PROCEDURE FOR THE TRANSPORTATION OF HEAVY RAW OILS IN THE FORM OF DISPERSION
DESCRIPTION OF THE INVENTION The present invention relates to the domain of the transport of viscous effluents, mainly the crude ones denominated "heavy", for example because of their proportion of asphaltenes. The methods of transporting the viscous crudes are known, which consist of fluidizing the crude oil by heating it, mixing it with a fluidizing product, or the pre-transport treatment, for example, the aqueous emulsification. However, these techniques are expensive in energy, or put into operation complex procedures that need important infrastructures that penalize the exploitation of the deposits. In the present description, it is designated by "slurry", a suspension, or a dispersion, of solid particles in a liquid that can be put into circulation, mainly by pumping. This type of slurry is already currently used in the course of dredging operations of estuaries, river banks, as well as in the mining industry. The interest is to transport a maximum of solid debris with the lowest possible pumping energy. As regards the oil sector, the
Ref.:161545
Suspended transport (slurry) is used to enrich fuel fuels with carbon particles and thus increase their calorific value. The proportion of solids can reach 60% by mass while always maintaining the acceptable flow properties. In this way, the present invention relates to a pipeline transport process of a viscous oil effluent. According to the invention, the following steps are carried out: the effluent is separated into at least one solid phase constituted by particles coming from the colloidal elements acting on the viscosity of said effluent, and in a fluidized liquid phase, a dispersed amount of particles in the fluidized liquid phase, in order to obtain a suspension, said suspension is circulated in the conduit. The separation step can be carried out by addition of an amount of n-alkane: such as butane, pentane, heptane. The particles can be removed from the fluidized liquid phase. The colloidal elements that act on the viscosity can be asphaltenes. The particles can be dispersed by mechanical mixing.
The temperature of the circulating suspension can be controlled to slow the dissolution of the particles in the effluent. The temperature of the suspension can be maintained below 40 ° C. The particles can be encapsulated after separation. The particles can be chemically modified before they are dispersed in the fluidized effluent. A dispersant additive of said particles can be added. A certain amount of a diluent of the liquid phase can be added. A poorly solubilizing diluent of the particles can be chosen. The precipitated asphaltenes can be added in an amount comprised between 1 and 30% by mass. The present invention will be better understood and its advantages will appear more clearly after reading the following description of the non-limiting examples illustrated by the figures appended hereto, among which: Figure 1 compares colloidal and suspended solutions (slurry), - Figures 2a and 2b show the evolution of
a suspension (slurry) as a function of time, figures 3 and 4 show the influence of shearing on a suspension (slurry), figures 5a and 5b show the influence of temperature on a suspension (slurry), figures 6a and 6b show the effectiveness of the encapsulation of the as-altenes. The present invention is preferably applied to heavy crudes. This consists in modifying the structural organization of heavy crude that behaves like a viscous colloidal suspension, to obtain a suspension of non-colloidal particles with a weaker viscosity. The particles related by this transformation are, in the framework of a preferred embodiment of the present invention, the asphaltenes. Asphaltenes are molecules of higher molecular weight contained in certain oil crudes. These are characterized by their strong polarity and the presence of polycondensed aromatic nuclei. The coating of these unfolded particles in the crude oil is largely responsible for the heavy viscosity of the heavy crudes. This coating can be suppressed by keeping the asphaltenes in the form of solid particles precipitated in the crude. This configuration change can be achieved by deasphalting the crude, then dispersing the precipitated asphaltenes in the liquid
of base, mainly under strong mechanical agitation. A mode of operation, null and limiting, has been put to the point and it has been verified that the change of morphology of the crude oil in the form of suspension that results, gives very well to a decrease in the viscosity. The protocol of preferred mode first needs a deasphalting of the crude oil. There are already procedures to carry out this operation. Advantageously, according to the invention, the asphaltene particles are transported in the form of a solid, by the base liquid of the crude oil in which these asphaltenes are dispersed, in such a way that the liquid obtained is more fluid than the crude oil. origin. In this way, the transport by pumping in the ducts is facilitated up to the refining units. In these refining units, the suspension (slurry) is either introduced as such in these treatment units, or after a phase of separation of the solid particles in suspension, the asphaltenes, which can simplify the downstream procedures. Example of mode of operation: Asphaltenes are precipitated with the aid of pentane following the American standard ASTM 893-69. Once filtered (with the help of a frit of porosity 4) and dried (at 80 ° C for 2 hours). The particles are crushed (Centrifugal crushed Retsch S 1000 spheres, 15 minutes at 350 revolutions / minute) then sieved between 100 and 500 μp ?.
For its suspension (slurry), or dispersion, the asphaltenes are dispersed in the deasphalted crude, with a mechanical agitator RW20 IKA, at 1200 revolutions / minute for 20 minutes. The agitation blade is chosen for its high shearing power. It is a serpentine vane type "butterfly knot" that allows an excellent dispersion in the area of turbulence between its windings. The temperature of the sample is maintained at 40 ° C. In each case described below, 25 g of product are prepared. Test 1: Comparison of two samples, one in the form of colloidal suspension and the other in the form of slurry: a) Two samples containing 10% by mass of asphaltenes were prepared. The asphaltenes are introduced into the same deasphalted crude following two different methods: one with the mode of operation described above one is given as a result of one product in the form of suspension (slurry), the other with a heating at 80 ° C for 1 hour that results in a product in the form of a colloidal solution. In this case, the viscosity of a crude having 10% asphaltenes is appreciably recognized. The two samples are immediately observed in the
same conditions in the optical microscope and its viscosity is measured with the help of a rheometer (type AR2000, flat-plane geometry, with an air gap of 1 mm). The results shown in Figure 1 (Viscosity in Pa.s as a function of the gradient of the G-zone) confirm the difference in the morphology of the samples: no particle is visible under the optical microscope for colloidal solution 1, while the suspension 2 contains it to a large extent. The standard deviations of the viscosity V (Pa.s) of the samples (135 Pa.s for the colloidal solution and 40 Pa.s for the suspension (slurry)) demonstrate the interest of the suspension (slurry) of the asphaltenes to decrease the viscosity of heavy crudes. b) A natural asphaltenic crude (with 17% asphaltenes in bulk) is compared with a suspension (slurry) obtained as previously described but including 17% by mass of asphaltene. To be comparable, the samples have been heated at 40 ° C for 20 minutes. The colloidal crude has a viscosity of 345 Pa.s, while the suspension (slurry) has a viscosity of 95 Pa.s. The effectiveness of the process is very well demonstrated since the decrease in viscosity is significant. It can be noted that the viscosity of the suspension (slurry) in this case is relatively strong for an efficient transport, also a dilution might be necessary.
Test 2: Followed in the time of the dissolution of the asphaltenes in the suspension (slurry): In order to observe the proportion in time of the morphology of a suspension (slurry), the rheological and microscopic evolution of the sample that has 10% of asphaltenes in suspension (slurry) is observed in a period of 146 days. During all this duration, the sample is left at rest, at room temperature (20 ° C) and samples are taken regularly. Figure 2a shows the evolution of the viscosity of the suspension (slurry) 3, as a function of time. The different curves (3 to 8) show a progressive asphaltene redissolution which results in an elevation of the viscosity up to the value of the colloidal viscosity 9. Figure 2b gives the viscosity values as a function of time t in days, and the photographs under the corresponding optical microscope show the dissolution of the asphaltenes. Although this evolution at room temperature is slow, this allows to obtain the benefit of the decrease in viscosity for a pipeline flow of several hours. Test 3: Influence of shear on the dissolution of asphaltenes: The shear suffered by the suspension (slurry) at the time of its runoff or flow in the pipeline, risks disturbing its morphology and destroying very
quickly the decrease in viscosity generated. In order to evaluate the incidence of shearing, different tests have been carried out. Two samples of slurry suspension containing 10% by mass of asphaltenes have been prepared following the protocol described above. One is left at rest, while the other is agitated with the help of a mechanical stirrer and a magnetic bar. The rheological evolution (viscosity in Pa.s) and morphological evolution has been followed in both cases. The results shown in figure 3 (viscosity as a function of t in days) by intermediation of the curve 10 corresponding to a sample under agitation, and curve 11 corresponding to a sample at rest, do not present any significant difference between the two samples Another test consisted in leaving a suspension sample in the slurry in the rheometer, under controlled shearing (50 s "1) and in recording its viscosity throughout the duration of the test, that is to say a dozen hours Figure 4 shows that, under these test conditions, some viscosity increase V is observed during shearing for a duration of about 8 hours.Two tests prove the absence of a strong influence of the flow or runoff on the transformation
of crude oil in the form of suspension "slurry" in colloidal suspension. It can also be noted that if the suspension configuration (slurry) that has been strongly sensitive to the 1 st cent, this could not have been carried out since the operation modality of the preparation in the samples imposes a 1 ami or very strong. Test 4: Influence of temperature on the dissolution of asphaltenes After having shown that the suspension morphology (slurry) of the crude oil is stable at room temperature (T = 20 ° C), the influence of temperature is determined. To control its stability at temperature, two samples containing 10% asphaltenes have been prepared following the described operation mode, and placed in the oven at 40 ° C and 60 ° C. Its rheological and microscopic evolution has also been observed. The results of Figure 5a (relationship of viscosity with respect to time t on viscosity at time 0: Vt / VO, as a function of time h in hours) show that a rise in temperature strongly favors the dissolution kinetics of the asphaltenes, the kinetics being represented by the slope of lines 12 (at 40 ° C) and 13 (at 60 ° C). Figure 5b
shows the effect of temperature on a sample after 24 hours. The suspension
(slurry) of heavy crude may need additional precautions, or specific treatments, to block or encourage the dissolution of asphaltenes in the crude and if it should be transported to a temperature above 40 ° C. Test 5: Pre-encapsulation of the asphaltenes: In order to block the dissolution of the asphaltenes to guarantee the stability of the suspension (slurry) at the temperature and consequently, to increase the amount of asphaltenes introduced in the suspension, the asphaltenes can be advantageously encapsulated before being mixed with the crude. The complex coacervation method has been employed, for example described by J. Richard and J-P Benoit in "Microencapsulation" - Techniques de l'Ingénieur: Gene des Procedes; J 2 210, 1-20. The experimental protocol used is as follows: two 100 ml solutions are prepared, one containing 1% gelatin, the other 1% gum arabic in milli-Q water and maintained at 40 ° C. The pH of the two solutions is adjusted to 6.5. The asphaltenes are immediately
dispersed in the gelatin solution using a Heidolph agitator for 30 minutes, always at 40 ° C. An agitation of the order of 700 minutes is used.1 This is followed by a dropwise addition of the gum arabic solution (approximately 3 ml per minute), then the pH of the mixture is adjusted to 4.5 with the help of a solution of 10% acetic acid (predetermined volume) In order that the droplets of the coacervate can be deposited around the oil droplets, the agitation is kept constant for one hour Finally, the temperature of the system is lowered to 8 ° C To allow the coacervate to gel, 2 ml of glutaraldehyde are added and the pH is finally adjusted to 9 with the help of a 10% sodium hydroxide solution (predetermined volume) and the whole is left under agitation at 4500 revolutions / minute for 12 hours The capsules obtained are then filtered, washed with water and with toluene, and finally dried A suspension sample (slurry) containing 10% encapsulated asphaltenes has been prepared and left in suspension. the stove at 40 ° C. Its stability to temperature has been verified by a rheological and microscopic monitoring. Figure 6a shows the structure of the suspension of
encapsulated asphaltenes after a day and after 36 days. The results show that the encapsulation has been effective to block the dissolution of the asphaltenes, leaving the configuration in suspension (slurry) intact after 30 days at the temperature of 400 C. A slight increase in viscosity is observed (from 50 Pa.s to 60 Pa.s). Figure 6b shows the structure of the suspension of asphaltenes not encapsulated in the same instants: the structure is no longer of the suspension type, and the viscosity becomes very important. Test 7: Inertisation of asphaltenes by surface polymerization: Always with the objective of blocking the solvation of the asphaltenes when they are placed in suspension, the asphaltenes precipitated by acrylic acid are modified. The acid adsorbed on the asphaltenes is then polymerized. To do this, to 4 grams of asphaltenes obtained by precipitation with heptane and dried for two hours under vacuum, add 4 grams of acrylic acid and 4 grams of heptane. The suspension is stirred for two hours at room temperature under an inert atmosphere (argon). Excess acrylic acid is removed by filtration
and the solid fraction is suspended in 8 grams of heptane. After the addition of 0.04 g of azo-bis-isobutyronitrile, the suspension is maintained at 4 hours at 60 ° C under agitation, always under an inert atmosphere. After filtration and washing with heptane, the modified asphaltenes are dried for 2 hours at 80 ° C. Prepare a suspension (slurry) (sample No. 1) composed of 2 grams of modified asphaltenes and 18 grams of deasphalted crude, following the mode of operation already described. Another suspension (slurry) is prepared in parallel (sample No. 2) containing 2 grams of unmodified asphaltenes and 18 grams of deasphalted crude. These two samples of suspensions (slurry) are kept at 80 ° C and the evolution of their viscosity is followed in the course of time. After a slight increase during the first hours of storage of sample No. 1, the viscosity is stabilized at a value that is approximately three times lower than that of sample No. 2 after a week of storage at 80 ° C . Storage time at 80 ° C (hours) Sample 0 2 5 170 viscosity at 20 ° C (Pa.s) No. 1 38 63 75 77 No. 2 43 132 194 202
The modification of asphaltenes allows better control of their capacity to be dissolved in deasphalted crude oil. Test 8: Inertisation of the asphitenes by surface modification: The modification of the surface of the asphaltene particles by the oleophobic compounds allows to inhibit the solvation of the asphaltenes. At 25 ° of perfluoroheptanoic acid, 4 grams of precipitated asphaltenes are added. The suspension is stirred at room temperature for 2 hours. After filtration and washing with heptane, the asphaltenes are dried at 80 ° C for 2 hours. A suspension (slurry) (sample No. 3) composed of 2 grams of modified asphaltenes and 18 grams of deasphalted crude oil is prepared following the above-described mode of operation. A suspension (slurry) is prepared in parallel (sample No. 4) containing 2 grams of unmodified asphaltenes and 18 grams of deasphalted crude. These two samples are stored at 80 ° C and the evolution of their viscosity is followed in the course of time. The viscosity of sample No. 3 is approximately twice less than that of sample No. 4 after one week of heating at 80 ° C.
Storage time at 80 ° C (hours)
Sample 0 2 5 170 viscosity at 20 ° C (Pa.s) No. 3 26 75 103 104 No. 4 43 132 194 202
It is therefore possible to improve the process according to the invention itself by treating the asphaltenes after their precipitation from the crude oils. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.