US3788396A

US3788396A - Well re-entry tool with bumperhead

Info

Publication number: US3788396A
Application number: US00204046A
Authority: US
Inventors: H Shatto; Dommelen J Van
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1971-03-10
Filing date: 1971-12-02
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: GB1343897A

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.

Description

United States Patent [191 Shatto, Jr. et al.

[ Jan. 29, 1974 WELL RE-ENTRY TOOL WITH BUMPERHEAD [75] Inventors: Howard L. Shatto, Jr.; Johannes A.

W. J. Van Dommelen, both of The Hague, Netherlands [73] Assignee: Shell Oil Company, New York, NY.

[22] Filed: Dec. 2, 1971 [21] Appl. No.: 204,046

[30] Foreign Application Priority Data Mar. 10, I971 Great Britain 6,446/71 [52] U.S. Cl. 166/.5, 175/5 [51] Int. Cl .1 E21b 7/12, E21b 33/035 [58] Field of Search 166/5, .6; 175/5, 7; 340/3, 340/6, 8 FT [56] References Cited UNITED STATES PATENTS 3,199,613 8/1965 Malott et al. 175/5 3,458,853 7/ 1969 Daniels et al. 3,516,492 6/1970 Petersen 3,547,189 12/1970 Bielstein et a1. 3,222,634 12/1965 Foster 3,491,842 l/l970 Delacour et al. 175/7 X Primary ExaminerMarvin A. Champion Assistant Examiner-Lawrence J. Staab [5 7] ABSTRACT To prevent damage to an orienting device used for reentry 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.

9 Claims, 6 Drawing Figures PATENTEDmz 1914 SHEEI 3 0F 3 FIGS WELL RE-ENTRY TOOL WITH BUMPERHEAD 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 Lli 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 guidecone. 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 reentry 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 reentry tool shaped as a cementing shoe.

FIG. 6 shows a longitudinal section through a well reentry 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 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 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 l 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 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 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 pyramidshaped 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 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 1 17. 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 1 10, 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. 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 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 is screwed to the cementing tube 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 and126 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 is retracted}? from the cementing string and the cementing string 120 is lowered until the top of the asing lands in the wellhead. The marine swivel is tlteri 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 thedrawing. 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 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.

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 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 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.

Claims

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.

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.

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* 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.