Boring or penetrating the earth – With tool drive prime mover or above-ground mechanical... – Rotary drive for a relatively advancing tool
Reexamination Certificate
2000-01-10
2002-03-12
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
With tool drive prime mover or above-ground mechanical...
Rotary drive for a relatively advancing tool
C166S084300
Reexamination Certificate
active
06354385
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention generally relates to rotary drilling heads for the oil industry and more particularly to a rotary drilling head that includes a diamond enhanced bearing assembly which can be retrieved through the rotary table of the drill rig and which increases rotational drilling speeds and lengthens service intervals.
Referring initially to
FIG. 1
, there is shown a conventional rig
10
for rotating a drill bit
12
on the end of a drill string
14
for drilling a well bore
16
. The drilling rig
10
includes a rotary table
18
located on the floor
20
of rig
10
for transmitting torque to the drill string
14
. The drill string
14
extends through a blowout preventer (“BOP”) stack located beneath the rig floor
20
and includes a kelly
22
at its upper end and a plurality of drill pipes
24
including a plurality of drill collars
26
connected at it lower end to the drill bit
12
. The drill string
14
transmits rotational and axial movements to the drill bit
12
for drilling the well bore
16
.
Referring now additionally to
FIGS. 2 and 3
, there is shown a typical kelly
22
having threaded rotary shouldered connections
28
at its top and bottom and a center section
30
with a polygonal outer cross section. The rotary table
18
includes a clearance hole, typically 17.5″ or 22.5″ in diameter, for housing a drive bushing that corresponds to the polygonal geometry
30
of kelly
22
for applying torque to kelly
22
. Kelly
22
in turn transmits torque to the drill string
14
and bit
12
at the bottom of well bore
16
.
Drilling fluids, often referred to as drilling mud, are pumped downward through the flowbore of the drill string
14
under high pressure, through drill bit
12
and then returns upwardly via the annulus
44
formed between well bore
16
and drill string
14
to remove the cuttings to the surface. The returning mixture of drilling fluids and cuttings is diverted beneath the rig floor
20
to a mud reservoir by means of a device commonly referred to in the industry as a rotary drilling head assembly
46
.
A rotary drilling head assembly
46
is typically mounted below the floor
20
of the drilling rig
10
on the top of the BOP stack to redirect the drilling fluid returning from the well bore
16
and to allow rotation and deployment of the drill string
14
through the rotary table
18
. During normal drilling operations, the blowout preventers are maintained in the “open” position, leaving only the rotary drilling head to divert the returning pressurized drilling fluids away from the rig
10
.
FIG. 2
illustrates a typical prior art rotary drilling head assembly
46
having an outer stationary housing or bowl
48
and an inner drive ring
50
with a bearing assembly
52
disposed in between allowing drive ring
50
to rotate within bowl
48
. Outer bowl
48
includes a flange
54
for mounting the assembly
46
to the BOP stack and a flow diverter port or outlet
56
having a flange
58
for the attachment of a pipe extending to the mud reservoir. Assembly
46
further includes an inner stripper assembly
60
slidably received within drive ring
50
and connected to the upper end of drive ring
50
by a retaining clamp
62
allowing stripper assembly
60
to rotate with inner drive ring
50
. Stripper assembly
60
includes an outer housing
66
bonded by a rubber insert
68
to inner drive bushing
32
. The lower end of outer housing
66
is bolted to a flange
64
which is bonded onto stripper rubber
42
. A primary non-rotary seal
70
and a secondary non-rotary seal
72
serve to statically seal the outside of stripper assembly
60
from bearing assembly
52
and rig floor
20
. Bearing assembly
52
includes an upper set of roller bearings
74
and a lower set of roller bearings
76
. Upper and lower roller bearings
74
,
76
, respectively, are separated axially by a bearing spacer
78
. An external pressurized oil system lubricates the bearings
74
,
76
through hydraulic quick connects
80
, and is maintained by rotary lubrication bearing seal members
82
above and below the bearing assembly
52
. Bearing seal members
82
are stationary even while there is full 360° rotation of stripper assembly
60
and drive ring
50
within outer bowl
48
. Since the clamp assembly clamps the rotating side of the bearing assembly, the clamp assembly must also rotate.
The rotary drilling head assembly
46
counteracts forces due to the upward pressure from the returning drilling fluids, the radial wobble of the drill string
14
, and the downward engagement forces of drill string
14
. The bearing assembly
52
of a conventional drilling head assembly
46
includes tapered roller bearings to enable rotation of the drive ring
50
with respect to the outer bowl
48
and to overcome these various forces. Previous designs utilize two horizontally opposed tapered roller bearings
74
,
76
spaced apart axially to handle the loads encountered during drilling operations, as shown in FIG.
2
. Because the design of tapered roller bearings allows them to counteract loads in both the thrust and radial directions, the lower set of bearings
76
encounters the upward annular fluid forces and radial wobble forces simultaneously, while the upper set of bearings
74
encounters the downward drill string and radial wobble forces. This arrangement allows radial and axial forces to be countered regardless of the direction that they may be acting upon rotary drilling head
46
.
During operation, individual sections of drill pipe
24
are connected to the upper end of drill string
14
with their upper end attached to the lower end of kelly
22
. The new section of drill pipe
24
is then lowered through the stripper assembly
60
. As the rotary table
18
rotates, rotary table
18
rotates kelly
22
and thus kelly bushing
34
disposed within drive bushing
32
and around kelly
22
. As shown in
FIG. 3
, drive bushing
34
includes an inside cutout geometry
36
, an outside geometry
38
, and a split cut
40
. Inside geometry
36
corresponds to polygonal section
30
of kelly
22
, and outside geometry
38
corresponds to a drive bushing seat
32
of a stripper assembly
60
hereinafter described. Split cut
40
facilitates the assembly and disassembly of drive bushing
34
about kelly
22
. Drive bushing
34
is slidably engaged both about polygonal section
30
of kelly
22
and within the corresponding geometry of drive bushing seat
32
. Kelly bushing
34
thereby allows kelly
22
to pass through the rotary drilling head
46
while also transmitting torque from the rotary table
18
to the drill string
14
and stripper assembly
60
of the drilling head
46
simultaneously.
Stripper rubber
42
seals with drill string
14
as the drill string
14
moves axially through stripper assembly
60
. Kelly
22
, drill pipes
24
, and threaded pipe connections
28
therebetween may be of many different sizes and shapes and yet must pass through stripper rubber
42
. Therefore, the stripper rubber
42
of rotary drilling head assembly
46
must be flexible to sealingly engage and accommodate the various sizes of the components of drill string
14
. Rubber stripper
42
also diverts the drilling mud through side port outlet
56
of drilling head
46
in maintaining the sealing engagement with drill string
14
.
From time to time the stripper assembly
60
must be removed to replace the stripper rubber
42
. This requires disconnecting the retaining clamp
62
to release outer housing
66
of stripper assembly
60
. When the outer housing
66
is larger than the opening through the rotary table
18
, the stripper assembly
60
must be removed from beneath the rig floor
20
which is expensive.
Further, when service intervals dictate, the bearing assembly
52
must be replaced. This requires that the drilling head assembly
46
be dismantled and the bearing assembly
52
lifted out of outer bowl
48
. This is done by removing bearing retaining screws
84
that secure bearing assembly
52
to outer barrel
48
. Once removed, be
Allison Glenn L.
Ford Garland Vance
Pfannenstiel Gary
Shelton Jaye M.
Conley & Rose & Tayon P.C.
Pezzuto Robert E.
Smith International Inc.
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