants and other amphiphilic molecules to diffuse and be adsorbed at the interface before arriving at the level of the nozzle of the interior capillary. This device has the advantage of allowing contact between the two fluids in a progressive manner by creating a layer at the interface of the two fluids from the end of the external flow member until the end of the inner flow member. The technical effect sought is the improvement of the precision of the observation of the interfacial tension and more precisely the possibility of measuring the interfacial tension at equilibrium, even in the case of the use of a surfactant characterized by a diffusion and adsorption kinetics at the so-called slow interface.

According to one embodiment of the invention, the fluids flowing in the intermediate flow member and in the inner flow member can be identical. In this way, the interfacial measurement between the two fluids is favored.

According to one embodiment of the invention, the intermediate flow member can be coaxial with the inner flow member.

According to one embodiment of the invention, the intermediate flow member can open out into a zone upstream or substantially at the location of the introduction of the fluid into the internal space of the outer flow member.

According to one embodiment of the invention, the inner capillary can be made of stainless steel or any other material allowing the flow of the fluid and adapted to the circumstances of the embodiments of the invention, for example glass, fused silica, Pyrex®, ceramic, polymer resistant to pressure, temperature and chemical conditions or quartz or sapphire. The wetting of the interior fluid on the interior capillary can be ensured by means of the judicious choice of the material used or by means of an additional surface treatment.

According to one embodiment of the invention, the outer capillary can be made of fused silica coated with polyimide or any other material allowing the flow of the fluid and adapted to the circumstances of the embodiments of the invention, for example Pyrex® silicon or Pyrex® or fused silica. Indeed, the nature of the material of this capillary must allow the implementation of the observation of the flow more particularly at the place of the contacting of the two fluids and the resistance to the pressure and temperature of work. If he wishes to use materials of the Pyrex® silicon type, the person skilled in the art can use any desirable method for their implementation, for example: etching an outer half-tube in a silicon plate and the other half-tube in a Pyrex® plate. By gluing the two plates together, we obtain the outer tube within the microfluidic chip. You can then insert the inner tubing in the middle of the channel that will have been engraved.

These flow organs (also identified as capillaries) are each supplied with a fluid by the supply means. According to one embodiment of the invention, these supply means may comprise one or more syringe pumps or any other fluid supply device such as pressure sources coupled to flowmeters. According to a variant of the invention, a syringe pump is connected to each capillary. Naturally, the supply means are connected to the flow members with pipes adapted to the circulation of fluids.

According to one embodiment of the invention, the means for supplying two fluids can be designed to apply flow rates between 2 μL/h and 336 mL/h, preferably between 2 μL/h and 8 mL/h. These flow rates allow interfacial tension measurements for fluids and surfactants used in the field of EOR and also for interfacial tension ranges between 10 ^-3 mN/m and 50 mN/m and viscosities between 1 and 300 mPa.s. Advantageously, the device can be optimized in order to design the inner flow member, the outer flow member, the means for supplying two fluids, the means for varying the flow rate of at least one of the fluids and the means for observing the nature of the flow to allow the flow of fluids having a viscosity between 1 cP and 300 cP and preferably from 1 to 10 cP.

According to one embodiment of the invention, the internal flow member can have an internal radius ranging from 50 to 200 μm, preferably from 100 to 180 μm and a length from 1 to 80 cm, preferably from 5 to 20 cm. . According to a variant, the ratio between the diameter of the outer flow member and the diameter of the inner flow member can be between 1.2 and 10, preferably between 1.5 and 5.

The interfacial tension is inferred from observing the nature of the flow downstream of the outlet of the inner flow member into the outer flow member. The means of observation can make it possible to provide information on the behavior of the flow downstream of the outlet of the internal flow member into the external flow member. According to one embodiment of the invention, the existence of drops or the existence of a jet can be identified by placing a laser emitter and a photodiode on either side of the external flow member, downstream of the outlet of the inner flow member. Advantageously, it is possible to use at least one optical sensor, at least one photodiode and a laser barrier, preferably a camera, preferably a CCD camera, optionally mounted on a microscope or an objective.

According to one embodiment of the invention, the device also comprises means for controlling the temperature and the pressure of at least one of the fluids. Preferably, the device can make it possible to work from ambient temperature to 150° C. and from atmospheric pressure to 150 bar. Advantageously, the different fluid pairs are prepared by modifying at least one condition of at least one fluid, in particular the concentration of surfactants, co-surfactants, hydrotrope, choatrope or salt, the pH and/or the temperature and/or the pressure.

According to one embodiment of the invention, the device may include temperature and pressure control means. The means for controlling the temperature and the pressure of at least one of the fluids are designed to bring at least the internal space of the external flow member under temperature and pressure conditions equivalent to the desired industrial conditions, this can also make it possible to reach the supercritical state for at least one of the fluids.

According to one embodiment of the invention, the device may comprise computer means, in particular a control PC. For example, the computer means can be connected to means for varying the flow rate of at least one liquid, the computer means can also be linked to the observation means. In this case, the computer means may contain software for analyzing images or an electrical signal connected to said means of observation. The computer means can also make it possible to control and control the pressure and the temperature at which the measurement is carried out.

According to one embodiment of the invention, the device may also comprise additional means for supplying a fluid intended to be mixed with the external fluid or with the internal fluid, preferably in the form of syringe pumps. It is thus possible to prepare the different fluid pairs by adding at least one substance to at least one fluid, this substance being in particular an amphiphilic molecule and/or a salt and/or a polymer and/or a solid particle. Advantageously, this embodiment also comprises a microfluidic mixer located between the supply means and the flow members, to perform a dilution upstream of the nested capillaries in order to measure the interfacial tension as a function of the concentration of a species in EHD (Broadband Experimentation). In this embodiment, for an EOR application, a surfactant and/or co-surfactant and/or a salt and/or a polymer can be added to at least one of the two fluids. Thus, it is possible to perform jet-drop transitions at different flow rates of external fluid, then to determine several values of interfacial tension between these two same fluids, as a function of the contact time between the fluids before the measurement, then to produce a curve representing the variation of this value of interfacial tension as a function of this time in order to identify the interfacial tension at equilibrium and the kinetics of diffusion, adsorption and rearrangement of the amphiphilic molecules present. In the context of EOR applications, the contact time between the fluid is chosen sufficiently high thanks to the object of this invention in order to only carry out measurements of interfacial tension at equilibrium.

According to one embodiment of the invention, inserts can be added occasionally in the outer capillary in order to guarantee the centering of the inner capillary, in particular in the measurement zone. These inserts can have a tubular, cylindrical, flat shape or any other shape making it possible to ensure the positioning of the internal, intermediate and external flow members with respect to each other. More particularly, this construction can be envisaged between the inner flow member and the outer flow member.

To summarize, this invention aims to modify the geometry of the gammadrop tensiometer in order to create an internal fluid film on the external face of the internal capillary. The outer fluid flowing around this film, a pre-equilibration zone is created upstream or substantially at the location of the outlet nozzle of the inner capillary.

For each flow rate of the fluid in the outer flow member, the flow rate Qie of the fluid in the intermediate flow member forming the film around the inner capillary is selected so as to be as low as possible while allowing the formation of the movie. Thus, the time allowed for surfactants to diffuse and adsorb at the inner fluid/outer fluid interface is maximized, ie. equilibration time is maximized. The length of the inner capillary is chosen in such a way as to allow the necessary time for the surfactants to adsorb at the interface.

Preferably, the method for determining at least one interfacial tension value according to the invention between two fluids implements the device according to any one of the variants or combinations of variants described above.

Figure 2 illustrates, schematically and in a non-limiting manner, a device for determining at least one interfacial tension value according to the prior art. Syringe pump 1 injects the inner fluid into the inner capillary and syringe pump 2 injects the outer fluid into the outer capillary. The inner capillary being shorter than the outer capillary, the inner fluid comes into contact with the outer fluid in the outer capillary. Macroscopically, different types of flow are observed at the outlet of the inner capillary depending on the flow rates of the inner and outer fluids with observation means. The device comprises observation means, which here comprise a CCD system 7 or a system comprising a photodiode and laser barrier 8. In addition, the device comprises computer means PC 9 which can control the syringe pumps and the means of observation.

FIG. 3 illustrates images obtained by the observation means for the device and the method according to the invention. At low flow rates of the interior and exterior fluids, drops of interior fluids in the exterior fluid are formed. With a fixed external flow rate, by increasing the internal flow rate, flows of the plug type, oscillating jet then flat jet are gradually observed. At high external flow maintained constant, the progressive increase of the internal flow leads to a transition between a jetting and a flat jet regime. Jetting corresponds to the formation of a jet which at a variable distance from the outlet of the inner capillary (less than 6 times the internal radius of the outer capillary) breaks into drops.

Figure 5 illustrates an embodiment of the invention in a schematic and non-limiting way. In this figure, the fluid supply means, the observation and control means are not represented, they may be identical to those illustrated in FIG. 2. The first representation in FIG. 5 illustrates the formation of drops (G ) of the interior fluid in a carrier phase (P) formed by the exterior fluid. The second representation in Figure 5 illustrates the formation of a continuous jet (J) of the interior fluid in the exterior fluid for the same device for measuring interfacial tension. The device comprises an inner flow member A which opens into an outer flow member C. In addition, the device comprises an intermediate flow member B. The flow members are substantially coaxial, and preferably have a shape tubular. In addition, the intermediate flow member B opens into the outer flow member C upstream of the outlet of the inner flow member A. Alternatively, the intermediate flow member B can open into the external flow member C substantially at the location of the outlet of the internal flow member A. In this figure, the fluid injections are represented: Qii represents the internal fluid flow, Qie represents the intermediate fluid flow and Qe represents the external fluid flow. Preferably, the intermediate fluid is identical to the interior fluid. Thanks to this device, a film D is formed on the periphery and along the outer flow member. The film D allows contact between the interior fluid and the exterior fluid. Thus, for this device, several zones can be identified: zone Z1 is an injection zone for the interior and intermediate fluid depending on the case, zone Z2 an injection zone for the exterior fluid, zone Z3 a zone for pre- balancing and zone Z4 a zone for measuring the interfacial tension between the fluids (the measuring means are not shown in these figures). Advantageously, the injection rate of the intermediate fluid will be chosen in order to be able to obtain the formation of a film up to the nozzle of the interior capillary, ie. without formation of drops upstream of the inner capillary nozzle. In order to facilitate the implementation of the invention, it is preferable to work at a fixed external and intermediate flow rate and to vary the internal flow rate in order to observe the jet/droplet transition.

FIG. 6 illustrates the fluidic connections connecting the supply means and the flow members for a device and a method according to one embodiment of the invention. In this figure, the observation and control means are not represented, they may be identical to those illustrated in FIG. 2. In this illustration, the supply means are represented in a simplified manner in the form of syringe pumps and the organs flow in the form of capillaries. In this case, the syringe pump 1 is connected to the internal flow member A, the syringe pump 2 is connected to the external flow member C and the syringe pump 3 is connected to the flow member intermediate B. In addition, this figure shows a syringe pump 4, which represents the additional supply means and which is connected to the microfluidic mixer 5 to add the additives or carry out dilutions or any other need to carry out the experiment. In this illustration, the additional supply means 4 are connected to the external flow member. However, the additional supply means 4 can be connected to the inner, intermediate and/or outer flow member, depending on the requirements of the experiment. Moreover, in this illustration the microfluidic mixer 5 connects the additional supply means 4 to the external flow member. However, the microfluidic mixer 5 can be connected to the inner, intermediate and/or outer flow member, depending on the requirements of the experiment. Obviously, these power supply means are controlled by the control PC, not shown.

In addition, the invention also relates to a method for determining at least one interfacial tension value between two fluids, comprising the following steps:

- a first fluid, called inner fluid (Qii), is caused to flow into the inner flow member, as well as a second fluid, called outer fluid (Qe), into the outer flow member, as well a third fluid, called intermediate fluid (Qie), in the intermediate flow member;

- we place ourselves first of all in conditions such that, downstream of the outlet of the inner flow member in the outer flow member, it forms,

. i) either drops (G) of the interior fluid in a carrier phase (P) formed by the exterior fluid,

. ii) or a continuous jet (J) of the interior fluid in the exterior fluid;

- The flow rate of at least one of the two fluids is varied;

- a pair of fluid flow rate values, called transition values, from which

. i) either a continuous jet of the interior fluid is now formed in the exterior fluid;

. ii) either drops of the interior fluid now form in the exterior fluid; And

- Said value (γ) of interfacial tension between these two fluids is deduced therefrom.

According to the method of the invention, a fluid flow film is created in contact with the periphery and along the internal flow member by means of an intermediate flow member, which opens into the internal volume of the outer flow member, in a zone upstream of the opening of the inner flow member into the outer flow member. In other words, the fluid flowing in the intermediate flow member passes through the intermediate flow member, and enters the outer flow member in an area where the outer fluid flows. The intermediate fluid then positions itself around the inner flow organ, due to the respective positioning of the flow organs and due to the interfacial tension between the fluids.

.

The creation of the fluid flow film in contact with the periphery and along the interior flow member makes it possible to create a progressive contact between the two fluids upstream of the nozzle of the interior capillary in order to allow time for the surfactants and other amphiphilic molecules to diffuse and adsorb at the interface before arriving at the nozzle of the inner capillary. This process has the advantage of allowing contact between the two fluids so that all of the amphiphilic molecules and possibly particles can diffuse, adsorb and rearrange themselves at the interface so that the interface is at equilibrium. when it reaches the nozzle, ie. the end of the inner flow member. The technical effect sought is the improvement of the precision of the observation of the interfacial tension and more particularly the obtaining of a measurement of interfacial tension at equilibrium.

According to one embodiment of the invention, the fluids flowing in the intermediate flow member and in the inner flow member can be identical. In other words, the interior fluid can correspond to the intermediate fluid.

According to one embodiment of the invention, the intermediate flow member can be coaxial with the inner flow member.

According to one embodiment of the method, the fluids are brought into contact for a sufficient time to allow the diffusion, absorption and rearrangement of the amphiphilic molecules, electrolytes and particles at the interface between the fluids, the contact time possibly reaching preferably 500 seconds.

According to one embodiment of the method, these flow members, also identified under the name of "capillaries" in the art of the technique, are preferably coaxial. In addition, they are arranged so that the inner flow member opens into the internal volume of the outer flow member.

According to one embodiment of the method, the three flow members are supplied by supply means with at least two fluids. The means for supplying two fluids make it possible to produce the flows in the inner and outer flow members. Preferably, the two fluids, called inner fluid and outer fluid, can be immiscible liquids, for example water and oil. Advantageously, one of the two fluids can comprise a surfactant.

According to one embodiment of the method, it is possible to modify the operating conditions within the internal and external flow members by means of the means for varying the flow rate of at least one of the fluids and/or the temperature and/or the the pressure and/or a modification of the chemical composition of at least one of the fluids. The flow variation means are linked on the one hand to the supply means and on the other hand to the internal, intermediate and external flow members.

According to one embodiment of the method, the inner capillary can be made of stainless steel or any other material allowing the flow of the fluid and adapted to the circumstances of the embodiments of the invention.

According to one embodiment of the method, the outer capillary can be made of fused silica coated with polyimide or any other material allowing the flow of the fluid and adapted to the circumstances of the embodiments of the invention, for example microfluidic chip Pyrex® silicon or Pyrex® or fused silica or sapphire. Indeed, the nature of the material of this capillary must allow the implementation of the observation of the flow more particularly at the place of the contacting of the two fluids.

These flow organs (capillaries) are each supplied with a fluid by supply means. According to one embodiment of the method, these supply means may comprise one or more syringe pumps or any other fluid supply device. According to a variant of the invention, a syringe pump is connected to each capillary. Naturally, the supply means are connected to the flow members with pipes adapted to the circulation of fluids.

According to one embodiment of the method, the intermediate flow member can emerge in a zone upstream or substantially at the same place of the introduction of the fluid into the internal space of the outer flow member.

According to one embodiment of the method, the means for supplying two fluids can be designed to apply flow rates between 2 μL/h and 336 mL/h, preferably between 2 μL/h and 8 mL/h. These flow rates allow interfacial tension measurements for fluids and surfactants used in the field of EOR and also for interfacial tension ranges between 10 ^-3 mN/m and 50 mN/m and viscosities between 1 and 300 mPa.s. Advantageously, the device can be optimized in order to design the inner flow member, the outer flow member, the means for supplying two fluids, the means for varying the flow rate of at least one of the fluids and the means for observing the nature of the flow to allow the flow of fluids having a viscosity of up to 1000 mPa.s.

According to one embodiment of the method, the internal flow member can have an internal radius ranging from 50 to 200 μm, preferably from 100 to 180 μm and a length from 1 to 80 cm, preferably from 5 to 20 cm. According to a variant, the ratio between the diameter of the outer flow member and the diameter of the inner flow member can be between 1.2 and 10, preferably between 1.5 and 5.

The interfacial tension is inferred from observing the nature of the flow downstream of the outlet of the inner flow member into the outer flow member. Appropriately positioned observation means provide information on the behavior of the flow downstream of the opening of the inner flow member into the outer flow member. According to one embodiment of the invention, the existence of drops or the existence of a jet can be identified by placing a laser emitter and a photodiode on either side of the external flow member, downstream of the outlet of the inner flow member. Advantageously, it is possible to use at least one optical sensor, at least one photodiode and laser barrier, preferably a camera, preferably a CCD camera, optionally mounted on a microscope or an objective.

According to one embodiment of the method, the method may include a temperature and pressure control step to control at least one of the fluids. Preferably, the method can make it possible to work over a temperature and pressure range starting from ambient temperature to 150° C. and from atmospheric pressure to 150 bar. Advantageously, the different fluid pairs are prepared by modifying at least one condition of at least one fluid, in particular the pH and/or the temperature and/or the pressure.

According to one embodiment of the method, the method may include a dilution step upstream of the nested capillaries in order to measure the interfacial tension as a function of the concentration of a species in EHD (High Throughput Experiment) using supply means additional devices, which may take the form of syringe pumps and a microfluidic mixer.

According to one embodiment of the method, one step thereof consists in achieving temperature and pressure conditions equivalent to the desired industrial conditions, this can also make it possible to reach the supercritical state for at least one of the fluids.

According to one embodiment of the method, the method may include a computer control step, in particular by means of a control PC, to control means for varying the flow rate of at least one liquid, by integrating the signals coming from the means optical measurement. In this case, this step can also control said means of observation, in particular by image analysis software connected to said means of observation.

According to one embodiment of the method, a step thereof can implement additional means for supplying a fluid intended to be mixed with the external fluid or with the internal fluid, preferably in the form of syringe pumps. It is thus possible to prepare the different fluid pairs by adding at least one substance to at least one fluid, this substance being in particular a surfactant and/or a polymer and/or a solid particle. Advantageously, this embodiment also implements a microfluidic mixer located between the supply means and the flow members. In this embodiment, for an EOR application, a surfactant can be added to at least one of the two fluids. Thus, it is possible to vary the time of formation of the drops, then to determine several values of interfacial tension between these two same fluids, relating to different times of formation of drops, then to produce a curve representing the variation of this value of interfacial tension in function of the formation time of the drops, and identifying a characteristic time of the surfactant, corresponding to the transition between a zone where the interfacial tension value is substantially constant as a function of the formation time, and an adjacent zone, where this interfacial tension value increases as the training time decreases.

The method described in the invention implements the device described above and, advantageously, the embodiments as described above. In general, the flow rate, called external, of the external fluid is fixed and the flow rate, called internal, of the internal fluid is varied and the value of the interfacial tension is deduced from the fixed flow rate of external fluid, from the transition flow the interior fluid, the diameter of the exterior capillary, as well as the viscosities of the interior and exterior fluids. The implementation of this process allows the determination of several interfacial tensions for different parameters (chemical composition, physical parameters) and choice of an optimal formulation in the conditions of the reservoir for an enhanced recovery of hydrocarbons.

The type of flow generated at the outlet of the inner capillary is due to Rayleigh-Plateau instabilities, it is therefore governed by the respective flow rates of the inner and outer fluids, their dynamic viscosity, by the inner radius of the outer capillary and by the interfacial tension between the inner and outer fluids. A model can be used to measure the interfacial tension from the flow diagram representing the nature of the flow as a function of the internal and external flow rates, see figure 3. This figure represents the typical diagram representing the type of flow obtained depending on the internal and external flow rates respectively of the internal and external fluids.

An example (non-limiting) of a model is detailed in the document “Ultralow Interfacial Tension Measurement through Jetting/Dripping Transition”, this model is based on the theory of absolute instabilities and convected instabilities. Absolute instabilities move up the flow, ie. the velocity of the disturbance envelope v* is negative and leads to the breakup of the jet into droplets. Conversely, convected instabilities propagate in the direction of the flow, v* is positive and lead to a jet. At the transition between absolute and convected instabilities, v* is equal to 0. The resolution of this last equation makes it possible to determine the interfacial tension since all the other parameters (viscosity, internal radius of the external capillary and flow rates) are known; the flow rates being determined using the flow diagram since v*=0 macroscopically corresponds to the transition between the regime of drops and jets. The flow diagram therefore makes it possible to solve the equation at each point of the jet-drop transition. For more precision, the least squares method is used to select the interfacial tension that best fits the jet-drop transition line of the flow diagram.

To summarize, the measurement is carried out using the observation of the type of flow resulting from the propagation of instabilities. One of the instabilities leads to the destruction of jets into droplets. The range of flow concerned by these absolute instabilities increases with the interfacial tension, cf. figure 4. This figure represents the evolution of the transition curve between a jet regime and a drop regime as a function of the interfacial tension γ.

It is therefore impossible to carry out a measurement at equilibrium, if the system is not yet balanced at a distance of one diameter from the jet after the exit of the interior capillary, since from this distance, the absolute instabilities are able to form and break the flow to the nozzle of the inner capillary. This is illustrated by two examples in the document “Ultralow Interfacial Tension Measurement through Jetting/Dripping Transition” for which the surfactants do not have time to diffuse at the interface before the onset of the propagation of instabilities. It is therefore imperative to modify the current geometry in order to be able to carry out the measurement at equilibrium; indeed, it is necessary to be able to create an interface upstream of the nozzle of the interior capillary without it being able to be destabilized by absolute instabilities.

It goes without saying that the invention is not limited solely to the embodiments of the recesses, described above by way of example, on the contrary it embraces all variant embodiments.

From this alternative embodiment, described immediately above, it is possible to implement a method for screening various surfactants. For this purpose, two basic immiscible fluids are used, which are caused to flow through the inner A and outer C flow members. Then, different surfactants are successively added to them, the interfacial tension of which is measured. , following the steps described above. The preferred surfactant(s) correspond(s) in particular to those whose characteristic times are less than the characteristic times of the application. Typically the characteristic time for spray additives is on the order of milliseconds, whereas that for detergent additives is on the order of seconds. This screening of surfactants can be advantageously implemented in many technical fields, such as detergents, or spray additives. Thus, in the case of detergents, the two fluids which are made to flow are, for example, oil and water, whereas the surfactants studied are from the family of ionic surfactants such as sulfonates, or nonionic surfactants. The invention makes it possible to achieve the previously mentioned objectives. Indeed, the method for determining the interfacial tension, in accordance with the invention, can be implemented simply and quickly. In addition, the various steps that it involves are likely to be carried out in an automated manner, for the most part. Moreover, the method of the invention makes it possible to access a wide range of interfacial tension values. In addition, it is possible to vary, very quickly, the nature of the two fluids, the interfacial tension of which one wishes to know. Finally, the installation according to the invention, allowing the implementation of the above method, is inexpensive.

In order to illustrate the advantage of the GammaDrop method compared to the hanging drop method, we propose below the account of an experiment implementing the current assembly allowing only to measure the interfacial tension for surfactants with kinetics fast. The internal flow member A is fed with a distilled water+glycerol solution (mass ratio 0.47) having dodecyltrimethylammonium bromide (DTAB) concentrations of between 1.8.10 ^-3 mol/L and 70.3.10 ^-3 mol/ L and viscosities between 18.3 and 22.7 mPa.s. The external flow member C is fed with a 247.3 mPa.s silicone oil. The inner radius of the outer capillary measures 265 µm, the flow rate range covered is between 0.1 and 10 mL/h. This made it possible to measure interfacial tensions between 9 and 27 mN/m, with accuracy and fidelity in agreement with the results of a commercial hanging drop tensiometer.

Claims (18)

Device for determining an interfacial tension value between two fluids comprising:
- an inner flow member (A) and an outer flow member (C), preferably coaxial, the inner flow member opening into the internal volume of the outer flow member;
- an intermediate flow member (B),
- Supply means (1, 2, 3, 4) with at least two fluids in the three flow members;
- Means for varying the flow rate of at least one of the fluids; And
- observation means (7, 8) of the nature of the flow downstream of the opening of the inner flow member into the outer flow member
characterized in that the intermediate flow member (B) opens into the internal volume of the outer flow member (C), the intermediate flow member (B) being configured to create a flow film (D) fluid contacting the periphery and along the inner flow member (A). Device according to claim 1, wherein said supply means (1, 2, 3, 4) supply the intermediate flow member (B) and the inner flow member (A) with the same fluid. Device according to one of the preceding claims, in which the intermediate flow member (B) is coaxial with the inner flow member (A). Device according to one of the preceding claims, in which the intermediate flow member (B) opens into a zone upstream of the opening of the inner flow member (A) into the outer flow member (C ). Device according to one of the preceding claims, in which the external flow member (C) is a tube based on fused silica coated with polyimide or microfluidic chip Pyrex® silicon or Pyrex® or fused silica. Device according to one of the preceding claims, in which the internal flow member (A) is a tube made of stainless steel, glass, fused silica, Pyrex®, ceramic, quartz, sapphire or polymer resistant to the conditions of pressure, temperature and chemical. Device according to one of the preceding claims, which comprises means for controlling the temperature and the pressure of at least one of the fluids. Device according to Claim 7, in which the means for controlling the temperature and the pressure of at least one of the fluids are designed to bring at least the internal space of the external flow member (C) under conditions supercritical temperature and pressure for at least one of the fluids or under conditions identical to the experimental process in question. Device according to one of the preceding claims, in which the means for observing the nature of the flow downstream of the opening of the inner flow member into the outer flow member comprises at least one optical sensor, at least one photodiode and laser barrier (8), preferably a camera, preferably a CCD camera (7). Device according to one of the preceding claims, in which the means (1, 2, 3, 4) for supplying two fluids comprise at least one syringe pump, preferably one syringe pump for each fluid. Device according to one of the preceding claims, in which the means (1, 2, 3, 4) for supplying two fluids are designed to apply flow rates between 2 µL/h and 336 mL/h, preferably between 2 µL/ h and 8 mL/h. Device according to one of the preceding claims, in which the inner flow member (A) has an internal radius ranging from 50 to 200 µm, preferably 100 to 180 µm and a length of 1 to 80 cm, preferably 5 at 20cm. Device according to one of the preceding claims, in which the inner flow member (A), the outer flow member (C), the fluid supply means (1, 2, 3, 4), the means for varying the flow rate of at least one of the fluids and the means for observing the nature of the flow are designed to allow the flow of fluids having a viscosity between 1 cP and 1000 cP and preferably from 1 to 300 cP Device according to one of the preceding claims, in which the means for varying the flow rate of at least one of the fluids comprise a control PC (9) containing software for analyzing images or an electrical signal connected to said means observation. Device according to one of the preceding claims, which comprises additional supply means (4) of a fluid intended to be mixed with the external fluid or the internal fluid, preferably in the form of syringe pumps. Device according to claim 15, which comprises a microfluidic mixer (5), located between the supply means and the flow members. Method for determining at least one interfacial tension value between two fluids, implementing the device according to one of the preceding claims, comprising the following steps:
- a first fluid, called inner fluid (Qii), is caused to flow into the inner flow member (A), as well as a second fluid, called outer fluid (Qe), into the flow member exterior (C), as well as a third fluid, called intermediate fluid (Qie), in the intermediate flow member (B);
- we place ourselves first of all in conditions such that, downstream of the outlet of the inner flow member in the outer flow member, it forms,
. i) either drops (G) of the interior fluid in a carrier phase (P) formed by the exterior fluid,
. ii) or a continuous jet (J) of the interior fluid in the exterior fluid;
- The flow rate of at least one of the two fluids is varied;
- a pair of fluid flow rate values, called transition values, from which
. i) either a continuous jet of the interior fluid is now formed in the exterior fluid;
. ii) either drops of the interior fluid now form in the exterior fluid; And
- Said value (γ) of interfacial tension between these two fluids is deduced therefrom. Process according to claim 17, in which the fluids are brought into contact for a time sufficient for the diffusion, absorption and rearrangement of the amphiphilic molecules and/or particles to take place and for the interface to have reached its equilibrium before the measurement, the contact time preferably being able to reach 500 seconds.