U.S. patent application number 14/657572 was filed with the patent office on 2015-09-17 for torque anchor to prevent rotation of well production tubing, system for pumping and rotation prevention, and pumping installation equipped with such a torque anchor.
The applicant listed for this patent is PCM Technologies. Invention is credited to Stephen Burrows, Francois Millet.
Application Number | 20150259997 14/657572 |
Document ID | / |
Family ID | 51417342 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150259997 |
Kind Code |
A1 |
Millet; Francois ; et
al. |
September 17, 2015 |
Torque Anchor to Prevent Rotation of Well Production Tubing, System
for Pumping and Rotation Prevention, and Pumping Installation
Equipped with Such a Torque Anchor
Abstract
The invention relates to a torque anchor which prevents rotation
of a tubing string with respect to a casing of a well for pumping a
fluid. The torque anchor comprises a frame intended to be mounted
in the casing, an internal channel formed in the frame; a cavity in
fluid communication with the internal channel, said cavity
extending along a radial direction, and an anchoring piston capable
of sliding relative to the frame along the radial direction and of
exerting torque on the casing, when the pumped fluid contained in
the internal channel exerts force on said anchoring piston. The
invention also relates to a system for pumping and rotation
prevention and a pumping device equipped with such a torque
anchor.
Inventors: |
Millet; Francois; (Antony,
FR) ; Burrows; Stephen; (La Chapelle Sur Erdre,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PCM Technologies |
Levallois-Perret |
|
FR |
|
|
Family ID: |
51417342 |
Appl. No.: |
14/657572 |
Filed: |
March 13, 2015 |
Current U.S.
Class: |
166/383 ;
166/212 |
Current CPC
Class: |
E21B 17/1078 20130101;
E21B 23/01 20130101 |
International
Class: |
E21B 23/01 20060101
E21B023/01; E21B 17/10 20060101 E21B017/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 17, 2014 |
FR |
1452171 |
Claims
1. A torque anchor for preventing rotation of a tubing string
relative to a casing of a well for the pumping of a fluid by a
progressive cavity pump, said torque anchor comprising: a frame
intended to be mounted in the casing, an internal channel formed in
the frame, said internal channel extending along an axial
direction; at least one cavity in fluid communication with the
internal channel, said cavity extending along a radial direction,
and at least one anchoring piston fitted to said radial cavity,
wherein said torque anchor comprises at least one pre-loading
spring adapted to act between said anchoring piston and the frame
to bias said anchoring piston in a radial direction against the
casing; and wherein said internal channel is traversed by the
pumped fluid, said anchoring piston being capable of sliding
relative to the frame along the radial direction; said anchoring
piston being capable of exerting torque on the casing, when the
pumped fluid contained in the internal channel exerts force on said
anchoring piston; said force being a function of the pressure
difference between the pressure inside the internal channel and the
pressure outside the frame.
2. The torque anchor according to claim 1, wherein the frame
comprises a flange facing the periphery of a flat face of the
anchoring piston, said flange forming a flat shoulder contained in
a plane perpendicular to the radial direction, said at least one
pre-loading spring being supported by said shoulder.
3. The torque anchor according to claim 2, wherein said flange
forms a wall provided with at least one opening suitable for
restraining the flow of pumped fluid; said at least one opening
having a surface area of between 0.5% and 5% of the surface area of
a cross-section of the radial cavity; said cross-section being
perpendicular to the radial direction.
4. The torque anchor according to claim 2, wherein the frame
comprises a sleeve interposed between the radial cavity and the
anchoring piston; said sleeve comprising said flange and at least a
portion of said flange extending into the internal channel.
5. The torque anchor according to claim 4, wherein said sleeve is
made of ceramic.
6. The torque anchor according to claim 2, wherein said anchoring
piston comprises a head and a skirt extending the periphery of the
head, said head and said skirt forming a chamber that opens to the
internal channel, said pre-loading spring being housed in said
chamber and guided by said skirt.
7. The torque anchor according to claim 1, wherein the anchoring
piston and the radial cavity have a cylindrical shape with a
circular base, the anchoring piston being prevented from rotating
relative to the frame by a rotation prevention device.
8. The torque anchor according to claim 7, wherein the rotation
prevention device comprises a groove and a tooth able to slide in
the groove in a radial direction, one of the groove and tooth being
integral to a free end of the skirt and the other to the frame.
9. The torque anchor according to claim 1, wherein a transverse
cross-section of the anchoring piston and of the radial cavity has
an oblong shape.
10. The torque anchor according to claim 1, wherein the anchoring
piston has an outer face facing the casing, said outer face being
provided with a lip that is preferably rectilinear.
11. The torque anchor according to claim 1, wherein, when the at
least one anchoring piston is arranged in a single plane, said lip
extends for a distance of between 30% and 70%, and preferably
between 30% and 48%, of the inside diameter of the casing, and when
the at least one anchoring piston comprises a plurality of pistons
arranged in a plurality of planes, the distance defined between the
ends of the lips of the end anchoring pistons is between 30% and
70%, and preferably between 30% and 48%, of the inside diameter of
the casing.
12. The torque anchor according to claim 5, which further comprises
a gasket ensuring a fluid-tight seal between the anchoring piston
and the frame or sleeve.
13. The torque anchor according to claim 1, which comprises at
least one brace adapted to retain the anchoring piston in a
retracted position when the torque anchor is being lowered
downhole, said brace being attached on the one hand to a face of
the anchoring piston and on the other hand to the frame.
14. A system for pumping and preventing rotation of a tubing string
relative to a well casing, said system comprising a progressive
cavity pump adapted to intake fluid for pumping through an inlet,
compress the pumped fluid, and discharge the compressed fluid
through an outlet, wherein the system comprises a torque anchor
defined according to the features of claim 1, said torque anchor
being secured downstream of the progressive cavity pump, relative
to the direction of flow of the fluid pumped within the internal
cavity, said torque being a function of the difference in pressure
generated by the progressive cavity pump between its inlet and its
outlet.
15. A pumping installation of a well equipped with a casing, said
pumping installation comprising: a tubing string arranged in said
casing; a progressive cavity pump adapted to move a fluid to be
pumped through an intake inlet, and to discharge the fluid through
a discharge outlet, wherein the installation comprises a torque
anchor defined according to the features of claim 1; said torque
anchor being secured downstream of the progressive cavity pump,
relative to the direction of flow of the fluid pumped within the
internal cavity; said force being a function of the difference in
pressure generated by the progressive cavity pump between its inlet
and its outlet.
16. A method for preventing rotation of a tubing string relative to
a casing of a shaft for pumping fluid by a progressive cavity pump,
said method being implemented by a torque anchor comprising a frame
intended to be mounted in the casing, an internal channel formed in
the frame, said internal channel extending along an axial
direction, at least one cavity in fluid communication with the
internal channel, said cavity extending along a radial direction,
and at least one anchoring piston fitted to said radial cavity,
wherein the method comprises the following steps: intake of a fluid
to be pumped, through an inlet of the progressive cavity pump;
traversal by the pumped fluid of said internal channel; discharge
of said pressurized fluid in the tubing string, through the outlet
of said progressive cavity pump; application of pressure by the
pumped fluid on a face of the anchoring piston; and sliding of said
anchoring piston relative to the frame in the radial direction,
said application causing torque to be applied by said anchoring
piston to the casing, said torque being a function of the pressure
difference between the inlet and the outlet of the progressive
cavity pump.
17. A centering device and/or a damper comprising: a frame intended
to be mounted in the casing; an internal channel formed in the
frame, said internal channel extending along an axial direction, a
pumped fluid traveling in said internal channel; at least one
cavity in fluid communication with the internal channel, said
cavity extending along a radial direction; and at least one
anchoring piston fitted to said radial cavity, said anchoring
piston being capable of sliding relative to the frame along the
radial direction and of exerting torque on the casing, when the
pumped fluid contained in the internal channel exerts force on said
anchoring piston.
Description
RELATED APPLICATIONS
[0001] This invention claims priority to French patent application
No. FR 14/52171 filed Mar. 17, 2014, the entirety of which is
hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a torque anchor which prevents
rotation of a tubing string relative to the casing of a well,
and/or a pumping system equipped with a progressive cavity pump
comprising such a torque anchor.
BACKGROUND OF THE INVENTION
[0003] Torque anchors for a pumping system are known, particularly
from document U.S. Pat. No. 6,155,346, which have teeth mounted on
a cam fixed to the tubing string. The teeth are displaced by the
cam between a retracted position inside the torque anchor and a
locking position where the teeth extend radially outward from the
frame of the torque anchor and grip the casing.
[0004] Such torque anchors have many disadvantages.
[0005] First, they are based on bracing technologies, and are
therefore likely to become unanchored during production due to the
heavy vibrations generated by the progressive cavity pump. This can
cause the tubing string to become unscrewed and fall downhole,
bringing production to a complete halt and resulting in the
significant costs of recovery operations.
[0006] Also, in some cases, the retraction mechanism may clog with
sand or be affected by corrosion. In this case, the torque anchor
is lifted upward by the forces exerted, damaging the casing and the
equipment downhole.
[0007] In addition, the teeth are brought into locking position by
operators using spanners to rotate the tubing string from the
surface. This rotation operation poses a hazard to operator safety
as they manipulate the spanners to apply torsional stress. When a
spanner slips, the operators may be injured.
[0008] Moreover, during normal operation, the very principle of the
bracing required means an extremely high contact pressure between
the teeth and the casing. Thus, given the high level of vibrations
during pumping, it is strongly suspected that the teeth, which must
necessarily have a destructive shape to initiate the bracing,
"machine" the casing.
[0009] In addition, some wells are subject to significant
temperature variations during production. These temperature
variations dilate the tubing string, which can grow by up to 6
meters in length but with little or no expansion in the casing
since the casing is cemented to the formation. During these
temperature variations, the torque anchor is pushed by the
expansion of the tubing, moving it relative to the casing along the
longitudinal axis of the well. As the teeth of the torque anchor
are always embedded in the casing, some scoring damage to the
internal wall of the casing is suspected but has not yet been
quantified.
[0010] Finally, to ensure that the teeth of the torque anchor are
properly gripping the casing, they may be driven into a locking
position at the well surface before the torque anchor is lowered
downhole. In this case, the casing tube assembly is torn and
damaged as the torque anchor is lowered downhole.
[0011] Document EP 1,371,810 describes an anti-rotation device of a
drilling device. The anti-rotation device is adapted to prevent
rotation of the drilling device within the formation being drilled.
It comprises pistons able to move radially between a retracted
position and an extended position where they extend radially
outside the frame and engage with the drilled formation. Movement
of the pistons into the extended position is achieved using a
hydraulic actuator. A spring returns the piston to the retracted
position (FIG. 10, paragraph 183).
[0012] However, this anti-rotation device is under-engineered for
the torsional forces applied by a stator to the production tubing
when the rotor is rotated. The anti-rotation device as described in
this document could not withstand such stresses. In addition, the
arrangement of the channels transporting pressurized fluid inside
the frame to actuate piston movement, is complex to manufacture.
Lastly, in case of failure, it would be too expensive to repair or
replace a hydraulic pump because this would require emptying the
production tubing. The average time between maintenance operations
is ten days for a drilling rig, while it is the approximately two
years for a fluid pumping system.
[0013] In addition, the temperatures in a drill hole are often much
higher.
[0014] Finally, this anti-rotation device is not suitable for use
in a pumping installation equipped with a casing because, in order
to anchor the pistons, the pistons must be fitted with sharp teeth
which bite into the formation being drilled. Such an anti-rotation
device would cut into and damage the casing of the pumping
installation. If the pins or teeth are eliminated, the
anti-rotation device does not prevent rotation of the production
string because the vibrations generated by rotation of the rotor in
the stator are very rapid, numerous, and of high amplitude. Damage
to the formation being drilled is not an issue because it will
later be covered by casing cemented to said formation.
SUMMARY OF THE INVENTION
[0015] The object of the present invention is to provide a torque
anchor capable of withstanding high torsional moments.
[0016] To this end, the invention relates to a torque anchor for
preventing rotation of a tubing string relative to a casing of a
well for the pumping of a fluid by a progressive cavity pump, said
anchor comprising: [0017] a frame intended to be mounted in the
casing, [0018] an internal channel formed in the frame, said
internal channel extending along an axial direction; [0019] at
least one cavity in fluid communication with the internal channel,
said cavity extending along a radial direction, and [0020] at least
one anchoring piston fitted to said radial cavity,
[0021] wherein said anchor comprises at least one pre-loading
spring adapted to act between said anchoring piston and the frame
to bias said anchoring piston in a radial direction against the
casing;
and wherein said internal channel is traversed by the pumped fluid,
said anchoring piston being capable of sliding relative to the
frame along the radial direction and of exerting torque on the
casing, when the pumped fluid contained in the internal channel
exerts force on said anchoring piston; said force being a function
of the pressure difference between the pressure inside the internal
channel and the pressure outside the frame.
[0022] Advantageously, the present torque anchor uses the pressure
difference between the internal channel and the pressure of the
annulus defined between the outer face of the frame and the casing
to prevent rotation of the tubing string relative to the casing.
This pressure difference is generated by the progressive cavity
pump. It can reach several tens of megapascals. The torque anchor
can therefore apply very high torque to the inner wall of the
casing. In addition, this torque adapts to the clamping torque
required since the torque is a function of the pressure difference
between the inlet and outlet of the progressive cavity pump. The
torque exerted by the torque anchor is automatically controlled by
the discharge pressure of the progressive cavity pump.
[0023] Advantageously, when there is no pressure difference between
the inlet and outlet of the progressive cavity pump, the torque
anchor becomes unanchored without any action being required.
Therefore, advantageously, the torque anchor cannot become stuck
downhole due to sand or scaling.
[0024] Advantageously, this torque anchor is compact. In
particular, a module having a plurality of pistons within the same
plane measures between one and two feet.
[0025] Advantageously, this torque anchor can be tested when the
torque anchor has been lowered several meters within the
casing.
[0026] This torque anchor is simple in design. In particular, the
anchoring pistons can be easily removed from the frame during a
maintenance operation.
[0027] According to certain embodiments, the torque anchor
comprises one or more of the following features:
[0028] The frame comprises a flange facing the periphery of a flat
face of the anchoring piston, said flange forming a flat shoulder
contained in a plane perpendicular to the radial direction, said at
least one pre-loading spring being supported by said shoulder.
[0029] Advantageously, the pre-loading spring allows applying
torque to the inner wall of the casing when there is no pressure
difference between the internal channel and the annulus, for
example at the time the rotor is inserted into the stator or at
startup of the progressive cavity pump.
[0030] The flange forms a wall provided with at least one opening
suitable for damping the flow of pumped fluid; said at least
opening having a surface area of between 0.5% and 5% of the surface
area of a cross-section of the radial cavity; said cross-section
being perpendicular to the radial direction.
[0031] The frame is subjected to strong vibrations generated by the
progressive cavity pump.
[0032] Advantageously, restrictor(s) are able to damp the flow of
pumped fluid and thereby cushion the frame vibrations.
[0033] The frame comprising a sleeve interposed between the radial
cavity and the anchoring piston; said sleeve comprising said flange
and at least a portion of said flange extending into the internal
channel.
[0034] Advantageously, this embodiment allows the use of longer
springs which are less sensitive to temperature fluctuations and
variations in the diameter of the casing, making the performance of
the torque anchor more stable.
[0035] Said sleeve is made of ceramic.
[0036] Advantageously, this equipment eliminates any risk of the
anchoring pistons seizing within the sleeve. This equipment also
helps to contain the risk of anaerobic corrosion. This embodiment
is desirable in applications requiring a long service life or
involving high temperatures.
[0037] Said anchoring piston comprises a head and a skirt extending
the periphery of the head, said head and said skirt forming a
chamber that opens to the internal channel; said pre-loading spring
being housed in said chamber and guided by said skirt.
[0038] Advantageously, the pre-loading springs can be easily
removed from the frame during a maintenance operation.
[0039] The anchoring piston and the radial cavity have a
cylindrical shape with a circular base, the anchoring piston being
prevented from rotating relative to the frame by a rotation
prevention device.
[0040] The rotation prevention device comprises a groove and a
tooth able to slide in said groove in a radial direction; one of
the groove and tooth being integral to a free end of the skirt and
the other to the frame.
[0041] A transverse cross-section of the anchoring piston and of
the radial cavity has an oblong shape.
[0042] Advantageously, this form prevents rotation of the anchoring
piston within the radial cavity, with no need for an added dog
clutch.
[0043] This form also allows increasing the surface area of the
piston and therefore the force applied to the casing. Lastly, this
form allows increasing the length of the contact with the casing,
which reduces the contact pressure and facilitates the passage of
casing collars under load.
[0044] The anchoring piston has an outer face facing the casing,
said outer face being provided with a lip that is preferably
rectilinear.
[0045] When the anchoring pistons are arranged in a single plane,
said lip extends for a distance of between 30% and 70%, and
preferably between 30% and 48%, of the inside diameter of the
casing, and when the anchoring pistons are arranged in a plurality
of planes, the distance defined between the ends of the lips of the
end anchoring pistons is between 30% and 70%, and preferably
between 30% and 48%, of the inside diameter of the casing.
[0046] Advantageously, this length allows the passage of casing
collars without damage to the casing.
[0047] The torque anchor comprises a gasket ensuring a fluid-tight
seal between the anchoring piston and the frame or sleeve.
[0048] The torque anchor comprises at least one brace adapted to
retain the anchoring piston in a retracted position when the torque
anchor is being lowered downhole; said brace being attached on the
one hand to a face of the anchoring piston and on the other hand to
the frame.
[0049] The invention concerns also a system for pumping and
preventing rotation of a tubing string relative to a well casing,
said system comprising a progressive cavity pump adapted to intake
fluid for pumping through an inlet, compress the pumped fluid, and
discharge the compressed fluid through an outlet,
[0050] wherein the system comprises a torque anchor defined
according to the above mentioned features; said torque anchor being
secured downstream of the progressive cavity pump, relative to the
direction of flow of the fluid pumped within the internal cavity;
said torque being a function of the difference in pressure
generated by the progressive cavity pump between its inlet and its
outlet.
[0051] The invention concerns further a pumping installation of a
well equipped with a casing; said pumping installation comprising:
[0052] a tubing string arranged in said casing; [0053] a
progressive cavity pump adapted to move a fluid to be pumped
through an intake inlet, and to discharge the fluid through a
discharge outlet,
[0054] wherein the installation comprises a torque anchor defined
according to the above mentioned features; said torque anchor being
secured downstream of the progressive cavity pump, relative to the
direction of flow of the fluid pumped within the internal cavity;
said force being a function of the difference in pressure generated
by the progressive cavity pump between its inlet and its
outlet.
[0055] The invention concerns also a method for preventing rotation
of a tubing string relative to a casing of a well for pumping fluid
by a progressive cavity pump; said method being implemented by a
torque anchor comprising a frame intended to be mounted in the
casing, an internal channel formed in the frame, said internal
channel extending along an axial direction; at least one cavity in
fluid communication with the internal channel, said cavity
extending along a radial direction, and at least one anchoring
piston fitted to said radial cavity, wherein the method comprises
the following steps: [0056] intake of a fluid to be pumped, through
an inlet of the progressive cavity pump, [0057] traversal by the
pumped fluid of said internal channel, [0058] discharge of said
pressurized fluid in the tubing string, through the outlet of said
progressive cavity pump; [0059] application of pressure by the
pumped fluid on a face of the anchoring piston;
[0060] sliding of said anchoring piston relative to the frame in
the radial direction; said application causing torque to be applied
by said anchoring piston to the casing; said torque being a
function of the pressure difference between the and the outlet of
the progressive cavity pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0061] The invention will be better understood by reading the
following description, given only as an example and with reference
to the figures, in which:
[0062] FIG. 1 is a schematic view of a pumping system according to
the present invention;
[0063] FIG. 2 is a cutaway perspective view of a torque anchor
according to a first embodiment of the invention;
[0064] FIG. 3 is an axial sectional view of a portion of the casing
and of the torque anchor illustrated in FIG. 1;
[0065] FIG. 4 is a graph showing the torque generated by the torque
anchor according to the invention as a function of the pressure
difference between the inlet and outlet of a progressive cavity
pump;
[0066] FIG. 5 is a cutaway perspective view of a torque anchor
according to a second embodiment of the invention;
[0067] FIG. 6 is a sectional view of a portion of the torque anchor
illustrated in
[0068] FIG. 5, the section plane being perpendicular to an axial
axis and passing through a groove of the torque anchor;
[0069] FIG. 7 is a cutaway perspective view of a portion of a
torque anchor according to a third embodiment of the invention;
[0070] FIG. 8 is a sectional view of a portion of the frame and of
an anchoring piston representing a variant of the first, second,
and third embodiments of the invention;
[0071] FIG. 9 is a sectional view of a portion of the frame and of
an anchoring piston representing another variant of the first,
second, and third embodiments of the invention;
[0072] FIG. 10 is a cutaway perspective view of a portion of the
frame and of an anchoring piston in a variant of the torque anchor
according to the invention;
[0073] FIG. 11 is a cutaway perspective view of a torque anchor
according to a fourth embodiment of the invention; and
[0074] FIG. 12 represents the steps of the method according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0075] In the following description, the terms "top", "bottom",
"lower", "upper", "right", and "left" are defined relative to the
torque anchor according to the invention being arranged as shown in
FIG. 1, and are in no way limiting.
[0076] The invention relates to a torque anchor and a pumping
installation of a well equipped with such a torque anchor.
[0077] The pumping installation 2 according to the invention is
primarily intended for pumping hydrocarbons, water, or gas.
Referring to FIG. 1, it comprises: [0078] a casing 6 cemented to
the formation 7 and comprising perforations 8 in its lower portion
to allow passage of the fluid to be pumped; [0079] a tubing string
10 arranged in the casing 6; [0080] a wellhead 12 mounted on a
"blowout preventer" 14 and containing a driving device that rotates
the drill string 16 (or one continuous drill pipe) located inside
and extending for the length of the tubing string 10, [0081] a
progressive cavity pump 18 having a rotor 20 secured to and rotated
by the drill string 16, and a stator 22 having an intake opening 24
known as the inlet located downhole, and a discharge opening 26
known as the outlet fixed at the end of the tubing string 10,
[0082] a filter element 28, commonly called a perforated pipe,
slotted screen, or sand screen, attached to the inlet 24 of the
progressive cavity pump, and [0083] a torque anchor 30 according to
the invention and described below. The torque anchor 30 is secured
downstream of the progressive cavity pump 18, relative to the
direction of flow of the fluid pumped within the tubing string 10.
In the embodiment represented, the torque anchor 30 is directly
fixed to the upper end of the stator 22. In a variant not
represented, thick-walled tubing called a "blast joint" is attached
between the progressive cavity pump 18 and the torque anchor 30 so
that this tubing is arranged facing the perforations 8 of the
casing.
[0084] During operation of the progressive cavity pump 18, the
fluid contained in the rock moves through the perforations 8 of the
casing, and flows into the annulus between the tubing string 10 and
casing 6. Then it passes through the slotted screen 28 and into the
inlet 24 of the progressive cavity pump.
[0085] The progressive cavity pump is composed of a number of
cavities defined by the fit between rotor and stator. This fit is
called the "seal line." This seal line generates head loss between
each pair of adjacent cavities and thus results in a noticeable
difference in pressure between inlet 24 and outlet 26. This
pressure difference is usually called the pressure rating.
[0086] The fluid is discharged through the discharge outlet 26 in
the tubing string 10. The fluid is then advanced to the blowout
preventer 14 by the force of the fluid moving in the stator 22,
where it is discharged through distribution lines 32. The torque
anchor 30 centers and prevents rotation of the pump stator 22 and
tubing string 10 during rotation of the rotor 20 of the progressive
cavity pump 18. As described below, the torque anchor 30 according
to the invention uses the pressure difference generated by the
progressive cavity pump 18 to press the anchoring pistons against
the inner wall 34 of the casing 6.
[0087] Referring to FIGS. 2 and 3, the torque anchor 30 according
to the first embodiment of the invention comprises a frame 36, six
anchoring pistons 38, 40, 42 supported by the frame, and six
pre-loading springs 44, 46, 48 suitable for pushing the anchoring
pistons 38, 40, 42 against the casing 6. Note that in the cutaway
perspective view of FIG. 2, only five pre-loading springs and three
anchoring pistons are visible.
[0088] The frame 36, for example generally cylindrical in shape, is
provided with an internal channel 50 and six cavities 52, 54, 56,
each accommodating one anchoring piston 38, 40, 42 and one
pre-loading spring 44, 46, 48. The frame 36 and the internal
channel 50 form a section of a pipe.
[0089] The internal channel 50 traverses the frame 36 from end to
end in an axial direction A-A. It opens onto the flat end walls 58,
60 of the frame. When the torque anchor 30 is mounted in the well,
the axial direction A-A is parallel to the longitudinal axis of the
shaft and the internal channel 50 is traversed by a drill pipe 62
of the drill string connecting the wellhead to the rotor 20.
[0090] The internal channel 50 has a diameter approximately three
to four times greater than the diameter of the drill pipe 62 so
that the annulus 64 defined between the drill pipe 62 and the
internal channel 50 of the frame 36 is sufficient to allow drill
string movement caused by eccentricity of the rotor/stator assembly
and to allow passage of all the pumped fluid which then rises along
the tubing string 10 with no significant head loss.
[0091] The radial cavities 52, 54, 56 open to the internal channel
50 and to the outer face 66 of the frame. They radially extend,
associated equiangularly, in a plane perpendicular to the axial
direction A-A. In the embodiment represented, three radial cavities
52 are arranged in a first plane 68 and the other three radial
cavities 54, 56 are arranged in a second plane 70 parallel to the
first plane 68. In FIG. 2, only five cavities are visible.
[0092] Alternatively, the frame 36 comprises a different number of
radial cavities and anchoring pistons in each plane and/or a
smaller or greater number of planes.
[0093] The radial cavities 52, 54, 56 have a shape complementary to
the shape of the anchoring pistons 38, 40, 42. In the embodiment
represented, the radial cavities 52, 54, 56 and anchoring pistons
38, 40, 42 have a cylindrical shape with a circular base.
[0094] The outer cylindrical face 72 of the anchoring pistons and
the inner cylindrical face 74 of the cavities are smooth and
continuous. The anchoring pistons 38, 40, 42 can therefore slide
out from the frame 36 when biased by the pre-loading springs 44,
46, 48, and under the pressure difference between the pressure of
the pumped fluid contained in the internal channel 50 and the
pressure in the annulus 75 defined between casing 6 and frame 36.
The pressure of the fluid being pumped against the radially sliding
anchoring pistons 38, 40, 42 increases the anchoring torque of the
torque anchor. This implementation also facilitates removal of
pre-loading springs 44, 46, 48 and replacement of anchoring pistons
38, 40, 42 during maintenance operations.
[0095] The anchoring pistons 38, 40, 42 are fitted within the
radial cavities 52, 54, 56 to allow the anchoring pistons to slide
radially while maintaining optimum sealing between frame 36 and
anchoring pistons 38, 40, 42. For example, a fit equal to H7 g6 or
H6 g5 is used.
[0096] The frame 36 comprises a flange 76 extending into each
radial cavity 52, 54, 56, opposite a flat face of the anchoring
piston. It is integral to the periphery of the inner cylindrical
face 74 of the cavities. A flat face of the flange 76 forms a
shoulder 78 contained in a plane perpendicular to the radial
direction. A pre-loading spring 44, 46, 48 is supported by this
shoulder 78.
[0097] Preferably, the flange 76 is positioned at the end of the
cavity 52 closest to the internal channel 50 to allow using the
longest possible pre-loading springs 44, 46, 48.
[0098] Alternatively, the flange 76 forms an L-shaped recess of
which the lower leg extends into the internal channel 50.
[0099] The anchoring pistons 38, 40, 42 comprise a disk-shaped head
80 and a skirt 82 integral with the periphery of the head 80 and
extending perpendicularly to the midplane of the head 80.
[0100] The head 80 and skirt 82 form a chamber 83 that opens to the
internal channel. Each pre-loading spring is housed in a chamber
83. The skirt 82 guides the pre-loading spring 44, 46, 48.
[0101] According to this embodiment, the shoulder 78 has a width
approximately equal to the thickness of the skirt 82 plus the
diameter of the torus formed by the pre-loading spring 44, 46,
48.
[0102] The head 80 of each piston has an inner face 84 and an outer
face 86 opposite the inner face. The inner face 84 is arranged so
that it faces the internal channel 50 when the anchoring piston 38,
40, 42 is mounted in the frame 36. The outer face 86 is arranged so
that it faces the casing 6 when the torque anchor 30 is installed
in the shaft.
[0103] The outer face 86 of the anchoring pistons is provided with
a lip or ridge 88 forming a portion of open torus, intended to be
pressed against the inner wall 34 of the casing. The cross-section
of the lip 88 is preferably rounded so that the lip 88 does not
damage the casing 6.
[0104] The lip 88 is provided with a coating to increase its wear
resistance. The friction coefficient of the coating optimizes its
adhesion to the casing. This coating is, for example, based on
tungsten carbide or synthetic diamond.
[0105] The lip 88 is positioned to form a straight line passing
through the center of the outer face 86 of the head. The lip 88 is
rounded at the ends to prevent catching during the passage of
casing collars. To facilitate lowering the torque anchor 30 within
the shaft and to provide maximum resistance to rotation about axis
A-A, the anchoring pistons 38, 40, 42 are arranged within the
radial cavities 52, 54, 56 so that the lips 88 are positioned
parallel to the axial axis A-A.
[0106] Alternatively, the lip 88 has a different shape. For
example, a serpentine or t-shape will be chosen if it is desired to
block both rotation and translation of the torque anchor 30 along
and about the axial axis A-A.
[0107] The distance D between the end edge of the lip 88 of an
anchoring piston 38 located in the first radial plane 68 and the
end edge of the lip 88 of the anchoring piston 40 located in the
radial plane located at the opposite end (in this case the second
radial plane 70) and contained in the same axial plane, is greater
than the length of a casing collar so that the torque anchor 30 can
traverse the casing collars without damaging them. For example,
this distance D is between 30% and 70%, and preferably between 30%
and 48%, of the inside diameter of the casing 6.
[0108] Alternatively, when the anchoring pistons 38, 40, 42 are
arranged in a single plane, the lip 88 of each anchoring piston
extends for a length equal to this same distance D, namely a
distance D of between 30% and 70%, and preferably between 30% and
48%, of the inside diameter of the casing.
[0109] In the first embodiment of the invention, the free end of
the skirt 82 is provided with a tooth 90 and the flange 76 located
at the foot of the radial cavity comprises a groove 92 in which the
tooth 90 is able to slide when the inside diameter of the casing
changes and under the pressure of the pumped fluid, as shown in
FIG. 3. This dog clutch 90-92 constitutes a rotation prevention
device for the anchoring pistons 38, 40, 42 relative to the frame
36 which ensures that the lip 88 remains parallel to the axial axis
A-A, in particular when lowering the torque anchor 30 downhole or
when the torque anchor 30 vertically shifts within the casing 6 due
to temperature variations.
[0110] Advantageously, the head 80 of the anchoring piston is
reinforced at the lip 88, for example by increasing the size of its
cross-section. For example, in the embodiment shown, the
cross-section of the head 80 in a plane perpendicular to the lip 88
has a triangular shape, as can be seen in FIG. 6.
[0111] The pre-loading springs 44, 46, 48 exert a defined force on
the anchoring pistons 38, 40, 42 in the direction of the casing 6,
such that the anchoring pistons 38, 40, 42 prevent rotation of the
torque anchor 30 when the pressure difference between the pressure
of fluid pumped within the internal channel 50 and the pressure in
the annulus 75 is low, in other words during startup of the
progressive cavity pump 18 or when the amount of pumped fluid is
low. The force exerted by the pre-loading springs 44, 46, 48 is
dependent on the internal friction torque of the progressive cavity
pump 18. It is also lower than the pressure exerted by the pumped
fluid, but is sufficient to provide sufficient locking at times
when the rotor 20 is not rotating within the stator and therefore
is not generating strong vibrations.
[0112] The spring constant of the pre-loading springs 44, 46, 48 is
calculated to ensure a sufficiently large force to prevent rotation
of the tubing string 10 during rotation of the rotor 20, without
the threaded connection between the last tube of the tubing string
10 and the torque anchor 30 becoming unscrewed, and without being
too high, avoiding damage to the casing 6 or lip 88 when the torque
anchor 30 is being lowered downhole.
[0113] The pre-loading springs 44, 46, 48 are coil springs. Each is
supported by the shoulder 78 at one end and by the inner face 84 of
the head at the other.
[0114] Alternatively, each anchoring piston 38, 40, 42 comprises a
wave spring, or two coil springs mounted coaxially one inside the
other preferably with opposite winding directions.
[0115] According to a less advantageous variant, the frame
comprises one cavity, one anchoring piston housed in said cavity,
and one stop. The cavity, anchoring piston, and stop are arranged
within the same radial plane 68. The stop extends radially and is
placed diametrically opposite the anchoring piston. When the torque
anchor is in place in the shaft, the stop and anchoring piston
press against the inner face of the casing.
[0116] In another variant, the frame comprises one anchoring piston
and one cavity in a first radial plane, one anchoring piston and
one cavity in a second radial plane, and one anchoring piston and
one cavity in a third radial plane. In addition, the cavities and
anchoring pistons are distributed equiangularly about the axial
axis A-A.
[0117] Alternatively, two anchoring pistons contained in two
different radial planes are interconnected so that their movements
are integral in the radial direction, to facilitate the passage of
casing collars under load. This connection may, for example, be
achieved by attaching a pin to the teeth 90 of each piston or by
attaching a ring of inconel or titanium alloy onto the braces of
each anchoring piston head.
[0118] During installation of the torque anchor 30 in the shaft,
the pre-loading springs 44, 46, 48 and anchoring pistons 38, 40, 42
are inserted into the frame 36 and are retained by a funnel-shaped
tool as the torque anchor is inserted into the casing 6 with the
tubing string 10. The torque anchor 30 is then lowered downhole.
During the lowering of the torque anchor 30 and when the rotor 20
begins to rotate, the pre-loading springs 44, 46, 48 press the
anchoring pistons 38, 40, 42 against the casing 6 with minimum
torque C1, as illustrated in FIG. 4. Due to its structure, the
progressive cavity pump 18 advances the fluid and pushes it into
the internal cavity 50 of the torque anchor. Then, the resisting
torque applied by the anchoring pistons 38, 40, 42 of the torque
anchor increases linearly, ignoring friction, according to the
pressure difference between the inlet and outlet of the progressive
cavity pump 18. This pressure difference approximately corresponds
to the difference in pressure between the pressure in the annulus
between the torque anchor 30 and casing 6 and the pressure inside
the internal cavity 50. As the pressure generated by the
progressive cavity pump 18 is significant, the pressure exerted by
the pumped fluid on the anchoring pistons 38, 40, 42 and therefore
the force exerted by the anchoring pistons 38, 40, 42 onto the
casing 6 is also significant. It can reach several hundred bar.
[0119] Thus, advantageously, the torque anchor 30 according to the
invention uses the pressure of the displaced fluid to enable or
disable anchoring by the torque anchor 30.
[0120] Advantageously, the anchoring is automatically controlled by
the pressure of the fluid (pressurized pumped fluid or air)
contained in the internal channel 50 and therefore by the
vibrational state of the tubing string 10 since this state is
directly related to the rotational speed of the rotor 20 within the
stator 22. It is therefore not necessary to mount a device to
control the disabling and enabling of anchoring by the torque
anchor 30. Such devices are difficult to implement because they
must provide a long service life that can withstand high pressures
and high temperatures of up to 200.degree. C.
[0121] Referring to FIGS. 5 and 6, the torque anchor 94 according
to the second embodiment of the invention is identical to the
torque anchor 30 of the first embodiment, except that the flange 76
extends into the radial cavity 52, 54, 56 to form a wall 96
provided with at least one opening 98 suitable for damping the flow
of pumped fluid coming from the internal channel 50. The surface
area of the opening 98 is about 0.5% to 5% of the surface area of a
cross-section of the radial cavity 52, 54, 56, the plane of the
cross-section being perpendicular to the radial direction.
[0122] The wall 96 is positioned between the internal channel 50
and the radial cavity 52, 54, 56. It narrows the passage between
the internal channel and the radial cavity. This narrowing
restrictor and the presence of the chamber 83 damps the flow of
pumped fluid and thus absorbs the shocks and vibrations to which
the torque anchor 94 is exposed. The diameter of the opening 98 is
calculated so that it allows enough pumped fluid to pass through to
obtain sufficient pressure of the anchoring pistons 38, 40, 42
against the casing 6 while damping the flow of pumped fluid.
[0123] In this embodiment, the torque anchor performs an additional
function of centering the tubing string relative to the casing and
damping the vibrations generated by the progressive cavity
pump.
[0124] The other technical features of the second embodiment of the
invention are identical or similar to the technical features of the
first embodiment. They are denoted by the same references and will
not be described again here.
[0125] Referring to FIG. 7, the torque anchor 100 of the third
embodiment of the invention is identical to the torque anchor 30 of
the first embodiment except that the frame 36 does not comprise a
flange 76 and the frame comprises sleeves 102 interposed between
the anchoring pistons 38, 40, 42 and the radial cavities 52, 54,
56.
[0126] The sleeves 102 have a shape complementary to the shape of
the radial cavities 52, 54, 56. In particular, in the embodiment of
the invention represented, the sleeves 102 are in the form of a
jacket provided with a flange 76 at one end, extending inwardly
into the sleeve. The flange 76 forms a shoulder 78 which supports
the pre-loading spring 44, 46, 48.
[0127] The sleeves 102 are attached to the hollow inner cylindrical
face 74 of the frame defining the radial cavities 52, 54, 56, such
that at least a portion of the sleeve 102 provided with its flange
76 is arranged within the internal channel 50.
[0128] Advantageously, this attachment is achieved by welding or
shrink fitting to ensure a fluid-tight seal.
[0129] In the embodiment shown, the flange 76 has a width
approximately equal to the thickness of the skirt 82 and the
diameter of the torus formed by the pre-loading spring 44, 46,
48.
[0130] The sleeve 102 is provided with a groove within which the
tooth 90 of the anchoring piston 38, 40, 42 is able to slide.
[0131] Advantageously, this embodiment makes it possible to use
longer pre-loading springs. This embodiment slightly reduces the
cross-section of the passage for the fluid pumped in the internal
channel 50.
[0132] Preferably, the sleeves are made of Y-TZP zirconia ceramic
to eliminate any risk of the pistons jamming as they slide and
reduce the risk of premature erosion of the openings 98.
[0133] In this embodiment, the frame comprises a supporting surface
103 on which a portion of the sleeve 102 rests. Alternatively, the
upper edge of the sleeve located at the external face of the frame
may be provided with a flange supported by the frame.
[0134] The other technical features of the third embodiment of the
invention are identical or similar to the technical features of the
first embodiment. They are denoted by the same references and will
not be described again here.
[0135] Alternatively, the flange 76 extends for a greater length so
as to create a restrictor as shown in the embodiment of the
invention illustrated in FIG. 5.
[0136] According to a variant of the invention, a gasket 104 is
provided between the anchoring piston 38, 40, 42 and the frame 36
or sleeve 102.
[0137] Referring to FIG. 8, this gasket 104 is arranged in a groove
106 formed in the frame 36 or sleeve 102. In this case, a chamfer
108 is formed on the periphery of the outer cylindrical face 72 of
the anchoring piston.
[0138] Alternatively and with reference to FIG. 9, a gasket 110 is
arranged in a groove 112 formed in the anchoring piston. In this
case, a chamfer 114 is formed on the frame 36 along the periphery
of the radial cavity 52, 54, 56 or along the inner face of the
sleeve 102.
[0139] According to a variant represented in FIG. 10, the anchoring
pistons 116 and radial cavities 118 have a cylindrical shape with
an elliptical base or an oblong cross-section.
[0140] The anchoring pistons 116 are formed as a solid block. Two
bores 120, 122 are pierced into the inner face 84 of each anchoring
piston. The bores 120, 122 extend in a radial direction. A
pre-loading spring 44, 46 is arranged in each bore 120, 122.
[0141] Preferably, the bores 120, 122 are arranged at each end of
the anchoring piston 116. Advantageously, one pre-loading spring 44
is able to retract while the other pre-loading spring 46 is able to
extend, when the anchoring piston 116 is in contact with an
isolated bump or recess. Alternatively, the two bores 120, 122 are
close to each other and are arranged toward the center of the
anchoring piston 116.
[0142] This alternative form of the anchoring pistons can be used
in the four disclosed embodiments of the invention.
[0143] Referring to FIG. 11, the torque anchor 124 according to the
fourth embodiment of the invention is identical to the torque
anchor 100 according to the third embodiment, except that it
includes braces 126 adapted to retain the anchoring pistons 38, 40,
42 in a retracted position when the torque anchor 124 is being
lowered. The braces 126 are adapted to break off when the torque
anchor 124 is in position downhole.
[0144] The frame 36 of the torque anchor 124 further comprises a
crossbar 128 connecting two diametrically opposed portions of the
flange. The brace 126 is attached to the inner face 84 of the
anchoring piston and to said crossbar 128 by mating threads 130 or
by pins.
[0145] The brace 126 is designed to have a sufficiently small
diameter for it to break under the pressure of fluid injected into
the tubing string by the wellhead.
[0146] Alternatively, the frame 36 comprises a hydraulic, electric
or acoustic thermal, chemical mechanism able to shear the braces
126 in order to actuate the anchoring springs 44, 46, 48 and
achieve the minimum torque C1 necessary to allow insertion of the
rotor 20 into the stator 22 without unscrewing the connection
between stator 22 and torque anchor 18 or the connection between
torque anchor and tubing string.
[0147] This embodiment can be implemented with a large opening 98
between the internal cavity 50 and the chamber 83 as illustrated in
the first embodiment of the invention, or with a smaller damping
opening 98 as in the second embodiment of the invention.
[0148] The other technical features of the fourth embodiment of the
invention are identical or similar to the technical features of the
third embodiment. They are denoted by the same references and will
not be described again here.
[0149] The invention also relates to a system for pumping and
preventing rotation of a tubing string relative to a well casing.
The system comprises a progressive cavity pump adapted to intake
fluid for pumping through an inlet, compress the pumped fluid, and
discharge the compressed fluid through an outlet. This pumping and
prevention system comprises a torque anchor according to the
invention and as described above. The torque anchor is secured
downstream of the progressive cavity pump, relative to the
direction of flow of the fluid pumped within the internal cavity.
The torque is a function of the difference in pressure generated by
the progressive cavity pump between intake and discharge.
[0150] In reference to FIG. 12, the invention concerns a method for
preventing rotation of a tubing relative to a casing of a shaft for
pumping fluid by a progressive cavity pump; said method being
implemented by a torque anchor comprising a frame intended to be
mounted in the casing, an internal channel formed in the frame,
said internal channel extending along an axial direction; at least
one cavity in fluid communication with the internal channel, said
cavity extending along a radial direction, and at least one
anchoring piston fitted to said radial cavity, characterized in
that the method comprises the following steps: [0151] intake (151)
of a fluid to be pumped, through an inlet (24) of the progressive
cavity pump (18), [0152] traversal (152) by the pumped fluid of
said internal channel (50), [0153] discharge (153) of said
pressurized fluid in the tubing string (10), through the outlet
(26) of said progressive cavity pump (18); [0154] application (154)
of pressure by the pumped fluid on a face of the anchoring piston
(38, 40, 42, 116); [0155] sliding (155) of said anchoring piston
(38, 40,42,116) relative to the frame (36) in the radial direction;
said application causing torque to be applied by said anchoring
piston (38, 40, 42, 116) to the casing (6); said torque being a
function of the pressure difference between the inlet (24) and the
outlet (26) of the progressive cavity pump.
[0156] The present invention also relates to a centering device
and/or a damper comprising: [0157] a frame 36 intended to be
mounted in the casing 6, [0158] an internal channel 50 formed in
the frame, said internal channel extending along an axial direction
(A-A), the pumped fluid traveling in said internal channel 50;
[0159] at least one cavity 52, 54, 56, 118 in fluid communication
with the internal channel 50, said cavity 52, 54, 56, 118 extending
along a radial direction, and [0160] at least one anchoring piston
38, 40, 42, 116 fitted to said radial cavity 52, 54, 56, 118, said
anchoring piston 38, 40, 42, 116 being capable of sliding relative
to the frame 36 along the radial direction and of exerting torque
on the casing 6, when the pumped fluid contained in the internal
channel 50 exerts force on said anchoring piston 38, 40, 42,
116.
[0161] The centering device and/or the damper comprises the
features described in relation to FIGS. 5 and 6 and possibly the
features described in relation to FIGS. 7 to 11.
[0162] Advantageously, the lip 88 of the centering device and/or
damper is not coated with tungsten carbide and preferably has a
rounded shape.
[0163] Advantageously, rotation of the piston within the frame is
prevented.
[0164] Advantageously, contact of the piston against the inside of
the casing is assured.
[0165] Advantageously, casing collars are not damaged when lowering
the torque anchor to the bottom of the casing.
* * * * *