U.S. patent application number 10/916773 was filed with the patent office on 2005-03-24 for releasable mill.
This patent application is currently assigned to Baker Hughes Incorporated. Invention is credited to Davis, John P., DeGeare, Joseph P., Dolyniuk, David A., Plante, Mark.
Application Number | 20050061551 10/916773 |
Document ID | / |
Family ID | 34215911 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050061551 |
Kind Code |
A1 |
DeGeare, Joseph P. ; et
al. |
March 24, 2005 |
Releasable mill
Abstract
A mill assembly having a milling head which is releasable from
the mill body, such as by shearing a shear pin. The release
mechanism can be released by dropping a pumpable plug through the
work string to block fluid flow through the releasable milling
head, or by increasing fluid flow through a constriction in the
releasable milling head to increase the back pressure above the
milling head. A check valve in the milling head can prevent uphole
flow through the work string in the event of a pressure excursion.
A fishing neck can be attached to the milling head.
Inventors: |
DeGeare, Joseph P.;
(Houston, TX) ; Plante, Mark; (Houston, TX)
; Dolyniuk, David A.; (Tomball, TX) ; Davis, John
P.; (Houston, TX) |
Correspondence
Address: |
GERALD W SPINKS
P. O. BOX 2467
BREMERTON
WA
98310
US
|
Assignee: |
Baker Hughes Incorporated
Houston
TX
|
Family ID: |
34215911 |
Appl. No.: |
10/916773 |
Filed: |
August 11, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60495021 |
Aug 13, 2003 |
|
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|
Current U.S.
Class: |
175/320 ;
166/242.6; 166/298; 175/327 |
Current CPC
Class: |
E21B 21/10 20130101;
E21B 10/62 20130101; E21B 10/60 20130101 |
Class at
Publication: |
175/320 ;
166/298; 166/242.6; 175/327 |
International
Class: |
E21B 010/62 |
Claims
We claim:
1. A milling head assembly for use on a work string, comprising: a
milling head; at least one cutting structure on said milling head;
a fluid path through said milling head; and a releasable fastening
mechanism fixedly attached to one of said milling head or a work
string, said fastening mechanism being adapted to attach said
milling head to a work string, said fastening mechanism being
adapted to selectively release said milling head from a work
string, thereby completely separating said milling head from a work
string.
2. The milling head assembly recited in claim 1, further comprising
a torque transfer device on said milling head, said torque transfer
device being adapted to transfer torque from a work string to said
milling head, said torque transfer device being adapted to allow
said separation of said milling head from a work string.
3. The milling head assembly recited in claim 2, wherein said
torque transfer device comprises a shoulder on said milling head,
said shoulder being adapted to transfer torque from a work string
to said milling head.
4. The milling head assembly recited in claim 1, wherein said
releasable fastening mechanism comprises a shear pin adapted to
shear at a predetermined hydraulic force on said milling head.
5. The milling head assembly recited in claim 1, wherein said
releasable fastening mechanism comprises a ball clutch
mechanism.
6. The milling head assembly recited in claim 1, further comprising
a flow restricting device, said flow restricting device being
adapted to impede fluid flow through said fluid path at a location
on said milling head, thereby creating a predetermined hydraulic
force on said milling head to release said fastening mechanism.
7. The milling head assembly recited in claim 6, wherein said flow
restricting device comprises a pumpable object, said pumpable
object being adapted to be pumped through a work string with fluid
flow, to land in said milling head to at least partially block said
fluid path at said location on said milling head.
8. The milling head assembly recited in claim 7, wherein said flow
restricting device further comprises a seat in said fluid path at
said location on said milling head, said seat being adapted to
receive said pumpable object.
9. The milling head assembly recited in claim 6, wherein said flow
restricting device comprises a constriction at said location in
said fluid path, said constriction being adapted to establish said
predetermined hydraulic force on said milling head by impeding
fluid flow, upon an increase in fluid flow rate into said fluid
path.
10. The milling head assembly recited in claim 1, further
comprising a check valve in said fluid path of said milling head,
oriented to prevent fluid flow in the uphole direction through said
fluid path.
11. The milling head assembly recited in claim 10, wherein said
check valve is a ball check valve.
12. The milling head assembly recited in claim 10, wherein said
check valve is a flapper check valve.
13. The milling head assembly recited in claim 1, further
comprising a fishing neck attached to said milling head.
14. A mill assembly for use on a work string, comprising: a mill
body adapted to be attached to a work string and lowered into a
well bore; a milling head; at least one cutting structure on said
milling head; a fluid path through said mill body and said milling
head; and a releasable fastening mechanism fixedly attached to one
of said milling head or said mill body, said fastening mechanism
being adapted to attach said milling head to said mill body, said
fastening mechanism being adapted to selectively release said
milling head from said mill body at a predetermined hydraulic force
on said milling head, thereby completely separating said milling
head from said mill body.
15. The mill assembly recited in claim 14, further comprising a
torque transfer device on said milling head, said torque transfer
device being adapted to transfer torque from said mill body to said
milling head, said torque transfer device being adapted to allow
said complete separation of said milling head from said mill
body.
16. The mill assembly recited in claim 14, wherein said releasable
fastening mechanism comprises a shear pin.
17. The milling head assembly recited in claim 14, wherein said
releasable fastening mechanism comprises a ball clutch
mechanism.
18. The mill assembly recited in claim 14, further comprising a
flow restricting device, said flow restricting device being adapted
to impede fluid flow through said fluid path at a location on said
milling head, thereby creating said predetermined hydraulic force
on said milling head.
19. The mill assembly recited in claim 18, wherein said flow
restricting device comprises a pumpable object, said pumpable
object being adapted to be pumped through a work string with fluid
flow, to land in said milling head to at least partially block said
fluid path at said location on said milling head.
20. The mill assembly recited in claim 18, wherein said flow
restricting device comprises a constriction in said fluid path at
said location on said milling head, said constriction being adapted
to establish said predetermined hydraulic force on said milling
head by impeding fluid flow, upon an increase in fluid flow rate
into said fluid path.
21. The milling head assembly recited in claim 14, further
comprising a check valve in said fluid path of said milling head,
oriented to prevent fluid flow in the uphole direction through said
fluid path.
22. The milling head assembly recited in claim 21, wherein said
check valve is a ball check valve.
23. The milling head assembly recited in claim 21, wherein said
check valve is a flapper check valve.
24. The milling head assembly recited in claim 14, further
comprising a fishing neck attached to said milling head.
25. A method for milling an object in a well bore, comprising:
providing a mill body attached to a work string and a milling head
mounted to said mill body with a releasable fastening mechanism,
said milling head having a cutting structure; lowering said mill
body and milling head into a well bore on the work string; rotating
said mill body and milling head to mill an object in the well bore
with said cutting structure; releasing said releasable fastening
mechanism to completely release said milling head from said mill
body; and retaining said releasable fastening mechanism to one of
said mill body or said milling head after said release of said
milling head from said mill body.
26. The method recited in claim 25, further comprising: providing a
separate torque transfer device on said milling head; transferring
torque from said mill body to said milling head with said torque
transfer device; and disengaging said torque transfer device upon
said complete separation of said milling head from said mill
body.
27. The method recited in claim 25, further comprising impeding
fluid flow at a location on said milling head, to increase
hydraulic pressure and release said releasable fastening
mechanism.
28. The method recited in claim 27, further comprising pumping a
plug through said work string with said fluid flow, to land at said
location on said milling head to at least partially block said
fluid flow, and achieve said hydraulic pressure increase at said
location on said milling head.
29. The method recited in claim 27, further comprising: providing a
constriction at said location in the path of said fluid flow; and
increasing said fluid flow into said work string to achieve said
hydraulic pressure increase at said constriction in said fluid flow
path.
30. The method recited in claim 25, further comprising: providing a
fishing neck attached to said milling head; and retrieving said
milling head from a well bore by attaching to said fishing neck.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Pat.
App. No. 60/495,021, filed Aug. 13, 2003, for "Releasable Bridge
Plug Mill".
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] Field of the Invention--This invention is in the field of
apparatus used to mill out downhole equipment in a well, such as in
an oil or gas well.
[0004] Background Art--Some oil or gas wells are drilled into
locations at which multiple oil or gas formations are found, at
different depths. That is, one hydrocarbon formation may be above
or below another, and there may be more than two such formations at
different depths. It is common to produce hydrocarbons from only
one selected formation at a time. One means used to assist in this
type of production is a plug, which can be installed in the bore
hole or casing, between two of the formations. Such a plug isolates
one formation from another, while allowing access to the upper
formation via the bore hole. It is also common to remove such a
plug, in order to allow access to the lower formation, via the bore
hole, for the purpose of producing hydrocarbons, or for other
purposes.
[0005] When such a plug is removed, it is often removed by lowering
a mill into the bore hole or casing, attached to a work string. The
mill is usually provided with some type of cutting structure on its
lower face, and this cutting structure is often dressed with some
type of cutting material, such as inserts or abrasives. The mill is
lowered into contact with the upper end of the plug; then, the work
string is rotated, thereby rotating the mill. Alternatively, a
downhole motor can be used on the work string, as is commonly known
in the art, and the mill can be rotated by operating the downhole
motor. In either case, as the mill is rotated, the cutting
structure cuts the plug into small cuttings, which are returned to
the surface entrained in the drilling fluid which is pumped
downhole through the work string. This operation is continued until
the entire plug is removed, or until a sufficient portion of the
plug is removed to allow the remaining portion to fall farther into
the borehole.
[0006] After this type of operation, it is necessary to remove the
mill from the bore hole before access to the lower formation is
available. This is because, although the mill may have passageways
for drilling fluid, these fluid passageways are not sufficiently
large to provide the desired degree of access to the lower
formation. The mill body itself is typically a substantially solid,
comparatively hard, metal body. Therefore, in order to complete the
operation, the work string and the mill must be pulled from the
bore hole to provide the desired access to the lower formation. As
is well known, tripping a work string into or out of a well is a
time consuming, expensive process. It is desirable to have a method
and apparatus for removing such plugs, or other types of objects in
a well bore, while eliminating the necessity for tripping the work
string out of the bore hole, to remove the mill and provide access
to the lower formation.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention provides a mill assembly having a
releasable milling head attached to a mill body with one or more
shear pins, or another releasable fastening feature. The mill
assembly can be lowered into a bore hole to mill out a plug, after
which the milling head can be completely released from the work
string, such as by shearing the shear pins, and allowed to drop
into the bore hole. Separation of the milling head from the mill
body leaves a substantially open bore into and through the work
string. The mill body and the work string can be left in the bore
hole while production from the lower formation takes place, through
this open bore. The milling head is provided with a check valve in
the fluid path, to allow the downhole flow of drilling fluid during
milling, but to prevent the uphole flow of fluids during a kick or
pressure excursion. A fishing neck can also be provided on the
milling head, to assist in the later removal of the milling head
where desired.
[0008] The novel features of this invention, as well as the
invention itself, will be best understood from the attached
drawings, taken along with the following description, in which
similar reference characters refer to similar parts, and in
which:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] FIG. 1 is a longitudinal section view of a first embodiment
of the apparatus of the present invention;
[0010] FIG. 2 is a lower end view of the milling head portion of
the apparatus shown in FIG. 1, and showing the location of the line
along which the section in FIG. 1 is taken;
[0011] FIG. 3 is an upper end view of the milling head portion of
the apparatus shown in FIG. 1;
[0012] FIG. 4 is a lower end view of the mill body portion of the
apparatus shown in FIG. 1;
[0013] FIG. 5 is a longitudinal section view of the apparatus shown
in FIG. 1, after complete separation of the milling head from the
mill body;
[0014] FIG. 6 is a longitudinal section view of a second embodiment
of the milling head of the present invention, with a ball check
valve;
[0015] FIG. 7 is an expanded longitudinal section view of a third
embodiment of the apparatus of the present invention, with a
flapper check valve and a fishing neck;
[0016] FIG. 8 is an assembled longitudinal section view of the
apparatus shown in FIG. 7;
[0017] FIG. 9 is a longitudinal section view of a ball clutch and
fishing neck for use in a fourth embodiment of the apparatus of the
present invention;
[0018] FIG. 10 is a longitudinal section view of a collet for use
in the fourth embodiment of the apparatus of the present invention,
along with the ball clutch and fishing neck shown in FIG. 9;
and
[0019] FIG. 11 is an assembled longitudinal section view of the
fourth embodiment of the apparatus of the present invention,
incorporating the ball clutch and fishing neck, and the collet,
shown in FIGS. 9 and 10.
DETAILED DESCRIPTION OF THE INVENTION
[0020] As shown in FIG. 1, the mill assembly apparatus 10 of the
present invention principally includes a mill body 12, to which a
milling head 14 is releasably attached, such as by one or more
shear screws or pins 16. The mill body 12 is adapted to be mounted
on a work string (not shown) as is commonly known in the art, such
as by threading thereto. A plurality of cutting inserts 18 can be
provided on the lower face 34 of the milling head 14 to form a
cutting structure. Alternatively, the cutting structure can include
milled teeth, crushed carbide, or abrasives, without departing from
the spirit of the present invention.
[0021] One or more torque lugs 20, better shown in FIG. 3, can be
provided on an upwardly facing annular shoulder 46 of the milling
head 14. These torque lugs 20 can extend into one or more torque
notches 28, better shown in FIG. 4, formed on the lower end 48 of
the mill body 12. An axially oriented inner face or shoulder 42 in
each torque notch 28 abuts an axially oriented outer face or
shoulder 40 on each torque lug 20. Rather than torque lugs and
notches, mating shoulders could alternatively be used. When the
milling head 14 is mounted to the mill body 12, the upwardly facing
annular shoulder 46 of the milling head 14 abuts the lower end 48
of the mill body 12. Also, the upper end 36 of the milling head 14
can abut a downwardly facing annular shoulder 38 within the mill
body 12.
[0022] The section shown in FIG. 1 is taken along a broken section
line as shown in FIG. 2, to better illustrate a possible placement
of the torque lugs 20 and torque notches 28, and the shear pins
16.
[0023] A fluid flow path can be provided through the mill body 12
and the milling head 14, which can for example include the inner
bore 44 in the mill body 12, and a first conical surface 50, a ball
seat 30, an inner bore 32, a second conical surface 52, an axial
jet 24, and a plurality of angled jets 26 on the milling head 14.
Drilling or milling fluid can be pumped down the work string (not
shown) to flow through this fluid path in the mill body 12 and the
milling head 14, as indicated by the arrows. In addition to the
mill assembly apparatus 10, a pumpable ball or plug 22 can be
provided for selectively restricting this fluid flow, as will be
described below.
[0024] The mill assembly apparatus 10, assembled as shown in FIG.
1, is mounted to a work string (not shown) and lowered into a well
bore, until the cutting structure on the lower face 34 of the
milling head 14 contacts a plug or other item to be milled out of
the bore hole. A rotatable work string or a downhole motor can be
used, without departing from the spirit of the present invention.
After contacting the plug to be milled, the mill body 12 is rotated
in the clockwise direction, as viewed from the upper end, rotating
the milling head 14 by virtue of the abutment of the axially
oriented torque shoulders 40 and 42, and causing the inserts 18 or
other cutting structure to mill the plug away. Cuttings or
fragments of the milled plug are removed from the bore hole
entrained in the milling fluid which is pumped through the mill
body 12 and the milling head 14 and returned up the annulus to the
surface.
[0025] After the plug has been milled away, the pumpable plug or
ball 22 can be pumped downhole through the work string to land in
the ball seat 30 in the milling head 14. Alternatively, the fluid
flow rate can simply be increased through the apparatus 10 by
increasing the speed of the fluid pumps. Either action results in
an increased hydraulic pressure at a location in the fluid flow
path as it passes through the milling head. If the pumpable ball 22
is used, the increased hydraulic pressure occurs primarily on the
first conical surface 50 and across the top of the ball 22. If the
increased pump speed is used, the increased hydraulic pressure
occurs in the fluid flow path 50, 30, 32, 52, 24, 26. This
increased hydraulic pressure exerts an increased downward hydraulic
force on the upwardly facing components of the surfaces of the
milling head 14 which are exposed to the increased pressure. As
this downward hydraulic force reaches a sufficient, predetermined,
level, it causes the shear pins 16 to shear.
[0026] When the shear pins 16 shear, the milling head 14 is
completely released from the mill body 12 and completely separates
therefrom, as shown in FIG. 5. This complete axial separation of
the milling head 14 from the mill body 12 allows the milling head
14 to fall downhole, completely opening up the borehole at the
previously plugged location. Since the torque shoulders 40 and 42
are axially oriented, they are adapted to separate from each other
easily when the shear pins 16 shear, and they do not interfere with
the shearing of the pins 16 or the complete axial separation of the
milling head 14 from the mill body 12.
[0027] After complete separation of the milling head 14 from the
mill body 12, the inner bore of the mill body 12 is completely open
to allow for flow of hydrocarbon fluids upwardly through the mill
body 12 as shown by the arrows in FIG. 5. The separated mill body
12 thus performs thereafter as simply an extension of the work
string, and the hydrocarbon fluid flow continues upwardly through
the work string to the surface. Therefore, the complete separation
of the milling head 14 from the mill body 12 allows for the
efficient production of hydrocarbons from the bore hole, through
the work string, without pulling and replacing the work string with
a production tube.
[0028] A second embodiment of the milling head is shown in FIG. 6.
This embodiment of the milling head 140 can be fitted with a check
valve comprising a ball seat 142, a check ball 144, and a spring
146. It can be seen that, as milling fluid passes downhole through
the fluid path in the milling head 140, the check ball 144 can be
lifted off its seat 142, against the bias of the spring 146, to
allow flow out the lower end of the work string. A kick or pressure
excursion sometimes occurs in the formation fluids, which could
create an undesirable flow in the uphole direction through the work
string. To prevent this, the spring 146 biases the check ball 144
toward engagement with its seat 142. As pressure below the milling
head 140 increases above the drilling fluid pressure, this causes
the check ball 144 to seat more securely, thereby preventing flow
in the uphole direction.
[0029] A third embodiment of the apparatus 210 of the present
invention is shown in FIGS. 7 and 8. In this embodiment, the mill
body 212 is secured to the milling head 214 by shear pins 216 in
shear pin bores 224 and 226 in the mill body 212 and the milling
head 214, respectively. Flow passages 228 are provided through the
milling head 214. However, in this embodiment, the check valve
comprises a swing check type valve, with a check valve body 262
assembled in the milling head 214, and with a flapper valve 264,
which is pivotably mounted to the check valve body 262 by a pivot
pin 266. The check valve body 262 can be retained in the milling
head 214 by one or more snap rings or pins, as is known in the art.
The flapper valve 264 is biased toward the closed position by a
spring. Flow of fluid down through the apparatus can open the
flapper valve 264 against the spring bias, but backflow through the
check valve is prevented by shutting of the flapper valve 264,
which seats against the lower side of the check valve body 262.
[0030] Also provided in this embodiment is a fishing neck 260,
which is retained in the milling head 214, above the check valve
body 262, by one or more snap rings or pins, as is known in the
art. A ball seat 230 is provided in the upper side of the check
valve body 262. When milling has been completed, and it is desired
to release the milling head 214 from the mill body 212, a ball 222
is pumped downhole through the work string, to seat in the ball
seat 230. Increasing pressure above the pumpable ball 222 then
shears the shear pins 216, releasing the milling head 214 from the
mill body 212, as in the first embodiment. If it is desired to
subsequently remove the milling head 214 from the well bore, known
fishing techniques can be used to attach to the fishing neck 260
and pull the milling head 214.
[0031] A fourth embodiment of the apparatus 310 of the present
invention is shown in FIGS. 9, 10, and 11. In this embodiment, a
ball clutch mechanism 360 is provided, incorporating a fishing
neck, and including one or more ball clutch bores 324 through the
wall of the ball clutch 360. One or more clutch balls 326 are
positioned in the clutch bores 324, when the ball clutch 360 is
assembled to the mill body 312. The clutch balls 326 are forced
outwardly in an inner annular groove within the mill body 312 by a
collet 370 which is positioned in the inner bore of the ball clutch
360. The fingers on the upper end of the collet 370 are outwardly
biased to seat in an inner shoulder of the fishing neck and ball
clutch 360. This positioning of the collet 370 releasably retains
the ball clutch 360 to the mill body 312. The ball clutch 360 is,
in turn, secured to the milling head 314 by one or more snap rings
or pins, as is known in the art. So, the ball clutch mechanism 360
releasably retains the milling head 314 to the mill body 312.
[0032] Flow passages 328 are provided through the milling head 314.
This embodiment of the apparatus 310 can be fitted with a check
valve comprising a ball seat 340 in the lower end of the ball
clutch 260, a check ball 344, and a spring 346. It can be seen
that, as milling fluid passes downhole through the fluid path in
the milling head 314, the check ball 344 can be lifted off its seat
340, against the bias of the spring 346, to allow flow out the
lower end of the work string. To prevent a kick or pressure
excursion, the spring 346 biases the check ball 344 toward
engagement with its seat 340. As pressure below the milling head
314 increases above the drilling fluid pressure, this causes the
check ball 344 to seat more securely, thereby preventing flow in
the uphole direction.
[0033] A ball seat 330 is provided in the upper side of the collet
370. When milling has been completed, and it is desired to release
the milling head 314 from the mill body 312, a ball 322 is pumped
downhole through the work string, to seat in the ball seat 330.
Increasing pressure above the pumpable ball 322 then forces the
collet fingers inwardly, releasing the collet 370 from the inner
shoulder in the ball clutch 360. After the collet 370 is released
in this fashion, it is forced further downwardly by fluid pressure.
This downward movement of the collet 370 allows the clutch balls
326 to be released from the inner groove in the mill body 312,
releasing the ball clutch 360 and the milling head 314 from the
mill body 312. If it is desired to subsequently remove the milling
head 314 from the well bore, known fishing techniques can be used
to attach to the fishing neck on the ball clutch 360 and pull the
milling head 314.
[0034] While the particular invention as herein disclosed is
capable of obtaining the objects hereinbefore stated, it is to be
understood that this disclosure is merely illustrative of the
presently preferred embodiments of the invention.
* * * * *