Note: Descriptions are shown in the official language in which they were submitted.
CA 02463808 2004-05-03
FLAMELESS HOT OILER
Field of The Invention
The present invention relates to a flameless system for use in the servicing
of oil
and gas wells and more particularly to a filameless hot oiler in which the
heat for heating
the batch process fluid primarily comes from the engine of the tractor
transporting the
hot oiler.
Background
Production tubing within a well bore requires periodic maintenance to remove
paraffin deposits that could restrict production. These deposits are generally
the result
of changing pressures and temperatures within a production system and the
removal of
these deposits is accomplished through a technique known as hot oiling in
which heated
fluids, typically oil, are circulated through the production system. As will
be appreciated
by those skilled in the art, hot oiling has other applications and the use of
the system
described and claimed below is not limited to any particular application.
Moreover, the
term "hot oiler" is itself merely generic, and the below described system can
be used to
heat different fluids for different applications including, but not limited to
water, treatment
fluids used for well stimulations and chemicals or virtually any other fluids
requiring
heating.
Standard hot oilers are diesel fired units that use an open flame to create
the heat
needed to heat the batch oil. This flame heats pipes that are in direct
contact with it as
the batch fluid to be heated flows through the pipes for thermodynamic heat
exchange.
Heating is performed at or close to atmospheric pressure.
Several problems exist, however, with open combustion burners. The use of
open flame is less controlled compared to the use of flameless systems.
Exhaust gasses
are often hotter in an open combustion system and if they are not monitored
these
systems can flood and expel flame. The temperatures can reach instantaneous
temperatures greater than that of the kindling temperatures of natural gas.
This means
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CA 02463808 2004-05-03
that if there was a natural gas leak, an ignition point is present. A diesel
or propane leak
in the vicinity of the burner can also be ignited.
Further, the combustion process in open flame systems is not as complete as in
closed systems, and free radicals thereby escape into the atmosphere. Closed
combustion engines have compression ratios commonly 14 times greater than open
combustion burners. This lack of compression negatively affects the
reactiveness of
oxygen. Hydrocarbonloxygen reactions are exothermic which provides the heat
energy
used by the hot oiler. Provided that the combustion is given enough oxygen,
heat and
time to complete the process, carbon dioxide and water are produced, which are
more
benign byproducts. However, nitrogen gas is also present during combustion and
if the
reaction is not ideal, some molecules of nitrogen attach themselves to oxygen
to
produce the poisonous gas NO. This gas is referred to as a free radical.
incomplete
combustion also produces carbon monoxide which also is a pollutant. NO and
carbon
monoxide are well recognized as being harmful to the environment.
Open flame systems also require more fuel than flameless systems. Fuel is
burned less efficiently in these systems, requiring a greater amount of fuel
to produce
an equivalent amount of heat in a flameless system.
Open flame units moreover are mandated by regulation to be , kept at a
predetermined safe distance from the wellhead. This presents the disadvantage
that
more tubing is required to bring the heated fluid to the well bore.
Summary of the Invention
The present invention seeks to overcome the above disadvantages by providing
a flameless heating system in which heat can be taken from the engines on a
rig and
transferred to the batch fluid. In the present invention heat is transferred
from the
engines using heat exchangers to transfer heat from the engine coolant to a
heat
exchange fluid. This heat is then transferred to the batch fluid through
another heat
exchanger.
The present invention further includes an exhaust heat exchanger to transfer
heat
from the engine exhaust to the heat exchange fluid. This allows the present
invention
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CA 02463808 2004-05-03
to recover more heat from the engine. In the present invention the engine is
preferably
the engine from the truck which supports 'and transports the oil heater.
To make use of available excess horsepower, water brakes are provided to load
the engines, thereby producing more heat from the engine. Further, the
shearing of the
fluid in the water brake produces heat on its own. The heat exchange fluid is
used to
load the water brake, and the shearing heat is transferred to the heat
exchange fluid
which is then used as an additional source of heat for heating the batch
fluid.
The water brake of the present invention further provides the advantage that
it
can run empty when no additional loading of the engine is required. This
removes the
requirement for the usual gearbox that disengages the water brake, saving
weight and
costs for the system.
The present invention therefore provides a flameless heating system for a
batch
fluid comprising at least one engine, each said engine producing hot exhaust
gas and
including a coolant for removing heat from said engine; a heat exchange
system, said
heat exchange system comprising a heat transferring fluid; a pump for
circulating said
heat transferring fluid through said heat exchange system; a first heat
exchanger for
transferring heat from said engine coolant to said heat transferring fluid; an
exhaust heat
exchanger for transferring heat from said exhaust gas to said heat
transferring fluid; and
a second heat exchanger for transferring heat from said heat exchange system
to said
batch fluid wherein heat is transferred from said engine to said heat exchange
system,
and from said heat exchange system to said batch fluid.
According to the present invention, there is also provided a flameless heating
unit
for heating a batch fluid, comprising an internal combustion engine; means for
deriving
heat from said internal combustion engine and transferring the heat to a heat
transferring
fluid; a first heat exchanger for transferring said heat from said heat
transferring fluid to
said batch fluid; means for circulating said heat transferring fluid through
said first heat
exchanger; means for circulating said batch fluid through said first heat
exchanger for
heating of said batch fluid; and means for pumping said heated batch fluid far
use where
required.
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CA 02463808 2004-05-03
According to yet another aspect of the present invention, there is also
provided
a method for flamelessly heating a batch fluid, said method comprising the
steps of
extracting heat from an internal combustion engine and transferring the heat
to a heat
transferring fluid; circulating said heat transferring fluid and said batch
fluid through a first
heat exchanger for effecting the transfer of heat from said heat transferring
fluid to said
batch fluid.
Brief Description of the Drawings
Preferred embodiments of the present invention will now be described in
greater
detail and will be better understood when read in conjunction with the
following drawings,
in which:
Figure 1 is a schematic flow diagram of the flameless oil heater;
Figure 2 is a side elevationai partially schematics! view of the flameless oil
heater
of Figure 1;
Figure 3 is a schematic flow diagram of a single engine version of the
flameless
oil heater;
Figure 4 is a perspective view of the flameless oil heater of Figure 3; and
Figure 5 is a pictorial representation of a water brake forming part of the
present
rig. .
Detailed Description of the Preferred Embodiments
Reference will now be made to Figure 1 for a more detailed description of a
two-
engined hot oiler 10. Flameless hot oiler 10 is preferably capable of
producing 5.4
million BTU/hour and captures this heat from three sources: engine water
cooling
systems; exhaust gases; and the use of excess engine horsepower to provide
shear
heat in a heat transfer filuid.
A hot oiler 10 capable of producing this amount of heat can have two engines
that
can be used to produce heat both as a by-product of their internal combustion
and by
converting available excess horsepower to heat. The truck's in-frame engine is
used by
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CA 02463808 2004-05-03
the rig and can be mechanically coupled to a water brake 20. A deck engine 25
is
mounted to the rig deck and can be mechanically coupled to a deck water brake
30.
Heat from the in-frame engine is transferred to the in-frame engine's water
cooling
system. These cooling systems are well known in the art, and the fluid used
can be
water,. glycol (anti-freeze) or a combination of the two. Water flows through
valve 40 into
a heat exchanger such as shell and tube heat exchanger 42 where heat is
transferred
to a heat exchange fluid. The engine fluid then exits heat exchanger 42
through valve
44. Valves 40 and 44 are located on the engine block and can be used to
isolate water
flow from heat exchanger 42. Opening valves 40 and 44 allows the engine
coolant to
circulate through heat exchanger 42.
Similarly, cooling water from deck engine 25 flows through valve 46 into a
second
heat exchanger such as shell and tube heat exchanger 48 where heat is
transferred to
the heat exchange fluid. The engine coolant then exits heat exchanger 48 and
flows
through valve 50. As with the in-frame engine, valves 45 and 50 can be used to
isolate
water flow from heat exchanger 48.
Heat from the rig's hydraulics can further be transferred to the deck engine
coolant by using valve 52. When valve 52 is open, the deck engine coolant
flows directly
to heat exchanger 48. Closing valve 52 causes the deck engine coolant to flow
through
a third heat exchanger 54, where heat from the hydraulic fluid that circulates
through the
present rig's hydraulic equipment is transferred to the deck engine coolant.
This heat
is then transferred to the heat transfer fluid in heat exchanger 48. Pressure
valves 52
and 46 ensure that the pressure within heat exchanger 54 is within operational
limits.
Heat from the engines is transferred to a closed heat exchange loop 60
containing
the heat exchange or transferring fluid. This heat exchange fluid preferably
is capable
of exchanging heat at temperatures of 40 to 200 degrees Celsius without
breaking down.
Such fluids are well known in the art, and one example of such a fluid is
Calflow-AFT""
from Petro Canada.
Heat exchange loop 60 incorporates a hydraulically actuated pump such as
centrifugal pump 64 which may be, for example, a Gould T"" 2 x 3. Pump 64 is
connected
at its intake end to two sources of heat exchange fluid. The first is supply
line 66 which
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CA 02463808 2004-11-15
delivers hot fluid from heat exchangers 42 and 48. The second source is supply
line 68
that delivers heat exchange fluid from heat exchange fluid tank 70. Valves 72
can be
used to isolate tank 70 if required.
Pump 64 forces the heat exchange fluid through a filter 74 following which the
flow is split up to four different ways. Part of the heat exchange fluid is
deviated into inlet
76 of heat exchanger 80. Another part is divided into feed lines 82 and 83
(eg. 1 inch)
that flow into water brakes 20 and 30 respectively. A smaller part is diverted
into 1/4
inch lines 86, 87, 90 and 91. These small lines fluidly connect with 1/8 inch
orifices
inside water brakes 20 and 30 that divert heat exchange fluid against the
water brakes'
seals and/or bearings when the water brakes run empty as will be described
below in
greater detail.
Water brakes generally are well known in the art and therefore will not be
described in great detail herein except with respect to certain modifications
that are
described below.
To maximize the production of heat from the truck and deck engine cooling
systems, it is necessary that these engines be fully loaded. Some of this load
will come
from parasitic loads such as alternators, water pumps and so forth, and some
from the
power required for the hot oiler's hydraulic motors and other systems. For
example, the
deck engine can be used to run the auxiliary hydraulics that actuate
centrifugal pumps
64 and 132. The truck's engine can be used for the larger hydraulics for
triplex pump
28 (figure 2) used to inject and then recover the batch fluid from the well
bore. These
loads are not sufficient by themselves however to cause the engines to produce
their
maximum horsepower and heat output. The engines are therefore mechanically
coupled
to water brakes 20 and 30 to produce the required added load.
The mechanical coupling between the engines and water brakes 20 and 30 is
conventional and numerous means of coupling them operationally together will
occur to
those skilled in the art. For example, as is known in the art, the truck's
gearbox (not
shown) will have one or more auxiliary power take-offs. One of these take-offs
can be
used to drive the rig's hydraulics and the other can be mechanically coupled
to water
brake 20 such as by means of a shaft, belt or chain. Or the engine's power
take-off can
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CA 02463808 2004-05-03
be drivingly coupled to a gearbox having for example two outlets. One outlet
can be
directly coupled to the water brake and the other to the rig's hydraulic
motors which in
turn drive the various pumps referred to above.
Generally, water brakes comprise a sealed chamber that is normally kept full
of
heat transfer fluid. A plurality of radially extending, shaft mounted blades,
impellers or
rotor/stators are disposed to rotate within the chamber against the shear
resistance of
the heat transfer fluid. The shaft is rotated by the motor being loaded
through a
mechanical coupling. The mechanical energy from the spinning rotors is
converted to
heat energy in the heat transfer fluid which is continuously circulated
through the
chamber to cool the water brake and its seals and to produce heated heat
transfer fluid
for circulation through heat exchanger 80.
Heat exchange fluid entering water brakes 20 and 30 drains through lines 94
and
96 back into tank 70.
In heat exchanger 80 heat is transferred to the batch fluid, such as hot oil,
as
described below, and the heat exchange fluid exits heat exchanger 80 through
outlet 100
into line 102. The heat exchange fluid next flows through exhaust heat
exchanger 110.
Exhaust heat exchanger 110 includes a full flow of heat exchange fluid running
through it at all times that pump 64 is operating. Exhaust gases are diverted
from both
the engines through exhaust heat exchanger 110 when the system is heating oil.
When
exhaust passes through exhaust heat exchanger 110, it passes over fins with
large
surface areas. The heat that is collected on the fins is transferred to the
heat exchange
fluid.
Heat exchange fluid leaves exhaust heat exchanger 110 and travels along line
112. Valves 114 and 116 determine whether the heat exchange fluid theh passes
through heat exchangers 42 and 48: If valve 114 is open and valve 116 is
closed, heat
exchange fluid is forced through bypass line 118 into line 66. Otherwise, if
valve 116 is
open and valve 114 is closed the heat exchange fluid travels through heat
exchangers
42 and 44. These heat exchangers transfer heat from the two engine coolants
into the
heat exchange fluid.
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CA 02463808 2004-05-03
One skilled in the art will realize that a temperature gradient is needed to
exchange heat from the engines to the oil being heated. If, for example, it
takes 30
degrees Fahrenheit difference to exchange the heat from the engine coolant to
the heat
exchange fluid, and it takes 30 degrees Fahrenheit difference to exchange the
heat from
the heat exchange fluid to the oil, then the engine temperature needs to be 60
degrees
F above the product temperature in the hot oiler tank. In this example, the
engine
coolant contribution to heating the product in the hot oiler tanks drops off
exponentially
once the temperature between the engine coolant and the liquid in the hot
oiler tanks
has reached a differential of 60 degrees F with the coolant being the hotter
fluid. Also,
the engine coolant should be isolated from the heat.exchange fluid when there
is a 30
degree F differential between the coolant and the product in the fluid and the
hot oiler
tank. After that point, the heat transfer fluid starts to transfer heat to the
engine coolant
and is transferred to the atmosphere via the radiator. When the heat exchange
fluid
reaches a temperature approaching that of the engine coolant, valve 116 is
closed and
valve 114 is opened, isolating the engine coolant from the heat exchange
fluid.
As indicated above, water brakes 20 and 30 can at times be allowed to run
empty.
This occurs if no additional load is required on the engine. In conventional
systems the
gearboxes splitting power to the water brake would be adapted to disengage the
brakes
from the engines. These gearboxes however are heavy and expensive. To avoid
this,
the present water brake in a preferred embodiment of the present invention has
been
adapted to run empty which otherwise would normally cause the brake and its
seals to
burn out.
In the present system, each brake's aluminum housing is hardened to 85
Rockwell, and supply lines 86 and 87 for water brake 20 and fines 90 and 91
for water
brake 30 continuously deliver a small amount of heat exchange fluid to the 1I8
inch
orifices which internally direct the heat exchange fluid against the seals
andlor bearings.
When valves 120 and 122 are closed to stop the delivery of heat exchange fluid
to water
brakes 20 and 30 respectively, pressurized air (7 to 10 psi) from heat
exchange fluid tank
70 flows through orifice 124 and through air hose 126 into lines 82 and 88 to
purge heat
exchange fluid from water brakes 20 and 30. Orifice 124 allows air to flow
freely but
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CA 02463808 2004-05-03
slows down the flow of heat exchange fluid into tank 70 when valves 120 and
122 are
open during normal operation. Without the heat exchange fluid in them, water
brakes
20 and 30 simply spin without loading the engines. The additional hardening of
the
water brake's housing and the continuous flow of heat exchange fluid against
the seals
prevents.erosion and pitting ofi the brake's inner walls and burnout,
respectively: Such
a water brake provides additional advantages over conventional systems where
water
brakes could not be run empty.
An additional advantage of the water brakes is that they provide shear heat.
Fluid
entering through fines 82 and 83 is forced to shear by the rotation of water
brakes 20
and 30.
The oil or fluid required to be heated is stored in batch tank 130. A pump
such
as a Viking pump 132 is used to pump fluid through line 134 into heat
exchanger 80.
The fluid is heated from the heat exchange fluid and leaves heat exchanger 80
through
line 136. The fluid can then be directed to the well through line 138 and
Triplex pump
28 if valve 140 is open, or back to batch tank 130 through line 142.
The fluid returns to the hot oiler from the well through line 144, and can
either be
directed back into the well or to the batch tank if valve 146 is open, or flow
back through
heat exchanger 80 through line 148 if valve 150 is open.
The present system therefore derives heat from two engine coolants, the
exhaust
from these engines, and from shear heat generators for heating the heat
transferring
fluid, which in turn provides heat to the oil or fluid being used for
servicing the well. The
inventors have found that a 500 hp engine rejects about 800,000 BTUIhr under
full load
to its water system. Further, this 500 hp engine rejects up to 4 million
BTUIhr from the
exhaust system. By adding a shearing system, an additional 2,500 BTUIhr is
generated
for each horsepower of load on an engine.
Reference is now made to Figure 2. All of the above described elements are
located on a truck 150. Truck 150 includes a cab, behind which is exhaust heat
exchanger 110. Located reanrvard of this on truck 150 is deck engine 25. Batch
tank
130 is located rearwardly of the deck engine. Triplex pump 28 regulates the
flow of the
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CA 02463808 2004-11-15
oil to and from batch tank 130 for injection into and recovery from the well.
Most of the
remaining components described above have been removed for clarity.
It will be appreciated that for smaller hot oilers requiring less heat, deck
engine
25 can be eliminated.
Reference is made to Figure 3 which is a flow diagram for a modified closed
loop
heat exchange system 61 for a single engined flameless hot oiler in which like
numerals
have been used to identify like elements.
Heat from the truck engine's (not shown) cooling system is captured by heat
exchanger 42 with the flow of engine coolant through the exchanger being
controlled by
valves 40 and 44. In this embodiment, flow can be boosted by the addition of a
circulation pump 86 (eg. from PriceT""). Heat from the rig's hydraulic fluid
can be
transferred to the truck engine's coolant by means of heat exchanger 54. Not
shown are
valves which can be used to control the flow of hot hydraulic fluid into
exchanger 54
depending upon whether or not this heat source is to be exploited.
Heat transfer fluid from exchanger 42 flows through line 168 into exhaust heat
exchanger 110. Heat transfer fluid discharged from exhaust heat exchanger 110
flows
through line 169 and then into line 66 which is in fluid communication with
the inlet to
centrifugal pump 64 which circulates the heat exchange fluid through closed
loop 61.
This is the first source of heat exchange fluid for pump 64. The second source
is supply
line 68 that delivers heat exchange fluid from heat exchange fluid tank 70.
Valves 72
can be used to isolate tank 70 if required.
As with the two engined version of the hot oiler described above, pump 64
forces
the heat exchange fluid through a filter 74 but the flow is split only three
different ways.
Part of the heat exchange fluid is diverted into inlet 76 of heat exchanger
80. Another
part is diverted into feed line 82 that flows into water brake 20. A smaller
part is diverted
into 1/4 inch lines 86 and 87 which deliver a continuous stream of fluid to
1/8 inch
orifices inside the brake that direct the fluid against the brake's seals
and/or bearings
when the brake is run empty as described above.
Heated exchange fluid discharged from brake 20 flows through line 94 into
reservoir 70.
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CA 02463808 2004-11-15
Valve 120 controls the flow of heat exchange fluid into water brake 20.
When running under load, temperatures in water brake 20 can be extremely high
and particularly if the brake is less than full, vapour pressures can rise to
the point of
possibly jeopardizing the brake's seals. To minimize this possible risk, brake
20 is
provided with an unrestricted anti-boil line 126. In operation, valve 72 in
line 94 is
stoppered down until a small amount of fluid is observed to be discharged from
line 126.
This is taken as an indication that brake 20 is running full of fluid. Valve
72 can then be
left more or less permanently in this position.
When valve 120 is closed, negative pressure develops in the brake which draws
air from the space above the fluid level in reservoir 70 through line 126 into
the brake
which allows it to drain thoroughly. The operation of the brake when empty is
then the
same as described above with respect to the embodiment of Figure 1.
As described above, heat exchanger 80 is used to transfer heat to the batch
fluid.
The heat exchange fluid exits exchanger 80 through outlet 100 into line 103 to
complete
the flow loop back into engine heat exchanger 42.
The means for circulating the batch fluid through heat exchanger 80 are the
same
as described above with respect to Figure 1.
Loop 61 can be provided with various pressure sensors connected to dials or
gauges that can be mounted onto a control panel 200 (shown covered) in Figure
4. The
sensors can include sensor 202 for system pressure, 204 for engine heat
exchanger
inlet pressure, 206 for exhaust heat exchanger inlet pressure, 208 for exhaust
heat
exchanger outlet pressure, 210 for water brake outlet pressure and 212 for an
anti-boil
return outlet pressure in flow line 126. This system can also be equipped with
temperature sensors for the temperature of the heat exchange fluid, hydraulic
fluid, the
batch fluid and the engine coolant. There will also be temperature and
pressure sensors
and gauges for triplex pump 28 used to pump the batch fluid into and from the
well.
In one embodiment constructed by the applicant, batch tank 130 can be
subdivided as shown in Figure 1 to include a principal reservoir 129 for batch
fluid and
a smaller reservoir 128 which can be used as a spare tank for additional batch
fluid or
for a second batch fluid such as methanol or water. In Figures 1 and 4, it can
be seen
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CA 02463808 2004-05-03
that there are two batch fluid supply lines 134 each with its own valve 157
for selecting
the appropriate reservoir. The tank can be further subdivided to include a
third chamber
for the truck's fuel supply.
The present rig can be optionally provided with additional bolt-on pumps that
can
be used to draw batch.fluid from an external. reservoir or even from a low
lying source
such as a pond or river.
The above-described embodiments of the present invention are meant to be
illustrative of preferred embodiments of the present invention and are not
intended to
limit the scope of the present invention. Various modifications, which would
be readily
apparent to one skilled in the art, are intended to be within the scope of the
present
invention. The only limitations to the scope of the present invention are set
out in the
following claims.
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