U.S. patent number RE38,249 [Application Number 09/219,475] was granted by the patent office on 2003-09-16 for rotating blowout preventer and method.
This patent grant is currently assigned to James D. Brugman. Invention is credited to James D. Brugman, Paul L. Tasson.
United States Patent |
RE38,249 |
Tasson , et al. |
September 16, 2003 |
Rotating blowout preventer and method
Abstract
The rotatable blowout preventer 10 comprises a stationary outer
housing 12 and a rotatable inner housing 38 having a curved surface
42 thereon defining a portion of a sphere. An annular packer
assembly 46 includes spherical packer elements for sliding
engagement with the curved surface of the inner housing such that a
packer assembly may seal against various sized tubulars. A lower
rotary seal 98 between a piston 56 and the outer housing 12 is
exposed to the differential between pressurized hydraulic fluid and
the well pressure within a lower end of the bore 32 within the
outer housing. A flow restriction member 114 between the rotatable
inner housing and the outer housing reduces fluid pressure
downstream from the flow restriction to less than 40% of the
upstream pressure. The upper rotary seal 120 is open to atmospheric
pressure and is subjected to this reduced pressure. Improved
techniques are provided for passing hydraulic fluid through the
blowout preventer for both closing and opening the sealing assembly
46.
Inventors: |
Tasson; Paul L. (Spring,
TX), Brugman; James D. (Spring, TX) |
Assignee: |
Brugman; James D. (Houston,
TX)
|
Family
ID: |
24043258 |
Appl.
No.: |
09/219,475 |
Filed: |
December 22, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
513436 |
Aug 10, 1995 |
05588491 |
Dec 31, 1996 |
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Current U.S.
Class: |
166/383; 166/387;
166/84.3; 166/85.4; 277/324 |
Current CPC
Class: |
E21B
33/085 (20130101) |
Current International
Class: |
E21B
33/08 (20060101); E21B 33/02 (20060101); E21B
033/06 (); E21B 033/08 () |
Field of
Search: |
;166/84.3,85.4,84.4,88.4,379,387 ;175/195 ;251/1.1,1.2
;277/324,326 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Design #5; Design Concept Shown at May '94 Offshore Technology
Conference, Houston, Texas. .
"Product Development of Pressure Control While Drilling" Shaffer,
disclosed to potential customers in the U.K. in Apr. '94. .
C. W. Williams, Jr., et al: "History and Development of a Rotating
Blowout Preventer," IADC/SPE 23931 (Society of Petroleum
Engineers), pp. 757-773. .
1970-1971 Brochure--Reagan Forge & Engineering Co., "Reagan
Blowout Preventers". 3 pgs..
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Primary Examiner: Tsay; Frank
Attorney, Agent or Firm: Browning Bushman, P.C.
Claims
What is claimed is:
1. A rotatable blowout preventer for .[.use in a hydrocarbon
recovery operation.]. .Iadd.sealing pressure in a well.Iaddend.
including a tubular member passing through the blowout preventer,
the rotatable blowout preventer assembly comprising: a stationary
outer housing defining a bore therein for receiving the tubular
member, the outer housing have a central axis generally concentric
with an axis of the tubular member, and the outer housing including
a fluid .[.closing.]. .Iadd.input .Iaddend.port and a fluid output
port therein; an inner housing rotatable within the outer housing
.[.and having an inner curved surface thereon substantially defined
by a portion of a sphere having a center substantially adjacent the
central axis of the bore.]. ; an annular sealing assembly supported
within the inner housing for sealed engagement with the tubular
member, .[.a sealing assembly including a plurality of rigid
elements circumferentially arranged about the bore of the outer
housing, each rigid element having an outer surface for sliding
engagement with the inner curved surface of the inner housing,
and.]. the sealing assembly including a resilient member for sealed
engagement with the tubular member; .[.a rotatable piston axially
movable within the outer housing in response to pressurized fluid
in the fluid closing port for causing both axial and radial
movement of the annular sealing assembly;.]. a lower rotary seal
.[.between the piston and a lower portion of the stationary outer
housing.]. for sealing pressurized fluid within the stationary
outer housing from a lower end of the bore in the outer housing; a
flow restriction member .[.between the rotatable inner housing and
an upper portion of the stationary outer housing.]. for reducing
fluid pressure downstream of the flow restriction member to less
than 40% of the pressure upstream from the flow restriction member;
and an upper rotary seal .[.between the rotatable inner housing and
the upper portion of the stationary outer housing and.]. downstream
from the flow restriction member for sealing the reduced pressure
fluid within the outer housing from an upper end of the bore in the
outer housing.
2. The rotary blowout preventer as defined in claim 1, further
comprising: an inner housing bearing for rotatably guiding rotation
of the inner housing relative to the outer housing, the inner
housing bearing being spaced radially outward from the flow
restriction member and within a plane perpendicular to the central
axis of the bore and inclusive of the flow restriction member.
3. The rotary blowout preventer as defined in claim 1, wherein the
flow restriction member is selected from the material consisting of
bronze, steel, and ceramic.
4. The rotary blowout preventer as defined in claim 1, further
comprising: a restriction member bearing for guiding rotation of
the flow restriction member relative to the inner housing while
maintaining a substantially uniform gap between a radially inward
surface of the flow restriction member and a radially outward
surface of the rotatable inner housing.
5. The rotary blowout preventer as defined in claim 1, further
comprising: the flow restriction member is spaced between a
radially outward cylindrical surface of the rotatable inner housing
and a radially inward cylindrical surface of the outer housing; and
a spacing member for radially spacing the flow restriction member
relative to the inner housing to maintain a substantially uniform
gap between a radially inward surface of the flow restriction
member and the radially outward surface of the rotatable inner
housing, such that eccentricity between the inner housing and the
outer housing varies a radial spacing between a radially outer
surface of the flow restriction member and the radially inward
surface of the outer housing.
6. The rotary blowout preventer as defined in claim 1, wherein:
each of the lower rotary seal and the upper rotary seal have a
diameter less than 20% greater than a diameter of the bore in the
stationary outer housing.
7. The rotary blowout preventer as defined in claim 1, further
comprising: a fluid flow path between the fluid .[.closing.].
.Iadd.input .Iaddend.port and the fluid output port, the fluid flow
path passing .[.by.]. .Iadd.fluid to .Iaddend.the lower rotary
seal, .[.radially outward of the piston, radially outward of the
rotatable inner housing, past.]. .Iadd.then through .Iaddend.the
flow restriction member, .[.past.]. .Iadd.then to .Iaddend.the
upper rotary seal, and then through the fluid output
.Iadd.port.Iaddend..
8. The rotary blowout preventer as defined in claim 1, further
comprising: .Iadd.a rotatable piston axially movable within the
outer housing in response to pressurized fluid in the fluid closing
port for causing both axial and radial movement of the annular
sealing assembly;.Iaddend. a rotatable adapter ring radially
outward of the piston; an upper adapter seal for sealed engagement
between the piston and the adapter ring; a lower adapter seal for
sealed engagement between the piston and the adapter ring; an
opening chamber between the piston and the adapter ring and between
the upper and lower adapter seals for receiving pressurized fluid
from a fluid opening port in the outer housing to move the annular
sealing assembly to an open position; and a bearing member for
guiding rotation of the adapter ring with respect to the outer
housing, the bearing member and the adapter ring each having a
metal surface thereon moved into engagement by pressurized fluid in
the fluid opening port for substantially restricting fluid flow
from the fluid opening port to the fluid closing port.
9. A rotatable blowout preventer system for use in a hydrocarbon
recovery operation including a tubular member passing through the
blowout preventer, the rotatable blowout preventer system
comprising: a stationary outer housing defining a bore therein for
receiving the tubular member, the outer housing having a central
axis generally concentric with an axis of the tubular member, and
the outer housing including a fluid closing port, a fluid opening
port, and a fluid output port therein; an inner housing rotatable
within the outer housing; an annular sealing assembly supported
within the inner housing for sealed engagement with the tubular
member; a pump for generating pressurized hydraulic fluid; a
control valve for selectively controlling flow of the pressurized
hydraulic fluid to one of the fluid closing port and fluid opening
port; a rotatable piston axially movable within the outer housing
in response to pressurized fluid in the fluid closing port for
causing radially inward movement to the annular sealing assembly; a
rotatable adapter ring radially outward of the piston; an upper
adapter seal for sealed engagement between the piston and the
adapter ring; a lower adapter seal for sealed engagement between
the piston and the adapter ring; an opening chamber between the
piston and the adapter ring and between the upper and lower seals
for receiving pressurized fluid from the fluid opening port to move
the piston and the annular sealing assembly to an open position; a
lower rotary seal between the piston and a lower portion of the
stationary outer housing for sealing pressurized fluid within the
stationary outer housing from a lower end of the bore in the outer
housing; a flow restriction member between the rotatable inner
housing and an upper portion of the stationary outer housing for
reducing fluid pressure downstream of the flow restriction member;
and a upper rotary seal between the rotatable inner housing and the
upper portion of the stationary outer housing and downstream from
the flow restriction member for sealing the reduced pressure fluid
within the outer housing from a upper end of the bore in the outer
housing.
10. The rotary blowout preventer system as defined in claim 9,
further comprising: an inner housing bearing for rotatably guiding
rotation of the inner housing relative to the outer housing, the
inner housing bearing being spaced radially outward from the flow
restriction member and within a plane perpendicular to the central
axis of the bore and inclusive of the flow restriction member.
11. The rotary blowout preventer system as defined in claim 9,
further comprising: a restriction member bearing for guiding
rotation of the flow restriction member relative to the inner
housing while maintaining a substantially uniform gap between a
radially inward surface of the flow restriction member and a
radially outward surface of the rotatable inner housing.
12. The rotary blowout preventer system as defined in claim 9,
further comprising: the flow restriction member is spaced between a
radially outward cylindrical surface of the rotatable inner housing
and a radially inward cylindrical surface of the outer housing; and
a spacing member for radially spacing the flow restriction member
relative to the inner housing to maintain a substantially uniform
gap between a radially inward surface of the flow restriction
member and the radially outward surface of the rotatable inner
housing, such that eccentricity between the inner housing and the
outer housing varies a radial spacing between a radially outer
surface of the flow restriction member and the radially inward
surface of the outer housing.
13. The rotary blowout preventer system as defined in claim 9,
wherein: a lower seal cartridge ring for supporting the lower
rotary seal thereon; an upper seal cartridge ring for supporting
the upper rotary seal thereon; and each of the lower rotary seal
and the upper rotary seal have a diameter less than 20% greater
than a diameter of the bore in the stationary outer housing.
14. A rotary blowout preventer system as defined in claim 9,
further comprising: a lower seal cartridge ring for supporting the
lower rotary seal thereon, the lower cartridge ring having a
passageway therethrough; an upper seal cartridge ring for
supporting the upper rotary seal thereon, the upper cartridge ring
having a passageway therethrough; and a fluid flow path between the
fluid closing port and the fluid output port, the fluid flow path
passing through the passageway in the lower seal cartridge ring,
radially outward of the piston, radially outward of the rotatable
inner housing, past the flow restriction member, through the
passageway in the upper seal cartridge ring, and then through the
fluid output port.
15. The rotary blowout preventer system as defined in claim 9,
further comprising: the adapter ring being axially movable in
response to fluid pressure in the fluid opening port to
substantially restrict fluid flow from the fluid opening port to
the fluid closing port.
16. A method of controlling actuation of a rotatable blowout
preventer for .[.for use in a hydrocarbon recovery operation.].
.Iadd.sealing pressure in a well .Iaddend.including a tubular
member passing through the blowout preventer, the rotatable blowout
preventer including a stationary outer housing defining a bore
therein for receiving the tubular member, an inner housing
rotatable within the outer housing, an annular sealing assembly
supported within the inner housing for sealed engagement with the
tubular member, .[.a piston movable within the outer housing for
causing radial movement of the annular sealing assembly,.]. and a
fluid .[.closing.]. .Iadd.input .Iaddend.port and a fluid output
port in the outer housing for passing pressurized fluid .[.to the
piston.]. .Iadd.through the rotatable blowout preventer.Iaddend.,
the method comprising: providing a lower rotary seal .[.between the
piston and a lower portion of the outer housing.]. for sealing
pressurized fluid within the stationary outer housing from a lower
end of the bore in the outer housing; providing a flow restriction
.[.between the rotatable inner housing and an upper portion of the
stationary outer housing.]. for reducing fluid pressure downstream
of the flow restriction member to less than 40% of the pressure
upstream from the flow restriction; and providing an upper rotary
seal .[.between the rotatable inner housing and an upper portion of
the stationary outer housing and.]. the downstream from the flow
restriction for sealing the reduced pressure fluid within the
stationary outer housing from an upper end of the bore in the outer
housing.
17. The method as defined in claim 16, further comprising:
providing an inner housing bearing for rotatably guiding rotation
of the inner housing relative to the outer housing; and spacing the
inner housing bearing radially outward from the flow restriction
and within a plane inclusive of the flow restriction.
18. The method as defined in claim 16, further comprising: guiding
rotation of the flow restriction relative to the inner housing
while maintaining a substantially uniform gap between a radially
inward surface of the flow restriction and a radially outward
surface of the rotatable inner housing.
19. The method as defined in claim 16, further comprising: forming
a flow path between the fluid .[.closing.]. .Iadd.input
.Iaddend.port and the fluid output port, the flow path passing
.[.by.]. .Iadd.fluid to .Iaddend.the lower rotary seal, .[.radially
outward of the piston, radially outward of the rotatable inner
housing, past.]. .Iadd.through .Iaddend.the flow restriction,
.[.past.]. .Iadd.to .Iaddend.the upper rotary seal, and then
through the fluid output port.
20. The method as defined in claim 16, further comprising:
.Iadd.providing a piston removable within the outer housing for
causing radial movement of the annular sealing assembly;.Iaddend.
providing a rotatable adapter ring radially outward of the piston;
providing an upper adapter seal for sealed engagement between the
piston and the adapter ring; providing a lower adapter seal for
sealed engagement between the piston and the adapter ring; forming
an opening chamber between the piston and the adapter ring and
between the upper and lower adapter seals; passing pressurized
fluid through a fluid opening port in the outer housing to move the
piston and the annular packer assembly to an open position; and
substantially restricting fluid flow from the fluid opening port to
the fluid closing port downstream from the opening chamber.
.Iadd.
21. The rotatable blowout preventer as defined in claim 1; the
inner housing having an inner curved surface thereon substantially
defined by a portion of a sphere having a center substantially
adjacent the central axis of the bore; and the annular sealing
assembly includes that plurality of rigid elements
circumferentially arranged about the bore of the outer housing,
each rigid element having an outer surface of a sliding engagement
with the inner curved surface of the inner
housing..Iaddend..Iadd.
22. The rotary blowout preventer as defined in claim 21, further
comprising: a rotatable piston axially moveable within the outer
housing in response to pressurized fluid for causing both axially
and radially movement of the annular sealing
assembly..Iaddend..Iadd.
23. The rotary blowout preventer as defined in claim 22, wherein
the lower rotary seal acts between the piston and a lower portion
of the stationary outer housing..Iaddend..Iadd.
24. The sealing assembly as defined in claim 1, wherein the upper
rotary seal is positioned between the rotatable inner housing and
an upper portion of the stationary outer
housing..Iaddend..Iadd.
25. The rotary blowout preventer as defined in claim 1, wherein the
flow restriction member is spaced between a cylindrical surface on
the stationary upper housing and another cylindrical surface on the
rotatable inner housing..Iaddend..Iadd.
26. The rotary blowout preventer as defined in claim 1, wherein an
inner surface of the annular sealing preventer is configured for
closing off flow of fluid through the annular sealing assembly when
no tubular member passes through the blowout
preventer..Iaddend..Iadd.
27. The method as defined in claim 16, wherein the upper rotary
seal is spaced between the rotary inner housing and an upper
portion of the stationary outer housing..Iaddend..Iadd.
28. The method as defined in claim 16, further comprising:
positioning the flow restriction between the cylindrical surface on
the stationary upper housing and another cylindrical surface on the
rotary inner housing..Iaddend..Iadd.
29. The method as defined in claim 16, further comprising: closing
the annular inner sealing assembly to prevent fluid from passing
therethrough when the tubular member does not pass through the
blowout preventer..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates to blowout preventers and, more
particularly, relates to a rotating blowout preventer with
spherical packing elements for use in hydrocarbon recovery
operation. The blowout preventer of this invention is able to
reliably withstand high pressure while maintaining sealed
engagement with a tubular rotating at relatively high speeds, and
also may be used to seal with a non-rotating tubular.
BACKGROUND OF THE INVENTION
Rotary blowout preventers for oil well drilling operations have
existed for decades. U.S. Pat. No. 3,492,007 discloses a blowout
preventer (BOP) for sealing well pressure about a rotating kelly or
other production tool. U.S. Pat. No. 3,561,723 discloses a blowout
preventer designed to prevent fluid from escaping from the well
while the pipe string is either rotating or stationary. U.S. Pat.
No. 4,098,341 discloses a rotating blowout preventer which is
supplied with pressurized hydraulic fluid to lubricate and cool
bearings within the BOP.
U.S. Pat. No. 4,378,849 discloses a blowout preventer with a
mechanically operated relief valve to release high pressure surges
in the annulus between the casing and the drill pipe sealed by the
BOP packing. U.S. Pat. No. 4,383,577 discloses a rotating drilling
head assembly which provides for the continuous forced circulation
of oil to lubricate and cool thrust bearings within the assembly. A
technique for fluidly connecting an outlet port of a BOP and an
inlet of a choke manifold is disclosed in U.S. Pat. No. 4,618,314.
The fluid may be injected into the blowout preventer for pressure
testing and for charging the equipment with a desired fluid.
U.S. Pat. No. 5,178,215 discloses a rotary blowout preventer with a
replaceable sleeve having a plurality of grippers therein. The
blowout preventer disclosed in the '215 patent utilizes an inner
packer which is responsive to hydraulic pressure to act against a
sleeve which engages the drill pipe. The hydraulic fluid pressure
which causes radial movement of the inner packer is sealed within
the body of the BOP by seal assemblies which must withstand a
pressure differential in excess of the difference between the well
pressure and atmospheric pressure.
Improvements in rotating blowout preventers are required so that
the blowout preventer may reliably withstand higher pressures, such
as the high pressure commonly associated with underbalanced
drilling. Underbalanced drilling occurs when the hydrostatic head
of the drilling fluid is potentially lower than that of the
formation being drilled. Underbalanced drilling frequently
facilitates increased hydrocarbon production due to reduced
formation damage, and results in both reduced loss of drilling
fluids and reduced risk of differential sticking.
The disadvantages of the prior art are overcome by the present
invention, and an improved blowout preventer and method of
operating a blowout preventer are hereinafter disclosed. The
blowout preventer is able to withstand high pressure while
maintaining sealed engagement with a tubular rotating at relatively
high speeds, and may also be used to seal with a non-rotating
tubular.
SUMMARY OF THE INVENTION
The rotating blowout preventer of the present invention may be
compatible with either kelly or top drive drilling systems. The
spherical sealing assembly is capable of being used to strip
tubulars and oilfield tubular connections, and will reliably seal
with different diameter tubulars. The seal assembly may also
maintain high pressure integrity when the tubular passing through
the assembly is not rotating. Further, the spherical sealing
assembly may seal off a well bore when no tubular is passing
through the sealing assembly.
The rotating blowout preventer (RBOP) of the present invention is
capable of reliable operation when the pressure differential
between the well bore and atmosphere is in excess of 2000 psi and
while the tubular is rotating at speeds of up to 200 rpm. The unit
may also function as a non-rotating annular BOP with working
pressure of up to 5000 psi. The assembly includes the ability for a
complete shutoff of the empty bore at up to 2500 psi.
The spherical sealing element is actuated in response to axial
movement of a fluid pressure piston. In order to minimize the
diameter of the rotating seals, no rotating seals are provided on
the outside diameter of the piston when applied fluid pressure
causes sealing engagement of the spherical sealing elements. The
piston closing force is generated by fluid pressure acting on the
relatively large cross-sectional rod area of the piston between the
lower seal and an upper adapter ting seal. The comparatively small
cross-sectional flange area of the piston between the upper and
lower adapter ring seals is used to open the RBOP. The piston and
the adapter ring rotate together, and accordingly seals between
these components are non-rotating.
The RBOP assembly includes a lower rotary seal between the
stationary lower housing and the inner sleeve of the rotating
piston. Closing pressure from the hydraulic supply to the RBOP is
maintained at a selected value above the well bore pressure, so
that this lower rotary seal is only exposed to a pressure
differential of this selected value, e.g., from 200 psi to 500 psi.
The upper rotary seal acts between the stationary upper housing and
the rotating inner housing. A significant pressure drop is achieved
across a restrictive flow bushing upstream of the upper rotary
seal. The restrictive bushing floats radially with the rotating
inner housing to accommodate eccentricity without generating
excessive friction. The piston effect of the restrictive bushing
prevents fluid flow between the bushing and the stationary upper
housing and then above the bushing to the fluid outlet port. The
hydraulic fluid thus passes between the outside diameter of the
rotating inner housing and the inside diameter of the restrictive
bushing to maintain a substantially uniform gap between the bushing
and the inner housing. This substantially uniform gap may be
maintained by a restrictive bushing radial bearing. The pressure of
the hydraulic fluid drops significantly and at a substantially
constant amount across the bushing, so that pressure acting on the
upper rotary seal is continually only slightly greater than
atmospheric pressure. Accordingly, the elastomeric upper rotary
seal reliably isolates the low pressure hydraulic fluid from the
environment.
The upper rotary seal and the lower rotary seal preferably have a
diameter as small as practical, and also preferably have
substantially the same diameter to balance the forces acting on the
rotary components of the assembly. Pressurized fluid to the RBOP is
provided in a closed loop system since fluid continuously flows
past the restrictive flow bushing to maintain the desired low
pressure drop across the upper rotary seal. The flow path of
hydraulic fluid through the RBOP when the sealing elements engage
the rotating tubular is past the lower rotary seal, then radially
outward of the piston and the sealing assembly, past an inner
housing thrust bearing, then past the restrictive flow bushing. The
thrust bearing is spaced radially outward of and axially within the
same plane as the restrictive flow bushing to reduce the axial
height of the RBOP. The restrictive flow bushing preferably fits
between cylindrical surfaces on the stationary upper housing and
the rotary inner housing which each have an axis concentric with
the central axis of the RBOP.
An opening chamber is formed between the upper and lower adapter
ring seals and between the adapter ring and the piston. Although no
outer rotating elastomeric seals are provided on the piston, the
opening pressure to the RBOP is substantially restricted from
passing beneath the piston by a metal-to-metal restriction between
the adapter ring and an adapter ring bearing race. Since the
sealing assembly is not rotating when the RBOP is opened, this
metal-to-metal restriction need only be a static restriction.
It is an object of the present invention to provide an improved
rotary blowout preventer which utilizes a spherical sealing
assembly. A further object of the present invention to reduce to
pressure applied to the upper rotary seal of an RBOP by providing a
flow restrictive member upstream of the upper rotary seal, and
continuously circulating fluid past the flow restrictive
member.
It is a feature of the present invention that hydraulic fluid
supplied to the RBOP for actuating the sealing assembly is first
directed past the lower seal assembly, then in a path radially
outward of both the actuating piston and the sealing assembly, then
past an inner housing thrust bearing, and finally past a
restrictive member which reduces the differential pressure applied
to the upper seal assembly. It is a further feature of the present
invention that the thrust member is radially outward of and in
substantially the same horizontal plane as the flow restrictive
member to reduce the height of the RBOP. A further feature of the
invention is that the flow restrictive member resides between the
cylindrical surfaces each having an axis substantially concentric
with a central axis of the RBOP. Still another feature of the
invention is the ability to reliably open the RBOP in response to
fluid pressure applied to the RBOP and without providing a dynamic
elastomeric seal on the outer diameter of the piston.
It is an advantage of the present invention that the rotating
blowout preventer may also reliably seal under high pressure
against a non-rotating tubular passing through the RBOP. The
sealing assembly of the RBOP is able to reliably seal against
different sized tubular members or against a non-tubular member
passing through the RBOP. The sealing assembly further has the
ability for a complete shutoff of the well with no tubular passing
through the RBOP. The RBOP assembly is capable of being used to
strip various tubulars and oilfield tubular connections. The
assembly may be used with either kelly or top drive drilling
systems.
These and further objects, features, and advantages of the present
invention will become apparent in the following detailed
description, wherein reference is made to the figures in the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial view, partially in cross-section, of a
rotating blowout preventer according to the present invention. The
side right of the centerline is shown in the open position, and the
side left of the centerline is shown in the closed position.
FIG. 2 is a detailed cross-sectional view illustrating one
embodiment of a fluid restrictive member and an upper rotary
sealing element as shown in FIG. 1 when the RBOP is in the closed
position.
FIG. 3 is a detailed cross-sectional view illustrating the position
of the adapter ring relative to the lower ball beating when the
RBOP is in the open-position.
FIG. 4 is a detailed cross-sectional view illustrating an
alternative embodiment of a fluid restrictive member and an upper
rotary sealing element when the RBOP is in the closed position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 depicts a rotating blowout preventer (RBOP) 10 according to
the present invention. The sealing assembly of the RBOP is open on
the right side of the figure, while the left side of the same
figure shows the sealing assembly in the closed position for
engagement with an oilfield tubular. Those skilled in the art will
appreciate that the RBOP 10 of the present invention is
functionally improved compared to most commercially available
blowout preventers, in that the assembly is designed so that the
sealing assembly discussed hereafter may remain in engagement while
the tubular member is rotating within a wellbore.
Assembly 10 comprises a stationary outer housing 12, which may be
formed from lower housing 14 and upper housing 16 each having
mating flanges for secured engagement by conventional bolts 18. A
static O-ring 19 provides sealed engagement between the stationary
lower housing 14 and the upper housing 16. Opposing housing ends
each include a respective planar surface 13 for sealed engagement
with conventional oilfield equipment. The end of each housing is
provided with a groove 15 for receiving a conventional ring gasket
for sealed engagement with such equipment. A plurality of
circumferentially spaced threaded ports 17 are provided for
receiving conventional securing members to connect such equipment
to the assembly 10. Accordingly, the assembly 10 is compatible with
various types of oilfield equipment.
Those skilled in the art will appreciate that hydraulic fluid may
be applied to actuate the assembly 10 as shown in FIG. 1 in a
conventional manner. The pressurized fluid source 20, such as a
pump, may be used to supply hydraulic fluid to the assembly 10 from
a hydraulic supply or reservoir 22. Pressurized hydraulic fluid is
supplied to the assembly 10 through lines 24, which interconnect
the pressurized source 20 with a fluid closing port 26 in the lower
housing 14, a fluid opening port 28 in the upper housing 16, and a
fluid output port 27 in the upper housing 16. As explained
subsequently, port 26 is the input port for hydraulic fluid when
the valve 30 is positioned for closing the RBOP about a tubular
member, and port 27 is an output port for returning the hydraulic
fluid to the reservoir 22. Those skilled in the art will appreciate
that the hydraulic system as shown in FIG. 1 may also include
conventional filters and heat exchangers. Moreover, the fluid
pressure supplied by the source 20 is preferably controlled in
response to measured pressure in the wellbore. Accordingly,
sensors, gauges, and a computer (not depicted) may be used for
controlling the supply of hydraulic fluid to the assembly 10.
The stationary housing 10 defines a cylindrical bore 32 through the
RBOP, which determines the maximum size of the tubular which may be
used for a particular assembly 10. The upper and lower inner
cylindrical walls 34 and 35 of the housing 12 thus determine the
nominal diameter of the RBOP. The housing 12 thus may define a
vertical centerline 36 which is coaxial with the centerline of the
tubular passing through the RBOP.
The assembly 10 also includes a rotatable inner housing 38 which is
rotatably guided by a large thrust bearing 40. Bearing 40 has its
upper race in engagement with the stationary housing 12, and its
lower race in engagement with the rotatable inner housing 38. The
upper race of the bearing 40 is retained in place by an
interference fit. Port 41 in the housing 16 is provided for
applying pressure to the upper race during disassembly for breaking
the interference fit connection between the bearing 40 and the
housing 16. The cylindrical inner surface 44 of the inner housing
sleeve has a diameter equal to or slightly more than the diameter
of cylindrical surface 34 on the stationary housing. The rotatable
inner housing includes a curved surface 42, which curved surface is
formed by a portion of a sphere having a center on or substantially
adjacent the centerline 36.
A sealing assembly 46 is provided within rotatable inner housing
38, and includes a plurality of circumferentially arranged metal
elements 48 and an annular elastomeric sealing element 52. Pins 49
keep the inner housing 38 within the upper housing 16 during
assembly of the upper and lower housings, thereby retaining in
place the bearings and seals between the inner housing 38 and the
upper housing 16. Each of the metal elements 48 has a curved outer
surface 50 for sliding engagement with the similarly configured
curved surface 42 on the inner housing as explained hereafter.
Annular elastomeric element 52 provides for sealing engagement with
the tubular, while the outer annular elastomeric element 54
provides sealing engagement between the metal elements 48 and the
rotatable inner housing 38.
It is a particular feature of the present invention that the RBOP
be provided with a spherical sealing assembly, i.e., a sealing
assembly adapted for sliding engagement with a spherical surface on
the rotatable inner housing. Spherical sealing assemblies of the
type generally shown in FIG. 1 have been reliably used for years in
non-rotating blowout preventers, and have advantages over other
types of sealing assemblies. Sealing assembly 46 as shown in FIG. 1
may maintain high pressure sealing integrity with various diameter
tubulars passing through the assembly, and may also seal with
non-cylindrical members. Assembly 10 according to the present
invention is thus compatible with either kelly or top drive
drilling systems, and is capable of being used to strip various
tubulars and oilfield tubular connections. Spherical sealing
assembly 46 also has the ability for complete shutoff of the well
with no tubular passing through the RBOP.
The assembly 10 includes an axially movable piston 56 which
comprises a radially outward sleeve-shaped ring member 57, a
radially inner sleeve-shaped ring member 58, and an upper collar 59
interconnecting the ring members 57 and 58. For manufacturing
purposes, the collar 59 and the outer ring member 57 may be formed
as one component, which may be interconnected with the inner ring
member 58 by conventional cap screws 61. A static seal 55 seals
between the outer ring member 57 and the collar 59. An upper
supporting surface 51 on the piston 56 is designed for engagement
with the lower surface 53 of the metal elements 48. Accordingly,
axial movement of the piston 56 causes corresponding axial and
radial movement of the sealing assembly, thereby controlling the
closing and opening of the RBOP on a tubular.
A lower flange 62 on the piston 56 is provided with a elastomeric
seal 72 for sealing engagement with adapter ring 64. Fluid
passageway 66 through the adapter ring 64 provides continuous fluid
communication between opening chamber 68 and an annular gap between
a radially exterior surface of the adapter ring and an interior
surface of the housing 12, as discussed subsequently. Another
elastomeric seal 70 and a backup U-cup elastomeric seal 71 provide
sealing engagement between an upper end of the adapter ring 64 and
the piston 56. The spacing between the piston 56 and the adapter
ring 64, and between the seals 70 and 72, thus define the opening
chamber 68. Upper and lower wear bands 74 may be provided to
centralize the piston 56 within the adapter ring 64, and to
minimize sliding friction when the piston is moved axially within
the adapter ring.
When the sealing assembly 46 is rotating in sealed engagement with
a tubular, the piston 56 and the adapter ring 64 are also rotating
members. The adapter ring is guided with respect to the outer
housing 12 by a lower bearing 76 and an upper bearing 84. When
closing the sealing assembly 46, pressurized fluid passes through
port 26 and through passageway 88 in the lower housing element 14,
and then past the seal cartridge 96 discussed subsequently and into
the chamber 90 between the radially outer and radially inner ring
members 57, 58 and beneath collar 59 of the piston. As shown on the
left side of FIG. 1, pressurized fluid flows under radially outer
ring member 57 of the piston 56, through the bearing 76, then up
the annular gap between the adapter ring 64 and the outer housing
element 14. Pressurized fluid continues to flow past the bearing
84, then through a gap provided between an outer surface of the
rotatable inner housing 38 and an inner surface of the upper
housing 16. Sealed engagement between the piston 56 and the adapter
ring 64 is provided by the seals 70, 74 and 71, and sealed
engagement between the adapter ring and the inner housing is
provided by elastomeric seal 86. Pressurized fluid thus fills the
chamber 92 surrounding the thrust bearing 40, then flows past the
flow restriction 114, past the upper seal cartridge 116, out the
port 27, then back to the reservoir 22.
Sealed engagement between the piston 56 and the lower housing
element 14 is provided by seal cartridge 96 which includes seal 98.
A suitable lower rotating seal 98 is an elastomeric rotary seal
manufactured by Kalsi Engineering. Fluid pressure to the rotating
BOP is preferably controlled in response to sensed fluid pressure
in the wellbore, which corresponds to the fluid pressure beneath
the cartridge 96 and between the piston 56 and the lower housing
14. Hydraulic fluid pressure to the RBOP is preferably maintained
in the range of from about 200 psi to 500 psi greater than wellbore
pressure, and accordingly only this limited pressure differential
exists across the seal 98.
The upper end of the flow passageway 88 is closed off with plug 87,
so that pressurized fluid must flow from the passageway 88 into the
annular cavity 102, then through passageways 104 provided in the
seal cartridge 96. Pressurized fluid then flows upward in an
annular gap between the inner piston ring 58 and the seal cartridge
96, then into the cavity 90. Seal cartridge 96 does not rotate with
the piston, and accordingly static seals 100 seal between the
cartridge 96 and the lower housing element 14. Spiral retainer ring
106 may be used to removably interconnect the seal cartridge 96
with the lower housing element 14.
High pressure hydraulic fluid within the cavity 92 in the upper
housing 16 is reduced to a low pressure fluid by the restriction
member 114, which as shown in FIG. 1 comprises a fluid restriction
bushing. As more clearly shown in FIG. 2, pressurized fluid from
the cavity 92 acts on the lower surface of the bushing 114. Seal 95
provides a static seal between the inner housing sleeve 110 and the
main body of the inner housing 38. These components may be secured
together by a plurality of conventional bolts 112. The upper seal
cartridge 116 is provided with a seal 120 similar to seal 98
previously discussed. Jacking holes 93 are provided to assist in
disassembly.
Pressurized fluid acting on the bushing 114 causes a bearing race
support surface 130 on the bushing to engage to radially outer race
117 on the bearing 118, forcing the bearing race 117 into
metal-to-metal engagement with surface 132 on seal cartridge 116.
At least substantial sealing of the sandwiched outer bearing race
causes fluid to flow in the annular gap between a radially inner
cylindrical surface 134 on the bushing and a radially outer
cylindrical surface 136 on the inner housing sleeve 110. Bearing
118 rotatably guides bushing 114 with respect to the inner housing
sleeve 110. Pressurized fluid is substantially restricted by the
bushing 114. According to the present invention, the restrictive
bushing 114 causes a significant pressure drop across the bushing,
such that the pressure downstream of the bushing is less than 40%
of the pressure upstream of the bushing. More preferably, the
pressure drop across the bushing 114 is such that the pressure
downstream from the bushing is from 10% to 20% of the pressure
upstream from the restrictive bushing. This lower pressure fluid
then flows through the passageway 119 provided in the cartridge
116, then trough the passageway 89 in the upper housing 16 and out
the port 27. The replaceable sleeve member 122 is secured to the
inner housing sleeve 110 by retaining ring 126, and a static seal
124 provides sealed engagement between the inner housing sleeve 110
and sleeve member 122. Upper and lower static seals 101 seal
between cartridge 116 and the upper housing element 16.
A particular feature of the present invention is that the piston 96
is not provided with rotating seals on the outside diameter of the
piston, so that no large diameter rotating seals are required to
cause pressurized fluid to actuate the sealing assembly 46 and
engage the tubular. The diameter of each of the lower rotating seal
element 98 and the upper rotating seal element 120 is minimized.
Each rotating seal has a nominal diameter less than 20% greater
than the diameter of the bore 32 through the BOP, and preferably
less than 10% greater than the diameter of the bore 32. A large
closing force is generated by the sizable rod area of the piston
56, which is the horizontal cross-sectional area between the seal
98 and the seal 70. A comparatively small flange area of the
piston, which is the horizontal cross-sectional area between the
seal 70 and the seal 72, is used to open the sealing assembly, as
explained subsequently.
During rotation of the seal assembly 46, the restrictive bushing
114 floats radially with the inner housing sleeve 110 to
accommodate eccentricity without generating excessive friction. The
restrictive bushing 114 is thus structurally interconnected with
the rotatable inner housing sleeve 110 by the bearing 118, so that
a uniform gap is maintained between the outer cylindrical surface
on the inner housing and the inner cylindrical surface on the
restrictive bushing. Eccentricity between the rotatable inner
housing sleeve 110 and the outer housing 12 will thus not cause a
variation in the radial spacing between the outer cylindrical
surface 134 on the bushing 114 and the inner cylindrical surface
136 on the inner housing 38. The restriction bushing 114 is
fabricated from a rigid material, such as steel, bronze or a
durable ceramic. Restrictive bushing 114 preferably fits between
cylindrical surfaces on the stationary upper housing and the
rotating inner housing which are each substantially concentric with
the central axis of the RBOP. This design is preferred compared to
providing a restrictive bushing between spaced substantially
horizontal surfaces on the upper housing 16 and the rotatable inner
housing 38.
The void above the seal 120 and in the annulus between the tubular
T and the cylindrical surface 34 on the upper housing 16 will
typically be open to atmospheric pressure. Preferably, restrictive
bushing 114 drops the pressure exposed to the seal 120 such that
pressure downstream from the bushing 114 is in a range from 100 psi
to 500 psi above atmospheric pressure. This pressure may be
reliably maintained by the seal 120 over a relatively long service
life of the RBOP. The seal cartridges 116 and 96 may be easily
replaced during periodic service on the BOP, if required. Each
rotating seal 98 and 120 is mounted on a metal seal cartridge ring
which includes radial passageways therethrough for transmitting
hydraulic fluid past the seal cartridge.
It may be seen that the diameter of the upper rotating seal 120 is
preferably substantially the same as the diameter of the lower
rotating seal 98 so as to balance the pressure acting on the
rotating assembly. When the sealing assembly 46 is in sealed
engagement with a rotating tubular, the inner housing 38, the
adapter ring 64 and the piston 56 thus rotate as an assembly. The
thrust bearing 40 opposes the upward force from the piston 56
acting against the rotating inner housing 38 through the sealing
assembly 46. To reduce the size of the assembly 10, the thrust
bearing 40 is preferably spaced radially outward of the flow
restriction member 114. The inner housing thrust bearing 40 is also
provided within a horizontal plane which is inclusive of the flow
restriction member, thereby reducing the height of the RBOP.
To open the sealing assembly 46, pressurized fluid is supplied
through lines 24 to the fluid opening port 28, then through
passageway 94 and into chamber 92. During opening, the fluid
control system blocks fluid from flowing out port 27. The hydraulic
fluid will flow in the annulus between the inner housing 38 and the
upper housing 16, then down the annulus between the adapter ring 64
and the lower housing 14. Pressurized fluid in the cavity 92 acting
on the inner housing 38 forces the inner housing downward, which
also forces the adapter ring 64 downward. This axial movement of
the adapter ring is relatively small, e.g., from "0.010 to 0.050",
although this movement is important as explained below.
As shown in FIG. 3, pressurized fluid in fluid open port 28 forces
a lower surface 78 on the adapter ring 64 into engagement with an
upper surface 80 on the inner race 82 of the bearing 76, thereby
substantially restricting fluid flow past the bearing 76. When
opening the BOP, the inner housing 38, the adapter ring 64 and the
piston 96 are not rotating, so that engagement of the surfaces 78
and 80 is static. Accordingly, pressure in the cavity 90 is
significantly lower than the pressure in the cavity 92 during
opening of the BOP. Fluid which flows past the bearing 76 then
flows in the gap between the lower housing element 14 and a lower
surface 83 on the piston, then past the inner rotating lower seal
98 and out the .[.pert.]. .Iadd.port .Iaddend.26.
When pressurized fluid is supplied to .[.pert.]. .Iadd.port
.Iaddend.28 to open the RBOP, high frictional forces are not
encountered within the assembly 10. It should be understood that
when closing pressure is supplied to the RBOP through port 26, the
adapter ring 64 is forced upward slightly into engagement with the
rotating inner housing 38, thereby separating the surface 78 and 80
so that fluid flows freely up into cavity 92.
FIG. 4 depicts an alternative embodiment of a flow restriction
member and an upper rotary seal. The embodiment as shown in FIG. 4
is similar to the embodiment as shown in FIG. 2, and accordingly
like reference numerals are used to depict like components. As
shown in FIG. 4, the flow restrictive bushing has been replaced
with a plurality of labyrinth rings. The flow restriction member
138 comprises a plurality of axially spaced static carrier rings
140 each supporting a metal flow restriction ring 142 thereon. The
rings 142 significantly reduce the pressure drop across the flow
restriction member 138. A top ring 152 includes circumferentially
spaced flow ports 154 for passing restricted fluid to passageway
89. Static seals 156 seal between the .[.carder.]. .Iadd.carrier
.Iaddend.rings 140. Carrier rings 140 remain in a fixed position
relative to the upper housing 16, while the rings 142 each move
radially with respect to the carrier rings to float and thereby
accommodate eccentricity between the stationary housing 16 and the
rotatable inner housing sleeve 110. The rings 142 preferably are
fabricated from bronze, although steel or ceramic material rings
may be used. The restricted pressure fluid in the passageways 154
then flows past the cartridge seal 146 then out the passageway 89
as previously described. The upper cartridge seal 146 includes an
elastomeric sealing member 148 which seals the restricted pressure
fluid from atmospheric pressure.
The rotating blowout preventer of the present invention may be used
to provide reliable sealing engagement with a tubular within a
wellbore having a pressure in excess of approximately 2000 psi
while the tubular is rotating at speeds of up to approximately 200
rpm. A BOP capable of such reliable operation has long been desired
by those skilled in the art. When the tubular is not rotating,
assembly 46 may reliable seal with a tubular when the wellbore
pressure is in excess of 5000 psi. As previously noted, the
assembly 10 also has the ability for complete shutoff from the
wellbore when no tubular is passing through the RBOP and the
wellbore is at a pressure of up to 2500 psi.
According to the method of the invention, the lower rotary seal
between the piston and the lower housing seals the differential
pressure between the supplied hydraulic fluid pressure and the
pressure in the well. As noted above, the hydraulic pressure may be
controlled by conventional techniques so that this pressure
differential is less than 500 psi. To seal between the rotating
inner housing and the upper stationary housing, this hydraulic
pressure is significantly reduced by at least 60%, so that the
upper rotary seal is exposed to less than 40% of the pressure
supplied to the lower rotating seals. The flow restriction is
guided to maintain a substantially uniform gap between a radially
inward surface of the flow restriction and a radially outward
surface of the rotatable inner housing. The inner housing bearing
is also positioned to reduce the size of the assembly, as explained
above.
While the .[.beating.]. .Iadd.bearing .Iaddend.118 is preferred for
maintaining a uniform gap between the flow restriction member and
the rotatable inner housing, a spacing member other than a bearing
could be used to maintain this uniform gap and thereby compensate
for limited eccentricity between the rotatable inner housing and
the stationary housing. While a fluid-tight seal between an upper
surface of the flow restriction member and the upper seal cartridge
is not essential, it is important that substantially all the
hydraulic fluid passing by the flow restriction member pass through
this uniform gap maintained by the bearing 118 or other suitable
spacing member. This .[.fluid-fight.]. .Iadd.fluid-tight
.Iaddend.seal between the flow restriction member and the upper
seal cartridge may be made directly, i.e., without sandwiching the
bearing race therebetween.
Those skilled in the art will also appreciate that some type of
fluid restriction other than the engagement of surfaces 78 and 80
on the adapter ring 64 and the bearing 76 may be used to create
pressure in the opening chamber 68 which is greater than the
pressure in chamber 90 when fluid pressure is applied to open the
RBOP. The techniques as disclosed herein are relatively simple,
however, and are considered highly reliable.
Various further modifications in the assembly 10 may be made. For
example, the .[.ranged.]. .Iadd.flanged .Iaddend.connection between
the upper and lower housings could be made with a quick release
clamp mechanism, thereby facilitating easy change-out of the
sealing elements. The inner housing and the inner housing sleeve
are preferably fabricated as separate components since the sleeve
may become dented or bent during use of the BOP. Less desirably,
the inner housing could include a sleeve integral therewith. The
foregoing disclosure and description of the invention are thus
illustrative and explanatory of preferred embodiments. Various
changes in the structure of the RBOP as well as in the method of
operating the RBOP will be made without departing from the scope of
the invention, which is defined by .[.depending.]. .Iadd.the
pending .Iaddend.claims.
* * * * *