Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR CLEANING SOLIDS FROM A TANK
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to removing solids from a tank in general, and
in
particular to a method and apparatus for removing solid particles from an oil
production tank.
2. Description of Related Art
In the collection of oil from oil wells, it is common to employ a storage tank
or
production tank at a well or another location. Such production tanks may be
used to perform a processing stage on the crude oil or as a means of
temporary storage to account for different flow rates out of and away from the
oil well.
In some areas, heavy oil wells are known to produce formation sand in
varying percentages with cold oil production that is entrained with the heavy
oil. Due to the decrease in velocity of the oil when located in a production
tank, entrained sand and other solid material may be allowed to settle and
accumulate on the bottom of the tank. These solid deposits accumulate in the
bottom of the production tanks until the amount of sand deposited becomes
problematic for the operator and the efficient operation of the production
tank.
The accumulated solids may be removed from the tank on a periodic basis by
a process that is commonly known as "stinging" the tank. A typical stinging
operation requires a pressure truck, a stinger assembly and at least one
vacuum truck. The pressure truck is connected via a pressure line to the
stinger assembly, which is inserted into the bottom of the tank. The first
vacuum truck connects to a "Suction Tee" located on a "Stuffing Box" of the
stinger assembly. The pressure truck pumps water through the stinger
assembly at low volume - high pressure directing the spray from the nozzle
onto the floor of the production tank. The water utilized for this pumping
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operation can be either transported to the location with the pressure truck or
can be drawn from an existing tank if it is available.
As the sand and settled solids inside the production tank are agitated or
"fluidized" by the spray from the nozzle, the vacuum truck draws the fluid and
solids from the production vessel via the "suction tee". The slurry drawn from
the tank is generally comprised of a mixture of sand, oil and water in varying
percentages, however the sand/solid content is generally quite low (10 - 20 %
for example) of the total volume withdrawn. This mixture is then accumulated
in a storage tank on the vacuum tank for disposal.
The typical method of cleaning a production tank as described above has
several difficulties. The relatively small percentage of solid material in the
total volume that must be disposed of results in a greater volume that is
required to be transported away for disposal. This requires the use of several
vacuum trucks so as to not interrupt the cleaning process unduly. 'Both of
these factors increase the cost of the clean-out process over what would be
necessary if only solid material was being removed and disposed of. The
disposal of oil with the solid material is also wasteful resulting in lost
production capacity.
What would be desirable is a method and apparatus for removing solid
materials from an oil production tank that removes substantially only the
solid
materials and returns the oil to the tank.
SUMMARY OF THE INVENTION
The present application provides a method and apparatus for removing solid
materials from an oil production tank in which the solid material is separated
from the oil and collected for disposal wherein the oil is returned to the
production tank.
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Accordingly, the present invention provides a method for removing solid
materials from an oil production tank containing a liquid hydrocarbon portion
and a solid portion, the method comprising
drawing off a portion of the liquid hydrocarbon and solid portions from
the tank;
separating the liquid hydrocarbon and solid portions through the use of
a rotational particle separator; and
collecting said separated solid portion, wherein said separated liquid
hydrocarbon portion is returned to the tank.
In a further aspect, the present invention provides a system for removing
solid
materials from an oil production tank containing a liquid hydrocarbon portion
and a solid portion, the apparatus comprising:
an intake for drawing off a portion of the liquid hydrocarbon and a solid
portions from the tank;
a rotational particle separator adapted to receive said portion of the
liquid hydrocarbon and a solid portions from said intake;
a collector for collecting said separated solid portion; and
a return for returning said separated liquid hydrocarbon portion to the
tank.
Other aspects and features of the present invention will become apparent to
those ordinarily skilled in the art upon review of the following description
of
specific embodiments of the invention in conjunction with the accompanying
figures.
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BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present invention are illustrated merely by way of example in
the
following drawing in which:
Figure 1 is a schematic diagram of the method of removing solids from an
oil production tank in accordance with a first embodiment of the
present invention.
DETAILED DESCRIPTION
Referring to Figure 1, a system for removing solid material from a oil
production tank 12 having an interior 13 and a bottom 15 according to a first
embodiment of the invention is shown generally at 10. The system 10
comprises a stinger assembly 20 which is insertable into the tank 12 and a
separation system 50. The tank contains a solid portion 70 which may be
settled on the bottom 15 and a liquid hydrocarbon portion 72.
The stinger assembly may be of a conventional design and comprises an
elongate rod 22 or stinger having a distal end 24 and a central bore. The
stinger 22 further includes a plurality of nozzles 26 adjacent to the distal
end
24. The stinger assembly further includes a stinger insertion port or stuffing
box 28 which attaches to an opening 32 of the tank and slidably and sealably
permits the stinger to be inserted into the tank 12. The stuffing box 28
includes a suction connection 34 in fluidic communication with the interior 13
of the tank 12 and a pressure connection 36 in fluidic communication with the
bore of the stinger 22.
The separation system 50 comprises a rotational particle separator 52
adapted to receive a solid and liquid mixture from the tank 12 and a
collection
bin 54 which receives the separated solid material from the rotational
particle
separator 52. The collection bin 54 may also have an associated conveyor 74
for removing the solid material from the collection bin 54 and delivery to a
transport vehicle for disposing of the solid material. The conveyor 74 may
comprise an auger, a conveyor belt or a downwardly inclined slide, for
example. It will be appreciated that the rotational particle separator 52 may
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comprise a cyclone separator or a centrifuge, for example, or any other
apparatus which separates solids from liquids through the use of centrifugal
forces.
The separation system 50 may also include a suction pump 56, a return pump
58, a high pressure pump 60 and an accumulator tank 62. The suction pump
56 is connected to the suction connection 34 of the stuffing box 28 by suction
line 64. The suction pump draws a mixture of the solid 70 and liquid portions
72 from the tank 12 and delivers it to the rotational particle separator 52.
The rotational particle separator 52 separates the solid portion 70 from the
liquid portion 72 and delivers the liquid portion to the accumulator tank 62
while depositing the solid portion in the collection bin 54. The accumulator
tank retains the liquid portion for return to the tank 12. A portion of the
liquid
may be delivered to the high pressure pump 60 for delivery to the pressure
connection 36 of the stinger box 30 through pressure line 66. The remainder
of the liquid in the accumulator tank 62 may be returned to the tank 12 by
return pump 58 and return line 68. It will be appreciated that the separation
system 50 may be mounted on a truck or a skid for ease of transpiration to a
desired location.
As the fluid portion drawn off the tank 12 may include a fluidizing liquid,
such
as water, for example, as well as a liquid hydrocarbon drawn from the tank 12,
the accumulator tank 62 may include both of these fluids as well. The fluid
portion drawn from tank 12 is not necessarily separated into fluidizing liquid
and hydrocarbon portions after processing through the rotational particle
separator 52. The liquid portion delivered to accumulator tank 62 may be
fluidizing liquid, hydrocarbon liquid or an emulsion of both if the liquids
are
immiscible. The outlets from the accumulator tank 62 are optionally
positioned such that fluidizing liquid is passed through the high pressure
pump 60 while the liquid hydrocarbon is passed through the return pump due
to the stratification between these two liquids within the accumulator tank
62.
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The high pressure pump 60 delivers a high pressure supply of fluidizing liquid
to the stinger assembly 20 at high pressure where it is spayed out of nozzles
26. The high pressure spray from the nozzles fluidizes, or converts the
accumulated solids on the bottom of the tank from a solid-like state to a
liquid-
like state. The fluidized solids may thereby be more readily drawn out of the
tank 12 by the suction pump 65. Designs for stingers are conventional and
known in the art. It will be appreciated that fluidization of the solid
material
may be enhanced by inserting and withdrawing the stinger from the tank so as
to fluidize a greater volume of the solid material.
The fluidizing liquid may be supplied to the system 10 by an external or
onsite
tank. The fluidizing liquid may be water or oil depending on what fluid is
stored in the production tank. Optionally, the accumulator tank 62 may
contain an initial charge of the fluidizing liquid sufficient to initiate the
operation of the system. In these embodiments, the fluidizing liquid may
comprise water. In another embodiment, the fluidizing liquid may be the liquid
hydrocarbon contained in the tank 12. An initial pilot amount of the liquid
hydrocarbon may be drawn off the tank 12 and supplied to the system 10 so
as to begin the operation of the system. It will be appreciated that the
separation system 50 may be mounted on a truck or a skid for ease of
transpiration to a desired location.
While specific embodiments of the invention have been described and
illustrated, such embodiments should be considered illustrative of the
invention only and not as limiting the invention as construed in accordance
with the accompanying claims.
