Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02946557 2016-10-27
PUMP FOR LOW PRESSURE CASING GAS
This disclosure relates to the field of oil wells and in particular a pump
system for
increasing the pressure of casing gas in an oil well to a usable pressure.
BACKGROUND
Oil wells typically comprise a well casing extending down from the surface to
an oil
bearing formation. In addition to oil, there is typically as well a
significant amount of
natural gas drawn from the formation and present in the casing. It is
desirable to use this
gas to operate various surface equipment, such as to drive the pump engine
that draws oil
from the well, to operate burners in cold weather operations, and so forth.
It is often the case that the casing gas is at a pressure that is not
sufficient to satisfactorily
operate the desired equipment, and so it may be necessary to bring in another
fuel, such
as propane, to operate the equipment, significantly increasing the cost of
operating the
well. Also where casing gas pressure is low, the casing gas is commonly simply
vented
to the atmosphere, which is a waste of resources and environmentally
undesirable.
SUMMARY OF THE INVENTION
The present disclosure provides a natural gas pump system for oil well sites
that
overcomes problems in the prior art.
The present disclosure provides a system for pumping oil from an oil well. The
system
comprises a well casing extending from a ground surface to an oil bearing
formation, the
well casing containing oil and casing gas. An oil pump is driven by an oil
pump engine
and is operative to pump oil from the well casing. A gas reservoir is
connected to the oil
pump engine to supply casing gas to fuel the oil pump engine, and a gas pump
is
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operative to draw casing gas from the well casing and pump the casing gas into
the gas
reservoir. A reservoir pressure of casing gas in the gas reservoir is greater
than a casing
pressure of casing gas in the well casing.
Commonly in such oil wells as are contemplated for use with the system of the
present
disclosure while the pressure of the casing gas in the casing is too low for
practical use,
the volume of casing gas flowing from the formation is quite sufficient, when
pressurized
by the disclosed system, to operate the equipment for significant lengths of
time, often as
long as the oil production warrants keeping the well in production.
It is contemplated that lowering the pressure of the casing gas in the well
casing by
sucking the gas out may also somewhat increase the flow of oil from the
formation and so
may increase production from the well.
DESCRIPTION OF THE DRAWINGS
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numbers, and where:
Fig. 1 is a schematic side view of an embodiment of a system of the present
disclosure;
Fig. 2 is a schematic cut-away side view of a gas pump apparatus for use with
the
embodiment of Fig. 1 showing the piston rod moving toward the left position;
Fig. 3 is a schematic cut-away side view of the gas pump apparatus of Fig. 2
showing
the piston rod moving toward the right position.
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DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Fig. 1 schematically illustrates an embodiment of a system 1 of the present
disclosure for
pumping oil from an oil well. The system 1 comprises a well casing 3 extending
from a
ground surface 5 to an oil bearing formation 7. The formation 7 contains both
oil and
natural gas which enter the well casing 3. The natural gas is herein referred
to as casing
gas, and the well casing 3 contains oil represented by the circles 9 and
casing gas
represented by the crosses 11. After flowing from the formation 7 the oil 9
pools in the
bottom portion of the casing 3 and an oil pump 13 driven by an oil pump engine
15 is
operative to pump the oil 9 from the well casing 3 into a storage container
17, or,
depending on the facilities available, into a pipeline.
The casing gas 11 rises to the upper portion of the casing 3 and commonly has
sufficient
pressure that same can be directed from the top of the casing 3 to the oil
pump engine 15
to be used as fuel to power the engine 15, and also to power burners or like
surface
equipment that might be required. Often the pressure of the casing gas 11 in
the casing 3
drops to a level where it is not sufficient to flow properly to the engine 15
or other
equipment, and a propane tank must be brought in to provide fuel.
In the present system, a gas pump 19 is operative to draw casing gas 11 from
the well
casing 3 and pump the casing gas 11 into a gas reservoir 21 which is connected
to the oil
pump engine 15 to supply casing gas 11 to fuel the oil pump engine 15. The gas
pump 19
increases the pressure of the casing gas 11 in the gas reservoir 21 to a
reservoir pressure
that is significantly greater than the casing pressure of casing gas 11 in the
well casing 3,
and that is sufficient to provide pressurized fuel to the oil pump engine 15,
and any other
required equipment.
Figs. 2 and 3 schematically illustrate a gas pump 19 for use with the
apparatus 1. The
illustrated gas pump 19 comprises a barrel 23 with a substantially cylindrical
barrel wall
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25 and right and left end walls 27R, 27L closing corresponding right and left
ends of the
barrel 23. Right and left gas ports 29R, 29L are defined in corresponding
right and left
end portions of the barrel 23. In the illustrated gas pump 19 the right and
left gas ports
29R, 29L are defined in corresponding right and left end portions of the
cylindrical barrel
wall 25, however same could also be defined in the right and left end walls
27R, 27L as
indicated by alternate gas ports 29' in Fig. 2.
A partition wall 31 extends across a mid-point of the barrel 23 to divide the
barrel into a
right chamber 33R and a left chamber 33L. A piston rod 35 extends along a
longitudinal
axis LA of the barrel 23 through a rod hole 37 in the partition wall 31 and is
sealed to the
rod hole 37 such that the piston rod 35 is free to slide in the rod hole 37.
Right and left
pistons 39R, 39L are attached to corresponding right and left ends of the
piston rod 35
and are configured to slide in sealing engagement along inner walls 41 of the
corresponding chambers 33.
A gas input conduit 43 is connected at a first end 43A thereof to an interior
of the well
casing 3 and a gas output conduit 45 connected at a first end 45 thereof to an
interior of
the gas reservoir. Right and left gas port valves 47R, 47L are connected to
the
corresponding right and left gas ports 29R, 29L, and each gas port valve 47 is
operative
in a first position to connect the corresponding gas port 29 to the gas input
conduit 43
and is operative in a second position to connect the corresponding gas port 29
to the gas
output conduit 45. Fig. 2 schematically illustrates the right gas port valve
47R in the first
position and the left gas port valve 47L in the second position.
A piston rod drive 49 is operative to move the piston rod 35 and attached
pistons 39
alternately right and left and a gas valve control 51 is operative to
synchronize movement
of the right and left gas port valves 47R, 47L between the first and second
positions such
that casing gas 11 is drawn through the gas input conduit 43 from the casing 3
and
expelled through the gas output conduit 45 into the gas reservoir 21. A check
valve 53 is
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operative to allow gas to flow from the gas output conduit 45 into the gas
reservoir 21
and operative to prevent gas from flowing out of the gas reservoir 21 through
the gas
output conduit 45.
The piston rod 35 is movable from a right position shown by the dotted lines
in Fig. 3,
where an outer face 55R of the right piston 39R is adjacent to the right gas
port 29R and
the right piston 39R is between the right gas port 29R and the partition wall
31, to a left
position shown by the dotted lines in Fig. 2, where an outer face 55L of the
left piston
39L is adjacent to the left gas port 29L and the left piston 39L is between
the left gas port
29L and the partition wall 31.
The right gas valve 47R is in the first position and the left gas valve 47L is
in the second
position when the piston rod 35 is moving toward the left position in
direction PL as
illustrated in Fig. 2, and the right gas valve 47R is in the second position
and the left gas
valve 47L is in the first position when the piston rod 35 is moving toward the
right
position in direction PR as illustrated in Fig. 3.
It can be seen that as the piston rod 35 moves to the left in direction PL as
shown in Fig.
2, gas is drawn from the casing 3 through the gas input conduit 43, the right
gas port
valve 47R, which is in the first position, and the right gas port 29R into the
right chamber
33R, and any gas in the left chamber 33L is forced out through the left gas
port 29L and
directed by the left gas port valve 47L, which is in the second position, to
the gas output
conduit 45 and into the gas reservoir 21. Significant reservoir gas pressure
can be
attained in the gas reservoir 21, depending on the relative volume of spaces
between the
outer faces 55 of the pistons 39 and the end walls 27 when the pistons 39 are
in the right
and left positions. Typically a gas pump control 57 is connected to a pressure
sensor 59
on the gas reservoir 21. The gas pump control 57 is operative to stop the gas
pump 19
when the reservoir pressure reaches a selected maximum reservoir pressure, and
to start
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the gas pump 19 when the reservoir pressure reaches a selected minimum
reservoir
pressure.
In the illustrated gas pump 19, hydraulic fluid substantially fills inner
portions 61R, 61L
of the right and left chambers 33R, 33L between inner faces 63R, 63L of the
corresponding right and left pistons 39R, 39L and the partition wall 31. The
piston rod
drive 49 comprises a hydraulic fluid pump 65 connected to a right fluid port
67R defined
in the cylindrical barrel wall 25 of the right chamber 33R adjacent to the
partition wall 31
and to a left fluid port 67L defined in the cylindrical barrel wall 25 of the
left chamber
33R adjacent to the partition wall.
The hydraulic fluid pump 65 is operative to draw hydraulic fluid from the
inner portion
61L of the left chamber 33L and pump the hydraulic fluid into the inner
portion 61R of
the right chamber 33R to move the piston rod 35 in direction PR toward the
right
position, and operative to draw hydraulic fluid from the inner portion 61R of
the right
chamber 33R and pump the hydraulic fluid into the inner portion 61L of the
left chamber
33L to move the piston rod 35 in direction PL toward the left position. A pump
control
69 controls the flow of hydraulic fluid, and also is connected to the gas pump
control 57
to stop and start movement of the piston rod 35 as required.
In a typical system of the present disclosure the hydraulic pump 65 is also
powered by
casing gas from the gas reservoir 21, and commonly by the oil pump engine 15.
Thus
fuel for all equipment is derived from the casing gas.
Commonly in such oil wells as are contemplated for use with the system 1 of
the present
disclosure while the pressure of the casing gas 11 in the casing 3 is too low
for practical
use, the volume of casing gas flowing from the formation 7 is quite
sufficient, when
pressurized by the disclosed system 1, to operate the equipment for
significant lengths of
time, often as long as the oil production warrants keeping the well in
production.
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A further benefit of the system 1 of the present disclosure may be found where
lowering
the pressure of the casing gas 11 in the well casing 3 somewhat increases the
flow of oil
from the formation and so increases production from the well.
The foregoing is considered as illustrative only of the principles of the
invention.
Further, since numerous changes and modifications will readily occur to those
skilled in
the art, it is not desired to limit the invention to the exact construction
and operation
shown and described, and accordingly, all such suitable changes or
modifications in
structure or operation which may be resorted to are intended to fall within
the scope of
the claimed invention.
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