Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02816133 2013-05-10
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Method
The present invention relates to a method for preparing a pipelineable
hydrocarbon mixture from a crude heavy hydrocarbon mixture comprising
visbreaking.
The invention also relates to a method of transporting a heavy hydrocarbon
mixture
recovered from a wellsite to a refinery and to a heavy hydrocarbon recovery
method.
Additionally the invention relates to the pipelineable hydrocarbon mixture and
visbroken
hydrocarbon mixture obtained in the methods.
BACKGROUND
Heavy hydrocarbons, e.g. bitumen, represent a huge natural source of the
world's total potential reserves of oil. Present estimates place the quantity
of heavy
hydrocarbon reserves at several trillion barrels, more than 5 times the known
amount of
the conventional, i.e. non-heavy, hydrocarbon reserves. This is partly because
heavy
hydrocarbons are generally difficult to recover by conventional recovery
processes and
thus have not been exploited to the same extent as non-heavy hydrocarbons.
Heavy
hydrocarbons possess very high viscosities and low API (America! Petroleum
Institute)
gravities which makes them difficult, if not impossible, to pump in their
native state.
This makes heavy hydrocarbon mixtures challenging to transport from wells to
refineries. Pumping of high viscosity fluids is also expensive. Generally
therefore the
flowability of heavy hydrocarbon mixtures obtained from heavy hydrocarbon
reservoirs
needs to be improved through partial or full upgrading before transportation
by pipeline
to a conventional refinery.
The transportability of viscous heavy hydrocarbon mixtures is conventionally
improved by dilution with a lighter hydrocarbon such as naphtha, a very light
crude oil
or a condensate. The dilution of the heavy hydrocarbon with the diluent
typically
reduces its overall API to about 20 degrees enabling it to be pumped to a
refinery.
Vast amounts of diluent are, however, required. For example 20-40 % by weight
of the
pumpable hydrocarbon mixture may be diluent.
There are numerous disadvantages to the use of a diluent in this way. These
include: ,
= The need to transport diluent on-site. This problem becomes particularly
acute
for off-shore well sites.
= The need to identify a compatible diluent for each heavy hydrocarbon
mixture,
e.g. one that does not cause precipitation of asphaltenes
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= The need to separate the diluent and the hydrocarbon mixture at the
refinery
prior to processing
= Down stream processing/cleaning of the diluent prior to its reuse or
disposal.
Often it is preferable to return it to the well site (i.e. to recycle it)
although this again
requires it to be pumped a significant distance.
Another approach that has previously been adopted is to upgrade heavy
hydrocarbon mixtures on site prior to transportation to a refinery. Thus a
heavy
hydrocarbon mixture recovered from a well may be upgraded to form lighter oil
having
an API of about 20-35 degrees on site and then pumped to a refinery. CA
1,314,260
and CA 2,195,165, for example, both disclose processes wherein heavy
hydrocarbon is
upgraded by visbreaking to produce a pipelineable product.
CA 1,314,260 discloses a process wherein heavy crude oil is thermally
processed by visbreaking and the resulting product is deasphalted to afford
syncrude.
The thermal visbreaking step is described as being more severe than
conventional
visbreaking processes that have been used in refineries on atmospheric
residues.
Thus the visbreaking is carried out a temperature of 426 to 510 C for a time
that
produces a certain level of severity in the visbroken product. Typical
pressures and
residence times given for the visbreaking are 2 to 30 bar and 0.5 to 50
minutes
respectively. The severity of the visbreaking conditions can be tolerated in
the process
because coke and other insoluble materials formed in the thermal reaction
under
severe conditions is removed, along with asphaltenes, in a subsequent
deasphalting
step. The deasphalting step substantially reduces the viscosity of the
visbroken
product and reduces the content of metal and sulphur in the product. Following
deaspalting, the deasphalting solvent is preferably removed from the upgraded
hydrocarbon by supercritical separation.
CA 2,195,165 describes a similar process for converting heavy crude oils and
bitumen to a stable product suitable for pipeline transportation. Like the
method in CA
1,314,260, the method involves visbreaking in severe conditions. More
specifically in
the method of CA 2,195,165 a heavy crude oil is preferably preflashed to
produce
heavy and light fractions and then the heavy fraction is fed to a severe
visbreaker
wherein a conversion exceeding 7.5 % by weight is carried out. CA 2,195,165
teaches
that it is advantageous to maximise visbreaking in order to produce a lower
viscosity
product and a maximum amount of lighter products. No specific temperatures,
pressures or residence times are disclosed in CA 2,195,165.
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CA 2,796,146 also discloses a process for reducing the viscosity of heavy
crude
oils at the well head or oil centre to improve their transportability based on
visbreaking.
The process of CA 2,796,146 involves reducing the viscosity of heavy crude
oils, in
situ, at the well head by visbreaking, wherein the energy required for the
visbreaking is
obtained by means of a solar concentration plant. The preferred conditions for
visbreaking in the process of CA 2,796,146 are a temperature of 350 to 400 C
and a
pressure of 5 to 50 bar for 20 minutes to 2.5 hours. In the examples of CA
2,796,146
the viscosity of the heavy crude oils is improved by about 90 %, specifically
by 95, 96,
88 and 93 % in each of examples 1 to 4 respectively. This level of viscosity
improvement requires a high level of conversion in the visbreaking process.
The
mechanism of capturing solar heat depends on the visbreaking reaction
conditions. If
the reaction temperature is higher than 380 C, the fluid used as heating
fluid for the
visbreaker is preferably a molten salt which is heated by a solar field. lithe
reaction
temperature is lower than 380 C, a diathermic oil may alternatively be used.
The
focus of CA 2,796,146 is very much on the use of solar energy to power the
visbreaking process.
Alternatively, a recovered heavy hydrocarbon mixture may be partially refined
or upgraded on-site, e.g. using a processing plant located close to the
production well.
CA 2,530,148, for example, discloses a process wherein part of a bitumen feed
is
upgraded and used to convert the overall feed into a pipeline-transportable
crude oil.
The process involves the following steps:
1. Separation of a bitumen feed into two parts, a first part and a second
part.
2. Separation of the first part into light and heavy fractions, preferably
by
distillation.
3. Thermally cracking, e.g. by visbreaker soaking, the heavy fraction into
a
second light fraction and a residual fraction and fractionating said
fractions.
4. Mixing the second part and the two light fractions to form a
transportable
hydrocarbon.
5. Using the residual fraction from thermal cracking for energy generation.
The process of CA 2,530,148 is therefore relatively complex involving several
energy intensive steps, e.g. distillation, thermal cracking and fractionation.
This is
undesirable, especially in a relatively remote location, e.g. offshore.
Moreover a
residual fraction of the bitumen feed is not incorporated into the pipeline-
transportable
crude oil and thus represents a loss in process yield.
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CA 2,773,000 also describes a process wherein heavy oil having an API gravity
of 20 or less is partially upgraded at the well site in order to improve its
pumpability. In
the method taught in CA 2,773,000 the heavy oil is thermally cracked in a
process
referred to as high conversion soaker cracking. In this process the heavy oil
is
thermally cracked at a pressure of 0 to 1 bar and at a temperature of 370 to
440 C for
to 150 minutes in a soaker drum whilst at the same time injecting stripping
steam
into the drum to separate thermally cracked oil. In preferred methods of CA
2,773,000
the stripping steam comprising the thermally cracked oil is separated into
different
fractions. The heavier fraction of the thermally cracked oil is discharged
from the
10 separator and used as fuel to produce steam for recovering further heavy
oil from the
reservoir. Thus like CA 2,530,148 a residual fraction of the bitumen feed is
not
incorporated into the pipeline-transportable crude oil and thus represents a
loss in
process yield.
A need therefore exists for alternative processes for treating crude heavy
15 hydrocarbon mixtures to improve their transportability by pipeline.
Simple and
economically attractive processes that utilise the whole spectrum of
hydrocarbons
recovered are clearly desirable.
SUMMARY OF INVENTION
Viewed from a first aspect the present invention provides a method for
preparing a pipelineable hydrocarbon mixture from a crude heavy hydrocarbon
mixture
comprising:
- visbreaking said crude heavy hydrocarbon mixture at a temperature of 350 to
440 C
and a pressure of 20 to 150 bar for 0.5 to 15 minutes to produce a visbroken
hydrocarbon mixture; and
- mixing said visbroken hydrocarbon mixture with a diluent to produce said
pipelineable
hydrocarbon mixture.
Viewed from a further aspect, the present invention provides A method of
transporting a heavy hydrocarbon mixture recovered from a wellsite to a
refinery
comprising:
- preparing a pipelineable hydrocarbon mixture from a crude heavy hydrocarbon
mixture by a method as hereinbefore defined at said wellsite; and
- pumping said pipelineable hydrocarbon mixture to said refinery.
Viewed from a further aspect, the present invention provides a heavy
hydrocarbon recovery process comprising:
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- extracting a heavy hydrocarbon and water mixture from a subterranean
formation;
- adding a diluent to said heavy hydrocarbon and water mixture;
- separating a crude heavy hydrocarbon mixture from said heavy hydrocarbon
and
water mixture in a separator;
5 -
visbreaking said crude heavy hydrocarbon mixture as hereinbefore defined to
produce a visbroken hydrocarbon mixture;
- mixing said visbroken hydrocarbon mixture with a diluent to produce a
pipelineable
hydrocarbon mixture; and
- pumping said pipelineable hydrocarbon mixture to a refinery.
Viewed from a further aspect, the present invention provides a system for
preparing a pipelineable hydrocarbon mixture from a crude heavy hydrocarbon
mixture
comprising:
- a separator for separating a heavy hydrocarbon and water mixture into a
crude heavy
hydrocarbon mixture and water, wherein said separator has an inlet for heavy
hydrocarbon and water mixture, an outlet for water and an outlet for crude
heavy
hydrocarbon mixture;
- a visbreaker for visbreaking said crude heavy hydrocarbon mixture having
an inlet for
crude heavy hydrocarbon mixture fluidly connected to crude heavy hydrocarbon
outlet
of said separator and an outlet for visbroken hydrocarbon mixture;
- a cooling means for cooling said visbroken hydrocarbon mixture having an
inlet for
visbroken hydrocarbon mixture fluidly connected to the visbroken hydrocarbon
mixture
outlet of said visbreaker and an outlet for cooled visbroken hydrocarbon
mixture; and
- a means for adding diluent to said cooled visbroken hydrocarbon mixture
to produce
said pipelineable hydrocarbon mixture.
Viewed from a further aspect, the present invention provides a pipelineable
hydrocarbon mixture obtainable by the method as hereinbefore defined.
Viewed from a further aspect, the present invention provides a pipelineable
hydrocarbon mixture obtained by the method as hereinbefore defined.
Viewed from a further aspect, the present invention provides a visbroken
hydrocarbon mixture obtainable by visbreaking a crude heavy hydrocarbon
mixture at a
temperature of 350 to 440 C and a pressure of 20 to 150 bar for 0.5 to 15
minutes.
Viewed from a further aspect, the present invention provides a visbroken
hydrocarbon mixture obtained by visbreaking a crude heavy hydrocarbon mixture
at a
temperature of 350 to 440 C and a pressure of 20 to 150 bar for 0.5 to 15
minutes.
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Viewed from a further aspect, the present invention provides a visbroken
hydrocarbon
mixture having an API gravity of 12 to 22 , a viscosity of 50 to 2000 cSt at
15 C, and
an olefin content of less than 3.0 %.
DEFINITIONS
As used herein the term "pipelineable hydrocarbon mixture" refers to a
hydrocarbon mixture that meets a pipeline specification.
As used herein the term "hydrocarbon mixture" refers to a combination of
different hydrocarbons, i.e. to a combination of various types of molecules
that contain
carbon atoms and, in many cases, attached hydrogen atoms. A "hydrocarbon
mixture"
may comprise a large number of different molecules having a wide range of
molecular
weights. Generally at least 90 % by weight of the hydrocarbon mixture consists
of
carbon and hydrogen atoms. Up to 10% by weight may be present as sulfur,
nitrogen
and oxygen as well as metals such as iron, nickel and vanadium (i.e. as
measured
sulfur, nitrogen, oxygen or metals).
As used herein the term "heavy hydrocarbon mixture" refers to a hydrocarbon
mixture comprising a greater proportion of hydrocarbons having a higher
molecular
weight than a relatively lighter hydrocarbon mixture. Terms such as "light",
"lighter",
"heavier" etc. are to be interpreted herein relative to "heavy".
As used herein the term "visbreaking" refers to a process wherein a
hydrocarbon mixture is heated to reduce its viscosity by cracking of heavy or
heavier
hydrocarbons into lighter hydrocarbons.
As used herein the term "visbreaking conversion" refers to the net conversion
of
heavy hydrocarbons in the feedstock having a boiling point of greater than 525
C that
are converted to hydrocarbons having a boiling point of less than 525 C in
the
visbreaking process. Visbreaking conversion (%) is 100 x ((quantity of 525 C+
in
feedstock minus quantity of 525 C+ in visbroken product)/quantity of 525 C+
in
feedstock). The quantity of hydrocarbon that has a boiling point above 525 C
in a
hydrcarbon mixture can be determined by plotting its distillation curve.
As used herein the term "upgrading" refers to a process wherein the
hydrocarbon mixture is altered to have more desirable properties, e.g. to
providing
lighter, synthetic crude oils from heavy hydrocarbon mixtures by chemical
processes
including visbreaking.
As used herein "kerosene" refers to a hydrocarbon fraction having a boiling
point between about 180 C and 240 C;
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As used herein "light gas oil" refers to a hydrocarbon fraction having a
boiling
point between about 240 C and 320 C;
As used herein "heavy gas oil" refers to a hydrocarbon fraction having a
boiling
point between 320 C and 375 C.
As used herein "vacuum gas oil" refers to a hydrocarbon fraction having a
boiling point between about 375 C and 525 C;
As used herein "vacuum residue" refers to a hydrocarbon fraction having a
boiling point of greater than about 525 C.
As used herein API gravity refers to API as measured according ASTM 0287.
As used herein viscosity refers to viscosity in cSt at 15 C as measured
according to ASTM 0445 method.
As used herein %wt olefins refers to olefin content as measured by NMR
according to CAPP (Canadian Association Petroleum Producers).
As used herein the term "fluidly connected" encompasses both direct and
indirect fluid connections.
DETAILED DESCRIPTION
The methods of the present invention are for preparing a pipelineable
hydrocarbon mixture that preferably meets a pipeline specification.
Pipeline
specifications vary in different countries and different networks and are also
varied on a
seasonal basis. A typical pipeline specification, e.g. for the Enbridge
pipeline system in
Canada, is a viscosity of 350 cSt at the pipeline reference temperature,
wherein the
pipeline reference temperature is varied between 6-18 C depending on the
season
and a density of less than 940 kg/I at 15 C.
The API and viscosity requirements of pipeline specifications ensure that the
pipelineable hydrocarbon mixtures can be pumped efficiently from wellsites to
refineries without destabilisation, e.g. precipitation, occurring. Preferred
pipelineable
hydrocarbon mixtures have an API gravity of at least 18 and more preferably
at least
20 . Particularly preferred pipelineable hydrocarbon mixtures have an API
gravity of 18
to 30 , more preferably 19 to 26 and still more preferably 20 to 24 .
Preferably the
viscosity of the pipelineable hydrocarbon mixture is in the range 100-500 cSt
at the
pipeline reference temperature, e.g. at 15 C, more preferably 300-350 cSt at
the
pipeline reference temperature, e.g. at 15 C, e.g. about 350 cSt at the
pipeline
reference temperature, e.g. at 15 C To meet these requirements many crude
heavy
,
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hydrocarbon mixtures must be processed to reduce their viscosity prior to
transport in
pipelines.
The method of the present invention is directed to the preparation of a
pipelineable hydrocarbon mixture from a crude heavy hydrocarbon mixture. The
crude
heavy hydrocarbon mixture preferably has an API gravity of less than about 18
. More
preferably the API gravity of the crude heavy hydrocarbon mixture is 10 to 18
, more
preferably 12 to 18 and still more preferably 16 to 18 . The viscosity of the
crude
heavy hydrocarbon mixture is preferably 250 to 3000 cSt at 15 C, more
preferably 400
to 2000 cSt at 15 C and still more preferably 500 to 1500 cSt at 15 C.
In the method of the present invention the viscosity of the crude heavy
hydrocarbon mixture is decreased for pipeline transportation by visbreaking at
a
temperature of 350 to 440 C and a pressure of 20 to 150 bar for 0.5 to 15
minutes to
produce a visbroken hydrocarbon mixture. The visbreaking conditions are much
milder
than those employed in conventional visbreaking processes and are specifically
selected to ensure that an appropriate balance between viscosity reduction and
visbroken hydrocarbon mixture stability is achieved. It is critical that the
visbroken
hydrocarbon mixture is both pumpeable and stable (e.g. does not form
precipates).
Stability is important since, unlike conventional visbreaking processes, in
the method of
the invention the entirety of the visbroken hydrocarbon mixture is preferably
incorporated into the pipelineable hydrocarbon mixture.
In preferred methods of the invention visbreaking is at a temperature of 390
to
430 C, still more preferably 395 to 425 C and yet more preferably 400 to 420
C.
More preferably visbreaking is at a pressure of 50 to 150 bar, still more
preferably 70 to
130 bar, yet more preferably 80 to 120 bar and especially preferably 90 to 110
bar.
More preferably visbreaking is for 1 to 10 minutes, still more preferably 2 to
8 minutes,
yet more preferably 3 to 7 minutes and especially preferably about 5 minutes.
The visbreaking process may be carried out in conventional visbreaking
apparatus. Preferably a coil visbreaker (sometimes referred to as a furnace
visbreaker) or soaker visbreaker is used.
In a coil visbreaker heating and cracking occurs in furnace tubes. The
visbroken hydrocarbon mixture is generally quenched upon exiting the
visbreaker to
stop the cracking reactions. As described below in more detail, this is
preferably
achieved by heat exchange with the crude heavy hydrocarbon mixture being fed
to the
coil visbreaker. The extent of the cracking reaction is preferably controlled
by
regulation of the speed of flow of the crude heavy hydrocarbon mixture through
the
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furnace tubes. Of course the temperature and/or pressure are also
preferably
controlled. The residence time in a coil visbreaker tends to be relatively
short. Thus
when visbreaking occurs in a coil visbreaker, visbreaking is preferably for 1
to 8
minutes, yet more preferably 2 to 6 minutes and especially preferably about 5
minutes.
Preferably visbreaking is at a temperature of 395 to 425 C and more
preferably 410 to
420 C.
A soaker visbreaker comprises a furnace and a soaker drum. The crude heavy
hydrocarbon mixture enters the furnace and is heated to a specified
temperature and is
then transferred to a drum fluidly connected to the furnace. The bulk of the
cracking
reaction occurs in this drum wherein the heated crude heavy hydrocarbon
mixture is
held at an elevated temperature for a pre-determined period of time. As in a
coil
visbreaker, the visbroken hydrocarbon mixture is generally quenched upon
exiting the
visbreaker, specifically the drum, to stop the cracking reactions, preferably
by heat
exhange with the crude heavy hydrocarbon mixture being fed to the furnace of
the
soaker visbreaker. The extent of cracking reaction is preferably controlled by
the
residence time in the drum of the soaker visbreaker. The temperature and/or
pressure
are also preferably controlled. The residence time in a soaker visbreaker
tends to be
longer than in a coil visbreaker. Then when visbreaking occurs in a soaker
visbreaker,
visbreaking is preferably for 1 to 12 minutes, more preferably 5 to 10 minutes
and
especially preferably about 10 minutes. Preferably visbreaking is at a
temperature of
390 to 410 C and more preferably 400 to 405 C.
As mentioned above, the conditions employed in the visbreaking reaction are
critical in the methods of the present invention. In a conventional
visbreaking process
the conversion is typically 15 %. This is the maximum level of conversion that
can be
achieved without generation of problematic precipitates. In the method of the
present
invention the conversion level is preferably 1 to 14 %, more preferably 5 to
12 A) and
still more preferably 8 to 10 %. These conversion levels are intentionally
significantly
lower than those used in conventional visbreaking processes. This reflects the
fact that
a less severe or milder cracking process is employed. This reduces the
viscosity of the
crude hydrocarbon mixture by a sufficient level to meet pipeline
specifications whilst
minimising the extent of unsaturated compounds in the visbroken hydrocarbon
mixture
thereby improving stability.
The visbreaking in the method of the invention upgrades the crude heavy
hydrocarbon mixture. Thus the average molecular weight of the hydrocarbons
present
in the visbroken hydrocarbon mixture is lower than the average molecular
weight of the
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hydrocarbons in the crude heavy hydrocarbon starting mixture. Advantageously
the
visbreaking may be carried out at the well site. This means that the crude
heavy
hydrocarbon mixture need only be transported a minimum distance.
In preferred methods of the present invention the crude heavy hydrocarbon
5 mixture is preheated prior to visbreaking. Preferably the crude heavy
hydrocarbon
mixture is preheated to a temperature of 300 to 400 C, still more preferably
320 to 390
C and yet more preferably 330 to 345 C. Preferably heating is at least
partially
carried out in a heat exchanger against the crude visbroken hydrocarbon
mixture
exiting the visbreaker.
10 In preferred methods of the present invention the crude heavy
hydrocarbon
mixture is separated from a heavy hydrocarbon and water mixture in a separator
prior
to visbreaking. Any conventional separator may be used. Representive examples
of
suitable separators are gravity separators or cyclone separators. Preferred
methods of
the invention therefore comprise:
- separating the crude heavy hydrocarbon mixture from a heavy hydrocarbon and
water
mixture in a separator;
- visbreaking the crude heavy hydrocarbon mixture as hereinbefore defined
to produce
a visbroken hydrocarbon mixture; and
- mixing the visbroken hydrocarbon mixture with a diluent to produce the
pipelineable
hydrocarbon mixture.
Optionally the crude heavy hydrocarbon mixture undergoes treatment(s) to
remove solids such as sands therefrom prior to visbreaking. Solids, such as
sand, may
be removed from a crude heavy hydrocarbon mixture by, e.g. hot water
extraction, by
filtration or by settling processes known in the art. The exact details of the
cleaning
process will depend on how the heavy hydrocarbon mixture has been recovered.
The
skilled man will readily be able to identify suitable cleaning techniques.
In particularly preferred methods of the invention a diluent is added to the
heavy
hydrocarbon and water mixture prior to, or during, separation in the
separator. Thus a
particularly preferred method of the invention comprises:
- adding a diluent to a heavy hydrocarbon and water mixture;
- separating the crude heavy hydrocarbon mixture from the heavy hydrocarbon
and
water mixture in a separator;
- visbreaking the crude heavy hydrocarbon mixture as hereinbefore defined
to produce
a visbroken hydrocarbon mixture; and
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- mixing the visbroken hydrocarbon mixture with a diluent to produce said
pipelineable
hydrocarbon mixture.
The purpose of the diluent is to improve the separation of the hydrocarbon and
water phases in the separator. Preferably the diluent has an API of 20-800 and
more
preferably 30-700. The diluent is preferably a hydrocarbon diluent.
Representative
examples of suitable diluents include naphtha, light crude oil or gas oils,
synthetic oil,
gas condensates and mixtures thereof.
Preferred diluents are naptha, gas
condensates, synthetic oil and mixtures thereof. Diluent may, for example,
comprise
0-100 %wt naptha, 0-70 %wt light crude oil or gas oil, 0-25% gas condensates,
0-3
%wt butane and 0-3 %wt BTEX. When naptha and/or gas condensate is used as the
diluent it prefeferably has an API of 40 to 600. When synthetic oil is used as
the diluent
it preferably has an API of 20 to 40 .
In preferred methods of the invention the amount of diluent added prior to or
during separation is 5 to 40 %wt and more preferably 10 to 35 %wt based on the
total
weight of the resulting crude heavy hydrocarbon mixture. When the diluent is
naptha
and/or gas condensate, the amount added prior to or during separation is still
more
preferably 15 to 30 %wt and yet more preferably 18 to 25 %wt based on the
total
weight of the resulting crude heavy hydrocarbon mixture. When the diluent is
synthetic
oil, the amount added prior to or during separation is still more preferably
25 to 40 %wt
and yet more preferably 30 to 38 %wt based on the total weight of the
resulting crude
heavy hydrocarbon mixture. Thus in the methods of the present invention the
crude
heavy hydrocarbon mixture that undergoes visbreaking preferably comprises 60
to 95
%wt heavy hydrocarbon and 5 to 40%wt diluent and more preferably 65 to 90 %wt
heavy hydrocarbon and 10 to 35 %wt diluent. Generally the majority of the
diluent will
survive the visbreaking process unchanged and will be present in the visbroken
hydrocarbon mixture.
In some preferred methods of the present invention substantially all of the
crude
heavy hydrocarbon mixture separated from the heavy hydrocarbon and water
mixture
is visbroken. In such methods at least 90 %wt, still more preferably at least
95 %wt
and still more preferably about 100%wt of the crude heavy hydrocarbon mixture
separated from the heavy hydrocarbon and water mixture is visbroken. In
particularly
preferred methods of the invention the entirety of the crude heavy hydrocarbon
mixture
separated from the heavy hydrocarbon and water mixture is visbroken.
In other preferred methods of the present invention, only a fraction of the
crude
heavy hydrocarbon mixture separated from the heavy hydrocarbon and water
mixture
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is broken. In such methods preferably 20 to 80 %wt, still more preferably 30
to 70 %wt
and yet more preferably 40 to 60 %wt of the crude heavy hydrocarbon mixture
separated from the heavy hydrocarbon and water mixture is visbroken.
Correspondingly in such methods preferably 20 to 80 %wt, still more preferably
30 to
70 % and yet more preferably 40 to 60 %wt of the crude heavy hydrocarbon
mixture
separated from the heavy hydrocarbon and water mixture is not visbroken. As
described below in more detail, this non-visbroken crude heavy hydrocarbon
mixture is
preferably blended with the visbroken hydrocarbon mixture.
In alternative methods, however, the crude heavy hydrocarbon mixture
separated from water is fractionated to produce at least a lighter fraction
and a heavier
fraction prior to visbreaking. In this case, the heavier fraction then
undergoes
visbreaking. The lighter fraction is preferably mixed with the visbroken
hydrocarbon
mixture, along with diluent, to produce the pipelineable hydrocarbon mixture.
Alternative methods of the invention therefore further comprise fractionating
the crude
heavy hydrocarbon mixture to produce a lighter fraction and a heavier fraction
and
visbreaking the heavier fraction. Thus a particularly preferred method of the
invention
comprises:
- adding a diluent to a heavy hydrocarbon and water mixture;
- separating the crude heavy hydrocarbon mixture from the heavy hydrocarbon
and
water mixture in a separator;
- fractionating the crude heavy hydrocarbon mixture to produce at least a
lighter
fraction and a heavier fraction
- visbreaking the heavier fraction of crude heavy hydrocarbon mixture as
hereinbefore
defined to produce a visbroken hydrocarbon mixture; and
- mixing the visbroken hydrocarbon mixture with a diluent and optionally the
lighter
fraction to produce said pipelineable hydrocarbon mixture.
In further preferred methods of the present invention no additives are added
to
the crude heavy hydrocarbon mixture following separation from water and prior
to or
during said visbreaking. Thus the visbreaking process is preferably non-
catalytic. This
is advantageous since the crude heavy hydrocarbon mixture fed to the
visbreaker
comprises heavy metals that would be likely to foul catalysts.
Preferred methods of the present invention further comprise recovering or
extracting a heavy hydrocarbon and water mixture from a subterranean
formation.
Thus a preferred method of the present invention comprises:
- extracting a heavy hydrocarbon and water mixture from a subterranean
formation;
CA 02816133 2013-05-10
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- adding a diluent to the heavy hydrocarbon and water mixture;
- separating the crude heavy hydrocarbon mixture from the heavy hydrocarbon
and
water mixture in a separator;
- visbreaking the crude heavy hydrocarbon mixture as hereinbefore defined to
produce
a visbroken hydrocarbon mixture; and
- mixing the visbroken hydrocarbon mixture with a diluent to produce said
pipelineable
hydrocarbon mixture.
The heavy hydrocarbon and water mixture may be extracted or recovered from
a subterranean formation using any recovery technique but is preferably a
thermal
recovery technique. A preferred method of the present invention further
comprises the
step of recovering a heavy hydrocarbon and water mixture. Representative
examples
of some techniques that may be used to extract or recover heavy hydrocarbon
mixture
include water flooding, cyclic steam injection (CSS), vapour extraction
(VAPEX), hot
solvent injection and steam assisted gravity drainage (SAGD), as well as
combinations
of the afore-going. Preferably the extracting or recovering is by SAGD.
The API gravity of the heavy hydrocarbon in the heavy hydrocarbon and water
mixture extracted from a subterranean formation is typically less than about
15 ,
preferably less than 12 , still more preferably less than 10 , e.g. less than
8 . Generally
the API gravity of the heavy hydrocarbon extracted from a subterranean
formation is
about 5 to about 15 , more preferably from about 6 to about 12 , still more
preferably
about 70 to about 12 , e.g. about 7.5-90. At such API gravities, viscosity and
flowability
are matters of concern. Examples of heavy hydrocarbon mixtures that typically
have
API gravities falling in the above-mentioned ranges are bitumens, tars, oil
shales and
oil sand deposits. Often heavy hydrocarbon mixtures are recovered at well
sites
located significant distances away from a refinery. For instance, the heavy
hydrocarbon mixture may be recovered offshore. The improvement in viscosity
that
can be achieved in the method of the present invention is therefore critical.
As described above, a diluent is preferably added to the heavy hydrocarbon
,
and water mixture prior to, or during, separation. Preferably this increases
the API
gravity of the crude heavy hydrocarbon mixture obtained from separation to 10
to 18 ,
more preferably 12 to 18 and still more preferably 16 to 18 . The viscosity
of the crude
heavy hydrocarbon mixture obtained from separation is preferably 250 to 3000
cSt at
15 C, more preferably 400 to 2000 cSt at 15 C and still more preferably 500
to 1500
cSt at 15 C.
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14
The API gravity of the visbroken hydrocarbon mixture is preferably 12 to 22 ,
more preferably 14 to 20 and still more preferably 17 to 19.5 . The viscosity
of the
visbroken hydrocarbon mixture is preferably 50 to 2000 cSt at 15 C, more
preferably
100 to 1000 cSt at 15 C and still more preferably 200 to 750 cSt at 15 C.
The
visbroken hydrocarbon mixture preferably comprises less than 3.0 %, more
preferably
less than 1.0 % and still more preferably less than 0.5 %wt olefins.
Particularly
preferably the visbroken product comprises no detectable (i.e. <0.5 wt%)
olefins.
In preferred methods of the invention the visbroken hydrocarbon mixture is
cooled, preferably in a heat exchanger. As described above, the visbroken
hydrocarbon mixture is preferably cooled against the crude heavy hydrocarbon
mixture
being fed into the visbreaker. Preferably the visbroken hydrocarbon mixture is
cooled
to a temperature of 20 to 80 C, more preferably 25 to 50 C and still more
preferably
25 to 30 C.
In a preferred method of the invention, the visbroken hydrocarbon mixture is
stripped of gases, e.g. H2S, after cooling. Thus in a preferred method the
cooled
visbroken hydrocarbon mixture is depressurised (e.g. by passing through a
valve) and
then flashed in a gas/liquid separator to produce gas and hydrocarbon mixture.
The
gas is preferably condensed and processed in a desulfurisation unit. The
hydrocarbon
mixture produced in the desulfurisation unit is preferably mixed with the
visbroken
hydrocarbon mixture obtained from the gas/liquid separator.
In preferred methods of the invention substantially all of the visbroken
hydrocarbon mixture is incorporated into the pipelineable hydrocarbon mixture.
Thus
preferably at least 90 %wt, more preferably at least 95 %wt and still more
preferably at
least 99 %wt of the visbroken hydrocarbon mixture is incorporated into the
pipelineable
hydrocarbon mixture. Preferably only gases produced during visbreaking are
removed
from the visbroken product. This is advantageous since it ensures that the
visbroken
product comprises a blend of hydrocarbons of a wide range of molecular
weights. In
particular heavier hydrocarbons are not removed, e.g. by deasphalting or
fractionating.
Thus in preferred methods of the invention the visbroken hydrocarbon mixture
is not
deasphalted. In further preferred methods of the invention the visbroken
hydrocarbon
mixture is not fractionated.
The visbreaking process employed in the present invention causes only a slight
or subtle change in the overall composition of the heavy hydrocarbon mixture.
Thus
essentially the same spectrum or range of hydrocarbons of different molecular
weights
is present in the visbroken product as in the crude heavy hydrocarbon
feedstock. The
CA 02816133 2013-05-10
visbreaking process slightly reduces the quantity of some of the heavier
hydrocarbons
present. An advantage of the methods of the present invention is therefore
that the
visbroken hydrocarbon mixture has a desirable hydrocarbon structure for
improving the
transportability of the mixture. The visbroken hydrocarbon mixture
preferably
5 comprises a blend of hydrocarbons of a wide range of molecular weights.
Particularly
preferably the visbroken hydrocarbon mixture comprises kerosene, light gas oil
and
heavy gas oil.
Particularly preferably the visbroken hydrocarbon mixture produced in the
method of the invention comprises a proportion of middle distillate, e.g. up
to and
10 including about 40% by weight of the mixture is kerosene, light gas oil
and heavy gas
oil. Preferably, the visbroken hydrocarbon mixture comprises at least 5% by
weight,
especially at least 10%, 15%, 20% or 30% by weight, of middle distillate. The
upper
limit on the amount of middle distillate present may be, e.g. 50 % by weight.
Furthermore, in some embodiments the visbroken hydrocarbon mixture
15 produced in the process of the invention preferably comprises a
proportion of
atmospheric residue, e.g. 1-45% by weight of the mixture is vacuum gas oil and
vacuum residue. Preferably, the visbroken hydrocarbon mixture comprises less
than
40% by weight of atmospheric residue, e.g. 5-35 % by weight. The visbroken
hydrocarbon mixture preferably comprises less than 15% by weight of vacuum
residue,
e.g. Ito 10%, more preferably 1-5% by weight.
In the methods of the present invention, the visbroken hydrocarbon mixture is
mixed with a diluent to produce the pipelineable hydrocarbon mixture. The
mixing of
the visbroken hydrocarbon mixture and the diluent may be carried out using
conventional equipment. The mixing or blending may, for example, be achieved
by
stirring or agitation in a vessel, using jet mixers or mixer nozzles, line
mixing or pump
mixing. Preferably the mixing step yields a homogenous product.
Preferably the diluent has an API of 20-80 and more preferably 30-70 . The
diluent is preferably a hydrocarbon diluent. Representative examples of
suitable
diluents include naphtha, light crude oil or gas oils, synthetic oil, gas
condensates and
mixtures thereof. Preferred diluents are naptha, gas condensates, synthetic
oil and
mixtures thereof. Diluent may, for example, comprise 0-100 %wt naptha, 0-70
%wt
light crude oil or gas oil, 0-25% gas condensates, 0-3 %wt butane and 0-3 %wt
BTEX.
When naptha and/or gas condensate is used as the diluent it prefeferably has
an API
of 40 to 60 . When synthetic oil is used as the diluent it preferably has an
API of 20 to
CA 02816133 2013-05-10
16
400. Preferably the diluent is the same diluent that is added to the heavy
hydrocarbon
and water mixture prior to, or during, separation.
Preferably the quantity of diluent added to the visbroken hydrocarbon mixture
is
0.5 to 20 %wt and more preferably 1 to 15 %wt based on the total weight of
said
pipelineable hydrocarbon mixture. When the diluent is naptha and/or gas
condensates
the amount of diluent added to the visbroken hydrocarbon mixture is still more
preferably 2.5 to 7.5 %wt and especially preferably 2.5 to 5%wt of based on he
total
weight of said pipelineable hydrocarbon mixture. When the diluent is synthetic
oil the
amount of diluent added to the visbroken hydrocarbon mixture is still more
preferably
10 to 20 %wt and especially preferably 12.5 to 17.5%wt of based on he total
weight of
said pipelineable hydrocarbon mixture.
As mentioned above, the majority of the diluent added to the crude heavy
hydrocarbon mixture prior to or during separation survives the visbreaking
process.
The total amount of diluent present in the final pipelineable hydrocarbon
mixture is
therefore approximately the sum of the diluent added prior to or during
separation and
the diluent added to the visbroken hydrocarbon mixture. Preferably the total
amount of
diluent in the final pipelineable hydrocarbon mixture is 5.5 to 60 %wt, more
preferably
11 to 50 %wt based on the total weight of the pipelineable hydrocarbon
mixture. When
the diluent used is naptha and/or gas condensates, the total amount of diluent
in the
final pipelineable hydrocarbon mixture is preferably 17.5 to 37.5 %wt, more
preferably
20.5 to 30 %wt, based on the total weight of the pipelineable hydrocarbon
mixture.
When the diluent used is synthetic oil, the total amount of diluent in the
final
pipelineable hydrocarbon mixture is preferably 35 to 60 %wt and more
preferably 42.5
to 55.5 %wt based on the total weight of the pipelineable hydrocarbon mixture.
In some preferred methods of the invention the visbroken hydrocarbon mixture
is mixed or blended with non-visbroken heavy hydrocarbon mixture to produce
the
pipelineable hydrocarbon mixture. The mixing of the visbroken hydrocarbon
mixture
and the non-visbroken heavy hydrocarbon mixture may be carried out using
conventional equipment. The mixing or blending may, for example, be achieved
by
stirring or agitation in a vessel, using jet mixers or mixer nozzles, line
mixing or pump
mixing. Preferably the mixing step yields a homogenous product. The mixing or
blending with non-visbroken heavy hydrocarbon mixture may be carried out
before or
after diluent addition but is preferably after diluent addition.
When the method additionally comprises mixing or blending the visbroken
hydrocarbon mixture with non-visbroken crude heavy hydrocarbon mixture, the
total
CA 02816133 2013-05-10
17
amount of diluent may be yet further reduced. In this case the total amount of
diluent in
the final pipelineable hydrocarbon mixture is preferably 2.5 to 30 %wt and
more
preferably 5.5 to 25 %wt based on the total weight of the pipelineable
hydrocarbon
mixture. When the diluent used is naptha and/or gas condensates, the total
amount of
diluent in the final pipelineable hydrocarbon mixture is preferably 8.5 to
18.5 %wt and
more preferably 10.5 to 15 %wt, based on the total weight of the pipelineable
hydrocarbon mixture. When the diluent used is synthetic oil, the total amount
of diluent
in the final pipelineable hydrocarbon mixture is preferably 17.5 to 30 %wt and
more
preferably 21.5 to 28 %wt based on the total weight of the pipelineable
hydrocarbon
mixture.
A significant advantage of the methods of the present invention is that the
amount of diluent added to produce the final pipelineable hydrocarbon mixture
is
relatively low. This means less diluent needs to be tranported to the
wellsite, less
diluent needs to be removed from the hydrocarbon mixture at the refinery and
less
diluent needs to be cleaned.
The pipelineable hydrocarbon mixture produced by the method of the invention
preferably has an API gravity of at least about 5 degrees higher than that of
the heavy
hydrocarbon mixture extracted from the formation, e.g. an API gravity of at
least about
8, 12, 15 or 18 degrees higher. In a preferred embodiment, the pipelineable
hydrocarbon mixture has an API gravity of greater than 20 degrees. Preferred
pipelineable hydrocarbon products have an API gravity of about 19-25 degrees,
more
preferably about 20-24 degrees.
In preferred methods of the present invention the pipelineable hydrocarbon
mixture produced has a viscosity of less than 500 cSt at pipeline reference
temperature
(e.g. 15 C), more preferably less than 400 cSt at pipeline reference
temperature (e.g.
15 C), still more preferably less than 350 cSt at pipeline reference
temperature (e.g.
15 C). Preferably the viscosity of the pipelineable hydrocarbon mixture is in
the range
100-500 cSt at pipeline reference temperature (e.g. 15 C), more preferably
300-350
cST at pipeline reference temperature (e.g. 15 C), e.g. about 350 cSt at
pipeline
reference temperature (e.g. 15 C). The pipelineable hydrocarbon mixture
preferably
comprises less than 1.5 %, more preferably less than 0.5 % and still more
preferably
less than 0.25 %M olefins. Particularly preferably the pipelineable
hydrocarbon
mixture comprises no detectable olefins.
A significant advantage of the methods of the present invention is that the
equipment required to carry out the method is all conventional. Thus the
separator,
CA 02816133 2013-05-10
18
visbreaker, heat exchanger and means for adding diluent are all commercially
available. Operators are also familiar with the operation and maintenance of
such
equipment.
The present invention also relates to a system for carrying out the method of
the present invention, i.e. for preparing a pipelineable hydrocarbon mixture
from a
crude heavy hydrocarbon mixture. The system comprises:
- a separator for separating a heavy hydrocarbon and water mixture into a
crude heavy
hydrocarbon mixture and water, wherein said separator has an inlet for heavy
hydrocarbon and water mixture, an outlet for water and an outlet for crude
heavy
hydrocarbon mixture;
- a visbreaker for visbreaking said crude heavy hydrocarbon mixture having
an inlet for
crude heavy hydrocarbon mixture fluidly connected to crude heavy hydrocarbon
outlet
of said separator and an outlet for visbroken hydrocarbon mixture;
- a cooling means for cooling said visbroken hydrocarbon mixture having an
inlet for
visbroken hydrocarbon mixture fluidly connected to the visbroken hydrocarbon
mixture
outlet of said visbreaker and an outlet for cooled visbroken hydrocarbon
mixture; and
- a means for adding diluent to said cooled visbroken hydrocarbon mixture to
produce
said pipelineable hydrocarbon mixture.
In some preferred systems the visbreaker is a coil visbreaker. In other
preferred systems the visbreaker is a soaker visbreaker.
A preferred system of the invention further comprises a means for adding
diluent to the heavy hydrocarbon and water mixture either prior to, and/or in,
said
separator. The means may be, for example, a valve, nozzle or spray device.
Further preferred systems of the invention further comprise a heating means in
between the separator and the visbreaker having an inlet for crude heavy
hydrocarbon
mixture fluidly connected to the crude heavy hydrocarbon mixture outlet of the
separator and an oulet for heated crude heavy hydrocarbon mixture fluidly
connected
to the inlet for crude heavy hydrocarbon of said visbreaker. Preferably the
heating
means is a heat exchanger.
In further preferred systems of the present invention the cooling means is a
heat exchanger. Preferably the cooling means also comprises a means for
stripping
gases from the visbroken hydrocarbon mixture.
Preferably the means for stripping gases comprises a valve, a flash drum, a
condenser and a desulfurisation unit. Preferably the inlet of the valve is
fluidly
connected to the outlet for cooled visbroken hydrocarbon mixture of the
cooling means
_ .
CA 02816133 2013-05-10
19
and has an outlet for depressurised cooled visbroken hydrocarbon mixture.
Preferably
the inlet of the flash drum is fluidly connected to the outlet for
depressurised cooled
visbroken hydrocarbon mixture of the valve. Preferably the flash drum further
comprises an outlet for gas and an outlet for cooled visbroken hydrocarbon
mixture.
Preferably the inlet of the condenser is fluidly connected to the outlet for
gas of the
flash drum. Preferably the condenser has an outlet for condensate. Preferably
the
inlet of the desulfurisation unit is fluidly connected to the outlet for
condensate of the
condenser. Preferably the desulfurisation unit comprises an outlet for H2S, an
outlet for
sour water, an outlet for gas and an outlet for hydrocarbon liquid. Preferably
the outlet
for hydrocarbon liquid is fluidly connected to the outlet for cooled visbroken
hydrocarbon mixture of the flash drum.
Further preferred systems of the invention further comprise a well arrangement
for extracting the heavy hydrocarbon and water mixture from a subterranean
formation,
wherein the well arrangement is fluidly connected to the inlet for heavy
hydrocarbon
and water mixture of the separator. Particularly preferably the well
arrangement
comprises at least one SAGD well pair.
A particularly preferred system of the invention comprises:
- a well arrangement for extracting the heavy hydrocarbon and water mixture
from a
subterranean formation;
- a means for adding diluent to the heavy hydrocarbon and water mixture either
prior to,
and/or in, the separator;
- a separator for separating a heavy hydrocarbon and water mixture into a
crude heavy
hydrocarbon mixture and water, wherein the separator has an inlet for heavy
hydrocarbon and water mixture fluidly connected to said well arrangement, an
outlet for
water and an outlet for crude heavy hydrocarbon mixture;
- a heating means for heating the crude heavy hydrocarbon mixture having an
inlet for
crude heavy hydrocarbon mixture fluidly connected to the crude heavy
hydrocarbon
mixture outlet of the separator and an oulet for heated crude heavy
hydrocarbon
mixture;
- a visbreaker for visbreaking the crude heavy hydrocarbon mixture having an
inlet for
crude heavy hydrocarbon mixture fluidly connected the heated crude heavy
hydrocarbon mixture outlet of the heating means and an outlet for visbroken
hydrocarbon mixture;
CA 02816133 2013-05-10
- a cooling means for cooling said visbroken hydrocarbon mixture having an
inlet for
visbroken hydrocarbon mixture fluidly connected to the visbroken hydrocarbon
mixture
outlet of the visbreaker and an outlet for cooled visbroken hydrocarbon
mixture; and
- a means for adding diluent to the cooled visbroken hydrocarbon mixture to
produce
5 the pipelineable hydrocarbon mixture.
Pipelineable hydrocarbon mixtures obtainable by, or obtained by, the methods
hereinbefore described form further aspects of the invention.
Visbroken hydrocarbon mixtures obtainable by, or obtained by, visbreaking a
crude heavy hydrocarbon mixture at a temperature of 350 to 440 C and a
pressure of
10 20 to 150 bar for 0.5 to 15 minutes form further aspects of the
invention.
A preferred visbroken hydrocarbon mixture has the following properties:
an API gravity of 12 to 22 , more preferably 14 to 200 and still more
preferably
17 to 19.5 ,
a viscosity of 50 to 2000 cSt at 15 C, more preferably 100 to 1000 cSt at 15
C
15 and still more preferably 150 to 750 cSt at 15 C; and
an olefin content of less than 3.0 %, more preferably less than 1.0 % and
still
more preferably less than 0.5 %wt olefins.
DESCRIPTION OF THE FIGURES
20 Figure 1 is a schematic of a preferred method and system of the
present
invention; and
Figure 2 is a schematic of the experimental set up used in the examples
hereinafter described.
DETAILED DESCRIPTION OF THE FIGURES
Referring to Figure 1, a heavy hydrocarbon and water mixture is extracted and
recovered from a formation 1 via a SAGD well arrangement 2. The heavy
hydrocarbon
and water mixture is pumped via line 3 to separator 4. A diluent 5 is added to
the
heavy hydrocarbon and water mixture during its transportation to the separator
4. The
separator is a gravity separator. In the separator water and hydrocarbon
phases are
allowed to separate and this process is enhanced by the diluent. Once
separation is
completed the crude heavy hydrocarbon mixture (and the diluent) is transported
via line
6 to a heat exchanger 7. A pump 13 is present in line 6 to increase the
pressure of the
crude heavy hydrocarbon mixture. The water phase is removed from the separator
via
line 8 and is transported to a water treatment facility.
CA 02816133 2013-05-10
21
In heat exchanger 7 the crude heavy hydrocarbon mixture is heated using
visbroken hydrocarbon mixture exiting the visbreaker 10. The
crude heavy
hydrocarbon mixture is heated to at least 350 C in the heat exchanger.
After heating in the heat exchanger 7 the heated crude heavy hydrocarbon
mixture is
transported via line 9 to visbreaker 10. It may be a coil visbreaker or a
soaker
visbreaker. In the visbreaker the crude heavy hydrocarbon mixture is visbroken
at 350
to 440 C and a pressure of 20 to 150 bar for 0.5 to 15 minutes. The visbroken
hydrocarbon mixture is transported via line 11 to heat exchanger 7 wherein the
visbroken hydrocarbon mixture is cooled. The cooled visbroken hydrocarbon
mixture
passes through a valve 14 in line 12 to a gas/liquid separator 15. Typically
gas/liquid
separator 15 is a flash drum. Gas produced in separator 15 is removed via line
16 and
transported to condenser 18 and then to desulfurisation unit 19. In unit 19
H2S, sour
water and gas are removed via lines 20, 21 and 22 respectively. The condensate
23
comprising hydrocarbon mixture is combined with the bottoms of the gas/liquid
separator in line 17 and transported to a cooler 24. After further cooling,
diluent is
added via line 25 to yield a pipelineable hydrocarbon mixture.
The advantages of the method of the present invention include:
= Improvement of heavy hydrocarbon viscosity and a reduction in the total
amount of diluent required
= Low olefin content in the pipelineable hydrocarbon mixture
= No hydrogenation
= Low capex/opex
= No volume loss of bitumen
= Installation at wellsite
= Less pipeline transportation volume
EXAMPLES
The experiments were carried out with partly diluted heavy oil from an oil
producing field in Canada. The experimental set up is shown in Figure 2. A
pump (2)
was used to bring the oil sample from a feed tank (1) to the first heater (3)
with a typical
flow of 10 liters per hour. The pressure downstream of the pump was typically
around
10000 kPa. The first heater (3) brought the oil up to about 390 C. Some
thermal
conversion took place in the first heater (3). The second heater (4) heated
the
hydrocarbon mixture further to the maximum temperature which was reached at
the
CA 02816133 2013-05-10
22
exit of the said heater. The hydrocarbons flowed further through a pipe (about
35 ml)
into a cooler (5). Assuming that thermal conversion of the hydrocarbon mixture
takes
place at temperatures above 380 C, the volume in which the thermal conversion
took
place was about 1 litre. The temperature was brought down to 60 C through the
first
cooler (5). The second cooler (6) reduced the temperature further to 15 C.
The
pressure was reduced to atmospheric pressure through three choke valves in
series (7)
between the first and the second cooler. Downstream of the second cooler (6)
the
hydrocarbon mixture flowed into a gas/liquid separator (8) from which the gas
(9) exited
through the top and the liquid (10) through the bottom. Both gas and liquid
were
sampled and sent to various analyses and tests.
The experiments described here were all performed with a hydrocarbon liquid
mixture with kinematic viscosity at 15 C of 832 cSt, a gravity of 18.0 API
and an olefin
content of about 0.3 wt-%. The results are summarised in the table below.
Experimental case 1:
The oil was treated at a maximum temperature of 390 C (mean of 388 C in
the thermal conversion temperature range (> 380 C)) and a pressure of 9500
kPa.
The residence time in the thermal conversion temperature range was about 4.6
minutes. The kinematic viscosity at 15 C of the liquid was reduced with 43 %
to 472
cSt, the gravity was increased with 0.7 units to 18.7 API and the olefin
contents
increased to 0.55 wt-%.
Experimental case 2:
The oil was treated at a maximum temperature of 410 C (mean of 401 C in
the thermal conversion temperature range (> 380 C)) and a pressure of 9900
kPa.
The residence time in the thermal conversion temperature range was about 4.5
minutes. The kinematic viscosity at 15 C of the liquid was reduced with 61 %
to 326
cSt, the gravity was increased with 0.9 units to 18.9 API and the olefin
contents
increased to 1.05 wt-%.
Experimental case 3:
The oil was treated at a maximum temperature of 430 C (mean of 411 C in
the thermal conversion temperature range (> 380 C)) and a pressure of 10500
kPa.
The residence time in the thermal conversion temperature range was about 4.5
minutes. The kinematic viscosity at 15 C of the liquid was reduced with 76 %
to 201
CA 02816133 2013-05-10
23
cSt, the gravity was increased with 1.3 units to 19.3 API and the olefin
contents
increased to 1.45 wt-%.
24
Process conditions Initial hydrocarbon
properties Visbroken hydrocarbon properties
Temperature Pressure Residence Viscosity Gravity
Olefin Viscosity Gravity Olefin (wt-
( C) (kPa) time (min) (cSt) ( API) (wt-%)
(cSt) ( API) cyo)
_
Case 1 390 9500 4.6
472 18.7 0.55
Case 2 410 9900 4.5 832 18.0 0.3
326 18.9 1.05
Case 3 430 10500 4.5
201 19.3 1.45 0
0
1.)
0
1-,
0,
1-,
w
w
1.)
0
1-,
w
1
0
01
1
1-,
0
