Note: Descriptions are shown in the official language in which they were submitted.
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[0001]TITLE OF THE INVENTION
[0002] IMPROVED STATOR ASSEMBLY FOR PROGRESSIVE CAVITY PUMPING
SYSTEMS
[0003] CROSS REFERENCE TO RELATED APPLICATIONS
[0004]The present application claims the benefit of and priority to U.S.
Provisional
Patent Application Serial No. 61/861,802, filed August 2, 2013, and the
contents of
which are hereby incorporated by reference in its entirety.
[0005]STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR
DEVELOPMENT
[0006] Not applicable.
[0007] REFERENCE TO APPENDIX
[0008] Not applicable.
[0009] BACKGROUND OF THE INVENTION
[0010] Field of the Invention. The inventions disclosed and taught herein
relate
generally to pumping equipment; and more specifically related to an improved
stator
assembly for use with progressive cavity and similar pumps, and a downhole
pump
assembly including said improved stator.
[0011] Description of the Related Art.
[0012]A progressive cavity or eccentric screw pump is generally known in the
art and is
suitable for many applications, including oil production. As is well
understood by those
skilled in the art, a progressive cavity pump assembly includes a stator and
rotor that
engage with each other to define cavities for receiving the material to be
pumped. In an
oil production application, the assembly is suspended in a wellbore in
communication
with a reservoir. Fluid from the reservoir flows into the wellbore and enters
the pump
assembly at an entrance of the stator, entering a cavity defined cooperatively
by the
rotor and stator. As the rotor rotates relative to the stator, the defined
cavities effectively
"travel" along the axis of the assembly, carrying the fluid upwards.
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[0013]The capacity and efficiency of the progressive cavity pump assembly is
determined at least in part by the correct engagement of the rotor with the
stator. For
instance, if the rotor is not fully extended through the stator, then the
overall capacity of
the pump assembly is reduced. However, in oilfield and similar applications,
the
positioning of the rotor in the stator must be accomplished remotely.
[0014]A prior art solution to the problem of aligning the rotor with the
stator was to affix
a tag plate or bar to the intake or suction end of the stator. The tag plate
or bar provided
an obstruction across the intake opening of the stator. When the rotor was
lowered into
the stator, the lower end of the rotor would pass through the stator and
eventually
contact the tag plate or bar. The contact could be detected by a weight
indicator at the
surface. Once contact had been achieved, the rotor could be retracted towards
the
surface by an appropriate amount, typically computed based on expected tension
on
the rod string. A disadvantage of the prior art tag plate, however, is that it
could restrict
slurries and solids from entering into the stator opening. It could also
obstruct the
passage of wireline tools that the operator wishes to lower into the wellbore,
past the
lower end of the stator. Moreover, the lower end of the rotor may strike or
drag across
the tag plate or bar during installation, potentially damaging the rotor or
coating.
[0015]Another proposed solution is the use of a tag shoulder provided in a sub
that is
mounted to the tubing string above the stator, which cooperates with a stop
mounted to
the rod string on which the rotor is suspended, as described in Canadian
Patent No.
2,567,989. As the rotor is lowered, the stop on the rod string comes into
contact with
the shoulder mounted on the tubing string, to land the rotor. Another proposed
solution
is a top-tag coupling assembly described in Canadian Patent No. 2,612,326, in
which
the rotor head, which is larger than the helical portion of the rotor, lands
on a narrowing
shoulder section of the tubing string collar or coupler, also located above
the stator.
However, because the shoulder is positioned in the tubing string or connector
above
the stator, these solutions present an additional obstacle to the rotor as it
is lowered
through the tubing string or connector above the stator. A metal shoulder may
cause
scratches or other damage to the rotor as it descends past the shoulder.
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[0016]The inventions disclosed and taught herein are directed to pumping
equipment,
and in particular to an improved stator assembly for use with progressive
cavity and
similar pumps, and a downhole pump assembly including said improved stator.
[0017] BRIEF SUMMARY OF THE INVENTION
[0018] The objects described above and other advantages and features of the
invention are incorporated in the application as set forth herein, and the
associated
drawings, related to systems an improved stator assembly for use with
progressive
cavity and similar pumps, and a downhole pump assembly including said improved
stator.
[0019] In accordance with a first embodiment of the present disclosure, a
stator for use
in a progressive cavity pump is disclosed. The stator typically includes a
housing
having a suction end and a discharge end, an elastomeric liner disposed within
the
housing and defining a passageway for receiving a rotor of the progressive
cavity
pump. The passageway typically comprises a reinforced component proximate to
the
discharge end of the housing. The reinforced component of the passageway
defines an
opening smaller in dimension than a head of the rotor. The reinforced
component of
the stator may define a shoulder adapted for contact with the rotor head. The
reinforced component of the stator may comprise at least one pin, may be
formed
integrally within the housing, may be mounted on the interior of the housing,
or may be
mounted through the housing. The elastomeric liner is typically deformable to
provide a
compression fit between the stator and a rotor to define discrete cavities
between the
stator and rotor. The elastomeric liner may extend from the suction end of the
stator
and terminates before the discharge end of the stator. The reinforced
component of the
stator may be comprised of a material with greater resistance to deformity
than the
elastomeric liner.
[0020] In accordance with another embodiment of the present disclosure, a
stator for
use in a progressive cavity pump is disclosed. The stator typically comprises
a housing
comprising a wall and at least one reinforcing component extending from an
interior
face of the wall. The stator may further comprise an elastomeric liner
disposed within
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the housing and extending over the at least one reinforcing component. The
elastomeric liner may further define a passageway for a rotor of the
progressive cavity
pump. A component of the elastomeric liner may extend over the at least one
reinforcing component defining a shoulder for engaging a rotor head of the
rotor. The
at least one reinforcing component is typically proximate to the discharge end
of the
housing. The reinforcing component may comprise of at least one pin, may be
formed
integrally with the housing, may be mounted on the interior of the housing, or
may be
mounted through the housing. The elastomeric liner may extend from the suction
end
of the stator and end before the discharge end of the stator.
[0021] In accordance with another embodiment of the present disclosure, a
method of
operating a progressive cavity pump is disclosed. The progressive cavity pump
may
comprise any stator includes those described herein. The stator typically
comprises a
housing having a suction end and a discharge end. The stator may comprise an
elastomeric liner disposed within the housing and defining a passageway for
receiving a
rotor of the progressive cavity pump. The elastomeric liner may comprise at
least one
reinforced component proximate to the discharge end, the at least one
reinforced
component providing a landing surface to resist passage of a rotor head of the
rotor
through the passageway. The method typically comprises installing the stator
in a
wellbore, lowering the rotor for the progressive cavity pump on a rod string
into the
stator until a lower surface of the rotor head of the rotor contacts the
shoulder of the
stator, and on detecting said contact, raising the rotor on the rod string to
a predefined
position. The method may further comprise rotating the rotor in an eccentric
rotation
along the interior surface of the stator. The method may further include
pumping
material through the progressive cavity pump. The method may further include
pumping material through an intake end of the progressive cavity pump and
through an
open cavity defined by the rotor and stator.
[0022] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0023] The following figures form part of the present specification and are
included to
further demonstrate certain aspects of the present invention. The invention
may be
better understood by reference to one or more of these figures in combination
with the
detailed description of specific embodiments presented herein.
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[0024] FIG. 1 illustrates a perspective view of a segment of a downhole pump
assembly
including a collar, stator assembly, and rotor.
[0025] FIG. 2A illustrates a top view of the segment of the downhole pump
assembly of
FIG. 1.
[0026] FIG. 2B illustrates a sectional view of the assembly of FIG. 1 in the
plane 2B
indicated in FIG. 2A.
[0027] FIG. 20 illustrates a plan sectioned view of the assembly of FIG. 1 in
the plane
indicated in FIG. 2B.
[0028] While the inventions disclosed herein are susceptible to various
modifications
15 and alternative forms, only a few specific embodiments have been shown
by way of
example in the drawings and are described in detail below. The figures and
detailed
descriptions of these specific embodiments are not intended to limit the
breadth or
scope of the inventive concepts or the appended claims in any manner. Rather,
the
figures and detailed written descriptions are provided to illustrate the
inventive concepts
20 to a person of ordinary skill in the art and to enable such person to
make and use the
inventive concepts.
[0029] DETAILED DESCRIPTION
[0030]The Figures described above and the written description of specific
structures
and functions below are not presented to limit the scope of what Applicants
have
invented or the scope of the appended claims. Rather, the Figures and written
description are provided to teach any person skilled in the art to make and
use the
inventions for which patent protection is sought. Those skilled in the art
will appreciate
that not all features of a commercial embodiment of the inventions are
described or
shown for the sake of clarity and understanding. Persons of skill in this art
will also
appreciate that the development of an actual commercial embodiment
incorporating
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aspects of the present inventions will require numerous implementation-
specific
decisions to achieve the developer's ultimate goal for the commercial
embodiment.
Such implementation-specific decisions may include, and likely are not limited
to,
compliance with system-related, business-related, government-related and other
constraints, which may vary by specific implementation, location and from time
to time.
While a developer's efforts might be complex and time-consuming in an absolute
sense, such efforts would be, nevertheless, a routine undertaking for those of
skill in
this art having benefit of this disclosure. It must be understood that the
inventions
disclosed and taught herein are susceptible to numerous and various
modifications and
alternative forms. Lastly, the use of a singular term, such as, but not
limited to, "a," is
not intended as limiting of the number of items. Also, the use of relational
terms, such
as, but not limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side,"
and the like are used in the written description for clarity in specific
reference to the
Figures and are not intended to limit the scope of the invention or the
appended claims.
[0031]Applicants have created an improved stator assembly for use with
progressive
cavity and similar pumps, and a downhole pump assembly including said improved
stator. The design and operation of progressive cavity pumps is generally
known in the
art. As will be understood by those skilled in the art, a progressive cavity
pump
assembly as contemplated herein includes a stator, typically cylindrical in
shape but
can embody alternate forms, with an interior surface defined to cooperate with
a rotor
so as to define one or more cavities between the interior surface of the
stator and a
surface of the rotor. Generally, an exterior surface of the rotor defines a
helical shape
and the interior surface of the stator defines a double helical passageway or
bore. The
typical shape is generally helical but variations are normal. When the rotor
is engaged
in the bore of the stator, the interior surface of the stator and exterior
surface of the
rotor contact to define cavities for receiving the material to be pumped.
Typically, the
rotor is manufactured of a rigid material such as an alloy steel or stainless
steel that
would typically include a wear resistant coating, while interior surface of
the stator is
provided by an elastomeric lining or insert in a metal stator housing. Being
deformable,
the elastomeric surface of the stator can provide for a compression fit
between the
stator and rotor so as to define discrete cavities. The selection of suitable
materials for
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the stator and rotor components, as well as the other components of the entire
pumping
system, will be known to those in the art.
[0032]The material to be pumped enters an intake or suction end of the pump
assembly, e.g., a suction end of the stator, and is typically received in an
open cavity
defined by the rotor and stator. The rotor is typically connected at a rotor
head end,
using couplings or other suitable connection means, on a drive shaft assembly
connected to a drive system that moves the rotor in an eccentric rotation
along the
interior surface of the stator. As the rotor rotates, the defined cavities
effectively "travel"
along the axis of the assembly. The material in the cavities is thus carried
along the
axis of the stator to a discharge end of the stator.
[0033] In an oil production application, the material to be pumped is
typically fluid, which
can have liquid and gaseous components; however, those skilled in the art will
appreciate that progressive cavity pumps, and the improvements discussed
herein, can
also be used in conjunction with slurries, solid matter, water, and gas. In an
oil well
application, the stator is typically suspended on a string of tubing within a
wellbore in
communication with a reservoir. The string of tubing itself may consist of an
integral
piece of tubing, or several segments screwed or otherwise joined together. The
stator is
fixed to the end of the tubing string by a collar. The interior diameters of
the tubing
string and the collar, as well as the stator itself, are dimensioned to admit
passage of
the rotor and any wireline tools that may be employed in the well. The drive
shaft
assembly on which the rotor is mounted may be a rod string, typically
comprising
segments of steel rods that are joined by screw couplings. The rotor, on its
drive shaft,
is lowered through the tubing string and into the stator.
[0034] The pump assembly can be located several thousand metres below the
surface
in an oilfield application. It can thus be appreciated that the actual
mounting of the rotor
within the stator occurs at a location remote from the operator, and that
visual
inspection of the pump assembly to ascertain that the rotor is correctly
positioned within
the stator is typically not possible. Generally, for optimum operation, the
end of the rotor
is expected to be substantially level with the suction end of the stator, and
the rod string
under tension; if the rotor ends some distance from the suction end, then the
pumping
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capacity and efficiency of the pump assembly may be reduced. The position of
the rotor
within the pump assembly varies according to the load on the assembly. As
fluid enters
the assembly, its weight causes the rod string to stretch, thus altering the
final position
of the rotor.
[0035]Accordingly, the embodiments described herein provide an alternative
alignment
mechanism for a progressive cavity pump assembly that permits the operator to
correctly position the rotor within the stator. In one example, tag pins are
provided
within the stator itself proximate to what may be considered the discharge end
of the
stator, which is the end opposing the suction end of the stator.
[0036]Turning now to the figures, FIG. 1 depicts a perspective view of a
portion of a
progressive cavity pump subassembly 100, comprising a stator 50 with a rotor
30
disposed within, and FIG. 2A illustrates a top view of the segment of the
downhole
pump assembly of FIG. 1. It will be understood by those skilled in the art
that the
examples depicted in the accompanying figures are only representative of an
actual
progressive cavity pump subassembly 100 and are not to scale; for instance the
rotor
30 and stator 50 can be considered to be segments of a full rotor and stator,
respectively, truncated for ease of illustration. The stator 50 is coupled to
the tubing
string (not shown) at the discharge end 54 of the stator 50, either directly
or by means
of the collar 10 shown in the drawings. The collar 10 in turn is coupled to
the tubing
string (not shown) of the complete downhole assembly. Coupling may be
accomplished
using any suitable means known in the art. The elastomeric lining 55 in the
stator 50 is
not visible in FIG. 1. Elastomeric lining 55 may be seen in FIGS. 2B and 2C,
and is
discussed in further detail below. However, as part of the housing 53, at
least one
reinforcing component, here shown as one of pins 60, provide reinforcement
and/or an
anchor for the elastomeric lining 55. Pins 60 may be more readily seen in FIG.
2B, and
are discussed in further detail below.
[0037]FIG. 2B provides a cross-sectional view of the progressive cavity pump
subassembly 100 of FIG. 1. The collar 10 is coupled to the stator 50 at the
discharge
end 54 of the stator 50. The collar 10 is generally a cylindrical walled
element. As
mentioned above, the collar 10 is mounted to the tubing string (not shown). An
inner
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diameter of the collar 10, as defined by interior surface 12, is large enough
to permit
passage of the rotor 30 therethrough. Fluid, or whatever material is being
pumped, may
pass from the rotor 30-stator 50 assembly into the collar 10 through the
tubing to an
outlet of the pumping system.
[0038]The stator 50 comprises a housing 53. Throughout a substantial part of
the
housing 53, an elastomeric liner, surface or wall 55 is provided. The
elastomeric liner
55 in this example is a wall with a varying thickness profile that defines the
interior
surface 56 of the stator 50 which, as described above, provides the
appropriate helical
passageway 44 for the progressive cavity pump. The typical shape of passageway
44
is generally helical but variations are normal. The helically-shaped
passageway 44 can
extend to or near the suction end 52 of the stator 50, but may end before the
discharge
end 54. Accordingly, the elastomeric liner 55 does not extend all the way to
the end 54
of the stator 50, but terminates before the end. It will be understood,
however, in other
collar-stator configurations, the elastomeric liner 55 may extend further
along the
interior of the stator 50. The elastomeric liner 55 is may be symmetrical at
both the
suction and discharge ends of the stator.
[0039] Within the elastomeric liner 55, one or more reinforcing components 60
are
provided, in this case pins on opposite sides of the bore. The reinforcing
components
60 extend at least from the interior face of the housing 53 into the
elastomeric liner 55
and can be formed or manufactured of steel or similar material to that used
for the
housing 53 or collar 10. Generally, the reinforcing components 60 are formed
of a
material with greater resistance to deformity than the elastomeric liner 55.
The
reinforcing components 60 in the example illustrated in the drawings are in
the form of
rounded pins or protrusions extending through the housing 53 and into the
interior of
the housing 53. The pins 60 provide a reinforced, substantially level surface
within the
stator (i.e., in a plane substantially perpendicular to the axis of the
stator). Here, the
reinforcing components 60 are formed separately from the housing 53 and are
inserted
through boreholes or apertures 62 provided in the housing 53, and are secured
in
place, for instance by welding. Turning briefly to FIG. 20, which illustrates
a cross-
sectional view of the progressive cavity pump subassembly 100 taken along
plane 20
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indicated in FIG. 2B, it can be seen that the exterior surface 61 of the
reinforcing
components 60 is substantially flush with the exterior surface of the stator
housing 53.
[0040] Returning to FIG. 2B, the reinforcing components 60 form part of the
stator
structure and are located within the elastomeric liner 55 defining the
interior surface of
the stator 50, and in this example, the interior surface 56 of the stator 50
defined by the
elastomeric liner 55 substantially maintains its helical configuration even at
the
reinforced sections 60 of the elastomeric liner 55, where the elastomeric
liner 55
includes the reinforcing components 60. The elastomeric liner 55 extends over
and
incorporates the reinforcing components 60, generally conforming to the shape
of the
components 60, and terminates at the housing 53 above the reinforcing
components
60.
[0041] In other examples, not shown in the figures, the reinforcing components
60 may
be formed integrally with the housing 53 or are mounted on the interior of the
housing
53 rather than through the housing 53. It will be appreciated by those skilled
in the art
that the rounded pin configuration of the reinforcing components 60 is not
necessary,
and that other shapes or configurations may be employed. It can be seen,
though, that
in this example, the reinforcing components 60 do not substantially interrupt
the profile
of the helical passageway 44 typically employed in progressive cavity pumps.
This can
be seen more readily in FIG. 2A, which is a top view of the progressive cavity
pump
subassembly 100, as well as in FIG. 20. The elastomeric liner 55, in addition
to defining
the helical passageway 44 by its interior surface 56, also defines an opening
65 in its
upper surface or shoulder 57. As is conventional in the art, the opening 65 is
generally
shaped to permit the required motion of the rotor 30 as it is moved and
rotated on its
drive shaft (not shown). The helical passageway 44 is defined by the interior
surface of
the elastomeric liner 55, and not the reinforcing components 60. The
reinforcing
components 60 thus do not unduly obstruct the passage of the rotor 30 or
wireline tools
into the stator 50. However, because the elastomeric liner 55 is now provided
with
reinforcement by the reinforcing components 60, the upper surface 57 can
function as a
landing surface or tag shoulder 57 that resists downward motion of the rotor
head 34
without substantial deformity of the upper surface 57 or the helical
passageway 44
defined by the elastomeric liner 55. Landing of the rotor head 34 on the
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stator upper surface 57 provides for proper alignment and positioning of the
rotor 30
within the stator 50.
[0042] Returning to FIG. 2B, an appropriately dimensioned rotor 30 is shown
inserted in
the collar 10 and stator 50. The rotor 30 includes a rotor head 34 and a
helical portion
40. The rotor head 34 is typically coupled to the rod string, not shown for
clarity in the
figures. The rotor head 34 is enlarged compared to the minor diameter of the
helical
passageway 44, and furthermore has a dimension greater than the distance
between
the reinforced portions 60 of the elastomeric liner 55. Thus, when the rotor
30, mounted
on its rod string or drive shaft (not shown), is lowered as far as possible
into the collar
10-stator 50 assembly, the lower surface 36 of the rotor head 34 will contact
the upper
surface or shoulder 57 defined by the elastomeric liner 55. The elastomeric
liner 55,
being reinforced by the reinforcing components 60 at or near the upper surface
57, is
sufficiently rigid to function as a tag shoulder. Contact between the rotor
head 34 and
the reinforced elastomeric liner 55 can be detected using a weight indicator
or other
means known in the art. When this contact between the rotor head 34 and the
stator 50
is detected, the rotor 30 can then be raised to the proper position as
determined by the
operator based on this reference point, and the rod string mounted to the
drive system.
In operation, a helix passageway 44 is formed by the cooperation of the
interior surface
56 of the elastomeric liner 55 and the exterior surface 41 of the helical
portion 40 of the
rotor 30.
[0043] It will be appreciated from the foregoing that by reinforcing the
elastomeric liner
55 of the stator 50 in this manner, it is not necessary to provide a separate
tag plate or
bar at the bottom of the stator 50, thus avoiding the prior art problems
mentioned
above. Furthermore, the reinforcement described herein effectively provides
the stator
50 with an integral tag shoulder or surface 57 without the need for
retrofitting or
adapting the collar 10 to have an abutment or shelf to provide the tagging
function, or
installing a stop or other component on the rod string to cooperate with the
adapted
collar. Since the reinforcing components 60 are encased in the elastomeric
liner 55, the
risk of damage to the rotor 30 as it is lowered into the stator 50 is
mitigated. The
adaptation of the collar 10 or rod string (not shown) in this manner presents
the
possible risk of changing the static or dynamic characteristics of those
components.
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[0044]Various embodiments of the present invention having been thus described
in
detail by way of example, it will be apparent to those skilled in the art that
variations and
modifications may be made without departing from the invention. The invention
includes
all such variations and modifications as fall within the scope of the appended
claims.
Throughout the specification, terms such as "may" and "can" are used
interchangeably
and use of any particular term should not be construed as limiting the scope
or
requiring experimentation to implement the claimed subject matter or
embodiments
described herein.
[0045]The proceeding examples are included to demonstrate preferred
embodiments
of the inventions. It should be appreciated by those of skill in the art that
the techniques
disclosed in the examples above represent techniques discovered by the
inventors to
function well in the practice of the inventions, and thus can be considered to
constitute
preferred modes for its practice. However, those of skill in the art should,
in light of the
present disclosure, appreciate that many changes can be made in the specific
embodiments which are disclosed and still obtain a like or similar result
without
departing from the scope of the inventions.
[0046] Other and further embodiments utilizing one or more aspects of the
inventions
described above can be devised without departing from the spirit of
Applicants'
invention. Further, the various methods and embodiments of the methods of
manufacture and assembly of the system, as well as location specifications,
can be
included in combination with each other to produce variations of the disclosed
methods
and embodiments. Discussion of singular elements can include plural elements
and
vice-versa.
[0047]The order of steps can occur in a variety of sequences unless otherwise
specifically limited. The various steps described herein can be combined with
other
steps, interlineated with the stated steps, and/or split into multiple steps.
Similarly,
elements have been described functionally and can be embodied as separate
components or can be combined into components having multiple functions.
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[0048]The inventions have been described in the context of preferred and other
embodiments and not every embodiment of the invention has been described.
Obvious
modifications and alterations to the described embodiments are available to
those of
ordinary skill in the art. The disclosed and undisclosed embodiments are not
intended
to limit or restrict the scope or applicability of the invention conceived of
by the
Applicants, but rather, in conformity with the patent laws, Applicants intend
to fully
protect all such modifications and improvements that come within the scope or
range of
equivalent of the following claims.
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