Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TREATMENT OF CRUDE OLL FROM A WELL INCLUDING EXTRACTION OF
PARTICULATES THEREFROM
This invention relates to a method for the treatment of crude oil from a
well. The arrangement as described hereinafter provides a mechanical pre-
heating
system for production crude between the wellhead and the production tank or a
system providing crude oil processing prior to pipe line transportation.
BACKGROUND OF THE INVENTION
Heavy crude oil produced from a well cantains the crude oil which is
generally highly viscous due to its low temperature, water and particulates of
sand.
It is necessary to separate out these materials and for this purpose the
production
material from the well is often pumped into a tank, which is in many cases
located
adjacent the well head, where the materials are allowed to settle so that the
particulates deposit in a layer at the bottom of the tank and above the
particulates
collects a layer of the water and above the water collects the crude oil. In
order to
accelerate the settlement, bearing in mind the high viscosity of the crude
oil, heat is
generally applied to the production tank so as to raise the temperature of the
materials within the tank to a predetermined temperature lower than the
boiling point
of the water. This heating is effected by a pipe inserted into the tank into
which heat
is injected. One example of a heating system is shown in published PCT
application
WO 02/084195 of Lange published October 24t" 2002, the disclosure of which is
co-
incorporated herein by reference.
For safety reasons it is required that the production tank is located 75
feet away from the well head so that a line extends horizontally from the well
head to
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the tank and introduces the mixed materials from the well head into the tank
at a
position at a height on the wall on the tank. The pressure from the well
therefore
must also supply the necessary pressure for forcing the viscous materials
through
the pipe from the well head to the tank.
In some cases processing chemicals are injected into the pipe at or
adjacent the well head so as to be mixed in with the production materials as
they are
transferred along the pipe to the production tank.
In other cases the product is transported from the well head to a
transfer pipe line which transfers it to a remote location for collection
andlor
treatment. Thus the product is merely collected and pumped through the pipe
over a
limited distance to a remote location. The pipe line can be of small diameter
such as
two inches for transfer over a limited distance of up to two miles.
The following problems are commonly encountered by heavy oil
producers using the above technology today:
1. High flow line pressure from the wellhead to the production tank
or transfer pipe caused by the heavy cold production fluids.
2. Increased flow line pressure which reduces oil production and
efficiency of the down hole pump.
3. Adequate heat from wellhead to storage tank for (gas and oil
flows) is not available other than wellhead engine glycol or exhaust, if there
is a
weilhead engine.
4. The cooling effect that the required 75 feet of exposed flow line
has on the production crude, insulated or not, especially in winter.
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5. The convection currents created in the production tanks to
current hard firing immersion tube heaters due to the large temperature
changes
which are necessary from the inlet temperature to the processing temperature..
These convection currents impact the ability of solids to settle and to
achieve clean
oil.
6. The ineffective introduction of treatment chemicals into the flow
line. The crude is cold. foamy and solids laden. The current flow line offers
no
method of chemical distribution in product and no method of de-sanding or
ensuring
full flow capability.
SUMMARY OF THE INVENTION
It is one object of the present invention therefore to provide an
improved method of treating crude oil.
According to one aspect of the invention there is provided a method of
crude oil production comprising:
producing at a well head a mixture of particulates, crude oil and water;
storing the mixture in a production tank for settlement of the mixture in
to the constituent parts for separate extraction from the tank;
transferring the mixture from the well head to the production tank
through a transfer duct;
and while transferring the mixture, commencing an initial separation of
the mixture.
Preferably heat is applied to the mixture as it is transferred.
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Preferably the heat is applied by a jacket surrounding a pipe through
which the material passes.
Preferably the pipe is of increased diameter to increase dwell time.
Preferably the pipe is at least 12 inches in diameter.
Preferably the pipe contains an auger flight.
Preferably the auger flight is rotated in a direction to move the
particulate materials in a direction toward the tank so as to move the
particulate
materials to a discharge at or within the tank.
Preferably the auger flight has a variable pitch.
Preferably the auger flight has at least a section with a ribbon flight.
Preferably the transfer duct is divided into at least two paths at its end
at the tank for feeding a lighter section including the crude oil through an
upper path
and a heavier section including the water through a lower path.
Preferably the upper path includes a heat exchanger for receiving heat
from the stack gases of the heater.
Preferably the transfer duct includes a gas vent which is located at the
tank so that gases are released from the stream above the liquid level to
avoid
discharging bubbles into the liquid which can cause circulating currents which
can
interfere with the settlement within the production tank.
According to a second aspect of the invention there is provided a
method of crude oil production comprising:
producing at a well head a mixture of particulates, crude oil and water;
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storing the mixture in a production tank for settlement of the mixture in
to the constituent parts for separate extraction from the tank;
transferring the mixture from the well head to the production tank
through a transfer duct;
5 and while transferring the mixture in the duct, heating the mixture.
Preferably heat is applied to the mixture in the duct sufficiently to avoid
the requirement for heating in the tank.
Preferably material from the tank is circulated through the duct and
back to the tank to avoid the requirement for heating in the tank.
According to a third aspect of the invention there is provided a method
of crude oil production comprising:
providing a mixture of particulates, crude oil and water;
transferring the mixture through a transfer duct;
while transferring the mixture in the duct, heating the mixture;
and providing an auger flight in the duct operable to carry the
particulate materials to one end of the duct for discharge, while the crude
oil and
water flow along the duct.
In one arrangement, the transfer duct transfers the mixture to a pump
and a pipe line for transferring the mixture to a remote location.
In this arrangement preferably the particulate material is discharged
from the transfer duct prior to the pump.
In this arrangement preferably the auger flight is arranged to form a
plug of the particulate material, a part of which is periodically released by
a valve
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BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described in conjunction with
the accompanying drawings, in which:
Figure 1 is a schematic view of a well head crude oil production system
according to the present invention.
Figure 2 is a side elevational view of a well head crude oil production
system of Figure 1.
Figure 3 is an end elevational view of the embodiment of Figure 1.
Figure 4 is a side elevational view of the production system according
to the present invention.
Figure 5 is a top plan view of the production system according to the
present invention.
In the drawings like characters of reference indicate corresponding
parts in the different figures.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In Figure 1 is shown schematically an oil production system including a
well 10 which provides oil production at a well head 11 for supply through a
pipe 12
to a production tank 13. The tank is arranged to receive the materials in
which
settling occurs to provide a layer of particulate material at the base of the
tank, a
layer of water on top of the sand and the required oil in a layer at the top
of the tank.
The conventional system is modified by the addition of an initial
production treating system generally indicated at 20 which includes a duct 21
containing an auger flight 22 and surrounded by a jacket 23. Steam is supplied
to
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the jacket 23 by a heating system 24 so that the steam condenses in the jacket
generated a liquid which runs back along the bottom of the jacket to an outlet
port 25
from which the liquid runs back to the heating system 24. The jacket surrounds
substantially the whole of the duct and the duct extends substantially the
whole of
the distance from the well head 11 to the tank 13.
The auger flight 22 is driven by a motor 26 on the well head end of the
duct 21. A temperature sensor 27 detects the temperature of the materials
within
the duct at the tank 13 so as to control the heat supply from the heating
system 24 to
maintain a required temperature as a material to enter the tank.
The motor 26 drives the auger flight in a direction so that the flight
tends to carry particulate materials within the bottom of the duct toward the
tank end.
The end of the duct within the tank includes a discharge mouth 33 which is
arranged
within the tank so that the discharged materials can rise centrally within the
tank if
lighter or can fall downwardly within the tank, primarily the particulate
materials, the
heavier materials falling into a collection system 34 arranged centrally of
the tank for
collecting and discharging the materials as a primary discharge system.(See
Figures
4 and 5)
The auger flight has a ribbon flight section 22C at least in the area
closest to the tank so as to allow the liquids to flow through the centre of
the ribbon
flight section with less turbulence providing a smoother flow of the liquids
after the
particulate materials have been primarily extracted for transport to the plug.
The
ribbon flight may extend along the complete length of the auger which is along
the
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CA 02466014 2004-04-30
complete length of the heated duct so as to allow the fluid to flow in the
center and
the particulates to be carried along the bottom of the duct to the tank.
The outlet mouth of the duct may be located at the tank wall rather
than in the centre as shown in Figure 1.
In Figure 2 is shown an arrangement in which the lighter materials rise
through a secondary inlet duct portion 40 so that the lighter materials,
primarily the
oil can be raised through the duct 40 to a mouth 41 injecting into the tank 13
at a
position above the expected water level. The heavier materials in the duct
transfer
through the mouth 33 at the side wall into the tank primarily below the water
level.
The liquid rising in the duct 40 can be heated by a heat exchanger 42 from the
flue
pipe of the heating system 24.
Also in Figure 2 is shown a vent duct 50 which allows gases in the
stream to be released from the stream above the liquid level to avoid
discharging
bubbles into the liquid which can cause circulating currents which can
interfere with
the settlement within the production tank. The heat in the transfer duct 20
can be as
much as 140 degrees C so that water can be converted to steam which would
generate bubbles in the tank if released into the tank. The vent 50 may
discharge
into the tank or may discharge to atmosphere.
An additional return line can be provided from the well head end of the
duct to the tank so as to use the system in reverse flow arrangement for
heating of
liquid within the tank by passing the materials through the duct in the
reverse
direction and then returning the materials to the tank through the return
duct. This
allows the tank to avoid the necessity for a specific heating system within
the tank
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since the majority of the tank can be initially heated using the circulation
system and
then when the production is started, the heat from the duct is sufficient to
maintain
the materials within the tank at the required separation temperature. This
avoids the
generation of convection currents within the tank and maximises the settling
action.
In Figure 3 is shown a end elevational view of the system including the heater
24
including a burner 24A and heat exchange tubes 24~. The flue 24C can be
allowed
to merely discharge the gases or can be connected to the heat exchanger 42
shown
in Figure 2. The steam from the heat exchange tube 24B is communicated through
a duct 24D to the inlet of the jacket 23. The return from the jacket returns
the liquid
to the heater 24. The duct is mounted on one or more support legs 50 and
arranged
so that it is generally horizontal but with a slight inclination so as to run
the return
liquid back toward the outlet for the heater.
There has been very little work done on technology involving the
atmospheric treating of petroleum products in recent years. It is believed
that by
incorporating a number of certain advancements in recent technology developed
by
the present Assignee, a significant step forward will be made.
In particular, the utilization of:
1. Auger tank de-sanding, as is known and provided by the
present Assignee.
2. Two phase thermo siphon tank heating as shown in the Lange
patent application mentioned herein before.
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3. And a combination of both between the flow line and storage
tank will create a low cost, very effective mini or micro treating system that
simply
does not exist today.
The components can be made any length, diameter or material make
5 up that is required to achieve the desired temperature rise or fall, (this
system may
also be a cooler).
The heating system disclosed in the above PCT application of Lange
has a condenser portion which may be the jacketed area however it may also
include the auger shaft as well as the flighting section if rotating
mechanical seals
10 and double wall auger flighting were incorporated. The heating system may
utilize a
condenser of standard design in the production tank (controlled by flow
valves) the
greatest amount of heat however will go to the heating of the duct 20.
The following features may be considered in the fligllting designs:
1. The auger design may incorporate multi purpose capability.
2. Simple helical flights of standard design can be used for low
cost solutions.
3. Variable pitch screw of same outside diameter to allow for
velocity drop after temperature is up and chemical is mixed.
4. Paddles or weirs in the auger tube can be used to enhance
mixing and heat distribution into petroleum products.
5. Perforations, slots, holes in the flight, or other flighting
modifications either whole or in part of the auger, can be used to both
promote
mixing, heating, shearing and subsequent separating of H20, crude and solids.
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6. An unimpeded fluid flow can be created by use of a ribbon
auger flight in last stages of the auger. The ribbon outer lead edge of the
flight still
allows for solids distribution into production tanks.
In one mode of operation the system is used in unidirectional operation
where in a first method of operation, the system is installed on typical
production well
with tank located 75 feet from the wellhead. The storage tank access port is a
standard 10'° full opening knife gate valve either retro-fit by hot tap
installation or
standard install when tank is empty, as is well known to one skilled in the
art.
The valve is installed inline with wellhead, approximately 5 feet above
tank floor. On a retrofit the existing crude flow line is cut, threaded and
with a flex
coupling and valve tied into the flow line inlet on the system. The original
flow line is
tied into the other side of the tee with a valve.
The production fluid follows the helical path defined by the flight taking
advantage of retention time and velocity drop through the larger diameter flow
line.
The internal screw, through a packing gland, is driven by hydraulic
return pressure or electric over gear drive.
The auger drive incorporates centralized and thrust components along
with secondary centralisers, throughout the length of the screw to maintain
the shaft
central within the duct. The auger is driven to rotate either continuously, or
intermittently from 0 to higher RPM, generally approximately 5 RPM.
The heating system is well known to one skilled in the art. A small 9-
burner unit can be affixed directly onto the transfer duct or alternatively
have hoses
and valves to control temperature to the tank condenser.
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The transfer duct may have flat irons affixed to direct steam away in
the upper half of the tube and return in the lower half. The transfer duct
will be
slightly sloped toward the return outlet so the jacket will quickly return
condensate
liquid to the heating system.
In a second method of operation, in a case where the tank is cold the
auger may be rotated in reverse to bring cold crude into the MPT for heating.
The
previous inlet to the NVT is now the exit with the crude being recycled into
the
production tank.
Chemical may be injected to batch treat slop or hard to treat crude in
this manner. Temperature rise could be achieved by counter rotation, and then
once
temperature rise was achieved, the auger would be rotated to the treating
mode.
The use of the auger flight improves chemical mixing.
In an alternative arrangement (not shown) where the duct 20
transports the production from the well to a pump. At the pump is provided a
discharge valve which is periodically operable to discharge the particulate
materials
into a collection system for discard.
The auger flight is arranged so that it increases the quantity of
particulate material at the discharge end adjacent the valve so as to form in
effect a
plug of the particulate material blocking the duct at that area. Thus when the
valve
is opened a portion of the plug can be discharged without the plug being
broken up
or wholly discharged so that the plug prevents the escape of the liquid
materials
within the duct while allowing the plug itself to be partially discharged. The
valve can
be operated periodically by a pressure sensor which detects the pressure in
the plug
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due to the packing of the plug with additional particulate materials as the
materials
are fed by the auger flight. The oil from the duct 20 is to the pump is
removed from
the duct 20 at an outlet point downstream of the plug.
Since various modifications can be made in our invention as herein
above described, and many apparently widely different embodiments of same made
within the spirit and scope of the Claims without department from such spirit
and
scope, it is intended that ail matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
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