CA2872383A1 - Process for determining the incompatibility of mixtures containing heavy and light crudes - Google Patents

Abstract

The object of the current invention is to provide a process for experimentally determining the incompatibility of crudes mixtures (heavy, light) at a constant temperature (from room temperature at 463 K and pressures of 0.1 to 68.9 MPa), based on the measurement of dynamic viscosity of crudes mixtures using an electromagnetic viscometer at a constant force. The blending comprises crudes with asphaltenes content. The blending process comprises the procedure for determining the incipient point of asphaltenes incompatibility threshold in crudes blending. The apparatus used in the current invention is based on an electromagnetic concept that uses only a mobile element (piston) through a fluid at a constant force. The time required for the piston to travel a fixed distance is related to the manner exact to dynamic viscosity of the fluid contained in a measuring chamber. When the fluid contained inside the measuring chamber is more viscous, the piston displacement will be slower.

Description

PROCESS FOR DETERMINING THE INCOMPATIBILITY OF MIXTURES
CONTAINING HEAVY AND LIGHT CRUDES
Description Technical field The invention refers to a process for determining the incompatibility in the heavy and light crudes mixture based on measurement of dynamic viscosity of crudes mixture using an electromagnetic viscometer at a constant force in a range of io temperature of 463 K at room temperature (293 K) and pressure of 0.1 to 68.9 MPa.
Background of the invention The study of petroleum analysis and its products would not e complete without considering the incompatibility that generates changes in its original properties, that is, during and after the blending process, various secondary products can be formed such as sludge, semi-solids or solid particles increasing mixture viscosity. The term incompatibility refers to the formation of a precipitate (sludge, sediment and deposition of material with asphaltene content) or separation of phases when two liquids are blended (Speight 1999, 2004).
The phenomenon of incompatibility was firstly used by Martin (1951) defining it as the tendency of the fuel oil to produce a deposit in the dilution or blending with other fuel oils. Martin (1951) made a difference between incompatibility and instability, defining this least as the tendency of a residual fuel to produce a deposit of asphaltic or carbonic material during storage or heating process. The instability during storage or during heating can be the result of the preparation of the fuel from incompatible components or can be the result of aging.
The term instability is frequently used referring to color formation, sediment or bubble gum in the liquid during a period of time; this term can be used to differentiate the formation of a precipitate in short time (almost immediately). Nevertheless, the terms incompatibility and instability are used interchangeably (Speight, 1999).
The phenomena of incompatibility and instability of petroleum and its products are invariably associated with the chemical composition and physical ratio of the components. In the most of cases, a certain component in one the crudes reacts with another component in the crude with which is blended resulting in a chemical reaction in the formation of a new product that, when it is soluble, affects the mixture properties and when it is insoluble, it is deposited as a semisolid or solid matter (Speight, 1999). Normally, the incompatibility processes increase viscosity of petroleum and its derivatives, inclusively at low temperatures also causes a change in viscosity in certain fuels (Speight, 1999). Various studies demonstrated that blending of different crudes can lead to flocculation/precipitation of asphaltenes (Wiehe and Kennedy, 2000a, 2000b; van den Berg et al., 2003; Schermer et al., 2004). This phenomenon, known as crudes incompatibility, causes much more problems in the transportation and refining process especially when the economical situation is obliging many refineries to carry out low cost crudes blending to improve the

-2-refining margins (van den Berg et al., 2003).
Instead of various studies carried out in the last decades, there are always important questions in the chemistry and physics knowledge of the incompatibility phenomenon (Speight, 1999; Wiehe, 2012). It is well know that this problematic did not lead to a standard method for determination and quantification of crudes incompatibility. Based on the above, there are various criteria for determining crudes incompatibility in literature.
US Patent No. 4,85,337 refers to a blending procedure of liquid io hydrocarbons to control incompatibility mentioning that the paraffinic and condensed liquids can be blended with the crudes meanwhile the incompatibility of the asphaltenes is controlled; the incompatibility is expressed as the relation between the aromatics and the content of asphaltenes of the crudes or liquid hydrocarbon.
Escobedo and Mansoori (1995) show the determination of an incipient point in asphaltenes flocculation by means of relative viscosity measurement of a crude diluting it with a precipitating agent (n-pentane, n-heptane, n-nonane). The phenomenon is graphically shown with the increase of viscosity during the precipitation of the crude observing a deviation of the initial behavior during asphaltenes flocculation.
Asomaning (1997) shows the incompatibility phenomenon associating it solubility as the mechanism for deposits formation.
Afterwards, Asomaning and Watkinson (2000) introduced an index of simple colloidal instability (CII) based on the analysis of saturated, aromatic compositions, resins and asphaltenes (SARA) of the crudes

-3-mixture, concluding that mixtures with 0II>1 tend to be incompatible and precipitate asphaltenes.
Buckley et al. (1998) associates the incipient point of precipitation to asphaltenes with solubility that depends on the refraction index (RI); in this work it is determined that the RI could be used to predict the incipient point of asphaltene precipitation. See also Buckley (1999) and Gimenez and Cabeza (2006).
US Patent No 5,871,634 refers to a method for blending two or more petroleum feedstreams, petroleum process streams or io combination thereof, at least one of which includes the steps of determining the insolubility number, (IN) for each feedstream, determining the solubility blending number, SBN, for each feedstream and combining the feedstreams in order of decreasing SBN number of each feedstream such that the solubility blending number of the mixture is greater than the insolubility number of any component of the mix, when the solubility blending numer of any of the feedstreams or streams is equal or less than the insolubility number of any of the streams. See also the works of Wiehe and Kennedy (2000a, 2000b).
US Patent N. 5,997,723 refers to a process for blending crudes with the purpose to avoid incrustation for crudes considering almost incompatible). See also the works of Wiehe et al. (2001) and Wiehe (2004).
Gharfeh et al. (2004) show an instrument for detection of diluted crudes incompatibility with heptane at low temperatures and atmospheric pressure. The measurement system consists in a titration container, an infrared laser and a detector for measuring light

-4-transmittance through the container. Initially, the transmittance increases and when it arrives to a flocculation point, it starts to decrease, then, the maximum point achieves it considered as the flocculation point of asphaltenes or the maximum dilution achieved.
US patent No. 7,029,570 refers to a process for determining incompatibility in the crudes mixtures through the change in length density of neutrons dispersion at the surface of asphaltene aggregates.
US patent No. US 7,618,822 B2 refers to crudes processing, mixtures and fraction in refines and petrochemical plants to decrease asphaltenes flocculation in the pre-heating train interchanger, ovens and other units of the refining process.
Flakler and Sandu (2010) show a technique for providing information on crudes stability on its mixtures detecting the incipient point of the asphaltenes flocculation based on very small changes of the composition of the mixtures using a source of transmission close to the infrared. The equipment used in this word has a detection system of solid able to measure the changes of intensity through the addition of a precipitate (n-pentane). An inflexion point of a transmittance graph based on the volume added of precipitate up to the start of flocculation can be observed. The inflexion point is expressed as the stability index of asphaltenes that corresponds to the precipitation point of asphaltenes and provided a relative measurement of the stability in the crude. Meanwhile, Sedghy and Goual (2010) determine the start of asphaltenes precipitation through the direct current conductivity technique in crudes diluted in toluene. Alvarez et al. (2012) use an ellipsometry technique to evaluate the compatibility of crudes mixtures.

-5-Mexican Patent application No. MX/2011/003287, publication date September 27, 2012 refers to a process for measuring dynamic viscosity of live heavy crude (monophasic samples taken from the well bottom) at a constant temperature and pressures from 68.9 MPa up to the atmospheric pressure, including the dynamic viscosity in the bubble pressure point and under this least; that is, removing the gaseous phase and measuring liquid phase viscosity up to achieving atmospheric pressure.
It is needless to say by the applicant that for effects of solving the current invention, the object is of blending heavy and light crudes is to decrease viscosity of the heavy crudes and to find the optimum concentration for maintaining the asphaltenes at a level under a predetermined level, reducing the tendency of asphaltenes formation.
Furthermore, an incipient point of the asphaltenes incompatibility threshold in the mixture is obtained that is a very important point to avoid said formation of asphaltene aggregates at a certain concentration of light crudes; the blending process comprises crudes with asphaltenes content.
In this sense, we consider convenient to define that a dead crude is the one that has a sufficiently low pressure, does not contain dissolved gas or that crude that did not release its volatile components.
Similarly, the API gravity is a measure of density that describes how heavy or light the petroleum is compared with water. If the API
grades are more than 10, it is lighter than the water and therefore will float on it. The API gravity is also used to compare densities of

-6-fractions extracted from petroleum. For example, is a petroleum fraction floats on another; it means that it is lighter and therefore its API gravity is bigger. Mathematically, the API gravity does not have units; nevertheless, always this number has the name of API grade.
The API gravity is measured with an instrument denominated densimeter; there are a great variety of these instruments. The API of crudes oils, generally are in an interval of 470 (for lighter crudes) to 100 (for heavier crudes). Based on this parameter it is possible to classify the crudes in: extra heavy ( API<10), heavy (10.1< API<22.3), io mean (22.4< API<31.1), light (31.2< API<38.9) and extra light (39.0< API). It is important to mention that this classification can vary depending on the considered source.
The applicant wants de mention that the room temperature is the one where the laboratory is installed without having an external control of the same, wherein any measurement is carried out, i.e. depending of the place where it can be found; therefore, subsequently during the description of the current invention, the room temperature will be considered between 293.2 and 298.2 K.
By the above, up to now, there is no any reliable technique destined to determine the crudes mixture incompatibility. Therefore, the current invention markedly overcomes the previous mentioned references, since it allows knowing the ratios of the blending wherein the incompatibility of light and heavy crudes can occur through the determination of dynamic viscosity.
Therefore, an object of the present invention is to provide a process for measuring the dynamic viscosity of heavy and light crudes

-7-mixtures through an apparatus containing a sensor based on a novelty technique; constant electromagnetic force.
In this regard, the apparatus mentioned uses a piston, calibrated in a determined interval of viscosities, that is submerges in a crudes mixture to analyze. The piston displacement is hampered by the viscous pull of the fluid, a characteristic that is used to obtain an exact measurement of absolute viscosity. The time required for the piston to go over a given distance is related to the dynamic viscosity of the fluid confined in a measurement chamber, therefore, as the fluid in the chamber is more viscous, the piston displacement will be slower.
Another object of the current invention is to contribute with a novel process for determining the cruds mixture incompatibility, due to the fact that it is possible to measure the dynamic viscosity of said mixtures at different temperature and pressure conditions.
Brief description of the figures The figures that accompany the current invention for having a better understanding of the indicated objects, without limiting is scope, are shown below:
Figure 1 shows a cross section of the electromagnetic viscometer 1 used in the current invention.
Figure 2 shows a schematic diagram for measurement of dynamic viscosity of reservoir fluids.
Figure 3 shows (in logarithmic coordinates in axis y) the typical behavior of the viscosity of a dead crude based on constant temperature and pressure; the viscosity decreases when the

-8-temperature increases. Generally, the laboratory studies measure the behavior of the dead crude viscosity based on the room temperature up to the reservoir temperature.
Figure 4 refers to the results of dynamic viscosity obtained for the mixture {light crude ¨ toluene + n-heptane} (in logarithmic coordinates), object of the present invention, adding n-heptane in excess at a constant temperature and 0.1 MPa. In literature, this behavior of slope change or inflexion point in the viscosity based on the volume of precipitating agent refers to, as the incipient point of asphaltenes flocculation.
Figure 5 shows (in logarithmic coordinates) three slopes of dynamic viscosity (at temperatures of 308.1 K, 313.2 K and 318.4 K
and a constant pressure of 0.1 MPa) for the system {light crude ¨
toluene + n-heptane}.
Figure 6 shows the results obtained from viscosities of a heavy and light crude mixture (including viscosities of heavy and light crude), object of the present invention, at 332.2K and pressure of 0.1 MPa.
Figure 7 shows (in logarithmic scale) dynamic viscosities of the mixtures {light crude + heavy crude} vs. volume percentage of light crude added, at different temperatures and pressure of 0.1 MPa.
Detailed description of the invention The current invention refers to a process based in the measurement of dynamic viscosities of crudes mixtures using a constant force electromagnetic viscometer to determine the incompatibility of heavy and light crudes in the interval of temperature

-9-of 463 K at room temperature and pressures of 0.1 to 68.9 MPa.
Blending comprises cruds with asphaltene content. The blending process included a procedure to determine the incipient point of the asphaltenes incompatibility threshold in the mixture. The apparatus used in the current invention is particularly easy from the mechanical point of view and the principle based for determining that viscosity is effective (Patent document US 6,584,831 B1; US 5,025,656, US
4,864,849, US 4,627,272, MX/2011/003287A). The apparatus is precise, reliable, and easy to use and with maintenance without any difficulty. It is based on a simple electromagnetic and reliable principle that uses only a mobile element (piston containing ferromagnetic material), at a constant force, submerged in the fluid to be analyzed.
The time required for the piston to go over a given distance is related exactly to the dynamic viscosity of the fluid confined in a measurement chamber (Figure 1).
The Applicant would like to repeat that the object of this invention is to measure the viscosity of a heavy crude diluted with a precipitating agent is to precisely know which concentration of precipitate has the asphaltenes formation, known as the incipient point or star of the asphaltenes precipitation to avoid formation or aggregation of asphaltenes in an industrial application or process in the field.
Figure 1 shows a cross section of the electromagnetic viscometer 1 used in the current invention. The apparatus consist of a measurement chamber 1 where piston 4 is located that makes a voyage of ahead and return through the alternative driving of electromagnetic coils 3 (A and B). One of the coils is placed in order for the magnetic

-10-filed occurred, when the current flows through it, to tend to drag the piston in a direction along the channel. The second coil is placed to frag the coil along the channel in an opposite direction.
This method is based in viscosity measurements of a crude that is diluted with a precipitating agent (i.e. n-pentane, n-heptane, etc.) at a defined concentration (interval of 0.01 to 99.9% volume), with a volume of 25 mL of sample, viscosities in the interval of 0.2 to 10000 cP, at a temperature up to 463 K and pressures of 0.1 to 68.9 MPa. The incipient point of flocculation/precipitation of asphaltenes is detected to for a remarkable increase of viscosity (relative) of the suspension where the asphaltene particles aggregation occurs (Escobedo and Mansoori, 1995).
It can be observed in figure 4 that the behavior of the mixture dynamic viscosity {light crude ¨ toluene + n-heptane} shows (in logarithmic scale) a decrease when it is added to the precipitating agent; the value of viscosity has a minimum value fro precipitate volume fraction in the interval of 2-35%, After this minimum value, the dynamic viscosity of the mixture increases in the flocculation/precipitation threshold up to obtaining a maximum value in this region.
Based on the above description, it can be concluded that the incipient point of flocculation/precipitation of asphaltenes corresponds to the immediately previous point when viscosity increases, that is, the 35% volume of n-heptane in the mixture.
It can be observed in figure 5 that the incipient point of asphaltenes flocculation/precipitation coincides in the same relation

-11-(35% of volume) of n-heptane in the mixture at three different temperatures, i.e. 308.1 K, 313.2 K and 318.4 K and a constant pressure od 0.1 MPa.
Figure 6 shows the dynamic viscosities measured at 333. K in various mixtures {light crude + heavy crude} between 0 and 100%
volume of light crude. At low volume fractions of the added light crude (up to ¨ 15%), viscosity gradually decreases and the has a considerable increase of viscosity when the volume fractions of light crude exceed 26.6&; this increase of viscosity achieves a maximum io value and then the viscosity of the mixture gradually decreases.
Based on the previously described criteria and that is the object of the current invention to prescribe, the incipient point of asphaltenes flocculation/precipitation or the incipient point of flocculation threshold (or in this case, the incipient point of asphaltenes incompatibility threshold) was determined in 26.6% of light crude in the mixture.
It can be seen in Figure 7 (in logarithmic scale) that the dynamic viscosity slopes vs. volume fraction of light crudes showed the same behavior at different temperatures, that is, firstly a decrease of viscosity until obtaining a minimum value afterwards an important increase in the asphaltenes incompatibility threshold. This figure shows the incipient point of the asphaltene incompatibility measured or mixtures of these two crudes (heavy and light) at four different temperatures and 0.1 MPa. In the temperature range of 293.2-353.2 K, the incipient point starts when the fraction of light crude in the mixture is of 26.7%. The shadowed area in figure 7 shows the incompatibility threshold for each temperature.

-12-It is evident that the asphaltenes are maintained in the crude in a delicate balance (Speight, 1999) and this balance can be easily disturbed by the addition of saturated and removal of resins and aromatic (Wiehe and Kennedy, 2000b; Wiehe, 2012); therefore, the crudes blending can greatly change the global concentration of these molecular types altering this balance and flocculation/precipitating the asphaltenes.
The following example is shown to illustrate the operation of the best novel process known by the applicant for the determination of io heavy and light crudes mixtures incompatibility. Of course, it must not be considered as a limitation of what is claimed herein but that it only describes the method through which the operation process, reason of the current invention is described:
EXAMPLE
Before including an example, it is important to mention that in order to guarantee that our determination of dynamic viscosities are reliable, we previously calibrated the piston to be used, as well as the pressure transducer and system temperature gauge. The calibration and verification of the piston was carried out with S20, N4, S6 standards) provided by Cannon Instrument Company, ASTM S2162) and it involves the measurement of a standard fluid that can be identified at a stable temperature and that adjust the calibration parameters related to the selected piston to reproduce dynamic viscosity (with a mean absolute deviation of +1.0%) corresponding to the known value of said calibration standards to the established

-13-temperature.
The following examples show the operation of the process and apparatus described herein to determine the incompatibility in the crudes blending (heavy, light) in an interval of temperature of 463 K
and room temperature and pressure of 0.1 MPa (See Figure 2).
Figure 2 shows a schematic diagram for measurement of dynamic viscosity of reservoir fluids. A small volume quantity of sample contained in the high-pressure stainless steel container is requested to carry out viscosity measurement at different temperature and pressure conditions. The temperature inside the measurement chamber is measured with a temperature gauge 17 connected to a digital indicator 23. A pressure transducer together with a digital indicator 16 is connected to viscometer 18 to monitor the pressure in the measurement system. A serial interface RS-232 allows the communication of viscometer 18 with a computer. In order to generate pressure in the system, a positive displacement pump 1 is used, meanwhile for temperature generation in the apparatus; a recirculating bath 22 is used (MX/2011/003287A).
Step A. Mixtures of heavy and light crudes of 0%, 25-35%, 40-50%, 60-75% and 100% volume of light crude were prepared.
Step B. The heavy and light crude mixture 1 is loaded in a high-pressure stainless steel container 10 and connected to the measurement circuit through the valves 7 and 11. The high-pressure stainless steel container 10 contains a high-pressure stainless steel piston 9 inside that freely floats through the stainless steel container

- 14 -separating the mixture 8 of the pressurization fluid 4. In order to maintain a homogeneous temperature in the measuring system, the high-pressure stainless steel container 10 is heated with a heating resistance. The stainless steel pipelines that integrate the measuring 5 circuit are also heated with heating tapes.
Step C. The temperature in the system is established through the recirculating bath 22. The temperature in the apparatus is measured by a temperature detector 17 that is connected to a digital indicator 23.
The pressure in the system is generated and controlled by a positive io displacement pump 1 that used a mineral oil 4 as pressurization fluid.
The pressure in the system is monitored by a pressure transducer connected to pressure digital indicator 16. When the temperature in the apparatus 18 is close to the measurement temperature, the apparatus 18 is vertically placed and is connected to a vacuum pump 15 by the valve 14. The valves 12, 13, 14 and 21 must be open during the vacuum process; meanwhile the valves 11 and 19 must be maintained closed. The measuring circuit is emptied up to obtaining an appropriate vacuum (generally, after 20 minutes approximately), close the valves 14, 12, 13 and 21. Establish the required pressure in the positive displacement pump 1 and open slowly the valves 3, 7, 11, 12, 13 and 21. The valve 2 must be maintained closed; meanwhile the valve 5 must be open. In order to ensure that the system was filled with the mixture, purge a small volume quantity for the valves 14 and 19. Close slowly the valve 21 and place the apparatus 20 in measuring position (45 C).
Step D. When the mixture is stabilized at a temperature and

-15-pressure of 0.1 MPa, the values of dynamic viscosity and measuring temperature were recorded. Afterwards, temperature in the system is increased through a recirculating bath 22; when the analysis temperature is newly stabilized, the viscosity values for temperature and pressure of 0.1 MPa are registered. Repeat Step D up to the temperature of 463 K or any other temperature.
Step E. Monitor the behavior of the mixture viscosity based on the light crude added at a constant temperature for experimental determination of the incipient point of asphaltenes incompatibility threshold in crudes mixture through the mixture viscosity behavior based on the light crude added at a constant temperature; i.e. through the graphic observation of the slope change of behavior vs. light crude added (`)/0).
Step F. If the behavior of the viscosity vs. percentage of volume added of light crude, is not the typical behavior shown in Figure 3, mixtures of heavy and light crudes are prepared with volume percentages of light crude less than the inflexion point found in Step E
and steps B, C, D and E are repeated.
Step G. Step F is repeated until the slope change in the dynamic viscosity behavior of the mixture corresponds to the minimum percentage of added light crude (as observed in Figure 6); the immediately previous point to the slope change (or inflexion point) of viscosity is considered as the incipient point of the asphaltenes incompatibility threshold.
Based on the above described, we want to emphasize that it is well known that the asphaltenes is a crude fraction that can be

- 16 -precipitated when it is blended with non-polar hydrocarbon (n-pentane, n-heptane) or when two or more crudes are blended, causing tamponades in the pipelines, tanks, heat interchanger, etc.
The present invention consists of determining the concentration when the precipitation starts, that is, when they are incompatible. The incompatibility can be determined from the viscosity measurement based on the concentration, at a given temperature that is object of the current invention.
The viscosity results shown in Figure 6 clearly indicate where io incompatibility occurs in a mixture of heavy and light crude showing the inflexion point in the graphic.
It is important to have an adequate mixing due to the fact that small quantities of flocculated material loose energy due to little transfer of heat. Moderated quantities of asphaltenes causes pressure drops ad interfere in the equipment operation, provoking an inefficient process. At last, big quantities of asphaltenes cause intolerable tamponades and cause the process to stop until the pipelines are clean. That is why it is important to find the incompatibility point (the optimum mixture) to avoid the above-mentioned damages.

-17-

Claims (6)

What is claimed is:

1. A process for determining the incompatibility of heavy and light crudes mixtures characterized because it comprises the following steps: A; prepare mixtures of heavy and light crudes with 0%, 25-35%, 40-50%, 60-75% and 100% volume of light crude; B: load the heavy and light crude mixture to a high-pressure stainless steel container (up to 68.9 MPa) for connecting the circuit of the measurement apparatus of dynamic viscosities; C: establish the temperature in the system through the recirculating bath (up to 463 K) for a transfer (isothermal and isobaric); D: stabilize the system at constant temperature (from 463 K to room temperature) and a pressure (from 0.1 to 68.9 MPa) to register dynamic viscosity values pod and measuring temperature for subsequently increasing the temperature in the system by means of a recirculating bath until the analysis temperature is newly established, the viscosity value for said temperature is registered at a constant pressure (of 0.1 to 68.9 MPa) and immediately step D is repeated up to the temperature of 463 K or any other temperature; E: monitor the viscosity behavior of the sample based in the light crude added to a constant temperature for experimental determination of the incipient point of asphaltenes incompatibility threshold in the crudes mixture through the viscosity behavior of the mixture based on the light crude added to a constant temperature; i.e. through the graphical observation of the slope change of behavior vs. light crude volume (%); F: prepare mixtures of heavy crude with light crude with percentages of light crude volume less than the inflexion point found in step E and repeating Steps B, C, D and E when the viscosity behavior vs. volume percentage added of light crude, is not the typical behavior; G: repeat step F until the slope change in the viscosity behavior of dynamic viscosity of the mixture corresponds to the minimum percentage of light crude added;
the immediately previous point to the slope change (or inflexion point) of viscosity is considered as the incipient point of the asphaltenes incompatibility threshold.

2. The use of a system in the process for determining the incompatibility of heavy and light crudes according to claim 1, characterized because it comprises (i) a piston containing a ferromagnetic material; (ii) a piston guide that leads it along an established pathway; (iii) two electromagnetic coils placed in the measurement chamber to produce respective magnetic fields that tend to lead the piston all along its path in respective opposite directions and (iv) a detector of position sensitive to inductance of the coils to produce an indicative detection signal that the piston has reached voyage extreme positions.

3.
The use of the system according to claims 1 and 2 characterized by the alternative conduction of the two coils with its particular conduction device and sensitive to the position detector that changes between the two electromagnetic coils; as well as the adjustment of the duration of the time interval predetermined used during the distance (traveled by the piston) of the conduction to a determined value based on the duration of at least a previous travel of the piston.

4. The use of the system according to claims 1 to 3, characterized because the response to the first travel of the piston to the end of a time interval (maintaining the duration of the time interval to a fixed value) for a period comprising a plurality of travels of the piston at least of the detection signal does not indicate that the piston has reached one of the final positions of the voyage.

5. The use of the system according to claims 1 to 4, characterized because the adjustment of the time duration predetermined for the first travel of the piston after the emptying period of values to a value of at least six times the emptying value; as well as the response to the duration of conduction travel.

6. The use of the system according to the claims 1 to 5, characterized because it includes the following peripherals: (i) a pressure transducer and its digital indicator, (ii) a recirculating bath, (iii) high-pressure stainless steel containers including stainless steel floating pistons, (iv) high-pressure stainless steel pipelines of 1/8"
internal diameter, (v) high-pressure stainless steel valves to control the flow of crudes mixture, (VI) a computer for registering and storing the data, (vii) a positive displacement pump to generate and control pressure in the system, (viii) pressurization fluid, (xi) a temperature gauge welded at the bottom of the body to the measurement apparatus, (x) a vacuum pump, (xi) a plastic pipeline of 1/8" internal diameter, (xii) heating or insulating tapes, (xiii) temperature controllers.