U.S. patent number 3,788,396 [Application Number 05/204,046] was granted by the patent office on 1974-01-29 for well re-entry tool with bumperhead.
This patent grant is currently assigned to Shell Oil Company. Invention is credited to Howard L. Shatto, Jr., Johannes A. W. J. Van Dommelen.
United States Patent |
3,788,396 |
Shatto, Jr. , et
al. |
January 29, 1974 |
WELL RE-ENTRY TOOL WITH BUMPERHEAD
Abstract
To prevent damage to an orienting device used for re-entry into
wells located on the floor of a body of water on which a guide cone
is mounted a bumperhead is mounted on the lower end of the tubing
string carrying the orienting device.
Inventors: |
Shatto, Jr.; Howard L. (The
Hague, NL), Van Dommelen; Johannes A. W. J. (The
Hague, NL) |
Assignee: |
Shell Oil Company (New York,
NY)
|
Family
ID: |
9814638 |
Appl.
No.: |
05/204,046 |
Filed: |
December 2, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Mar 10, 1971 [GB] |
|
|
6,446/71 |
|
Current U.S.
Class: |
166/341;
175/5 |
Current CPC
Class: |
E21B
7/122 (20130101); E21B 41/0014 (20130101); E21B
33/035 (20130101) |
Current International
Class: |
E21B
33/035 (20060101); E21B 33/03 (20060101); E21B
7/12 (20060101); E21B 41/00 (20060101); E21b
007/12 (); E21b 033/035 () |
Field of
Search: |
;166/.5,.6 ;175/5,7
;340/3,6,8FT |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Champion; Marvin A.
Assistant Examiner: Staab; Lawrence J.
Claims
We claim as our invention:
1. A well re-entry tool in combination with a guide funnel mounted
on a wellhead located adjacent the floor of a body of water, said
tool comprising:
a tube with connecting means at its upper end for mating with
another tube, said tube having an internal seat at its lower
end;
an orienting device axially movable within said tube for resting on
said internal seat, a portion of said orienting device extending
below the lower end of said tube; and
a bumper head carried outwardly on the lower end of said tube and
extending radially outwardly therefrom to a distance and at an
angle to form an outwardly extending lower surface configuration
that protectively surrounds the portion of said orienting device
extending below said bumper head and which contacts the inner wall
of the guide funnel during re-entry operations while maintaining
the orienting device in spaced relation to said inner wall of said
guide funnel when the bumper head touches said inner wall in a
position in which the longitudinal axis of the tube and the funnel
are substantially parallel.
2. A well re-entry tool of claim 1 wherein the bumper head forms an
integral part of said tube.
3. A well re-entry tool of claim 1 wherein the bumper head is
connected to said tube by at least one shearable pin.
4. A well re-entry tool of claim 2 further including latching means
carried by the bumper head which can be moved between two end
positions, the latching means being within the wall of the bumper
head in a first end position, and extending beyond said wall in a
second end position thereby locking said bumper head against
movements parallel to the longitudinal axis of the wellhead
carrying the guide funnel.
5. A well re-entry tool of claim 4 wherein means are provided for
retracting the latching means from said second end position to the
first end position.
6. A well re-entry tool of claim 5 wherein the means provided for
retracting the latching means are operable by displacement of the
orienting device.
7. A well re-entry tool of claim 5 wherein locking means preventing
the latching means from retracting are provided, said locking means
being operable by a lever extending outside the wall of said bumper
head.
8. A well re-entry tool according to claim 1 further including a
drill bit connected to the lower end of said tube wherein the
bumper head is in the form of a cylindrical shroud encircling the
bit and connected at its upper end to the tube by shear pins.
9. A well re-entry tool according to claim 1 wherein the upper
surface of the bumper head is arranged at an angle of at least
45.degree. with respect to the longitudinal axis of the tube
whereby jet noise is reflected out at an angle up from the
horizontal and away from objects on the ocean floor preventing
erroneous signals from being received by the orienting device.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a well re-entry tool used for
re-entering a well located below the water level and for making a
tubular connection with said well from a vessel or platform
structure floating on the surface of the water.
It has long been known to drill wells into underground formations
lying below the sea bottom. The entrances to these wells are often
located above the water level, in which case fixed structures
mounted on the sea bottom are used to support the riser pipe of the
well and the wellhead mounted thereon. After completion, re-entry
of the well for work-over operations is relatively easy since these
operations can be carried out from a platform mounted on the
structure above the water level.
However, not all wells have a wellhead installed above water level.
Completing wells below sea level is often attractive when the wells
are located in areas with dense shipping traffic, or in areas that
are notorious for bad weather. Re-entry of such wells may then take
place by means of guide lines, each having one end attached to the
wellhead, and the other end attached to a buoy. The guide lines are
picked up from a work-over vessel by retrieving the buoys,
whereupon equipment for re-entering the well is guided along the
lines onto the submerged wellhead. To guide the equipment into the
well entrance, this entrance may be provided with a guide means
consisting of a conical funnel mounted with the small diameter part
thereof on the well entrance.
When no guide lines are used, communication with a submerged well
can be established by lowering a tube to the location where the
well is expected to be, with an orienting device such as a
television camera or equipment known by the trade name "Sonar" on
the lower end of the tube. Propulsion means are arranged on the
tube, which can displace the tube during lowering thereof, so that
it will land in the center of the wellhead. The position of the
tube with respect to the wellhead is continuously watched by the
operator on the monitor of the orienting device, and any deviation
from the required position, i.e., any deviation from a line
extending vertically through the axis of the well entrance, is
compensated by the action of the propulsion means which are
controlled by the operator (or automatically) by varying the
direction and magnitude of thrust exerted by the propulsion
means.
A suitable propulsion means for controlling the position of a
tubing string which is applied for re-entering a submerged well, is
a jet nozzle which is formed by an opening in the wall of the
tubing string. By supplying pressurized water to the string, the
water flow issuing from this opening will laterally displace the
pipe in a direction opposite to the direction of the water flow.
Displacement of the pipe in a rotational sense will enable the
operator to displace the lower end of the pipe in any desired
direction. By varying the pressure of the water jet, the distance
over which the lower end of the pipe is displaced can be
controlled. Suitable valve sleeve means may be provided to open or
close the entrance to the jet opening at will.
The entrance to the well is preferably provided with a guide means
comprising a conical funnel mounted with the small diameter part
thereof on the entrance of the well and having a number of
reflectors mounted around the large diameter part thereof, said
reflectors being suitable for reflecting the signals of the
orienting device so that a clear indication of these reflectors
will be visible on the monitor of the orienting device.
An unobstructed view of the wellhead entrance, which by means of
the guide funnel and the reflectors connected thereto is
distinguishable from any other objects lying on the sea bottom, can
be obtained if the orienting device is mounted below the lower end
of the tube which is to be let down on the wellhead entrance.
Moreover, the orienting device should preferably be in the center
of the tube to increase the accuracy of operation.
In known equipment, the orienting device is mounted in the lower
exit of the tube and extends partly therefrom. The device is
suspended from a cable, by which it can be lowered into its
operative position in the lower part of the tube. The tube is
lowered towards the sea bottom and at the same time maneuvered by
the propulsion means to a location in which the lower end of the
tube is above the center of the guide cone. The orienting device is
then retracted by the cable into the tube before the latter is
lowered to enter the guide cone. This retraction of the orienting
device is necessary to prevent damage thereof by the inner wall of
the guide cone.
SUMMARY OF THE INVENTION
A drawback of this known system is that during the descent of the
tube the last few feet of this descent has to be covered blind, as
the orienting device is retracted within the protective shroud
formed by the lower end of the wall of the tube.
An object of the present invention is to provide a well re-entry
tool for use in combination with a conical guide funnel, the
position of which tool can be controlled over the lower part of the
descent of the tool by means of an orienting device and a
propulsion means.
Another object of the present invention is to provide a well
re-entry tool which can be lowered from a vessel or floating
structure onto a wellhead entrance without damaging the orienting
device used for indicating the position of the tool relative to the
well entrance.
Still another object of the invention is to provide a well re-entry
tool which can be lowered into a submerged wellhead within a
relatively short time and with only a minimum chance of
failure.
A further object of the invention is to provide a well re-entry
tool which can be automatically connected to and controllably
released from the wellhead.
According to the invention, a well re-entry tool for use in
combination with a guide funnel comprises a tube provided with
connecting means at its upper end suitable for connection to
another tube, and with an internal seat at its lower end suitable
for supporting an orienting device, which orienting device when
supported by the internal seat is partly within the tube and partly
extends beyond the lower end of the tube, and a bumper head on the
lower end of the tube, the lateral dimensions of the bumper head
being sufficient to prevent the orienting device from contacting
the inner wall of the guide funnel when the bumper head touches
this inner wall in a position in which the longitudinal axes of the
tube and the funnel are substantially parallel.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described with reference to the drawing,
in which some embodiments of the invention are shown by way of
example in which:
FIG. 1 represents a vertical section over a submerged well
entrance, on which a well re-entry tool is being lowered.
FIG. 2 shows a vertical section of a submerged well entrance, on
which a well re-entry tool of an alternate construction from the
tool shown in FIG. 1 and over which re-entry tool a marine riser
has been guided into the wellhead for coupling the lower end of the
riser to the wellhead.
FIG. 3 illustrates, on a larger scale than in FIG. 2, details of
the latching means for coupling the well re-entry tool to the
wellhead.
FIG. 4 shows a well re-entry tool combined with a drill bit, partly
in longitudinal section.
FIG. 5 shows a longitudinal section through a well re-entry tool
shaped as a cementing shoe.
FIG. 6 shows a longitudinal section through a well re-entry tool of
a construction different from that shown in FIGS. 1-5.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to FIG. 1, a wellhead 1 is carried by a base member 2,
which incorporates a ball-type joint 3, allowing the base to rest
on the sea bottom 4, which may slope with respect to casings 5 and
6, that are supported by the base member 2 and extend into a well
7. The outer casing 5 has a relatively short length and supports a
guide means 8, which guide means is used for guiding a well
re-entry tool towards well entrance 9.
The guide means 8 consists of a frustoconical member 10 supported
by a frame member 11 connected to the upper end of the first casing
5. The means 8 also incorporates reflectors 13 carried by the upper
rim of the frustoconical member 10.
The inner casing 6 is suspended in the well 7 from the outer casing
5 by a casing hanger 14.
The well re-entry tool comprises a tube 20 forming the lowermost
member of a string of tubing consisting of a number of tube
elements threadably connected and suspended from a vessel (not
shown in the drawing). The tube 20 has a jet opening 21 that can be
used for jetting a flow of water (arrow 22) supplied under pressure
at the upper end of the tubing string. The inner wall of the tube
20 has a seat 23 for supporting an orienting device 24. This device
comprises a housing 25 containing the electronic equipment
necessary for operating a rotatable head 26 which is equipped with
means 27 for transmitting acoustic waves as well as for detecting
the reflections of these waves. The housing 25 is within the tube
20, whereas the head 26 is located outside the tube 20 when the
orienting device 24 is in the operative position. The housing 25
carries driving means (not shown in the drawing) for rotating the
head 26 with respect to the housing 25 and with respect to the tube
20. The information received by the means 27 is passed via a cable
29 to the ship (not shown) from which the tube 20 is suspended. The
cable 29 is further used for carrying the orienting device 24 when
it is being lowered onto the seat 23, or raised therefrom, and for
supplying energy to the electronic equipment in the housing 25.
Since orienting devices operating according to acoustic principles
are known per se, no details of the modes according to which such
devices may operate will be described hereinafter.
A bumper head 30 is connected to the lower end of the tube 20 by
means of a shear pin 31. The lateral dimensions of the bumper head
have been chosen such that when the head is in contact with the
inner wall of the frustoconical guide member 10, the rotatable head
26 is (in all positions of this head) free from this wall. This is
illustrated in FIG. 1 by the dashed lines 26' and 30'. Lines 26"
and 30" indicate the position of the rotatable head and the bumper
head respectively, just prior to the latter entering the entrance 9
of the wellhead 1. The dashed line 30'" indicates the contours of
the bumper head in the position wherein the shear pin 31 has been
sheared and the tube 20 (as indicated by the dashed lines 20'") has
entered the well. The bumper head can be retrieved from this
position by raising the tube which engages the bumper head by means
of seat 32 on its way upwards.
In operation at a location where the well 7 is known to be
positioned, the tube 20 carrying the bumper head 30 at the lower
end thereof, and forming part of a tubing string (not shown in the
drawing), is lowered to a depth at which the wellhead 1 is within a
range at which the signals transmitted by the means 27 of the
rotating head 26 of the orienting device 24 which has been lowered
by cable 29 onto the seat 23 of the tube 20 can be received by this
means 27.
When the signal contact between the orienting device 24 and the
reflectors 13 carried by the conical guide member 10 has been
established, the position of the reflectors with respect to the
center of the tube 20 is visible from the display of the signals
which are transmitted to the ship via the cable 29. Subsequently
the water jet 22 is brought into operation to move the lower end of
the tube 20 such that the axis thereof will coincide as closely as
possible with the center of the set of reflectors 13. By rotating
the upper end of the tubing string on board of the ship for varying
the direction of the thrust exerted by the water jet 22, and by
varying the pressure of the water supplied to the tubing string for
controlling the magnitude of this thrust, the lower end of the tube
20 can be moved at will.
When the information obtained on board of the ship indicates that
the position of the lower end of the tube 20 is directly above the
center of the entrance 9 of the well 7, the tube 20 is lowered
slowly. Based on the information obtained from the measuring head
26 of the orienting device 24, the position of the lower end of the
tube 20 is now controlled by the operation of the jet flow 22 so as
to maintain the position of the lower end of the tube 20 as closely
as possible on the central axis of the well entrance 9 over the
whole range of this downward displacement.
The rotating head 26 of the orienting device 24 is protected by the
bumper head 30 when the lower end of the tube 20 enters the conical
guide means 10. The bumper head, when in the position 30', will be
guided towards the well entrance 9 along the inner surface of the
guide member 10. If desired, the detecting head 26 can be retracted
before the bumper head enters the well entrance 9 (position 30"),
but this is not necessary.
After the bumper head has entered the entrance 9, it is lowered
into the casing 5 until it comes to rest on the casing hanger 14.
The weight of the tubing string, then shears pin 31 and the tube 20
enters the casing 6. Thereafter a sufficient length of the tubing
string, of which tube 20 is the lowermost element, is lowered into
the casing 6 to prevent inadvertent retraction of the tube 20 from
the casing 6.
Subsequently a marine riser (not shown in the drawing) may be
passed over the tube 20, which then acts as a guide for the marine
riser to guide the lower end of the riser to the upper end of the
casing 5. To center the lower end of the riser with the upper end
of the casing 5, centralizers known per se may be arranged on the
outer wall of the tubing. The lower end of the marine riser is
passed over the top of the casing 5 and suitable coupling means
arranged at the lower end of the riser may be used for coupling the
riser to the casing 5 by means of locking dogs (not shown)
cooperating with the annular groove 33 arranged in the outer wall
of the casing 5. The tubing string is then retracted and the tube
20 is retrieved together with the bumper head 30, whereafter the
well 7 can be entered by any equipment which is lowered through the
marine riser from the ship from which the marine riser is
suspended.
An alternate embodiment of a well re-entry tool according to the
present invention is shown in FIG. 2. The guide means used for
guiding the lower end of the tube towards the well entrance differs
from the guide means as shown in FIG. 1, since the well entrance
tube 59 in FIG. 2 is provided with an internal coupling groove for
the marine riser. Consequently there is no need for an annular free
space between the frustoconical guide 40 and the well entrance tube
59, and the guide 40 is directly in contact with the upper rim of
the tube 59. The frustoconical guide 40 is supported by columns 41
and 42 which in turn are supported by the frame work 43 connected
to and carried by the well entrance tube 59.
The well re-entry tool according to FIG. 2 can be automatically
coupled to the wellhead parts surrounding the well entrance. In
this position of the well re-entry tool, a tube 51 can be brought
under tension by exerting a pulling force thereon from the ship,
via the tubing string, so that the string, of which the tube 51
forms the lowermost element, can be applied as a guide for guiding
downwards the marine riser 60 which is to be coupled to the
wellhead. As the lower end of the tubing is coupled to the
wellhead, the tube 51 need not be introduced over a long distance
into the well to prevent inadvertent retraction therefrom. Thus,
the well re-entry tool according to FIG. 2 can be applied for
connecting a guide string to the wellhead which is closed off by
blow-out preventers or other suitable means.
The bumper head 50 in FIG. 2 is formed as part of the tube 51 which
is the lowermost element of a tubing string (not shown in the
drawing) suspended from a ship (also not shown in the drawing). An
orienting device 53 is supported by the internal seat 54A of the
central opening 54 of the bumper head 50, and connected by an
electric cable 55 to the vessel. This cable can also be applied for
suspending the device 53 therefrom. The orienting device 53 has a
measuring head 56, which extends beyond the lower end of the bumper
head 50 and can be rotated with respect to the bumper head by
actuating means (not shown) arranged within the housing of the
device 53.
The bumper head 50 further carries a number of latching dogs 57,
one of which is shown in FIG. 2 of the drawing. The design of this
dog will be described hereinafter in more detail with reference to
FIG. 3. The dog 57 automatically couples with the groove 58
arranged in the inner wall of the well entrance tube 59 (which
forms part of an underwater wellhead) when the bumper head 50 is
sliding downwards in the well entrance tube 59. As can be seen in
FIG. 2, the dog 57 locks against movements of the bumper head 50 in
upward as well as in downward direction, which means that the
bumper head cannot be pushed into the well entrance tube 59 to such
an extent that it will damage the measuring head 56 of the
orienting device 53 by coming into contact with the closed blow-out
preventers (not shown) which are arranged to close off the passage
through the well entrance tube 59. Further, since the bumper head
50 is also locked against upward movement, the tubing string, of
which tube 51 forms the lowermost element, can be tensioned from
the ship, and can be used as a guide for passing a marine riser
string therealong to the well entrance tube 59 for coupling this
riser string at the lower end thereof to the well entrance tube
59.
The marine riser string is suspended from the ship and comprises a
number of tubes, of which tube 60 is the lowermost element. The
lower end of tube 60 is connected to the coupling unit 61 by means
of a (schematically indicated) blow-out preventer 64 and a coupling
ring 65. The coupling unit 61 comprises locking dogs 66 suitable
for cooperation with an annular groove 67 arranged in the inner
wall of the well entrance tube 59. The locking dogs 66 are operated
by an annular piston 68 slidably arranged within the cylinder 68A.
Since this type of coupling is known per se, no further details
thereof (such as the hoses and channels for passing hydraulic fluid
to and from the cylinder spaces) are shown in the drawing.
The lower rim of the coupling 61 is adapted to actuate a lever 70.
As will be explained hereinafter, this lever in one position keeps
the locking dog 57 via a spring-loaded rod 71 in the locked
position, and in a second position allows the locking dog to be
retracted into the opening 72 by spring action when the orienting
device 53 has been retrieved.
The locking dog 57 and the springs used to control the positions of
this dog are shown in FIG. 3 on a scale larger than in FIG. 2.
Referring to FIG. 3, the locking dog 57 forms part of a lever 73,
which is retained in the opening 72 in the wall of the bumper head
50 by means of an O-shaped spring 74. A ball-shaped knob 75 is
connected to the lever 73, which knob is enclosed by a housing 76,
in which the knob can oscillate over limited angles. The housing 76
is slidable within a second housing 77 and a spring 78 is arranged
to move the two housings apart. A stop ring 79 is mounted on the
housing 77. The housing 76 is pressed against this ring 79 by the
action of the spring 78.
The housing 77 is pressed towards the central axis of the bumper
head 50 by a spring 80. One end of the spring 80 is supported by a
ring member 81 screwed into an opening 82 in the body of the bumper
head 50, and the other end of the spring 80 acts on an annular part
83 of the housing 77. One end of the housing 77 passes through the
opening of the ring 81, whereas the other end 84 of the housing
passes through an opening 85 in the bumper head 50, which opening
extends between the opening 82 and the central opening 54 of the
bumper head 50.
The operation of the locking means shown in FIG. 3 will now be
described with reference to FIGS. 2 and 3 of the drawing.
By lowering the orienting device 53 onto the seat 54A (FIG. 2), the
end 84 (FIG. 3) of the housing 77 is pushed outwards with respect
to the central axis of the bumper head 50 against the action of the
spring 80. The top end 86 of the lever 73 is subsequently moved
outwards, whereas the locking dog 57 remains within the opening 72
due to the action of the spring 74. The bumper head 50 is lowered
onto the wellhead in the manner described hereinbefore with
reference to FIG. 1, and protects the measuring head 56 against
damage when entering the guide cone 40 mounted on the well entrance
tubing 59. On further lowering, the bumper head 50 enters this well
entrance tubing 59 with the locking dog 57 in the retracted
position. However, the upper end 86 of the lever 73 is forced into
the opening 72 by the inner wall of the tubing 59 on further
lowering of the bumper head 50 in this tubing, thereby compressing
the spring 78. As a result the locking dog 57 is displaced outwards
against the inner wall of the tubing 59. Further downward movement
of the bumper head 50 brings the locking dog 57 into line with the
annular groove 58 (the position as shown in FIG. 2) whereafter the
dog 57 snaps into the groove 58 preventing any further displacement
of the bumper head 50 in a vertical direction.
Without a stop member 87 in the bumper head 50, the locking dog 57
could be uncoupled by pulling the orienting device 53 upwards by
the cable 55. This would result in a decrease of the outwardly
directed force exerted by the spring 78 on the ball joint 75 of the
lever 73, which would in turn result in an inwardly directed
displacement of the locking dog 57 under influence of the spring
75, thereby retracting the dog 57 from the groove 58. Thereafter,
the bumper head 50 could be retracted from the well entrance tubing
59.
When guiding the marine riser string 60 (FIG. 2) together with
blow-out preventer 64 and coupling member 61 over the tubing string
of which tube 51 forms the lowermost member, the cable 55, where it
emerges from the upper end of the tubing string, is often a
nuisance when the separate elements of the marine riser string have
to be passed over the top of the tubing string. Therefore, the
cable 55 together with the orienting device 53 is removed from the
tubing string prior to lowering marine riser string 60. Since this
action would decouple the latching dog 57, a stop member 87 (FIG.
3) is provided which in a first position thereof is between the
ring 83 on the housing 77 and the end wall of the opening 82, and
in a second position is retracted so as to allow the ring 83 to
contact the end wall of the opening 82 under the action of the
spring 80. The stop member 87 is pressed into the first position
thereof under influence of the rod 71 which is loaded by a spring
71A (FIG. 2). Thus removal of the orienting device 53 will not
influence the position of the latching dog 57 as shown in FIG. 2,
as the stop member 87 remains in place. Thus the latching dog 57
remains in the groove 58 to withstand the upward force exerted on
the tube 51.
When the coupling member 61 of the marine riser string 60 has been
guided into the well entrance tubing 59, the lower rim of the
member 61 will actuate the lever 70, which will retract the rod 71
and the stop member 87 allowing the latching dog 57 to be pulled
out of the groove 58 under influence of the spring 74 (FIG. 3).
Preferably, the load exerted on the tubing string is removed to
facilitate the retraction of the locking dog 57 from the groove
58.
After the coupling unit 61 has been coupled to the well entrance
tubing 59 by actuation of the piston 68 displacing the locking dogs
66 into contact with the groove 67, the tubing string of which the
tube 51 is the lowermost member may be pulled up.
Subsequently the equipment to be used in the well can be lowered
through the marine riser string into the well.
The application of the well re-entry tool according to the
invention is not limited to the use thereof in combination with a
conical guide funnel. The tool may also be used in combination with
a truncated pyramid-shaped guide funnel, which preferably has three
or more side planes.
A bumper head combined with a drill bit is shown in FIG. 4. The bit
is of the roller type comprising a body 100, provided with pins 101
(only one of which is shown) around which cutting rollers, such as
a cutting roller 102, are rotatably arranged. The body 100 is
provided with a coupling screw thread 103 to couple the body 100 to
a connecting member 104 that is screwed to the lower end of a tube
105 forming part of a drill string (not shown).
The connecting member 104 comprises a seat 106 for the shoulder 107
of an orienting device 108 provided at one end thereof with a
rotatable measuring head 109 and connected at the other end thereof
to an electric cable 110.
The measuring head 109 transmits acoustic waves, receives
reflections of these waves, which are transformed into electric
currents and passed to the ship (not shown) via the electric cable
110.
Openings 111 and 112 are arranged in the connecting member 104 and
the body 100, respectively to allow a flow of mud to pass from the
interior of the tube 105 to the cutting rollers 102.
The drill bit is surrounded by a bumper head 115 which is connected
to the connecting member 104 by break pins 116 at its upper
end.
Part of the upper surface of a frustoconical guide member which is
adapted to cooperate with the drill bit/bumper head combination
shown in FIG. 4 is schematically indicated by the dashed line 117.
It will be appreciated that, after the combination has been lowered
onto the surface of the guide member the combination is guided to
the lower part of the guide member adjoining the well entrance in a
manner such that the measuring head 109 of the orienting device 108
will not come into contact with this guide surface and be damaged
thereby. Damage of the surface of the guide member by the teeth of
the rollers 102 is prevented by the bumper head 115, the lower rim
of which is in contact with the guide surface when the bumper
head/bit combination is guided over the guide surface to the well
entrance.
After having entered the well on which the guide 117 is mounted,
the bumper head 115 may be hampered on its way down by a decrease
in diameter of the well entrance. The pins 106 are then sheared off
and the bit is lowered into the well by means of the drilling
string of which the tube 105 forms the lowermost element. Before
lowering the bit onto the bottom of the well, the orienting device
108 is retracted by the cable 110, and a drilling insert piece (not
shown) is lowered via the drill string on the seating 106 and
locked to the connecting member 104 in a manner known per se, so
that the cutting elements of this drilling insert piece together
with the cutting rollers 102 form a bit capable of cutting a full
sized hole.
When retracting the bit from the well, the bumper head 115 is
picked up again and retrieved to the ship from which the drilling
operations are being carried out.
A bumper head which is shaped as a cementing shoe is shown in FIG.
5 of the drawing. This bumper head is used for guiding the lower
end of a casing into a submerged well entrance by means of acoustic
equipment and a frustoconical guide member mounted on the well
entrance. The lower end of the casing 120 is provided with a casing
shoe 121 having a coupling groove 122 in the inner wall thereof. A
groove 123 in this inner wall carries a sealing member 124.
The casing shoe 121 carries a cementing shoe consisting of an inner
part 125 and an outer part 126, both parts being made of drillable
material. The outer part 126 of the cementing shoe is supported in
the casing shoe 121 by means of a locking dog 127 cooperating with
the annular groove 122. The locking dog is movable around a pin 128
and held in the position shown in FIG. 5 by the action of a spring
129.
The inner part 125 of the cementing shoe is provided with a latch
130, hingeably mounted on a pin 131 and operated by a spring 132 to
cooperate with a shoulder 133 of the outer part 126 of the
cementing shoe. The inner part 125 may be pushed in a downward
direction into the outer part until the shoulders 134 and 134A of
these parts cooperate. An annular groove with sealing member 135 is
arranged in the outer part 126 of the cementing shoe to seal the
passage between the two parts of this cementing shoe. The inner
part 125 of the cementing shoe further carries a valve 136
hingeably mounted on a pin 137 and actuated by a spring 138 to
close the passage 139 through the inner part 125 of the cementing
shoe. In the situation shown, the valve 136 is kept in the open
position by the lower end of a cementing tube 140, which is passed
through the passage 139 in the inner part 125 of the cementing shoe
and screwed to this inner part 125 by screw thread 141. When
unscrewing the tube 140 from the inner part 125 of the cementing
shoe, rotation of this inner part with respect to the casing shoe
121 is prevented by a cam 133A on the shoulder 133 and by cams (not
shown) in the groove 122.
When the lower ends 142 and 143 of the inner and outer cementing
shoe parts 125 and 126, respectively, cooperate with the upper
surface of a guide cone mounted on a well entrance, they prevent
the measuring head 144 of an orienting device 145 from becoming
damaged by contact with the upper surface of the guide cone. The
orienting device 145, when in the position shown by dashed lines,
rests on a shoulder 146 of the cementing tube 140 and is connected
to the ship from which the cementing operations may take place, by
an electric cable (not shown), which cable can also be used for
lowering or lifting the orienting device 145 with respect to the
cementing tube 140.
The way in which the bumper head/cementing shoe shown in FIG. 5 can
be used will now be described.
The outer cementing shoe part 126 is locked to the casing shoe 121
by the locking dog 127 cooperating with the groove 122 in the part
126 of the cementing shoe. Thereafter the casing shoe 121 is
screwed to the lower end of the casing 120 which is subsequently
lowered into the sea from the ship from which the cementing
operation is going to take place, by adding casing elements so as
to form a casing string of sufficient length. Subsequently the
inner cementing shoe part 125 is screwed to the cementing tube 140
by the screw coupling 141. The part 125 and the tube 140 are then
introduced into the upper end of the casing string and lowered
therein by adding further cementing tube elements to form a
cementing string. When the inner part 125 is landed on the outer
part 126 of the cementing shoe, the inner part is latched to the
outer part by the latch 130. Further penetration of the inner part
125 into the outer part 126 unlatches the dog 127 from the groove
122 by the action of the shoulder 147 of the inner part 125.
By further downward movement of the cementing tube 140 with respect
to the casing 120, the two parts 125 and 126 of the cementing shoe
are passed out of the casing shoe 121 and lowered so as to expose
at a level below the lower end of the casing shoe 121 a jet nozzle
(not shown) in the cementing string 140. In this position the top
of the casing string 120 is suspended on J-slots on a marine swivel
(not shown) placed in the cementing string 140. By adding further
cementing tube elements the whole casing assembly is lowered to a
point above the wellhead cone.
The orienting device 145, which has been lowered through the
cementing tube string onto the shoulder 146 protrudes with the head
144 thereof through the central opening of the cementing shoe. The
display of the position of the measuring head 144 with respect to
the (not shown) guide cone mounted on the well entrance, will allow
the operator on board the ship to take all measures necessary to
bring the central axis of the measuring head into coincidence with
the central axis of the guide cone. This can be achieved by
displacing the ship or displacing the cementing tube by propulsion
means mounted thereon, such as a jet nozzle arranged in the wall
thereof. Since the operation of such a jet nozzle has already been
extensively explained with reference to FIG. 1, no further
description will be given.
Once the cementing shoe is in close alignment with the well
entrance, the cementing tube 140 is lowered onto the guide cone on
the well entrance. Since the measuring head 144 is protected
against damage from the surface of the guide cone by the presence
of the surfaces 142 and 143 of the cementing shoe, the head 144 may
remain in its operative position until the cementing shoe has
entered the guide cone, and has been inserted into the well bore
far enough to prevent inadvertent withdrawal of the cementing tube
from the wellhead.
Subsequently, the orienting device 145 is retracted from the
cementing string and the cementing string 120 is lowered until the
top of the casing lands in the wellhead. The marine swivel is then
released from the J-slots and the cementing string is raised until
the cementing shoe latches with dog 127 in the casing shoe 121.
Cementing is then effected through the cementing string. After
cementing, the cementing string 140 is released by unscrewing the
coupling 141, and retracted from the well. The central passage 139
through the inner part 125 of the cementing shoe is closed by the
valve 136 when the tube 140 is retracted from this passage, thereby
preventing backflow of cement to the interior of the casing 120.
After the cement has set, drilling is resumed in the well by
introducing a bit through the casing string 120. The cementing shoe
being made of drillable material, the drill will pass through the
shoe and any cement present therebelow to deepen the well.
Another design of the bumper head according to the invention is
shown in FIG. 6. The head 149 forms part of a tube 150 which is
arranged at the lower end of a string of tubing (not shown)
suspended from a vessel (not shown). The head 149 comprises a
plurality of arms 151 which are hingeably mounted around pins 152.
The arms are maintained in the position shown in the drawing by
springs 153 which are sufficiently strong to maintain the arms 151
in their outwardly directed position when the bumper head 149 is
lowered onto the upper surface of the guide cone 154 mounted on the
frame work 155, which is connected to the casing 156 cemented to
the sea bottom 157. However, the springs 153 cannot prevent folding
of the arms into the recesses 149A when the bumper head is entering
the casing 156 since in this position of the bumper head the
vertical load thereon is increased by lowering the tubing string of
which tube 150 forms the lowermost element.
As shown in FIG. 6, the measuring head 158 of the orienting device
159 protrudes through the central opening of the bumper head 158
and is prevented from being damaged by contact with the guide cone
154 by the arms 151 which slide over the upper surface of the guide
cone 154 and bridge the annular gap between the cone 154 and the
entrance to the casing 156, thereby keeping the measuring head 158
free from contact with the guide cone 154 and the casing 156. After
the bumper head 149 has entered the casing 156, the orienting
device 159 is retracted by a cable 160.
It will be appreciated that the well re-entry tool according to the
invention can also be used in combination with orienting devices
other than those described with reference to FIGS. 1-5 of the
drawing. If desired, these orienting devices may operate according
to principles different from the acoustic principle.
An additional advantage of the use of a bumper head according to
the invention is that, when applying such head in combination with
a tube carrying a jet nozzle for displacing the tube laterally with
respect to the wellhead on which it is to be landed, the bumper
head masks the acoustic orienting device from direct receipt of
high frequency jet noise. Preferably the top surface of the bumper
head slopes at an angle of 45.degree. or more from the longitudinal
axis of the tube. The jet noise is then reflected out at an angle
up from the horizontal and away from objects on the ocean floor
which prevents erroneous signals from being received by the
orienting device.
* * * * *