U.S. patent application number 13/143390 was filed with the patent office on 2011-11-03 for sand decanter.
This patent application is currently assigned to M-I L.L.C.. Invention is credited to David Aldus, Gary E. Fout, Steve Williams.
Application Number | 20110265993 13/143390 |
Document ID | / |
Family ID | 42317109 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110265993 |
Kind Code |
A1 |
Williams; Steve ; et
al. |
November 3, 2011 |
SAND DECANTER
Abstract
A method for processing hydrocarbons recovered from a
subterranean formation is disclosed. The method includes: feeding a
stream including water, sand, and heavy hydrocarbons produced from
a subterranean formation to a separation vessel; concurrently in
the separation vessel: heating the stream components to an elevated
temperature to reduce a viscosity of the heavy hydrocarbons; and
separating the sand, the heavy hydrocarbon, and the water to form a
water fraction, a hydrocarbon fraction, and a sand fraction
comprising sand and at least one of water and heavy hydrocarbons;
and recovering the water fraction from the separation vessel;
recovering the hydrocarbon fraction from the separation vessel; and
withdrawing the sand fraction from the separation vessel. Also
disclosed are apparatus suitable for performing the above described
method.
Inventors: |
Williams; Steve; (Mies,
CH) ; Aldus; David; (Calgary, CA) ; Fout; Gary
E.; (Cypress, TX) |
Assignee: |
M-I L.L.C.
Houston
TX
M-I DRILLING FLUIDS CANADA, INC.
Calgary
AB
M-I DRILLING FLUIDS UK LIMITED
Aberdeen, Scotland
|
Family ID: |
42317109 |
Appl. No.: |
13/143390 |
Filed: |
January 6, 2010 |
PCT Filed: |
January 6, 2010 |
PCT NO: |
PCT/US2010/020182 |
371 Date: |
July 6, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61143052 |
Jan 7, 2009 |
|
|
|
Current U.S.
Class: |
166/267 ;
166/75.12 |
Current CPC
Class: |
C10G 1/045 20130101;
B01D 21/009 20130101; B01D 21/2461 20130101; B01D 21/009 20130101;
C10G 1/047 20130101; B01D 21/2461 20130101; C10G 2300/805
20130101 |
Class at
Publication: |
166/267 ;
166/75.12 |
International
Class: |
E21B 43/00 20060101
E21B043/00; E21B 21/06 20060101 E21B021/06 |
Claims
1. A method for processing hydrocarbons recovered from a
subterranean formation, comprising: feeding a stream comprising
water, sand, and heavy hydrocarbons produced from a subterranean
formation to a separation vessel; concurrently in the separation
vessel: heating the stream components to an elevated temperature to
reduce a viscosity of the heavy hydrocarbons; and separating the
sand, the heavy hydrocarbon, and the water to form a water
fraction, a hydrocarbon fraction, and a sand fraction comprising
sand and at least one of water and heavy hydrocarbons; and
recovering the water fraction from the separation vessel;
recovering the hydrocarbon fraction from the separation vessel; and
withdrawing the sand fraction from the separation vessel.
2. The method of claim 1, wherein the separating comprises
separating the sand, the heavy hydrocarbon, and the water by a
density separation technique; wherein the withdrawing comprises:
feeding the sand fraction to a screw conveyor; and concurrently in
the screw conveyor: transporting the sand fraction from a screw
conveyor inlet to a screw conveyor outlet; and separating the sand
fraction from at least a portion of the at least one of water and
heavy hydrocarbons; and recovering the sand fraction from the screw
conveyor outlet.
3. The method of claim 1, wherein the heating comprises: combusting
a fuel to form a flue gas; and heating the stream components via
indirect heat exchange with the flue gas.
4. The method of claim 3, further comprising: heating the sand
fraction during the withdrawing via indirect heat exchange with at
least a portion of the flue gas.
5. The process of claim 3, wherein the fuel comprises at least one
of a natural gas and a portion of the recovered hydrocarbon
fraction.
6. The process of claim 1, further comprising washing the sand
fraction to recover at least a portion of any residual
hydrocarbons.
7. The process of claim 6, further comprising at least one of
reinjecting at least a portion of the washed sand into a
subterranean formation and landfilling at least a portion of the
washed sand.
8. The process of claim 1, wherein the separation vessel comprises:
a vertical portion on top of an angled portion; at least one inlet
nozzle for feeding a stream comprising water, sand, and heavy
hydrocarbons produced from a subterranean formation into the vessel
for separation into a hydrocarbon fraction, a water fraction, and a
sand fraction comprising sand and at least one of water and heavy
hydrocarbons; an indirect heat exchange device disposed within at
least one of the vertical portion and the angled portion for
heating the water, sand, and heavy hydrocarbons; at least one
outlet nozzle for recovering the hydrocarbon fraction; a screw
conveyor located at a bottom of the angled portion to concurrently
transport the sand fraction from the bottom of the angled portion
to a screw conveyor outlet and separate the sand fraction from at
least a portion of the at least one of water and heavy
hydrocarbons
9. The method of claim 8, wherein the separation vessel further
comprises at least one outlet nozzle for recovering the water
fraction;
10. The method of claim 8, wherein the screw conveyor comprises a
drying auger unit comprising: a. an inclined housing having side
walls joined by a bottom and having an inlet end and an outlet end;
b. at least one inlet fluidly connected to the bottom of the angled
portion for feeding the sand fraction comprising sand and at least
one of water and heavy hydrocarbons to the inlet end; c. a helical
auger located in the housing for transporting the sand fraction
from the inlet end of the housing to the outlet end of the housing,
and a drive for rotating the auger, d. an elevated pan disposed in
and extending at least a portion of the length of the housing and
having an arcuate cross section with a radius greater than a radius
of the helical auger, wherein the pan is disposed proximate at
least a lower quadrant of the helical auger; e. the housing further
comprising a liquid recovery zone adjacent to the pan for
transporting the at least one of water and heavy hydrocarbons,
separated from the sand during transport along the pan by the
helical auger, to a liquid collection zone; f. an outlet for
recovering the at least one of water and heavy hydrocarbons from
the liquid collection zone; and g. at least one outlet for
recovering sand having a reduced content of the at least one of
water and heavy hydrocarbons.
11. A system for processing hydrocarbons recovered from a
subterranean formation, comprising: a separation vessel comprising:
a vertical portion on top of an angled portion; at least one inlet
nozzle for feeding a stream comprising water, sand, and heavy
hydrocarbons produced from a subterranean formation into the vessel
for separation into a hydrocarbon fraction, a water fraction, and a
sand fraction comprising sand and at least one of water and heavy
hydrocarbons; an indirect heat exchange device disposed within at
least one of the vertical portion and the angled portion for
heating the water, sand, and heavy hydrocarbons; at least one
outlet nozzle for recovering the hydrocarbon fraction; at least one
outlet nozzle for recovering the water fraction; a screw conveyor
located at a bottom of the angled portion to concurrently transport
the sand fraction from the bottom of the angled portion to a screw
conveyor outlet and separate the sand fraction from at least a
portion of the at least one of water and heavy hydrocarbons; and at
least one outlet for recovering the sand fraction from the screw
conveyor.
12. The system of claim 10, further comprising an indirect heat
exchange device disposed at an exterior of at least a portion of
the screw conveyor for heating the sand fraction during
transport.
13. The system of claim 11, further comprising a combustion system
for combusting a fuel to produce a flue gas for use in indirect
heat exchange in at least one of the indirect heat exchange device
disposed within at least one of the vertical portion and the angled
portion and the indirect heat exchange device disposed at an
exterior of at least a portion of the screw conveyor.
14. The system of claim 10, further comprising a sand wash system
for washing the sand fraction to recover at least a portion of any
residual hydrocarbons.
15. The system of claim 11, wherein the screw conveyor comprises a
drying auger unit comprising: a. an inclined housing having side
walls joined by a bottom and having an inlet end and an outlet end;
b. at least one inlet fluidly connected to the bottom of the angled
portion for feeding the sand fraction comprising sand and at least
one of water and heavy hydrocarbons to the inlet end; c. a helical
auger located in the housing for transporting the sand fraction
from the inlet end of the housing to the outlet end of the housing,
and a drive for rotating the auger, d. an elevated pan disposed in
and extending at least a portion of the length of the housing and
having an arcuate cross section with a radius greater than a radius
of the helical auger, wherein the pan is disposed proximate at
least a lower quadrant of the helical auger; e. the housing further
comprising a liquid recovery zone adjacent to the pan for
transporting the at least one of water and heavy hydrocarbons,
separated from the sand during transport along the pan by the
helical auger, to a liquid collection zone; f. an outlet for
recovering the at least one of water and heavy hydrocarbons from
the liquid collection zone; and g. at least one outlet for
recovering sand having a reduced content of the at least one of
water and heavy hydrocarbons.
Description
BACKGROUND OF DISCLOSURE
[0001] 1. Field of the Disclosure
[0002] Embodiments disclosed herein relate generally to processing
hydrocarbons recovered from a subterranean formation. More
specifically, embodiments disclosed herein relate to processing
heavy hydrocarbons, such as viscous oils, oil shale, tar sands, and
other heavy hydrocarbons.
[0003] 2. Background
[0004] Large deposits of heavy hydrocarbons (e.g., heavy oil and/or
tar) contained in relatively permeable formations (e.g., in tar
sands) are found in North America, South America, Africa, and Asia.
Tar can be surface-mined and upgraded to lighter hydrocarbons such
as crude oil, naphtha, kerosene, and/or gas oil. Surface milling
processes may further separate the bitumen from sand. The separated
bitumen may be converted to light hydrocarbons using conventional
refinery methods. Mining and upgrading tar sand is usually
substantially more expensive than producing lighter hydrocarbons
from conventional oil reservoirs.
[0005] In situ production of hydrocarbons from tar sand may be
accomplished by heating and/or injecting a gas into the formation.
U.S. Pat. Nos. 5,211,230 and 5,339,897, for example, describe a
horizontal production well located in an oil-bearing reservoir. A
vertical conduit may be used to inject an oxidant gas into the
reservoir for in situ combustion. U.S. Pat. No. 7,431,076, which is
incorporated herein by reference, describes several additional
processes for the production of heavy hydrocarbons.
[0006] Due to the high viscosity of heavy hydrocarbons, natural
production rates are low, and the total volume of reservoir that
can be economically drained with one wellbore is than that with
less viscous oils. Indeed, in the case of bitumen, the oil often
cannot be produced without thermal stimulation or solvent
injection.
[0007] In some cases, a relatively permeable formation may be
predominantly heavy hydrocarbons and/or tar with no supporting
mineral grain framework and only floating (or no) mineral matter
(e.g., asphalt lakes).
[0008] The relatively permeable formations may also include heavy
hydrocarbons entrained in, for example, sand or carbonate. A tar
sands formation, for example, is a formation in which hydrocarbons
are predominantly present in the form of heavy hydrocarbons and/or
tar entrained in a mineral grain framework or other host lithology
(e.g., sand or carbonate).
[0009] The high viscosity of the heavy hydrocarbons may result in
co-production of sand or carbonate when recovering the heavy
hydrocarbons from a well or a mine. Produced heavy hydrocarbons, as
a result, generally include a combination of clay, sand, water, and
bitumen or other heavy hydrocarbons.
[0010] The co-produced solid materials, such as sand, must be
separated from the heavy hydrocarbons before the hydrocarbons are
further processed or upgraded. One such process is to feed the
co-produced mixture to a settling vessel, wherein the mixture is
heated, decreasing the viscosity of a portion of the hydrocarbons.
The lower viscosity hydrocarbons float to the top of the settling
vessel and are recovered, and the sand and a portion of the heavy
hydrocarbons settle to the bottom of the vessel and are allowed to
accumulate. The sands, having solidified in the bottom of the
settling vessel, must then be periodically hydroblasted to regain
the settling volume for further production. Depending upon well
production rates, a production site using this hydrocarbon recovery
technique may require several settling vessels, where service is
continually rotated allowing for production and cleaning cycles.
Further, the sand recovered from the settling vessels during
cleaning contains a significant amount of hydrocarbons, requiring
the sands to be disposed of in hazardous waste sites or otherwise
processed before disposal. This type of separation process thus
incurs a very large operating expense.
[0011] Accordingly, there exists a need for improved processes for
the separation of heavy hydrocarbons from co-produced sand.
SUMMARY OF THE DISCLOSURE
[0012] In one aspect, embodiments disclosed herein relate to a
method for processing hydrocarbons recovered from a subterranean
formation, including: feeding a stream comprising water, sand, and
heavy hydrocarbons produced from a subterranean formation to a
separation vessel; concurrently in the separation vessel: heating
the stream components to an elevated temperature to reduce a
viscosity of the heavy hydrocarbons; and separating the sand, the
heavy hydrocarbon, and the water to form a water fraction, a
hydrocarbon fraction, and a sand fraction comprising sand and at
least one of water and heavy hydrocarbons; and recovering the water
fraction from the separation vessel; recovering the hydrocarbon
fraction from the separation vessel; and withdrawing the sand
fraction from the separation vessel.
[0013] In another aspect, embodiments disclosed herein relate to a
system for processing hydrocarbons recovered from a subterranean
formation, including: a separation vessel comprising: a vertical
portion on top of an angled portion; at least one inlet nozzle for
feeding a stream comprising water, sand, and heavy hydrocarbons
produced from a subterranean formation into the vessel for
separation into a hydrocarbon fraction, a water fraction, and a
sand fraction comprising sand and at least one of water and heavy
hydrocarbons; an indirect heat exchange device disposed within at
least one of the vertical portion and the angled portion for
heating the water, sand, and heavy hydrocarbons; at least one
outlet nozzle for recovering the hydrocarbon fraction; at least one
outlet nozzle for recovering the water fraction; a screw conveyor
located at a bottom of the angled portion to concurrently transport
the sand fraction from the bottom of the angled portion to a screw
conveyor outlet and separate the sand fraction from at least a
portion of the at least one of water and heavy hydrocarbons; and at
least one outlet for recovering the sand fraction from the screw
conveyor.
[0014] Other aspects and advantages will be apparent from the
following description and the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a schematic diagram of a sand decanter according
to embodiments disclosed herein.
[0016] FIG. 2 is a schematic diagram of a sand decanter according
to embodiments disclosed herein.
[0017] FIG. 3 is a schematic diagram of a helical auger useful in
sand decanters according to embodiments disclosed herein.
DETAILED DESCRIPTION
[0018] In one aspect, embodiments disclosed herein relate to
processing hydrocarbons recovered from a subterranean formation.
More specifically, embodiments disclosed herein relate to
processing heavy hydrocarbons, such as viscous oils, oil shale, tar
sands, and other heavy hydrocarbons.
[0019] Production of heavy hydrocarbons from subterranean
formations, as described above, typically results in the
co-production of water and sand from the subterranean formation.
Embodiments disclosed herein provide for apparatus and methods for
the separation of the heavy hydrocarbons from the co-produced water
and sand.
[0020] "Heavy hydrocarbons," as used herein, refers to viscous
hydrocarbon fluids. Heavy hydrocarbons may include highly viscous
hydrocarbon fluids such as heavy oil, tar, and/or asphalt. Heavy
hydrocarbons may include carbon and hydrogen, as well as smaller
concentrations of sulfur, oxygen, and nitrogen. Additional elements
may also be present in heavy hydrocarbons in trace amounts. Heavy
hydrocarbons may be classified by API gravity. Heavy hydrocarbons
generally have an API gravity below about 20.degree. C. Heavy oil,
for example, generally has an API gravity of about 10-20.degree.
C., whereas tar generally has an API gravity below about 10.degree.
C. The viscosity of heavy hydrocarbons is generally greater than
about 100 centipoise at 15.degree. C. Heavy hydrocarbons may also
include aromatics or other complex ring hydrocarbons.
[0021] Tar generally refers to a viscous hydrocarbon that generally
has a viscosity greater than about 10,000 centipoise at 15.degree.
C. The specific gravity of tar generally is greater than 1. Tar may
have an API gravity less than 10.degree. C.
[0022] Certain types of formations that include heavy hydrocarbons
may also be, but are not limited to, natural mineral waxes, or
natural asphaltites. Natural mineral waxes typically occur in
substantially tubular veins that may be several meters wide,
several kilometers long, and hundreds of meters deep. Natural
asphaltites include solid hydrocarbons of an aromatic composition
and typically occur in large veins.
[0023] The above described heavy hydrocarbons may be produced from
formations including various mineral matrices. "Sand," as used
herein, refers to sedimentary rock, sands, silicilytes, clays,
carbonates, and other media that may be co-produced with heavy
hydrocarbons, such as heavy hydrocarbons co-produced with sand as a
slurry.
[0024] As produced from a well, a produced fluid including water,
sand, and heavy hydrocarbons may be fed to a sand decanter
according to embodiments disclosed herein, in which the produced
fluid is concurrently i) heated to an elevated temperature to
reduce the viscosity of the heavy hydrocarbon and ii) separated to
form a water fraction, a hydrocarbon fraction, and a sand fraction.
The sand fraction recovered may also include water and/or
hydrocarbons, due to immersion in the liquid phases present (the
hydrocarbon and/or the water being separated). The water fraction,
the hydrocarbon fraction, and the sand fraction may then be
separately recovered from the sand decanter.
[0025] The water fraction and the hydrocarbon fraction may be
withdrawn from the sand decanter via a liquid draw. The sand
fraction may be withdrawn from the sand decanter via a helical
auger or screw conveyor. For example, the sand fraction may be fed
from a lower portion of the sand decanter to an inlet of a screw
conveyor. In some embodiments, the screw conveyor may concurrently
i) transport the sand fraction from the inlet of the screw conveyor
to the outlet of the screw conveyor, and ii) separate the sand
fraction from at least a portion of the water and/or hydrocarbons
present.
[0026] Heating of the co-produced heavy hydrocarbons, water, and
sand within the sand decanter may be performed via indirect heat
exchange. Heat exchange may be performed using various heat
exchange media, including steam/water, hot oil, and hot gases. In
some embodiments, hot gases produced from a burner, such as a
natural gas burner, may be used. Combustion fuels used to produce
gases for use in heat exchange may also include, for example, a
portion of the heavy hydrocarbons recovered from the sand decanter
or other hydrocarbons that may be present in the fluid produced
from the subterranean formation. In other embodiments, electrical
heating coils may be used for the heating.
[0027] The particular choice of heat exchange medium may depend
upon the availability of each at the production site. For example,
high pressure steam or other heat exchange medium may not be
readily available. Natural gas, however, is often a readily
available fuel at most production sites, and may be used to perform
the desired separations within the sand decanter.
[0028] The sand, water, and heavy hydrocarbons in the fluids
produced from a well may be heated to an elevated temperature
sufficient to reduce the viscosity of the heavy hydrocarbon to
promote separation of the fractions by gravity. In some
embodiments, the fluid produced from the subterranean formation may
have a temperature of 25.degree. C. or less, such as about
15.degree. C. or less. Heating of the produced fluid may increase
the temperature of the mixture to a temperature in the range from
about 50.degree. C. to less than about 100.degree. C., such as a
temperature in the range from about 60.degree. C. to 90.degree. C.
in some embodiments, and a temperature in the range from about
70.degree. C. to about 80.degree. C. in other embodiments. As
produced, the heavy hydrocarbons may be of a sufficiently high
viscosity such that it adheres to the sand. When heated, the lower
viscosity of the heavy hydrocarbon allows the sand to settle out of
solution, resulting in separation of the sand from the heavy
hydrocarbon and the water. The lower viscosity of the hydrocarbon
additionally facilitates separation of the hydrocarbon from any
water present, resulting in the production of two or three phases
within the sand decanter (water/hydrocarbon and sand or water,
hydrocarbon, and sand, depending upon the quantity of water
produced and the solubility of water within the hydrocarbon phase).
The resulting phases, sand (solids), hydrocarbons, and/or water,
may then be recovered from the sand decanter as described
above.
[0029] Separation and recovery of the heavy hydrocarbons from the
co-produced sand may be performed in a sand decanter as disclosed
herein, one embodiment of which is illustrated in FIG. 1. The
produced fluid from the subterranean formation may be fed via flow
line 10 to an inlet 12 of sand decanter 14. Sand decanter 14 may
include a vertical portion 16 on top of an angled portion 18.
Vertical portion 16 may be open to the atmosphere or may include a
top 20, enclosing the vessel and allowing for insulation of the
vessel top and retention of heat.
[0030] The co-produced fluids may be heated within the vessel via
indirect heat exchange with a heat exchange medium passed through
heating coils 22. In some embodiments, for example, when a burner
24 is used to combust a fuel, such as natural gas, to produce a
flue gas used as a heat exchange medium, heating coils 22 may be
referred to as a fire tube.
[0031] As the fluid is heated within sand decanter 14, the
viscosity of the heavy hydrocarbons is reduced, allowing the sand
to settle to a bottom portion 26 of sand decanter 14. The oil
and/or water phases, essentially free of sand, may be recovered via
one or more fluid outlets 28. A feed port 30 to a screw conveyor 32
may be provided to continuously or intermittently remove sand from
bottom portion 26.
[0032] Screw conveyor 32 may include a helical auger 34, rotation
of which may result in the transport of sand from feed port 30
toward screw conveyor outlet 36. Rotation of helical auger 34 may
be performed, for example, via coupling of shaft 38 to a drive unit
40, including a motor. A liquid level 42 may result within screw
conveyor 32, and may have a height similar to that of the fluid
level 44 within sand decanter 14. Screw conveyor 32 may have a
height extending above fluid levels 42, 44, allowing for the sand
to be separated from at least a portion of the fluid, which may
include water and/or hydrocarbons, during transport of the sand to
outlet 36.
[0033] Subterranean formations co-producing heavy hydrocarbons and
sand may be located in regions having sub-zero temperatures for at
least a portion of the year. Due to fluids, including hydrocarbons
and/or water, remaining with the sand during transport via screw
conveyor 32, insulation of screw conveyor 32 or heating of the sand
during transport within screw conveyor 32 may be required to ensure
transportability of the sand when ambient conditions may result in
an unacceptable increase in hydrocarbon viscosity or freezing of
water, each of which may result in undesired buildup within screw
conveyor 32 or blockage of outlet 36.
[0034] Heating of screw conveyor 32 may be performed using heat
tracing (electrical or heat exchange tubing or jacketing for flow
of a heat exchange medium) around at least a portion of an exterior
surface 46 of screw conveyor 32. As illustrated in FIG. 1, for
example, the flue gas passed through fire tubes 22 may be fed to
jacket 48 for heating of the contents in screw conveyor 32. The
flue gas may then be recovered from jacket outlet 50 for exhaust to
the atmosphere or for further processing. The exterior of sand
decanter 14 may additionally be insulated or jacketed to promote
efficient heat transfer (not illustrated).
[0035] Referring now to FIG. 2, a schematic diagram of a sand
decanter according to other embodiments herein is illustrated,
where like numerals represent like parts. In this embodiment, a
portion 32A of screw conveyor 32 may be positioned horizontally
along the length of bottom portion 26 for transport of the sand
fraction from sand decanter 14. Screw conveyor 32 may also include
transverse portion 32B for concurrently transporting the sand and
separating the sand from at least a portion of the hydrocarbons
and/or water that may be present. The helical auger located in
portions 32A and 32B may be coupled for use with a single drive
unit 40 or may be rotated using separate drive units (not
illustrated). Also in this embodiment, screw conveyor inlet 30 may
extend the length of horizontal portion 32A.
[0036] As mentioned above, liquids, such as hydrocarbons, water, or
both, may be initially conveyed with the sand by screw conveyor 32.
The length of the screw conveyor between liquid level 44 and outlet
36 may be sufficient to only remove a portion of the water and/or
hydrocarbons from the sand. Further, wetting of the surface area of
the sand may result in carryover of a significant amount of
fluids.
[0037] In some embodiments, screw conveyor 32 may be a drying auger
unit, allowing for the concurrent transportation of the sand and
separation of a greater portion of the water and/or hydrocarbons
from the sand fraction. Separation of hydrocarbons and water from
sand during transport may be facilitated as shown in FIG. 3, which
may be a cross-sectional view of a drying auger unit 60, such as
taken from section 3-3 shown in FIG. 1. A drying auger unit 60
according to embodiments disclosed may include an inclined housing
62 having side walls 64 joined by a bottom 66.
[0038] A sand fraction, including sand, water and/or hydrocarbons,
may be fed to drying auger unit 60 as described above. A helical
auger 34, located at least partially within housing 62, may be used
to transport the sand from feed port 30 toward outlet 36. Helical
auger 34 may include multiple flights 68.
[0039] An elevated pan 70 is disposed in and extends along at least
a portion of the length of housing 62. Due to liquid head
requirements, a drying auger unit 60 may be located only at an
upper portion of screw conveyor 30. Elevated pan 70 may have an
arcuate cross section with an effective radius R greater than a
radius r of helical auger 34. For example, elevated pan 70 may have
a general half-u shaped cross-section.
[0040] Elevated pan 70, for example, may be located proximate a
lower quadrant of the helical auger 34, preferably along the lower
quadrant proximate the upward rotation U of flights 68. In some
embodiments, elevated pan 70 may extend at least 90.degree., such
as from a lowermost portion P, in the direction of rotation U of
helical auger 34.
[0041] As the sand is transported via the rotation of helical auger
34 from inlet end 30 toward outlet end 36, the sand gathers on
elevated pan 70 due to the rotational forces and friction generated
by rotation of flights 68, and is transported toward outlet end 36.
Gravitational forces acting upon the sand and/or compression of the
mixture along the length of the helical auger 34 separates at least
a portion of the hydrocarbons and/or water from the sand. The
separated water/hydrocarbons may then flow into liquid recovery
zone 72 for collection in a liquid collection zone (not shown). A
sand fraction, having a decreased amount of water/hydrocarbons, may
then be recovered via outlet 36.
[0042] As mentioned above, compression may be used in conjunction
with gravity to separate the drilling fluid from the drill
cuttings. For example, flights 68 of helical auger 34 may be evenly
spaced in some embodiments, thus using primarily gravitational
forces to separate the drilling fluid. In other embodiments,
flights 68 may have a decreasing spacing along the length of
elevated pan 70, thus compressing the cuttings slurry as it
traverses from inlet end 30 toward outlet end 36, facilitating
additional separation of drilling fluid from the cuttings slurry.
Additionally, although only one helical auger is illustrated, two
or more augers may be used.
[0043] Hydrocarbon fractions recovered from sand decanters
according to embodiments disclosed herein may be forwarded for
storage, transport, or further processing, such as to convert the
heavy hydrocarbons to lighter hydrocarbons, such as light
hydrocarbons (C1 to C6 hydrocarbons, including olefins), gasoline
range hydrocarbons (C6 to C10 hydrocarbons, for example), diesel
range hydrocarbons, light cycle oils, and he like, as known to
those skilled in the art.
[0044] A water fraction recovered from sand decanters according to
embodiments disclosed herein may contain some hydrocarbons. Thus,
water fractions recovered may be further processed to remove the
hydrocarbons, resulting in a water fraction suitable for disposal
or reuse within the production facilities.
[0045] The sand fraction recovered from sand decanters according to
embodiments disclosed herein may contain some hydrocarbons, as
mentioned above. For example, heavy hydrocarbons remaining with
sand during settling, such as due to adhesion or insufficient
increase of viscosity, may result in the sand being unsuitable for
non-hazardous disposal.
[0046] Sand fractions recovered according to embodiments disclosed
herein may be rendered suitable for non-hazardous disposal using a
sand cleaning system, such as that disclosed in U.S. Provisional
Patent Application Ser. No. 61/014,262, filed on Dec. 17, 2007,
which is hererby incorporated by reference. The cleaning of the
sand may result in recovery of additional hydrocarbons that may be
further processed as described above. Sand, having been cleaned to
meet various regulations for non-hazardous disposal, may then be
landfilled, re-injected into a well, or otherwise used or disposed
of, on site or at a remote facility.
[0047] As described above, embodiments disclosed herein provide for
the separation and recovery of sand from heavy hydrocarbons, such
as bitumen or other heavy hydrocarbons produced from a low-pressure
well. Advantageously, embodiments disclosed herein may provide for
concurrently heating the heavy hydrocarbons to reduce a viscosity
thereof and separating of the heavy hydrocarbons from co-produced
sand.
[0048] The separations performed using sand decanters according to
embodiments disclosed herein may allow for the continuous
separation of sand, in contrast to current processes. Due to the
continuous or intermittent withdrawal of a sand fraction from the
sand decanters, buildup of sand in the separation vessel is
reduced, requiring less intensive maintenance and the associated
costs. Further, continuous separations according to embodiments
disclosed herein may reduce the number of separation vessels
required to perform the separations.
[0049] While the disclosure includes a limited number of
embodiments, those skilled in the art, having benefit of this
disclosure, will appreciate that other embodiments may be devised
which do not depart from the scope of the present disclosure.
Accordingly, the scope should be limited only by the attached
claims.
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