Note: Descriptions are shown in the official language in which they were submitted.
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CA 02642188 2008-10-28
DOWNHOLE WELL PUMP
Field of the Invention
This invention relates to an apparatus for pumping fluid from a well to the
surface.
Back2round of the Invention
Within an oil or gas well, production fluids (liquids, gases, or any fluid
produced from a
wellbore) are produced to the surface within a production string placed in a
wellbore. The
production string is typically assembled with production tubing and completion
components in a
configuration that suits the wellbore conditions and the production method.
Since oil wells
typically vary from a few hundred to several thousands of feet in depth, there
is often insufficient
pressure to effect the flow of production fluids through the production string
out of the well to
the surface.
Several prior art systems involving different pumping and extraction devices
have been
developed to lift production fluids from a well. The most common is a downhole
pump installed
deep within the well. A surface hydraulic pump pressurizes power oil which
drives the
downhole pump. When a single production string is used, the power oil is
pumped down the
tubing and a mixture of the formation crude oil and power oil are produced
through the casing-
tubing annulus. If two production strings are used, the power oil is pumped
through one of the
pipes, and the mixture of formation crude oil and power oil are produced in
the other, parallel
pipe. Prior art artificial lift systems include for example, the progressive
cavity pump and
plunger lift, both of which are installed on jointed or continuous rods;
electric submersible
pumps; gear pumps installable on tubing and powered by downhole electric or
hydraulic motors;
and the Venturi Lift which is run on coiled tubing but is not a total
production system. However,
such systems tend to be complex or of substantial size and weight, requiring
significant structural
support elements at the wellhead which increase the expense of the overall
system. Therefore,
there is a need in the art for an apparatus which mitigates these limitations.
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CA 02642188 2008-10-28
Summary of the Invention
The present invention relates to an apparatus for pumping fluid from a well to
the surface.
In one aspect, the invention provides an apparatus for use with production
tubing to pump
fluid from a well to the surface comprising:
(a) a tubular conduit comprising an upper portion having an open upper end and
a
lower portion having an open lower end, the upper portion being releasably
engaged to the lower portion, the lower portion having an inner or outer
diameter
greater than the diameter of the upper portion, forming a first internal or
external
shoulder where the lower and upper portions are engaged;
(b) sealing means disposed on the tubular conduit for sealing between the
conduit and
a well casing; and
(c) at least one valve section having a one-way valve adapted to allow fluid
to pass
upward through the valve but not downward, the valve section being adapted to
releasably engage either the upper end or the lower end of the conduit.
In one embodiment, the valve section engaging the upper end of the conduit has
an
external diameter greater than the upper portion, forming a second external
shoulder wherein the
valve section and the upper portion are engaged.
In one einbodiment, the valve section engaging the upper end of the conduit is
configured
for releasably engaging a lower end of the productiori tubing. In one
embodiment, the valve
section releasably engages the lower end of the production tubing by a
threaded connection.
In one embodiment, the sealing means engages the upper portion of the conduit
and is
retained by the first and second shoulders. In one embodiment, the sealing
means comprises at
least one ring-shaped V cup having an interior diameter substantially equal to
the outside
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CA 02642188 2008-10-28
diameter of the upper portion. In one embodiment, the sealing means comprises
a plurality of V
cups.
In one embodiment, the valve section is tubular, having an open upper end and
an open
lower end and defining a bore extending therethrough between the ends. In one
embodiment, the
valve section includes a valve at the upper end. In one embodiment, the
apparatus has one valve.
In one embodiment, the apparatus has two valves. In one embodiment, the valve
is selected from
a hinged flapper valve or a ball valve. In one embodiment, the apparatus has
two hinged flapper
valves.
In another aspect, the invention provides a method of pumping fluid from a
well to the
surface using the above apparatus comprising the steps of:
(a) attaching an upper end of the production tubing to a reciprocating pumping
assembly;
(b) attaching the apparatus to a l'ower end of the production tubing; and
(c) reciprocating the production tubing and the attached apparatus until the
production fluid is removed from the well for recovery to the surface.
Additional aspects and advantages of the present invention will be apparent in
view of the
description, which follows. It should be understood, however, that the
detailed description and
the specific examples, while indicating preferred embodiments of the
invention, are given by
way of illustration only, since various changes and modifications within the
spirit and scope of
the invention will become apparent to those skilled in the art from this
detailed description.
Brief Description.of the Drawings
The invention will now be described by way of an exemplary embodiment with
reference
to the accompanying simplified, diagrammatic; not-to-scale drawings. In the
drawings:
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CA 02642188 2008-10-28
Figure 1 is a diagrammatic representation of an embodiment of the invention.
Figure 2 is an exploded diagrammatic representation of the various components
of an
embodiment of the invention.
Figure 3 is a diagrammatic representation of an embodiment of the invention
during
upstroke of the apparatus, showing the valves in a closed position.
Figure 4 is a diagrammatic representation of an embodiment of the invention
during
downstroke of the apparatus, showing the valves in an open position.
Detailed Description of Preferred Embodiments
When describing the present invention, all terms not defined herein have their
common
art-recognized meanings. To the extent that the following description is of a
specific
embodiment or a particular use of the invention, it is intended to be
illustrative only, and not
limiting of the claimed invention. The following description is intended to
cover all alternatives,
modifications and equivalents that are included in the spirit and scope of the
invention, as
defined in the appended claims.
The invention will now be described having reference to the accompanying
figures. The
apparatus (10) pumps production fluid from a formation to the surface. It will
be understood by
those skilled in the art that the apparatus (10) is mounted at a lower end of
production tubing (12)
in a concentric orientation within the well tubulars, for example, the
production casing (14) of a
conventional gas well, to contact the wellbore fluid. As used herein and in
the claims, the term
"concentric" refers to components sharing a common center and thus a uniform
annular
dimension. However, one skilled in the art-will recognize that two tubular
members where one
has a smaller diameter and is placed within the other may be considered
concentric, even if they
do not share the exact geometric centre, and even if they are not circular in
cross-section.
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CA 02642188 2008-10-28
A conventional gas well typically comprises a wellbore extending from the
surface
through the earth to intersect a production formation to produce natural gas,
condensate (i.e.,
natural gas liquids such as propane and butane) and occasionally water.
Similarly, an oil well
typically varies from a few hundred to several thousand feet in depth, and
there is often
insufficient formation pressure to cause the flow of production fluids (i.e.,
predominantly oil,
some gas) to the surface. The apparatus (10) may be placed in vertical,
horizontal or inclined
wellbores. "Horizontal" means a plane that is substantially parallel to the
plane of the horizon.
"Vertical" means a plane that is perpendicular to the horizontal plane. Such
variations of well
design are known to those skilled in the art.
The apparatus (10) is generally shown in Figures 1-2 to include a tubular
conduit (16), at
least one valve section (18), and sealing means (20). The tubular conduit (16)
comprises an
upper portion (22) having an open upper end (24), and a lower portion (26)
having an open lower
end (28). The upper end (24) is adapted to releasably engage a first valve
section (18). The
upper end (24) may have threads (30) on its outer wall (32) to attach to
mating threads of the
inner wall (not shown) of the first valve section (18). The lower end (28) is
adapted to engage a
second valve section (18). The lower end (28) may have threads on its inner
wall (not shown) to
attach to mating threads (34) of the second valve section (18). Suitable
engagement means other
than threaded connections are well known to those skilled in the art.
The lower portion (26) has an inner or outer diameter greater than the
diameter of the
upper portion (22), forming a first intemal or external shoulder (36) at the
junction of the lower
and upper portions (26, 22). The first valve section (18) to which the upper
portion (22) is
connected has an external diameter greater than the upper portion (22),
forming a second
external shoulder (38) at the junction of the first valve section (18) and
upper portion (22).
Suitable engagement means known in the art such as, for example, threaded
connections, may be
used to connect the upper and lower portions (22, 26).
The sealing means (20) is placed on the upper portion (22), with its
longitudinal
movement restricted to the length of the upper portion (22) located between
the first and second
shoulders (36, 38). The first shoulder (36) acts as a physical barrier to
prevent the sealing means
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CA 02642188 2008-10-28
(20) from slipping off the lower end (28) of the conduit (16) on the upstroke
of the apparatus
(10). The second shoulder (38) acts as a physical barrier to prevent the
sealing means (20) from
slipping off the upper end (24) of the upper portion (22) on the downstroke of
the apparatus (10).
The sealing means (20) is sized so as to seal between the conduit (16) and the
well casing
(14). Suitable sealing means (20) as are known in the art may be used. The
sealing means (20)
may be formed of, for example, synthetic rubbers, thermoplastic materials,
perfluoroelastomer
materials, or other suitable substances known to those skilled in the art.
Appropriate sealing
means (20) are sufficiently resilient for providing a good seal and
sufficiently rigid for providing
a relatively long life therefore. The dimensions of the sealing means (20) are
not essential to the
invention and are dictated by the size of the production tubing (12) and well
casing (14).
In one embodiment, the sealing means (20) may comprise one or more ring-shaped
V
cups, with each having an inner diameter substantially equal to the outside
diameter of the upper
portion (22). The outer diameter of the V cup (20) is substantially equal to
the diameter of the
well casing (14). The V cup (20) is a resiliently flexible disk shaped body
having a central hole.
The diameter of the central hole is substantially equal to the outer diameter
of the upper portion
(22) such that the V cup (20) is placed onto the upper, portion (22) in a
collar-like manner. The
walls of the V cup (20) extend radially from the central hole at an angle
below the horizontal
plane of the central hole such that the outer edge of the cup terminates at a
position below the
plane of the central hole. The V cup (20)-is orientated so that the cup walls
extend radially
towards the lower portion (26). The V cup (20) may be made of rubber or any
other suitable
resiliently flexible material. When more than one V cup (20) is used, the V
cups (20) are
oriented in a stacked relationship over the upper portion (22), as shown in
Figures 1, 3 and 4.
Each valve section (18) is tubular, having an open upper end (40) and an open
lower end
(42) and defining a bore (not shown) extending therethrough between its ends
(40, 42). The
valve section (18) includes a valve (44) at the upper end (40). The valve (44)
is one-way,
allowing fluid to pass upward through the valve but not downward. The valve
(44) is thus
configured to open during downwards motion through fluid, and to close during
upwards motion
through liquid. In one embodiinent, the apparatus (10) has one valve (44). In
one embodiment,
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CA 02642188 2008-10-28
the apparatus (10) has two valves (44). The presence of two valves (44)
minimizes the risk of
valve failure in the event for example, that one valve becomes worn or
damaged. In one
embodiment, the valve (44) is selected from a hinged flapper valve or a ball
valve. In one
embodiment, the apparatus (10) has two hinged flapper valves. Hinged flapper
valves are less
susceptible to wear, and allow the passage of large volumes of sand, debris
and solid particulate
matter. It will be understood by those skilled in the art that other suitable
valves may be used,
interchanged or selected in accordance with the type of fluid being pumped;
for example, a
flapper valve may be used with heavy oil and sand, while a ball valve may be
used with lighter
fluids and in the absence of solid particulate material.
The apparatus (10) can be constructed from any material or combination of
materials
having suitable properties such as, for example, mechanical strength, ability
to withstand cold
and adverse field conditions, corrosion resistance, and ease of machining. In
one embodiment,
the conduit (16) and valve sections (18) are formed of steel or stainless
steel.
As shown in the Figures, the apparatus (10) may be formed from the assembly of
separate
components. However, those skilled in the art will understand that various
modifications can be
made without altering the substance of the invention. For example, the upper
and lower portions
(22, 26) may be manufactured as a monolithic unit.
During installation, the apparatus (10) may be assembled at the surface with
the
components attached in sequence; for example, the second valve section (18) is
connected to the
lower portion (26). The upper portion (22) is attached to the lower portion
(26) over which the
sealing means (20) is slid to rest against the first shoulder (36). The second
valve section (18) is
attached to the upper portion (22). The fully assembled apparatus (10) is then
connected to the
lower end of the production tubing (12). The apparatus (10) may also be
assembled with each
component being individually attached in sequence to the lower end of the
production tubing
(12); for example, the first valve section (18b), upper portion (22), sealing
means (20), lower
portion (26), and the second valve section (1 8a). With the assistance of a
conventional service
rig, the production tubing (12) and apparatus (10) are deployed into the
wellbore until reaching
the desired zone as will be described.
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The operation of pumps is commonly known to those skilled in the art and will
not be
discussed in detail. Pumping strings are well known in the art and are
attached to the production
tubing (12) to reciprocate the apparatus (10). Conventional machinery such as,
for example, a
pump jack or driver (46), is used to raise and lower the pumping string in
order to effect
alternating upstrokes and downstrokes of the apparatus (10). The conduits
defined by the
pumping string (not shown), production tubing (12) and apparatus (10) define a
fluid flow
passage which extends from the welibore to the surface in order to deliver the
pumped fluid to
the surface.
In another aspect, the invention provides a method of pumping fluid from a
well to the
surface using the above apparatus comprising the steps of attaching an upper
end of the
production tubing to a reciprocating pumping assembly; attaching the apparatus
to a lower end of
the production tubing; and reciprocating the production tubing and the
attached apparatus until
the production fluid is removed from the well for recovery to the surface.
In operation, the pumping string is driven by conventional machinery to effect
upstrokes
and downstrokes of the apparatus (10). During each upstroke, the apparatus
(10) is raised above
a plurality of perforations (48) which are diametrically opposed and spaced
intermittently along
the closed casing (14), as shown in Figure 3. Both the valves (44a, 44b) and
the sealing means
(20) are thus raised above the perforations (48). The valves (44a, 44b) are in
the closed position.
The sealing means (20) is in a sealing engagement with the casing (14). The
upwards vertical
movement of the apparatus (10) allows the sealing means (20) to create a
suctioning force which
draws production fluids from the formation through the perforations (48) into
the casing (14).
The valves (44a, 44b) of the valve sections (18a, 18b) close during the
upstroke. Upon
completion of the upstroke, the lower annulus (50) of the casing (14) is
replete with production
fluid to be produced from the well.
During each downstroke, the apparatus (10) is lowered past the perforations
(48), as
shown in Figure 4. Both the valves (44a, 44b) and sealing means (20) are thus
driven below the
perforations (48). The valves (44a, 44b) are in the open position. The sealing
means (20) is in a
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CA 02642188 2008-10-28
sealing engagement with the casing (14). The downwards vertical movement of
the apparatus
(10) enables the sealing means (20) to apply a compressive force to the
production fluid in the
lower annulus (50) of the casing (14), pushing the fluid upwardly through the
lower valve section
(18a). The upwards motion of the fluid opens the valve (44a) to pass into the
conduit (16) and
into the upper valve section (18b). The continued upwards motion of the fluid
opens the upper
valve (44b) to pass into the production tubing (12) to the surface.
Upon completion of the downstroke, the apparatus (10) is positioned at the
bottom of the
casing (14), and then is raised upwardly during the next upstroke. As the
upstroke is initiated,
the compressive force is removed from below the perforations (48), and the
valves (44a, 44b)
return to their closed positions. The valves (44a, 44b) remain closed
throughout the upstroke of
the apparatus (10). As the sealing means (20) moves upwardly past the
perforations (48),
production fluid from the formation is drawn into the lower annulus (50) of
the casing (14).
Alternating upstrokes and downstrokes of the apparatus (10) are repeated
within the well until
the production fluid has been removed from the formation and pumped for
recovery at the
surface.
In the event the sealing means (20) becomes worn or is otherwise damaged
during
operation, the valve section (1 8b) may be easily removed from the upper
portion (22) by
unthreading their connection, whereupon replacement sealing means (20) may be
installed over
the upper portion (22), and a continued efficient operation of the apparatus
(10) will be provided.
The apparatus (10) pumps production fluids from a formation into a well and
then to the
surface. Importantly, the apparatus (10) is simple and efficient in operation.
The valves (44a,
.44b) of the apparatus (10) may be interchanged or selected in accordance with
the type of fluid
being pumped. Support of the apparatus (10) by the production tubing (12)
eliminates the
requirement for anchoring means within the well. The apparatus (10) or
components thereof (for
example, the valve sections (1 8a, 18b) and sealing means (20)) can be readily
assembled, or
unassembled for inspection, reinsertion or replacement if necessary in a
minimum of time and
effort, thus reducing the cost of operation of the apparatus (10). Further,
the apparatus (10)
requires few components, thereby eliminating the requirement for complex,
downhole moving
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CA 02642188 2008-10-28
parts and minimizing expense in manufacturing. Conveniently, unassembled
components of the
apparatus (10) can be stored and carried in a small tool box for assembly on
the servicing rig,
eliminating the expense of equipment transport and rig jobs.
As will be apparent to those skilled in the art, various modifications,
adaptations and
variations of the foregoing specific disclosure can be made without departing
from the scope of
the invention claimed herein.
