Note: Descriptions are shown in the official language in which they were submitted.
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ANNULAR PRESSURE SPOOL
FIELD OF THE INVENTION
This invention relates to oil and gas well
drilling as well as to completion and production of the
same, and more particularly to pressure containment for
using tools in under balanced drilling and snubbing
operations.
BACKGROUND OF THE INVENTION
In the drilling, completion, and production of oil
and gas wells, it is common practice to work with formation
pressure. There are various stages and conditions of an oil
or gas well during which access to the inside of the well is
required. In underbalanced drilling, drilling occurs
without restricting pressure from the well bore. Completion
is a stage during which the well is perforated by shooting
holes in the casing, while well servicing occurs during
workover operations. In all of these cases, when drilling,
completion or workover operations are performed, it is
necessary in order to prevent hydrocarbons from leaking to
atmosphere, to provide a containment device to contain gas
within the well bore. This containment is important at all
times but more particularly during snubbing operations when
tool strings or tubing is jacked into and out of the well
while the well is live. During snubbing, a stripping device
is required for containment of the hydrocarbons, and the
well bore pressure. Some standard containment approaches
include a Blow Out Preventer (BOP) or an annular preventer,
which comprise a piston which squeezes rubber to seal
mechanically and may sit above a BOP. These systems may
also be rotating pressure control systems. The standard
approaches have limits with respect to the size or diameter
of tool string or tubing that can be stripped in and out of
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the containment device for access to the well bore. Often
if tool strings or tubing are of widely differing diameters,
multiple annular containment spools are required, increasing
costs incurred by the purchase and maintenance of multiple
devices, and delays and lost production time due to the need
to fit a new spool or containment device which fits the new
tool string or tubing. This is particularly the case when
switching between different tool strings and tubing used in
drilling and work over operations. Due to the limits of the
ranges of tool string and tubing shaft sizes compatible with
standard devices, safety also becomes an issue when the size
of a tool string or tubing is not within the safe range of
shaft sizes compatible with the containment device. Size of
the containment device itself is also an issue as it is more
desirable to have a closely configured hydraulic jacking
system.
It would be desirable in drilling and snubbing
operations for there to a be a single stripping and
containment device which has a wide range of tool string or
tubing size compatibility. This is desirable for safety
reasons and for cost efficiency. It is also desirable to
find a single device which can be used for well bore
pressure containment during underbalanced drilling,
completion and work over operations. It is also more
desirable to implement a smaller device than standard
existing ones.
SUMMARY OF THE INVENTION
The present invention provides a single stripping
and containment device which has a wide range of tool string
and tubing shaft size compatibility, can be used for well
bore pressure containment during underbalanced drilling,
completion and work over operations, and can be integrated
into rotating pressure control systems, and moreover is in
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general smaller in size than existing pressure control
systems.
Accnrdinn tn a firsfi broad asnect the invention
provides an apparatus for use in containing well bore
pressure, comprising: a spool having a wall defining a
passage therethrough for receiving a shaft; a seal disposed
within said passage and having a flexible seal wall having
first and second opposed surfaces, the first surface
defining an aperture for receiving the shaft, the flexible
seal wall being capable of flexing away from the spool wall
to sealably engage the shaft in response to a force applied
thereto, the seconcl surface of the flexible seal wall being
accessible for receiving a controllable force directed away
from the spool wall. and towards said aperture for urging the
flexible seal wall inwardly of said passage; and a plurality
of members positioried about the flexible seal wall, each for
engaging said flexi_ble seal wall and capable of receiving a
force for urging the flexible seal wall radially towards an
axis extending through said aperture.
According to a second broad aspect the invention
provides an apparatus for use in containing well bore
pressure, comprisirig: a spool having a wall defining a
passage therethrough for receiving a shaft; a seal
comprising a tubular bladder, disposed within said passage
and having a flexible wall having first and second opposed
surfaces, the first surface defining an aperture for
receiving the shaft, the flexible wall being capable of
flexing away from the spool wall to sealably engage the
shaft in response to a force applied thereto, the second
surface of the flexible wall being accessible for receiving
a controllable force directed away from the spool w'all and
towards said aperture for urging the flexible wall inwardly
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of said passage; a rigid annular piston sealably receivable
within said spool; an outer spool having an outer spool wall
extending outside and about the spool; a plurality of
cylindrical guiding fingers; and an outer rigid annular
piston sealably receivable inside of the outer spool and
extending sealably about the spool and capable of
translating in a direction along the axis of the spool;
wherein an outer surface of the flexible wall, an inner
surface of the outer spool wall, and a first end surface of
the rigid annular piston define a chamber adapted for a
fluid for use in exerting the controllable force, wherein
the bladder is sealably fixed at one end to an inner surface
of the spool, and is sealably secured to the first end
surface of the rigid annular piston at the other end of the
bladder, wherein the rigid annular piston is capable of
translating in a direction along an axis of the spool in
response to variations in a pressure of a fluid in the
chamber, wherein the spool comprises an upper portion a
lower portion with a gap therebetween, wherein an axis of
each cylindrical guiding finger lies in a plane passing
through an axis of the spool, and wherein the plurality of
cylindrical guiding fingers are fixed at respective first
ends to the inner surface of the outer spool wall, and are
secured to the outer annular piston at respective second
ends, and wherein the plurality of cylindrical guiding
fingers are adapted to be controllably deformed to forceably
engage the outer surface of the flexible wall at portions
thereof located at the gap in the spool using pressure
exerted on the outer annular piston in a direction toward
the first ends of the plurality of cylindrical fingers,
thereby providing centering forces to the outer surface of
the flexible wall.
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According to a third broad aspect the invention
provides a method of operating a seal for sealing to a shaft
in a well bore, the method comprising: providing a seal
having a flexible seal wall, said flexible seal wall having
first and second opposed surfaces, the first surface
defining an aperture for receiving said shaft; applying a
force to said second surface to urge said flexible seal wall
against said shaft; and providing a plurality of members
about the flexible seal wall for applying a force thereto,
and causing each of said members to move radially towards or
away from a central axis of said aperture by a substantially
equal displacement.
According to a fourth broad aspect the invention
provides a method of operating a seal for sealing to a shaft
in a well bore, the method comprising: providing a seal
having a flexible seal wall, said flexible seal wall having
first and second opposed surfaces, the first surface
defining an aperture for receiving said shaft; applying a
force to said secorid surface to urge said flexible seal wall
against said shaft; providing pressurized fluid against said
second surface of said flexible seal wall to urge said seal
against said shaft; and providing a plurality of members
about the second surface of the flexible seal wall for
applying a force thereto, and causing each of said members
to move radially towards or away from a central axis of said
aperture by a substantially equal displacement,
independently of ariy displacement by said fluid.
Other aspects and features of the present
invention will become apparent to those of ordinary skill in
the art upon review of the following description of specific
embodiments of the invention in conjunction with the
accompanying figures.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater
detail with reference to the accompanying diagrams, in
which:
5 FIG. 1A is a side view of a well bore pressure
containment device according to the invention;
FIG. 1B is a side view of a well bore pressure
containment device according to the invention rotated 90
degrees around the vertical axis relative to the view shown
in FIG 1A;
FIG. 1C is a top view of a well bore pressure
containment device according to the invention;
FIG. 2 is an isometric view of the well bore
pressure containment device of FIGs lA, 1B, and 1C in use,
with the containment device shown sectioned along its length
to expose its interior;
FIG. 3 is an isometric view of the well bore
pressure containment device of FIGs 1A, 1B, and 1C in an
unpressurized state, with the containment device shown
sectioned along its length to expose its interior;
FIG. 4A is a side view of an alternate well bore
pressure containment device incorporating bladder guiding
polyurethane fingers;
FIG. 4B is a side view of the alternate well bore
pressure containment device according to the invention
rotated 90 degrees around the vertical axis relative to the
view shown in FIG 4A; and
FIG. 4C is a top view of the alternate well bore
pressure containment device according to the invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGs. 1A, 1B, 1C, and 3, a well bore
pressure containment device constructed according to the
invention is described in terms of its structure. The well
bore pressure containment device, generally indicated by 10,
comprises an annular pressure spool 100 and a bladder 106.
The spool 100 is an annular metal spool which consists of an
annular flange 102 at one end of a hollow cylinder
comprising an annular spool wall 104. Inside the annular
spool 100 and extending concentric therewith is located the
bladder 106 which is constructed as a hollow cylinder and
may be made of rubber, polyurethane, or other appropriate
flexible material. The bladder 106 has an outer radius
smaller than that of the annular spool wall 104. An end of
the bladder 106 is bonded to the flange end of the annular
spool 100 and the opposite end of the bladder 106 is free
floating. The floating end is secured to an annular sliding
piston 108 which floats freely within the annular spool 100.
The piston has an annular seal 110 which serves to seal the
piston against the inner surface of the annular spool wall
104. Two holes are located in the annular spool wall 104 at
positions along its height which overlap with the bladder,
one hole serving as an inlet valve 112 and the other serving
as an outlet valve 114. The annular flange 102 has an
aperture 117 for passage of a tool string or tubing
therethrough. In the preferred embodiment, the annular
flange 102 has holes located exterior to the annular spool
wall 104 for mounting the annular spool 100 to other
equipment which in the preferred embodiment of the invention
is the rig BOP which serves as a backup system for pressure
containment.
Referring now to FIG. 2 the operation of the
pressure containment device 10 shown in FIGs. lA, 1B, 1C,
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and 3, is described. The device may be pre-set to withstand
different pressure demands for different jobs, and may
accommodate tool strings and tubing of differing diameters.
FIG. 2 depicts the pressure containment device 10 with a tool
string 118 present. In order to maintain pressure and
contain the hydrocarbons a seal must be made between the
inner surface of the bladder and the outer surface of the
tool string. By pumping and releasing pressure respectively
through the inlet valve 112 and the outlet valve 114
respectively into and out of the space interstitial of the
bladder and the annular spool wall using a special hydraulic
or pneumatic valving system, the bladder 106 may be made to
expand or contract to varying degrees between a cylindrical
tube-like shape and. a roughly hyperbolic shape. The
bladder 106 is able to freely deform in this manner due to
one of its ends being a floating end secured to the floating
piston 108 which is free to move along the axis of the
annular spool. In this way pumping and releasing fluid
pressure through the valves enables the diameter of the inner
surface of the bladder to constrict at the bladder's apex
(halfway along its length) to the diameter of the tool string
118 passing through the device. The pressure may be pre-set
to the required pressure to maintain a sufficient seal for
the particular operation. In some embodiments, additional
guiding elements are provided to ensure the bladder
concentrically engages the tool string in a symmetric manner.
Referring to FIGs. 4A, 4B, and 4C an alternative
embodiment of the pressure containment device 10 utilizing
polyurethane fingers to help guide the bladder 106 and
ensure that it concentrically engages the tool string
passing therethrough, is described. To house the system by
which the guide firigers are provided, the alternate
embodiment has an outer spool 200 which is an annular metal
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spool concentric with the annular spool 100 having a
diameter larger than that of the annular spool 100. One end
of the outer spool 200 is fixed to the flange 102, the other
end is fixed to the annular spool 100 via an annular member
220. The flange 102 is modified in this embodiment in that
it is of a larger diameter. The annular spool 100 is
modified in this embodiment to consist of two portions with
a gap between them. An upper portion 100a of the annular
spool 100 is fixed to the outer spool 200 via the annular
member 220, and engages the annular sliding piston 108 as
described in association with FIGs 1A, 1B, 1C, 2, and 3. A
lower portion of the annular spool 100b is fixed to the
flange 102. An outer fixed piston 202 is fixed to the outer
surface of the annular spool wall 104 of the lower portion
100b of the annular spool 100 and the inner surface of an
outer spool wall 204 of the outer spool 200. An outer
sliding piston 208, floats freely between the outer surface
of the annular spool wall 104 of the upper portion 100a of
the annular spool 100, and the inner surface of the outer
spool wall 204. The outer sliding piston 208 has an inner
annular seal 210a which serves to seal the outer sliding
piston 208 against the outer surface of the annular spool
wall 104, and an outer seal 210b which serves to seal the
outer sliding piston 208 against the inner surface of the
outer spool wall 204. Twelve cylindrical polyurethane
fingers 206 have respective first ends bonded to the outer
fixed piston 202 at evenly spaced angular positions. The
second ends of the polyurethane fingers 206 are secured to
the outer sliding piston 208 also at evenly spaced angular
positions. The gap between the upper and lower portions
100a, 100b of the annular spool 100 exposes the bladder 106
to a first hydraulic chamber 118 in which the polyurethane
fingers 206 are situated. Two holes are formed in the outer
spool wall 204, one serving as the outlet valve 214 and the
other serving as the inlet valve 212 to the first hydraulic
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chamber 118. The outer sliding piston 208, the upper
portion 100a of the annular spool 100, the annular member
220, and the outer spool 200 define a second hydraulic
chamber 216. Two apertures 218 and 220 are situated in the
outer spool wall 204, one serving as a second hydraulic
chamber outlet valve 220 and the other serving as a second
hydraulic chamber inlet valve 218 to the second hydraulic
chamber 216. In some embodiments a stop is located at a
lower edge of the upper portion 100b of the annular spool
100 to prevent either or both of the annular sliding piston
108 and the outer sliding piston 208 from disengaging from
the upper portion 100b of the annular spool 100.
The pressure containment device 10 functions in a
similar manner to that described in association with FIGs
1A, 1B, 1C, 2, and 3. By pumping and releasing pressure
respectively through the inlet valve 212 and the outlet
valve 214 respectively into and out of the first hydraulic
chamber, the bladder 106 may be made to expand or contract
to varying degrees between a cylindrical tube-like shape and
a roughly hyperbolic shape. The bladder 106 is able to
freely deform in this manner due to one of its ends being a
floating end secured to the floating piston 108 which is
free to move along the axis of the annular spool within the
upper portion 100a of the annular spool. To assist in
guiding the annular spool into symmetric and concentric
engagement with a tool string or tube passing therethrough,
polyurethane fingers 206 are made to forceably engage the
outer surface of the bladder 106 by pumping and releasing
pressure respectively through the second hydraulic chamber
inlet valve 218 and the second hydraulic chamber outlet
valve 220 respectively into and out of the second hydraulic
chamber 216, to move the outer sliding piston 208 towards or
away from the outer fixed piston 202. The movement of the
outer sliding piston 208 in relation to the position of the
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outer fixed piston 202 causes the polyurethane fingers to
bend or straighten to varying degrees between a bow-shaped
cylindrical shape and a roughly straight cylindrical shape.
The polyurethane fingers 206 are biased towards bending
5 towards the axis of the annular pressure spool 100 by having
in their relaxed state a slight bend inwards towards said
axis. Each of the axes of the polyurethane fingers during
their entire range of movement lies in a plane passing
through the axis of the annular spool 100. By pumping and
10 releasing fluid pressure through the second hydraulic
chamber input and output valves, the polyurethane fingers
engage and apply a force to the outer surface of the bladder
106, thereby keeping it engaged to the tool or tubing in a
symmetric and concentric manner. The pressure may be pre-
set to that required to maintain a sufficient force against
the bladder 106. In a preferred embodiment the control of
the hydraulic pressures in the first and second hydraulic
chambers 118 and 216 is coordinated so that the proper
pressure is applied to the bladder 106 while at the same
time the outer piston 208 is movable in the desired
direction.
In a preferred embodiment, the pressure
containment device 10 sits above a BOP, and is mounted
thereon using bolts passing through holes 116 of the flange
102 of the annular spool 100, and can be integrated into a
rotating pressure control system. The pressure containment
device 10 is flexible with respect to the size or diameter
of tool string or tubing that can be stripped in and out of
the pressure containment device 10 for access to the well
bore. Tool strings and tubing of widely differing diameters
may be accommodated by the pressure containment device 10
avoiding the increased costs incurred by the purchase and
maintenance of multiple standard containment devices, and
delays and lost production time due to the need to fit new
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standard spools or containment devices which fit each new
tool string or tubing. This pressure containment device 10,
due to its flexibility may be used in drilling and work over
operations. Due to the flexibility of the pressure
containment device, safety is increased since a wider range
of sizes of tubing and tool strings are within the safe
range of sizes compatible with the pressure containment
device 10. Due to its design, the pressure containment
device 10 is also smaller than standard devices and therefor
lends itself to closely configured hydraulic jacking
systems.
Although the preferred embodiments have been
described as using a fluid to flex the bladder against the
tool string or tubing passing therethrough, it should be
understood that other mechanisms for applying a controllable
force against the bladder, directed away from the spool wall
and towards a tool passing therethrough, are possible. In
fact, mechanical pressure exerted by rigid or semi-rigid
fingers similar those described in association with the
alternate embodiment could be used, or other mechanical
members.
What has been described is merely illustrative of
the application of the principles of the invention. Other
arrangements and methods can be implemented by those skilled
in the art without departing from the spirit and scope of
the present invention.
