U.S. patent number 3,750,771 [Application Number 05/251,394] was granted by the patent office on 1973-08-07 for underreamer having variable arm extension.
This patent grant is currently assigned to Grant Oil Tool Company. Invention is credited to Edward T. Cugini.
United States Patent |
3,750,771 |
Cugini |
August 7, 1973 |
UNDERREAMER HAVING VARIABLE ARM EXTENSION
Abstract
An underreamer for enlarging a well bore wherein a plurality of
cutter cones are rotatably supported on pivoted cutter arms which
pivot outwardly from the body of the tool in response to fluid
pressure. The amount of outward pivotal movement is adjustable
without the removal and replacement of the cutter arms. This
permits the same tool body and pivotable arms to be used for bore
enlargements to different diameters relative to the contracted
diameter of the tool.
Inventors: |
Cugini; Edward T. (Brea,
CA) |
Assignee: |
Grant Oil Tool Company (Los
Angeles, CA)
|
Family
ID: |
22951779 |
Appl.
No.: |
05/251,394 |
Filed: |
May 8, 1972 |
Current U.S.
Class: |
175/269;
175/287 |
Current CPC
Class: |
E21B
10/345 (20130101) |
Current International
Class: |
E21B
10/34 (20060101); E21B 10/26 (20060101); E21b
009/26 () |
Field of
Search: |
;175/267,269,287 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Claims
What is claimed is:
1. An expandable underreamer which comprises an elongate, generally
cylindrical tool body adapted to be suspended from and rotatably
driven by a drill string;
roller cutter cones supported on respective cutter arms;
said arms being peripherally spaced and arranged generally
longitudinally of said body and being pivotally connected to the
body adjacent their upper ends and supporting the respective cutter
cones thereon adjacent their lower ends;
said arms being pivotal between an inoperative position at which
said cutter cones are retracted and wherein said arms are generally
recessed within elongated slots in the body and an operative
position at which said cutter cones are projected radially
outwardly from said body wherein the arms incline downwardly and
radially outwardly from their pivotal connections with the body,
the pivot axes of said arms being substantially horizontally
coplanar and said arms having substantially the same length, each
of said arms including a cam follower plate and a radius limiting
plate;
said radius limiting plate being engageable in bearing contact with
a load bearing shoulder on said tool body to limit the outward
extension of the cutter assembly;
said cam follower plate having a cam follower surface thereon;
said radius limiting plate and cam follower plate being removable
and replaceable;
a vertically extending actuating member movable longitudinally
downwardly within the tool body in response to fluid pressure;
a cam member affixed to said movable actuating member having a cam
surface in camming engagement with the cam plate of said cutter arm
assembly; and
the construction of said cam surface and cam follower surface being
such as to move said cutter arm to a predetermined radius upon
downward movement of said actuating member.
2. The apparatus as defined in claim 1 in which the cam follower
plate is removably inserted in a longitudinal slot defined in said
respective cutter arm.
3. The apparatus as defined in claim 2 in which two radius limiting
plates are utilized and are positioned at opposite transverse sides
of the respective cutter arm.
Description
BACKGROUND OF THE INVENTION
Underreamers are employed extensively for enlarging portions of the
well bore in oil and gas wells for various purposes, as for
example, to provide clearance for running casing, to obtain
adequate annular space in the hole for cemeting, to enlarge zones
for gravel pack completion or cemeting and for other purposes.
One type of underreamer known to the prior art employs three cutter
cones that are rotatably supported on respective pivoted arms which
swing from an initial retracted position, wherein the arms and
cutter cones are completely withdrawn into the body of the tool,
outwardly to an extended or expanded position, wherein the cutter
cones project radially outward from the body of the tool so as to
enlarge the existing bore. In such conventional underreamers the
cutter cones are all of the same length in the radial direction
relative to the body of the tool. Similarly, in conventional
underreamers the three pivoted arms upon which the cutter cones are
rotatably supported swing outwardly to the same radial extent. The
length of the cutters is limited in such conventional underreamers
by the requirement that the cutters all fit completely within the
diameter of the body of the tool when in the retracted position.
The amount of hole enlargement that can be accomplished is in
general limited to the cutter length since the cutters must
generally operate upon the full annular formation area between the
wall of the original bore and the wall of the enlarged bore. It can
thus be seen that conventional underreamers having cutter cones of
equal length and cone support arms which swing outwardly to equal
extents are limited in the amount of bore enlargement which they
can achieve. It is desirable with this type of tool to obtain the
largest possible effective cutting diameter relative to the
retracted tool diameter, i.e., it is desirable to obtain the
maximum possible outward extension of the cutters consistent with
efficient cutting and durability of the cutters in operation.
One prior art attempt to obtain a greater amount of cutter
extension is described in U. S. Pat. No. 3,483,934 by Benjamin H.
Fuchs which patent is assigned to the assignee of the present
application. The underreamer of that patent utilizes pivoted arms
which swing outwardly from the body of the tool by different radial
amounts to thereby dispose the respective cutter cones in radially
stepped relationship. By means of this arrangement the underreamer
obtains a greater radial spread of cutter surface and provides
greater bore enlargement relative to the contracted diameter of the
tool than with conventional underreamers described above wherein
the arms all swing out by the same amount.
The present invention is equally applicable to underreamers of both
types, i.e., those in which the cutter cones all swing outwardly to
the same radii and those described in the aforementioned patent in
which the cutter cones swing out to different radii. The present
invention is, however, presently utilized with an underreamer of
unequal arm extension and will accordingly be described in
connection with such a utilization.
SUMMARY OF THE INVENTION
In the underreamers of both types described above it is desirable
to utilize the same tool body for underreaming several sizes of
holes. For example, the tool body for underreaming holes to
diameters from seven to eleven inches all utilize a 53/8th inch
outside diameter tool body. However, in order to underream to the
desired diameter it is necessary to have a specific set of arms. In
order to change the diameter to which the underreamer opens the
hole, a different set of arms must be inserted into the tool body.
The necessity of changing cutter arms for each different bore
radius results in the need for a large inventory of cutters and
results in large expense. The present invention provides an
underreamer apparatus which utilizes the same tool body and the
same pivoted arms for underreaming holes to different predetermined
diameters. The construction of the apparatus is such that easily
replaceable portions of the expansion assembly are utilized to
pivot the cutter arms outwardly to different desired radii.
An underreamer in accordance with the present invention comprises
an elongate body with the series of circumferentially spaced cutter
arms pivotally mounted thereon. A longitudinally movable
wash-barrel includes a plurality of cams which engage cam follower
surfaces on the respective cutter arms to force the cutter arms
outwardly to the desired respective radius. The cam follower
surfaces are defined by a replaceable cam follower plate mounted
upon the respective cutter arm. The cam follower surface which is
removable and replaceable upon the cutter arm without removal of
the arm from the body determines the radius to which the arm is
extended by the action of the cam. At least one radius limiter
plate is replaceable affixed to the respective cutter arm to define
a surface which comes into bearing engagement with a bearing
shoulder on the tool body at the predetermined radius to limit the
radially outward movement of the cutter arm.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view in elevation illustrating an underreamer
embodying the present invention with the cutter arms disposed in
the collapsed position;
FIG. 2 is a view elevation taken along line 2--2 of FIG. 1;
FIG. 3 is a sectional view taken along line 3--3 of FIG. 1;
FIG. 4 is a detailed partial view in elevation showing the cutter
arms in the collapsed position;
FIG. 5 is a view comparable to FIG. 4 showing the arms in the
extended operative position; and
FIG. 6 is an enlarged view in exploded perspective of the various
components of the cutter arm.
DETAIL DESCRIPTION
Referring now to the drawings an expendable underreamer embodying
the present invention is shown. The underreamer is illustrative of
the type known as a full coverage underreamer which has two arms
which are extendable to gauge size while the third arm is only
partly extended from its cone pocket. It has been found that the
most common problem in maximum size hole opening has been cone
failure which occurs not at the gauge area but at the cone ends
nearest the tool body. This is due to the fact that the amount of
cone available at the end nearest the tool body is substantially
less in proportion to the amount of material to be removed. By only
partially extending the third arm a larger tooth area works upon
the formerly weak zone of the underreamer.
The arm with the smaller radius engages the formation at a lower
plane creating a two-level saucer shaped pattern on the bottom of
the shelf. By means of the present invention the same relationship
of the cutter arms can be employed at different diameters in order
to utilize the same apparatus to underream through a range of hole
sizes without the necessity of replacing the cutter arms. The
apparatus of the present invention comprises a tubular elongated
body 12 which is threadedly connected to a suitable tubular top sub
14.
Three cutter arms 16, 18 and 20 described in detail hereinafter are
circumferentially arranged at regularly spaced intervals about the
tubular body 12 in the lower portion thereof. The arms 16, 18 and
20 are pivotally supported in respective elongated slots 22, 24 and
26 in the body 12. The cutter arms 16, 18 and 20 are pivotally
supported proximate their upper ends to swing generally in
respective vertical planes which are radially oriented relative to
the axis of the body 12 on horizontal support pins 28 which are
mounted in the body 12. The cutter arms 16, 18 and 20 are provided
with arcuate upper ends which are seated in complimentary recesses
in arm retainers 30 which are welded or otherwise secured to the
body 12 and serve as thrust bearing means for applying drill string
weight to the cutters. Conventional cutter cones 32 and 34 (only
two of which are visible in the views) are rotatably mounted at the
lower ends of the respective cutter arms 16, 18 and 20.
A wash barrel 38 is axially mounted within the tubular body 12 and
is slidably supported nears its lower end in a bushing 40. The wash
barrel has a piston 42 secured to its upper end portion which
piston is slidable within an enlarged cylindrical portion 44 of the
tubular body 12. In the collapsed or retracted position of the
underreamer the wash barrel 38 and piston 42 are in the uppermost
position as shown in FIG. 1. In the expanded or fully operative
position of the tool the wash barrel 38 and piston 42 are in the
lowermost position as shown in FIG. 5. The lowermost position of
the piston is determined by engagement of the piston with an
upwardly facing shoulder 46 at the bottom of the cylinder 44. A
helical spring 50 is mounted in an enlargement of intermediate
diameter surrounding the wash barrel beneath the piston 42 and
normally urges the piston and wash barrel toward their uppermost
positions as illustrated in FIG. 1. The piston and wash barrel are
moved downwardly to the extended position of the tool by the
pressure of drilling fluid introduced into the drill string and
through the sub 14 into the cylinder 44.
Positioned proximate the lower end of the wash-barrel 38 are three
radially projecting cams 48, 49 and 50. The cams are affixed to the
wash-barrel in any suitable manner such as by welding. The cams are
circumferentially spaced about the wash-barrel and are in alignment
with the longitudinal center line of a respective one of the cutter
arms. Each of the cams extends the same radial distance from the
center line of the wash-barrel which is coincident with the
longitudinal center line of the tool. The thickness of the cams,
i.e., in the transverse direction is such as to be matable with a
pocket formed in the interior surface of the respective cutter arm
as described more fully hereinafter.
Referring now particularly to FIGS. 4, 5 and 6 an illustrative
cutter arm is shown in detail and is shown in exploded perspective
in FIG. 6. Each of the cutter arms comprises an arm section 52, a
center block 53 and two identical side blocks 54 and 55. The arm
section 52 has an upper portion 52a of lesser transverse thickness
than the lower portion 52b upon which a cutter cone 56 is rotatably
mounted in the conventional manner. The lesser thickness of the
upper arm portion and greater thickness of the lower portion form
upwardly facing shoulders 56 and 57 on the side surfaces of the arm
section 52. A downwardly extending recess 58 is formed in the side
surface of the arm section extending downwardly from the shoulders
56 and 57. A side plate 55 has a mating section 59 matable with the
recess 58 and a downwardly facing shoulder 60 which bears against
the inner portion of the upwardly facing shoulder 57. When mated in
the recess the side block has its inner edge 61 coincident with the
inner surface 62 of the arm section 52. A fastening pin 62 extends
through aligned pin openings 63 to securely retain the side plate
in the recess such that it becomes an integral portion of the
cutter arm. The side plate 54 is comparable in construction and the
manner in which it is fastened to the opposite side of the cutter
arm. Thus, the side plates when affixed to the arm section of the
cutter arm assembly provide two bearing shoulders 64 and 65 on
opposite sides of the cutter arm assembly. The bearing shoulders 64
and 65 are radially outwardly facing and downwardly inclined when
the cutter assembly is mounted in the tool body. The shoulders 64
and 65 form bearing shoulders matable with load bearing shoulders
66 in the wall of the tool body 12 to thereby limit the amount of
radial outward travel of the cutter arm assemblies. Thus, referring
to FIGS. 4 and 5 it can be seen that as the cutter arm moves from
its collapsed position of FIG. 4 to its fully extended position of
FIG. 5, the bearing shoulders of the cutter arm assembly are moved
into bearing contact with the bearing shoulders 66 of the tool body
and the expansion of the cutter arm assembly is complete when the
bearing engagement is made. The radius of extension of the cutter
arms is thus limited through the shoulder 66 which is formed by a
replaceable element 30. The slope of the bearing shoulder 66 of the
tool body is constant whereas the replaceable side plates of the
cutter arm assembly will determine by their slope the amount of
extension allowable to the cutter arm assembly. For example, to
provide a cutter arm assembly with a greater degree of extension
than is shown in FIG. 5 the side plates of the cutter arm
assemblies are replaced with side plates having a greater degree of
inclination than those shown in the Figures. The greater degree of
inclination will allow more extension before the shoulder 64 comes
into bearing contact with the bearing shoulder 66. Conversely if
less extension is desired side plates 54 and 55 are affixed to the
cutter arm section 52 having a lesser inclination from horizontal
such that they come into bearing contact with the stop shoulders
when the cutter arm assembly has not been extended as far as is
shown in FIG. 5.
Referring now again particularly to FIG. 6, a pocket or recess 70
is formed in the inner surface of the arm section of the cutter
assembly symmetrically about the longitudinal center line of the
cutter arm. The width of the pocket is substantially equal to, but
greater than, the width of the cam which is matable with the
respective cutter arm assembly. The downward movement of the cam 48
causes the cutter arm assembly to be extended by engagement of the
camming surface 48 with the camming follower surface 71 of the
cutter arm. The camming follower surface 71 of the cutter arm is
provided by a center block 53 which is removably positioned within
the pocket 70 and retained therein by fastening pins 73 which
extend transversely through the cutter arm. The center block has a
cam follower surface 71 with a radially downward and inward
inclination which determines the extent to which the cutter arm is
extended by the cam mounted upon the wash-barrel during the
downward movement of the wash-barrel. As can be seen most clearly
in FIG. 5 the cam follower surface 71 has a downward inclination
which is substantially vertical at its fully extended position of
the cutter arm assembly and is thus matable with the vertical
caming surface of the cam 48.
By reference particularly to FIG. 5 it can be seen that the slope
of the cam follower surface 72 on the removable center block 53 and
the slope of the bearing shoulders 64 and 65 at opposite sides of
the cutter arm assembly are interrelated such that the cam follower
surface 71 and the cam surface 72 are in bearing engagement at the
same amount of radial extension at which the bearing shoulder 64 is
in bearing engagement with the stop shoulder 66 of the tool body.
For different amounts of radial extension it is necessary only to
replace the center block 53 and the two side blocks 54 and 55 on
the cutter arm assembly with center and side blocks having
different but related bearing shoulders and cam follower surfaces.
Accordingly, if a greater amount of extension is required, the cam
follower surface is of greater radially inward slope and conversely
if less extension is required the cam follower surface 71 has a
slope which more nearly approaches the vertical.
In the presently preferred embodiment of the present invention the
slope of cam follower surface 71 and the bearing shoulders 64 and
65 on two of the cutter assemblies is the same and is such that the
two cutter arms are extended to the full gauge to be underreamed
whereas the third cutter assembly arm has a lesser degree of slope
to the cam followers surface and a correspondingly lesser amount of
slope to the bearing shoulders such that when fully extended the
third cutter arm is at a lesser radius than the two full gauge
cutter arm assemblies.
Three fluid passages 80 extend longitudinally through the tool body
with fluid jets 81 positioned in the passages. The jet orifices are
located as close as practical above the cutter cones and each jet
orifice opens into a recess in the outer space of the body that is
formed by a downwardly and outwardly extending guide surface. These
jet guide surfaces 83 provide a convenient means for directing the
jet flow of pressurized fluid in a downwardly and outwardly
diverging stream. The fluid passages and jets are circumferentially
disposed in the tool body 12 intermediate the cutter arms 16, 18,
and 20. Thus when the tool is rotating during a cutting operation
to ream a portion of a hole out to the enlarged bore, as
illustrated in FIG. 5, each of the cutting cones is lead by a jet
stream which is directed generally into the region of the cutting
plane and in this manner the jet stream will provide a full high
velocity washing flow directly in the region of the cutting ledge
where it is most effective, the flow being unimpaired by any
structure on the underreamer or by the ledge itself.
The opening for the cutter arm assembly in the tool body is such
that the upper portion of the opening is matable with the upper
section of the arm and is expanded to a greater width to accomodate
the increased width of the lower portion of the cutter arm assembly
and finally terminates in a circular opening 84 through the wall of
the tool body into which the cutter cone is retractable. Thus, in a
retracted position as shown in FIGS. 1 and 4 the cutter arm
assemblies are generally within the overall radius of the tool body
and can be lowered into a bore hole having a diameter only slightly
greater than the diameter of the drill string.
In the inoperative or retracted position of the underreamer as it
is being lowered through the hole to a desired region of operation,
drilling fluid is not pumped through the drill string into the
cylinder 44 and the biasing force of the spring 50 will hold the
piston, wash-barrel, and cams in their uppermost position as
illustrated in FIGS. 1 and 4. In this inoperative or collapsed
condition of the underreamer the three cutter arms are held in
their retracted position by gravity and also by the spring bias
engagement of the cams against shoulders 86 in the respective
cutter arms.
When the tool is at the desired position in the hole, to commence
reaming the tool is rotated and drilling fluid is introduced under
pressure through the sub into the cylinder 44. Some of the drilling
fluid will pass on downwardly through the wash-barrel 38 and thence
through the hollow lower portion of the body 12 into the hole below
the underreamer and the flow of this fluid back upwardly around the
tool washes away the cuttings which are relatively free and which
are freed by the jet streams provided from the orifices 81.
Preferrably there is a constriction in the wash pipe which serves
to build up fluid pressure in the cylinder so as to more
effectively actuate the cutters and provide high pressure and
velocity to the jet streams from the orifices. The fluid pressure
forces the piston 42 downwardly from the position of FIG. 1 to the
position of FIG. 5. This in turn moves the wash-barrel and cams
downwardly so as to swing the respective cutter arms 16, 18 and 20
outwardly to their operative position.
When it is desired to change the underreaming diameter of the tool,
in accordance with the present invention it is necessary only to
remove the side plates and center plate from each of the cutter arm
assembly and replace them with a center plate and side places which
define a different fully extended position of the cutter arm
assemblies as described hereinbefore. Accordingly, by means of the
present invention the single tool body and plurality of cutter arm
assemblies can be utilized to underream holes to different gauges
by merely replacing the cam follower center plates and bearing
shoulder side plates of the cutter arm assemblies.
* * * * *