Note: Descriptions are shown in the official language in which they were submitted.
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AGITATOR TOOL
FIELD OF THE INVENTION
The present invention relates to tools for use with hydrocarbon or water
production, and
more particularly to tools that are employed with pumping mechanisms.
BACKGROUND OF THE INVENTION
In the context of hydrocarbon or water production, conventional pumping means
are of
great utility where the production fluid is relatively clean and free of
debris or other
particulate matter. However, where debris or other particulate matter are
present in the
production fluid, conventional pumping means can experience failure. For
example,
production fluids may contain "sand slugs" which can be sucked into a pump
mechanism
intake and either cause "sanding" of the pump, requiring costly servicing, or
plugging of
the intake which results in hysteresis in progressive cavity pumps or other
failures in the
ability to produce fluids.
Also, gas lock can occur with progressive cavity (PC) pumps where entrained
gas
passes into the pump mechanism, comes out of solution and accumulates in the
cavities; such gas lock may block the ability of the pump to pass fluids
through the
pump. Unless something intervenes to break the gas out of solution, allowing
it to pass
up the annulus of the wellbore, the gas will be drawn into the pump.
As production fluid may comprise a combination of oil, water, gas, sand and
other
particulates, these problems are of significant concern to companies involved
in
hydrocarbon production, as the problems can result in costly servicing and
pump
damage, not to mention the loss of operation efficiency and actual production.
Prior attempts to address these problems include the commercially-available
GizmoT""
downhole agitator of Innovative Production Technologies Ltd., which agitator
attaches to
the bottom of a PC pump; one portion of the Gizmo T"~ is rotatable and mates
with the
rotor, while a stationary portion mates with the stator. A steel spring
rotates past
CA 02518340 2005-09-07
production ports in the GizmoT"" to agitate adjacent production fluids. It has
been found
that only limited agitation is generated, and the entire pump must be pulled
if the agitator
experiences wear. Also, the drive spear fastened to the rotor has been found
to break in
some instances, possibly due to the rotor eccentricity and oscillation, and
the GizmoT"'
itself can break off of the pump, requiring "fishing" efforts to remove any
broken parts.
Another attempt to address these problems is the combination of a "paddle
rotor" with a
slotted tag bar, as manufactured by numerous companies. The paddle rotor has a
flat
portion on the rotor surface, such that landing the rotor in a slotted tag bar
is alleged to
generate a mixing action at the pump intake. This, too, has been found to
produce only
limited agitation.
As can be seen, therefore, a simple cost-effective solution to these
continuing problems
is still needed. What is required is an agitator tool that is cost-effective
to produce and
purchase, provides for ease of servicing, and generates substantial turbulent
flow to
break up particulate matter in production fluids, keep the particulate matter
in
suspension, and help break entrained gas out of solution so that it can
migrate up the
well annulus rather than enter the PC pump.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a
rotatable tool for
use with a pump mechanism, for agitating production fluid and breaking out
entrained
gas, comprising an elongate shaft, connecting means on the elongate shaft for
connecting a downstream end of the elongate shaft to a rotating element of the
pump
mechanism, and at least one agitation member on and extending outwardly from
the
elongate shaft.
In exemplary embodiments of the present invention, the rotatable tool and pump
mechanism are housed within a surface flowline or downhole casing, and can be
housed
within a tag bar adjacent the pump mechanism. The pump mechanism is preferably
a
progressive cavity pump (although other rotary pumps could be employed),
wherein the
rotating element is a rotor housed within a stator. The elongate shaft may be
either
straight or of irregular orientation along its length. The connecting means
preferably
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comprise a slim-hole coupling welded to the downstream end of the elongate
shaft, with
a female thread in the slim-hole coupling and a corresponding male thread on
an
upstream end of the rotating element, although they may also comprise a quick-
connect
coupling enabling disengagement of the elongate shaft from the rotating
element.
The at least one agitation member is preferably a plurality of bristles (which
may be
composed of nylon, steel or rubber) extending substantially perpendicular to
the long
axis of the elongate shaft (although other orientations may be desirable in
different
contexts) and connected to the elongate shaft by means of a casing wrapped
around the
elongate shaft, the casing connected to the elongate shaft by spot welds, and
the
bristles held in the casing by crimping of the casing around an inner end of
the bristles.
The plurality of bristles are most preferably folded around a wire core, the
wire core
located in the casing and sized to be held in the casing by the crimping of
the casing.
The casing may be in the form of a helical track of even or uneven phasing,
and in the
latter case the phasing may be closer adjacent the downstream end of the
elongate
shaft than adjacent the upstream end of the elongate shaft. The at least one
agitation
member is preferably adjacent an intake of the pump mechanism, and may be
sized to
enable contact of the at least one agitation member with at least a portion of
inner walls
of the surface flowline or downhole casing. Where a casing is employed to
house the at
least one agitation member, the rotatable tool may further comprise a first
bushing
connected to an upstream end of the elongate shaft and a second bushing
connected to
a downstream end of the elongate shaft by bushing welds for retaining the
casing on the
elongate shaft, and the spot welds and bushing welds are then preferably
breakable to
allow removal of the casing from the elongate shaft (for example, where the at
least one
agitation member has become worn and replacement is desirable). The at least
one
agitation member is preferably flexible to enable it to deform to be pulled
through the
stator where the rotating element is a rotor that can be pulled downstream of
the stator.
According to a second aspect of the present invention there is provided a
rotatable tool
for use with a pump mechanism having a rotating element, for agitating
production fluid
and breaking out entrained gas, comprising an elongate shaft of unitary
construction with
the rotating element and extending upstream of the rotating element, and at
least one
agitation member on and extending outwardly from the elongate shaft.
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According to a third aspect of the present invention there is provided a
rotatable tool for
use with a pump mechanism having a rotating element, for agitating production
fluid and
breaking out entrained gas, comprising an elongate shaft fixedly attached to
the rotating
element and extending upstream of the rotating element, and at least one
agitation
S member on and extending outwardly from the elongate shaft.
According to a fourth aspect of the present invention there is provided a tool
for use with
a pump mechanism, for agitating production fluid and breaking out entrained
gas,
comprising an elongate shaft, connecting means on the elongate shaft for
connecting a
downstream end of the elongate shaft to the pump mechanism, and at least one
agitation member on and extending outwardly from the elongate shaft. The pump
mechanism according to this aspect is preferably a reciprocating pump.
An agitator tool in accordance with the present invention, therefore, can
create strong
turbulent flow to effectively agitate production fluid, keeping debris
suspended in the
emulsion while breaking out entrained gas, preventing pump intake plugging,
agitating
the wellbore sump, and keeping the production fluid energized. The agitator
tool is cost-
effective to produce, adaptable to pumps of different sizes, is easily
installed, can be
removed with the rod string due to bristle flexibility, and can have
substantial bristle outer
diameter (OD) due again to flexibility of the bristles.
A detailed description of an exemplary embodiment of the present invention is
given in
the following. It is to be understood, however, that the invention is not to
be construed
as limited to this embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate an exemplary embodiment of the
present
invention:
Figure 1 is a side elevation view of an agitator tool according to the present
invention, in
a vertical orientation such as would be used in a downhole context, partially
cut away at
the first and second bushings to show the casing; and
Figure 2 is a detailed sectional view of a helical casing holding bristles by
means of
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crimping around a wire core.
DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT
Referring now in detail to the accompanying drawings, there is illustrated an
exemplary
embodiment of the agitator tool according to the present invention, generally
referred to
by the numeral 10. The agitator tool 10, for use in surface flowlines or
downhole casings
(not shown), comprises an elongate shaft 12 having a downstream end 14 and an
upstream end 16. The elongate shaft 12 is a 16" 4140 steel shaft having an
outer
diameter OD, of %2'. The length of the elongate shaft 12 depends on how much
sump is
required or desired in a given context, and the outer diameter ODD and shaft
geometry
(for example, having a bend in the elongate shaft 12, or some other irregular
form) can
also be adjusted to address specific needs (the outer diameter OD, will depend
to a
large degree on the stator/rotor dimensions). Other materials can also be used
to
manufacture the elongate shaft 12. The elongate shaft 12 is welded to a slim-
hole
coupling 18 at the downstream end 14, the slim-hole coupling 18 housing female
threads
20 for receipt of corresponding male threads on the upstream end of a rotor
(not shown);
the means for connecting the elongate shaft 12 to the rotation means will vary
depending on such factors as the pump type, tubing inner diameter (ID), and
stator ID.
A first bushing 28 is positioned at the upstream end 16 of the elongate shaft
12 and
welded thereto by a bushing weld 38 (a tap weld), while a second bushing 34 is
positioned at the downstream end 14 of the elongate shaft 12 and similarly
welded
thereto by bushing weld 36. The first and second bushings 28, 34 are provided
to assist
in retaining the casing 24 on the elongate shaft 12, as described below.
A casing 24 in the form of a helical track is wrapped around the elongate
shaft 12,
secured to the elongate shaft 12 by means of spot welds 26. The spot welds 26
can be
broken to allow removal of the casing 24 and repair/replacement thereof where,
for
example, the agitation members become worn (and the bushing welds are then
also
breakable). If the spot welds 26 were to fail, the first and second bushings
28, 34 are
intended to retain the casing 24 on the elongate shaft 12. The first and
second bushings
28, 34 are provided with set screws 40 which further serve to secure the
casing 24
against the elongate shaft 12; although shown in Figure 1 as simply inserted,
the set
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screws 40 are preferably also welded at the heads and ground off. The casing
24 is a
track '/8' in width and composed of galvanized or stainless steel, and is
generally
channel-shaped.
Bristles 22 are retained in the casing 24 by means of crimping, as can best be
seen in
Figure 2 where the bristles 22 are held by means of crimps 30 (the crimps 30
formed
from the arms of the channel shape). In the preferred embodiment, the bristles
22 are
folded over a wire core 32, which wire core 32 is of diameter sufficient to be
retained
within the casing 24 once crimped, and the bristles 22 are thereby more firmly
secured
within the casing 24. The bristles 22 are positioned along almost the entire
length of the
casing 24 (a few empty courses of the casing 24 are provided at either end
allowing
smaller diameter bushings 28, 34 in the preferred embodiment), then
essentially forming
a helical or spiral brush in this exemplary embodiment, although other
configurations are
possible within the scope of the invention (although it is generally desirable
to have at
least some of the bristles 22 adjacent the pump intake). The bristles 22 are
composed
of nylon in this embodiment due to the inherent flexibility of the material,
which allows
the agitator tool 10 to be pulled through a stator (not shown) even though the
outer
diameter ODZ of the agitator tool 10 with bristles 22 may be greater than the
OD of the
stator (in the illustration, the outer diameter OD2 is 23/4'). The optional
use of a tag bar
(not shown) can also affect the outer diameter OD2. The number and density of
bristles
22 may be increased to enhance durability, and the material used for the
bristles 22 may
need to be varied in different contexts (such as highly corrosive downhole
environments). In the illustrated embodiment, the bristles 22 are positioned
generally
perpendicular to the long axis of the elongate shaft 12, but various bristle
angles may be
employed where desired (for example, where an auguring effect is required),
and even
different angles for different courses on the same agitator tool 10.
The distance ("phasing") "d" between the courses of the casing 24 can be
adjusted to
create different effects. While agitation of production fluid (not shown) is
enhanced by a
narrower phasing, as is demonstrated in the appended drawings (where distance
"d" is
relatively small and constant for all courses of the casing 24), auguring
effects are
enhanced by broader phasing. In certain instances it would be advantageous,
therefore,
to have a larger distance "d" between courses of the casing 24, or even a
combination of
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narrow and broad phasing (or a continuum of narrow to broad) on the same
agitator tool
10. For example, having broader phasing distant from the pump intake and
narrower
phasing adjacent the pump intake could produce an increasing
auguring/agitation
velocity as the production fluid draws nearer.
Where the bristles 22 are composed of stronger material, such as steel, it may
be
difficult to withdraw the agitator tool 10 out of the stator without damaging
the
elastomeric coating of the stator inner walls. In this case, it would be
advantageous to
house the agitator tool 10 in a tag bar (not shown) upstream and adjacent the
pump
mechanism, and employ a quick-connect coupling (not shown) to connect the
rotor and
elongate shaft 12. In this case, the rotor could be withdrawn from the stator
by
disconnecting the agitator tool 10 from the rotor and leaving the former
within the tag
bar.
While the exemplary embodiment described above has a threaded mating of the
elongate shaft 12 and rotor by means of a slim-hole coupling 18, it may be
desirable to
have a permanent mating of the elongate shaft 12 and rotor, or even
manufacture the
elongate shaft 12 as an upstream extension of the rotor itself (unitary
construction).
An agitator tool 10 constructed in accordance with the present invention was
tested with
a PC pump and proved highly effective in agitating production fluid. Debris,
including
sand slugs, was placed upstream of the agitator tool 10 in a test facility,
and the sand
slugs were decreased in size by approximately 60% before they could enter the
pump
intake, due to the agitation generated by the agitator tool 10. The risk of
sand plugging
the pump was therefore greatly minimized. Various sand concentrations were
tested,
and while pumps without the agitator tool 10 experienced operation difficulty
when sand
concentrations approached 40-50%, the agitator tool 10 was found to
effectively address
much higher concentrations and prevent operation difficulty. At greater
rotational
speeds, the agitator tool 10 could address very high sand concentrations due
to the
more vigorous agitation. In addition, use of the agitator tool 10 was found to
create a
cellar and clean perforated intervals. After testing, the agitator tool 10 was
examined
and no significant wear had occurred.
The present invention has demonstrated a broad range of utility, especially in
downhole
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settings. Where a wellbore is known or found to generate production fluid
comprising
sand and/or solution gas, the agitator tool 10 can be used to break up sand
slugs and
break out some of the gas. In similar fashion, the present invention can also
be used to
prevent sand blockages in surface flowlines. However, the agitator tool 10 can
also be
used to clean out a PC pump by running the agitator tool 10 in and out of the
stator (by
extracting and inserting the rotor), which can assist in removing sand and
debris from
the elastomeric pump cavities. The agitator tool 10 can also be run above the
pump with
appropriate connection modifications, to agitate the production fluid and
prevent settling
of sand and debris that might otherwise cause sand/solids tubing bridges
(blockages
that inhibit discharge and prevent fluid movement to the surface, they can
also cause
high-pressure loading on the pump resulting in pump damage and premature
failure);
the agitator tool 10 can be run in series with appropriate connection
modifications, as
well, with no limit on the number of agitator tools 10 that could be run in a
string above
the pump, even to the surface. If the outer diameter ODZ is great enough to
reach the
inner walls of the surface flowline or downhole casing, it can be used to
clean the inner
walls; this is especially useful in the downhole context, where the perforated
interval can
be kept clean by the agitator tool 10. Sump cleaning is also possible with the
present
invention, keeping clean an area roughly equal to the length of the agitator
tool 10 (with
various lengths being possible). Finally, it is also possible to use the
present invention
with coiled tubing for wellbore clean-outs. The present invention can
therefore be run
below, within, or above a pump mechanism, alone or in series, with varying
utility in
varying contexts. Also, its utility is not dependent on rotation of the
agitator tool 10 in all
instances, as it could be run, for example, with a reciprocating pump without
any
rotation.
While a particular embodiment of the present invention has been described in
the
foregoing, it is to be understood that other embodiments are possible within
the scope of
the invention and are intended to be included herein. It will be clear to any
person
skilled in the art that modifications of and adjustments to this invention,
not shown, are
possible without departing from the spirit of the invention as demonstrated
through the
exemplary embodiment. For example, the agitation members may be rubber
"fingers"
instead of nylon bristles, which are also flexible and can effectively agitate
production
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fluid. Also, the agitation members could be housed in a series of stacked
circular
casings rather than a single helical casing, or the agitation members could be
directly
connected to the elongate shaft. As stated above, many of the dimensions and
configurations will be context-dependent, which would be clear to one skilled
in the art.
S The invention is therefore to be considered limited solely by the scope of
the appended
claims.
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