U.S. patent application number 10/522021 was filed with the patent office on 2006-06-08 for method of transporting heavy crude oils in dispersion.
Invention is credited to Jean-Francois Argillier, Patrick Gateau, Isabelle Henaut.
Application Number | 20060118467 10/522021 |
Document ID | / |
Family ID | 30011454 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060118467 |
Kind Code |
A1 |
Argillier; Jean-Francois ;
et al. |
June 8, 2006 |
Method of transporting heavy crude oils in dispersion
Abstract
The invention relates to a method of transporting a viscous
petroleum effluent in pipes, wherein the following stages are
carried out: separating the effluent into at least a solid phase
consisting of particles coming from the colloidal elements acting
on the viscosity of said effluent and into a fluidized liquid
phase, keeping an amount of particles dispersed in said fluidized
liquid phase so as to obtain a suspension (2), and circulating the
suspension in the pipe.
Inventors: |
Argillier; Jean-Francois;
(Saint Cloud, FR) ; Henaut; Isabelle; (Rueil
Malmaison, FR) ; Gateau; Patrick; (Maurepas,
FR) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
30011454 |
Appl. No.: |
10/522021 |
Filed: |
July 8, 2003 |
PCT Filed: |
July 8, 2003 |
PCT NO: |
PCT/FR03/02115 |
371 Date: |
June 28, 2005 |
Current U.S.
Class: |
208/370 ;
208/309 |
Current CPC
Class: |
F17D 1/16 20130101 |
Class at
Publication: |
208/370 ;
208/309 |
International
Class: |
C10G 31/00 20060101
C10G031/00; C10C 3/14 20060101 C10C003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2002 |
FR |
0209407 |
Claims
1) A method of transporting a viscous petroleum effluent in pipes,
characterized in that the following stages are carried out:
separating the effluent into at least a solid phase consisting of
particles coming from the colloidal elements that act on the
viscosity of said effluent and into a fluidized liquid phase,
keeping an amount of particles dispersed in said fluidized liquid
phase so as to obtain a suspension, circulating said suspension in
the pipe.
2) A method as claimed in claim 1, wherein separation is carried
out by addition of an amount of n-alkane such as butane, pentane,
heptane.
3) A method as claimed in claim 1, wherein the particles are
removed from the fluidized liquid phase.
4) A method as claimed in claim 1, wherein said elements are
asphaltenes.
5) A method as claimed in claim 1, wherein said particles are
dispersed through mechanical mixing.
6) A method as claimed in claim 1, wherein the temperature of said
circulating suspension is controlled so as to slow down dissolution
of the particles in the effluent.
7) A method as claimed in claim 6, wherein the temperature of the
suspension is kept below 40.degree. C.
8) A method as claimed in claim 1, wherein said particles are
encapsulated after separation.
9) A method as claimed in claim 1, wherein said particles are
chemically modified prior to being dispersed in the fluidized
effluent.
10) A method as claimed in claim 1, wherein an additive is added to
disperse said particles.
11) A method as claimed in claim 1, wherein a predetermined amount
of a diluent for said liquid phase is added.
12) A method as claimed in claim 11, wherein a badly-solubilizing
diluent of said particles is selected.
13) A method as claimed in claim 4, wherein the precipitated
asphaltenes are added in proportions ranging between 1 and 30% by
mass.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the sphere of
transportation of viscous effluents, notably crudes referred to as
"heavy" crudes, for example because of their asphaltenes
content.
BACKGROUND OF THE INVENTION
[0002] There are known viscous crude transportation methods which
consist in fluidizing the crude by heating, mixing with a
fluidizing product, or treatment prior to transportation, for
example bringing into an aqueous emulsion. However, these
techniques are energy-consuming, or use complex processes that
require large infrastructures which penalize the development of
reservoirs.
[0003] In the present description, what is referred to as slurry is
a suspension or a dispersion of solid particles in a liquid that
can be circulated, notably by pumping. This slurry flow type is
already commonly used during estuary or river dredging operations,
and in the mining industry. What is most interesting is that it
allows to transport a maximum amount of solid spoils with as little
pumping energy as possible. Concerning the petroleum industry,
slurry transportation is used to enrich fuels with coal particles
and thus to increase their calorific value. The solid content can
reach 60% by mass while keeping acceptable flow properties.
SUMMARY OF THE INVENTION
[0004] The present invention thus relates to a method of
transporting a viscous petroleum effluent in pipes. According to
the invention, the following stages are carried out:
[0005] separating the effluent into at least a solid phase
consisting of particles coming from the colloidal elements that act
on the viscosity of said effluent and into a fluidized liquid
phase,
[0006] keeping an amount of particles dispersed in said fluidized
liquid phase so as to obtain a suspension,
[0007] circulating said suspension in the pipe.
[0008] The separation stage can be carried out by adding an amount
of n-alkane such as butane, pentane, heptane.
[0009] The particles can be removed from the fluidized liquid
phase.
[0010] The colloidal elements acting on the viscosity can be
asphaltenes.
[0011] The particles can be dispersed through mechanical
mixing.
[0012] The temperature of said circulating suspension can be
controlled in order to slow down the dissolution of the particles
in the effluent.
[0013] The temperature of the suspension can be kept below
40.degree. C.
[0014] Said particles can be encapsulated after separation.
[0015] Said particles can be chemically modified prior to being
dispersed in the fluidized effluent.
[0016] An additive can be added to disperse said particles.
[0017] A predetermined amount of a diluent for said liquid phase
can be added.
[0018] A badly-solubilizing diluent can be selected for said
particles.
[0019] The precipitated asphaltenes can be added in proportions
ranging between 1 and 30% by mass.
BRIEF DESCRIPTION OF THE FIGURES
[0020] Other features and advantages of the present invention will
be clear from reading the description hereafter, given by way of
non limitative examples, with reference to the accompanying figures
wherein:
[0021] FIG. 1 compares colloidal and slurry solutions,
[0022] FIGS. 2 and 2a show the evolution of a slurry as a function
of time,
[0023] FIGS. 3 and 4 show the influence of shear on a slurry,
[0024] FIGS. 5 and 5a show the influence of temperature on a
slurry,
[0025] FIGS. 6a and 6b show the efficiency of the encapsulation of
asphaltenes.
DETAILED DESCRIPTION
[0026] The present invention preferably applies to heavy crudes. It
thus consists in modifying the structural organization of the heavy
crude which behaves like a viscous colloidal suspension, to obtain
a suspension of non-colloidal particles of lower viscosity. The
particles concerned by this change are, within the context of a
preferred embodiment of the present invention, asphaltenes.
Asphaltenes are molecules of higher molecular weight contained in
some crude oils. They are characterized by their high polarity and
by the presence of polycondensed aromatic rings. The overlap of
these particles spread out in the crude is greatly responsible for
the high viscosity of the heavy crudes. This overlap can be
eliminated by keeping the asphaltenes in form of solid particles
precipitated in the crude. This configuration change can be
obtained by deasphalting the crude, then by dispersing the
precipitated asphaltenes in the base liquid, notably under strong
mechanical stirring. A non limitative method of operation has been
developed and it has been checked that the resulting morphology
change of the crude in suspension form actually leads to a
viscosity decrease. The protocol of the preferred embodiment first
requires deasphalting the crude. Methods already exist to carry out
this operation.
[0027] Advantageously, according to the invention, the asphaltene
particles are transported in solid form in the crude base liquid in
which these asphaltenes are dispersed so that the liquid obtained
is more fluid than the original crude. Thus, transportation by
pumping through the pipes is facilitated up to the refining plants.
In these refining plants, the slurry is either fed as it is in
these treating plants, or after a stage of separation of the
suspended solid particles, the asphaltenes, which can simplify the
downstream processes.
EXAMPLE OF A METHOD OF OPERATION
[0028] The asphaltenes are precipitated by means of pentane
according to the American standard ASTM 893-69. Once filtered (by
means of sintered material of porosity 4) and dried (at 80.degree.
C. for 2 hours), the particles are crushed (centrifugal ball
crusher Retsch S 1000, 15 minutes at 350 rpm), then screened
between 100 and 500 .mu.m.
[0029] In order to obtain a slurry, or dispersion, the asphaltenes
are dispersed in the deasphalted crude with a mechanical agitator
RW20 IKA, at 1200 rpm for 20 minutes. The stirring paddle is
selected for its high shearing power. It is a "bow tie" type
serpentine paddle which allows excellent dispersion by means of the
turbulence zone existing between its coils. The temperature of the
sample is kept at 40.degree. C. In each case described hereafter,
25 g product are prepared.
[0030] Test 1: Comparison of Two Samples, One in Colloidal
Suspension Form and the Other in Slurry Form
[0031] a) Two samples containing 10% by mass of asphaltenes were
prepared. The asphaltenes are brought into the same deasphalted
crude according to two different methods:
[0032] one with the method of operation described above, which
leads to a product in slurry form,
[0033] the other by heating to 80.degree. C. for 1 hour, which
leads to a product in colloidal solution form. In this case, the
viscosity is substantially that of a crude having 10%
asphaltenes.
[0034] The two samples are then observed under the same conditions
with an optical microscope and their viscosity is measured by means
of a rheometer (AR2000 type, of plane-plane geometry, with a 1-mm
air gap). The results shown in FIG. 1 (viscosity in Pas versus
shear gradient G) confirm the morphology difference of the samples:
no particle is visible with the optical microscope for colloidal
solution 1, whereas slurry 2 contains a large proportion thereof.
The differences in viscosity V (Pas) of the samples (135 Pas for
the colloidal solution and 40 Pas for the slurry) show the
relevance of slurrying the asphaltenes to decrease the viscosity of
the heavy crudes.
[0035] b) A natural asphaltene-containing crude (with 17% by mass
of asphaltenes) is compared with a slurry obtained as above, but
comprising 17% by mass of asphaltenes. To be comparable, the two
samples were heated to 40.degree. C. for 20 minutes. The colloidal
crude has a viscosity of 345 Pas, whereas the slurry has a
viscosity of 95 Pas. The efficiency of the method is clearly shown
since the viscosity decrease is significant. It can be noted that
the viscosity of the slurry in this case is relatively high for
efficient transportation, a dilution would therefore be
necessary.
[0036] Test 2: Monitoring of the Dissolution of the Asphaltenes
Suspended in the Slurry
[0037] In order to observe the behaviour with time of the
morphology of a slurry, the rheologic and microscopic evolution of
the sample containing 10% asphaltenes in slurry is observed over a
146-day period. During this time, the sample is left to rest, at
ambient temperature (20.degree. C.), and samples are regularly
taken. FIG. 2 shows the evolution of the viscosity of slurry 3 as a
function of time. The various curves (3 to 8) show a progressive
redissolution of the asphaltenes, which is translated into a
viscosity rise up to the viscosity value of colloidal solution 9.
FIG. 2a gives the viscosity values as a function of time t in days,
and the corresponding optical microscope photographs show the
dissolution of the asphaltenes. However, this evolution at ambient
temperature is slow, which allows to keep the benefits from the
viscosity decrease for a flow in a pipeline during several
hours.
[0038] Test 3: Influence of Shear on the Dissolution of
Asphaltenes
[0039] The shear undergone by the slurry as it flows in a pipeline
may disturb its morphology and annihilate too quickly the viscosity
decrease generated. In order to evaluate the incidence of shear,
various tests were carried out.
[0040] Two samples of a suspension in a slurry containing 10% by
mass of asphaltenes were prepared according to the protocol
described above. One is left to rest, the other is stirred by means
of a magnetic agitator and a bar magnet. The rheologic (viscosity
in Pas) and morphologic evolution was followed in both cases. The
results shown in FIG. 3 (viscosity as a function of t in days) by
means of curve 10 which corresponds to a sample being stirred and
curve 11 which corresponds to a sample at rest show no significant
difference between the two samples.
[0041] Another test consisted in leaving a sample of a suspension
in a slurry in the rheometer, under controlled shearing (50
s.sup.-1), and in recording its viscosity throughout the test, i.e.
during approximately ten hours h. FIG. 4 shows that, under such
test conditions, no increase in viscosity V is observed during
shearing for about 8 hours.
[0042] These two tests prove the absence of a strong influence of
the flow on the change from a crude in slurry suspension to a
colloidal suspension. It can also be noted that, if the slurry
configuration had been highly sensitive to shearing, it could not
have been carried out because the sample preparation procedure
requires very high shearing.
[0043] Test 4: Influence of Temperature on the Dissolution of the
Asphaltenes
[0044] After showing that the crude slurry morphology is stable at
ambient temperature (T=20.degree. C.), the influence of temperature
is determined. In order to control its resistance to temperature,
two samples containing 10% asphaltenes were prepared according to
the procedure described and placed in a drying oven at 40.degree.
C. and 60.degree. C. Their rheologic and microscopic evolution is
observed. The results of FIG. 5 (ratio of the viscosity at time t
to the viscosity at time 0: Vt/V0, as a function of time h in hour)
show that a temperature rise greatly favours the asphaltene
dissolution kinetics, the kinetics being shown by the slope of
lines 12 (at 40.degree. C.) and 13 (at 60.degree. C.). FIG. 5a
shows the effect of temperature on a sample after 24 hours.
Slurrying the heavy crude can require additional precautions or
specific treatments to block or to slow down the dissolution of the
asphaltenes in the crude if it has to be transported at a
temperature above 40.degree. C.
[0045] Test 5: Preliminary Encapsulation of the Asphaltenes
[0046] In order to block dissolution of the asphaltenes to
guarantee the stability of the slurry at the temperature and to be
able thereafter to increase the amount of asphaltenes suspended,
the asphaltenes can be advantageously encapsulated prior to being
mixed with the crude. The complex coacervation method was used,
described for example by J. Richard and J.-P. Beno t in
"Microencapsulation"--Techniques de l'Ingenieur: Genie des
Procedes; J 2 210, 1-20. The experimental protocol used is as
follows: two 100-ml solutions, one containing 1% gelatin, the other
1% arabic gum, are prepared in milli-Q water and maintained at
40.degree. C. The pH value of these two solutions is adjusted to
6.5. The asphaltenes are then dispersed in the gelatin solution
using a Heidolph agitator for 30 minutes, still at 40.degree. C. A
stirring rate of the order of 700 min.sup.-1 is used. This is
followed by a dropwise addition of the arabic gum solution (about 3
ml per minute). Then, the pH value of the mixture is adjusted to
4.5 by means of a 10% acetic acid solution (predetermined volume).
In order to allow the coacervate droplets to settle around the oil
drops, stirring is maintained constant for one hour. Finally, the
temperature of the system is lowered to 8.degree. C. to allow the
coacervate to gel. 2 ml glutaraldehyde is added and the pH value is
finally adjusted to 9 by means of a 10% sodium hydroxide solution
(predetermined volume) and the whole system is left under stirring
at 4500 rpm for 12 hours. The capsules obtained are then filtered,
washed with water and toluene, and finally dried.
[0047] A slurry sample containing 10% encapsulated asphaltenes was
prepared and left in a drying oven at 40.degree. C. Its resistance
to temperature was checked by rheologic and microscopic monitoring.
FIG. 6a shows the structure of the encapsulated asphaltene
suspension after 1 day and after 36 days. The results show that
encapsulation has been efficient to block dissolution of the
asphaltenes, the slurry configuration remaining intact after more
than 30 days at a temperature of 40.degree. C. A slight viscosity
rise (from 50 Pas to 60 Pas) is observed. FIG. 6b shows the
structure of the non-encapsulated asphaltene suspension at the same
times: the structure is no longer of the suspension type, and the
viscosity becomes very high again.
[0048] Test 7: Inerting the Asphaltenes by Surface
Polymerization
[0049] Still in order to block solvation of the aspahltenes when
they are suspended, the precipitated asphaltenes are modified by
acrylic acid. The acid adsorbed on the asphaltenes is then
polymerized. 4 grams acrylic acid and 4 grams heptane are therefore
added to 4 grams asphaltenes obtained by heptane precipitation and
dried for two hours under vacuum. The suspension is stirred for two
hours at ambient temperature in an inert atmosphere (argon). The
excess acrylic acid is eliminated by filtration and the solid
fraction is suspended again in 8 grams heptane. After addition of
0.04 g azo-bis-isobutyronitrile, the suspension is maintained for 4
hours at 60.degree. C. under stirring, still in an inert
atmosphere. After filtration and washing with heptane, the modified
asphaltenes are dried for 2 hours at 80.degree. C. A slurry (sample
No.1) consisting of 2 grams modified asphaltenes and 18 grams
deasphalted crude is prepared according the procedure already
described above. Another slurry (sample No.2) containing 2 grams
non-modified asphaltenes and 18 grams deasphalted crude is prepared
in parallel. These two slurry samples are stored at 80.degree. C.
and the evolution of their viscosity is monitored in the course of
time.
[0050] After a slight increase during the first storage hours of
sample No.1, the viscosity stabilizes at a value that remains
approximately three times lower than that of sample No.2 after a
week's storage at 80.degree. C. TABLE-US-00001 Storage time at
80.degree. C. (h) 0 2 5 170 Sample Viscosity at 20.degree. C. (Pa
s) No. 1 38 63 75 77 No. 2 43 132 194 202
[0051] Modification of the asphaltenes allows to better control
their capacity to be dissolved in the deasphalted crude.
[0052] Test 8: Inerting the Asphaltenes by Surface Change
[0053] Changing the surface of the asphaltene particles by means of
oleophobic compounds allows to inhibit solvation of the
asphaltenes. 4 grams of precipitated asphaltenes are added to 25
cm.sup.3 perfluoroheptanoic acid. The suspension is stirred at
ambient temperature for 2 hours. After filtration and washing with
heptane, the asphaltenes are dried at 80.degree. C. for 2
hours.
[0054] A slurry (sample No.3) consisting of 2 grams modified
asphaltenes and 18 grams deasphalted crude is prepared according to
the procedure already described. A slurry (sample No.4) containing
2 grams non-modified asphaltenes and 18 grams deasphalted crude is
prepared in parallel. These two samples are stored at 80.degree. C.
and the evolution of their viscosity is monitored in the course of
time.
[0055] The viscosity of sample No.3 remains approximately two times
lower than that of sample No.4 after a week's storage at 80.degree.
C. TABLE-US-00002 Storage time at 80.degree. C. (h) 0 2 5 170
Sample Viscosity at 20.degree. C. (Pa s) No. 3 26 75 103 104 No. 4
43 132 194 202
[0056] The method according to the invention can thus be clearly
improved by treating the asphaltenes after their precipitation from
the crudes.
* * * * *