Wells – Above ground apparatus – With seal for reciprocating member
Reexamination Certificate
2003-02-14
2004-03-09
Tsay, Frank (Department: 3672)
Wells
Above ground apparatus
With seal for reciprocating member
C166S383000, C175S084000
Reexamination Certificate
active
06702012
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to removable subassemblies in sealing equipment. Specifically, the invention relates to removable subassemblies in oil field rotary drilling head assemblies.
2. Description of the Related Art
Drilling an oil field well for hydrocarbons requires significant expenditures of manpower and equipment. Thus, constant advances are being sought to reduce any downtime of equipment and expedite any repairs that become necessary. Rotating equipment is particularly prone to maintenance as the drilling environment produces abrasive cuttings detrimental to the longevity of rotating seals, bearings, and packing glands.
FIG. 1
shows an exemplary drilling rig
10
. The drilling rig
10
is placed over an area to be drilled and a drilling bit (not shown) is attached to sections of drill pipe
12
. Typically, a rotary turntable
14
rotates a drive member
16
, referred to as a kelly, which in turn is attached to the drill pipe
12
and rotates the drill pipe to drill the well. In some arrangements, a kelly is not used and the drill string is rotated by a drive unit (not shown) attached to the drill pipe itself. Typically, a mixture of drilling fluids, referred to as mud, is injected into the well to lubricate the drill bit (not shown) and to wash the drill shavings and particles from the drill bit and then return up through an annulus surrounding the drill pipe
12
and out the well through an outflow line
22
to a mud pit
24
. New sections of drill pipe
12
are added to the drill pipe in the well using a crane
26
and a block and tackle
28
to collectively form a drill string
30
as the well is drilled deeper to the desired underground strata
32
. A power unit
34
powers a control unit
36
and associated motors, pumps, and other equipment (not shown) mounted on a drilling platform
38
.
In many instances, the strata
32
produce gas or fluid pressure which needs control throughout the drilling process to avoid creating a hazard to the drilling crew and equipment. To seal the mouth of the well, one or more blow out preventers (BOP) are mounted to the well and can form a blow out preventer stack
40
. An annular BOP
42
is used to selectively seal the lower portions of the well from a tubular body
44
which allows the discharge of mud through the outflow line
22
. A rotary drilling head
46
is mounted above the tubular body
44
and is also referred to as a rotary blow out preventer. An internal portion of the rotary drilling head
46
is designed to seal around a rotating drill pipe
30
and rotate with the drill pipe by use of a internal sealing element, referred to as a packer (not shown), and rotating bearings (also not shown) as the drill pipe is axially and slidably forced through the drilling head
46
. However, the packer wears and occasionally needs replacement. Typically, the drill string or a portion thereof is pulled from the well and a crew goes below the drilling platform
38
and manually disassembles the rotary drilling head
46
. Typically, a crane
26
is used to lift the rotary drilling head
46
which can weigh thousands of pounds. Because of the size of the drilling head
46
, portions of the drilling platform
38
and equipment are disassembled to allow access to the drilling head and to remove the drilling head from the BOP stack
40
. The drilling head
46
is replaced or reworked and crew goes below the drilling platform to reassemble the drilling head to the BOP stack
40
and operation is resumed. The process is time consuming and can be dangerous.
Prior efforts have sought to reduce the complexity of the drilling head replacement. For example,
FIG. 2
is a schematic cross sectional view of a rotary blow out preventer, similar to the embodiments shown in U.S. Pat. No. 5,848,643, which is incorporated herein by reference. A rotating spindle assembly
48
is disposed within a non-rotating spindle assembly
50
, which in turn, is disposed within a body
52
and held in position by lugs
54
. To remove the entire non-rotating and rotating spindle assembly from the body
52
, lugs
54
are rotated in horizontal grooves
56
and then lifted upwardly through vertical slots
58
in a “twist and lift” motion. However, the assembly can weigh about 1,500 to about 2,000 pounds and still requires use of extra lifting equipment such as the crane
26
. In addition, disassembly of the drilling platform
38
is necessary to provide access and requires manual efforts by the drilling crew.
Similarly, U.S. Pat. No. 3,934,887, incorporated herein by reference, discloses a BOP body having an assembly of a lower stationary housing
22
and an upper stationary housing
24
. The upper stationary housing
24
houses a stationary tapered bowl
60
, a rotating bowl
62
disposed inwardly of the tapered bowl, and bearings
66
,
68
disposed between the stationary bowl and rotating bowl. A stripper
40
is connected to the rotating bowl
62
. A clamp
28
retains the assembly of the stationary tapered bowl
60
, the rotating bowl
62
, the bearings
66
,
68
, and associated equipment to the upper stationary housing
24
. By unclamping the clamp
28
, the entire assembly may be removed from the BOP body. However, the removable assembly is of such size and weight with the result that crews are needed below the drilling platform and lifting equipment is necessary to lift the assembly from the BOP body.
FIG. 3
is a schematic cross sectional view of another rotary BOP
60
, similar to the embodiments disclosed in U.S. Pat. No. 4,825,938, incorporated herein by reference. To avoid removing the entire rotary BOP, the reference discloses a pneumatically actuated series of “dogs”
64
which engage a groove
66
on a retainer collar
68
, referred to in that disclosure as “massive”. By actuating pneumatic cylinders
70
to rotate the dogs
64
away from the groove
66
, the “massive” retainer collar
68
, the stinger
72
, stinger flange
74
, a stripper rubber
76
, and associated bearing surfaces
78
,
80
and
82
can be removed and access gained to the inner structures to repair or replace the stripper rubber
76
. This device is similar to the preceding references in that both rotating and non-rotating portions are removed, which add weight and size to the assembly that is removed.
Another challenge to the rotary drilling head maintenance is bearing life. In a rotary BOP, bearings are used to reduce the friction between the fixed portions of the drilling head and the rotating drill string with rotating portions of the drilling head. As shown in
FIG. 2
, the typical assembly includes a lower bearing
84
and an upper bearing
86
axially disposed between a rotating portion
48
and a non-rotating portion
50
of the rotary BOP
50
. The bearings are tightened in position, referred to as pre-loading the bearing, by typically turning a threaded bearing retainer
88
until the bearings are pre-loaded to a desired level. As the bearings wear or otherwise change, the loading changes. The BOP must be disassembled, the bearing readjusted, and the BOP reassembled. Otherwise, the bearings can fail prematurely, causing downtime for the drilling operations. Typically, the bearing retainer is directly inaccessible after assembly into the drilling head and the drilling head must be at least partially disassembled for readjustment.
There remains a need for an apparatus and method for decreasing the downtime in drilling an oil well by decreasing the time required for removal and replacement/repair of the packer and decreasing the time required to adjust the bearing loading.
SUMMARY OF THE INVENTION
The present invention generally provides an apparatus and method for sealing about a member inserted through a rotatable sealing element disposed in a drilling head. The rotatable sealing element is removable separately from non-rotating and/or other rotating portions. More specifically, the invention allows a rotatable packer in a drilling head to be removable separately from non-rotating and/or other rotating portions of
Bailey Thomas F.
Luke Mike A.
Moser, Patterson & Sheridan L.L.P.
Tsay Frank
Weatherford / Lamb, Inc.
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