Method and Apparatus for Through-Cut Verification

Abstract

A method and apparatus for verifying the complete cut through of a tubular member by a fluid cut through device. A follower runs in the kerf created in the tubular member by the fluid cut through device until the follower encounters an incomplete cut, or hanger. The follower rotates away from the fluid cut through device when the follower encounters a hanger, thereby disengaging a switch to interrupt the fluid cut through device.

Description

This application claims priority and the benefit under 35 U.S.C. §119(e) from U.S. provisional patent application 61/237,607 for “Method and Apparatus for Through-Cut Verification” filed Aug. 27, 2009, which is hereby incorporated by reference.

BACKGROUND

1. Field of the Invention

The present invention relates generally to apparatus and methods for confirming thorough cut-through of a down hole abrasive fluid jet cutting device.

2. Description of Related Art

Down hole operations sometimes require a tubular string to be cut with an abrasive fluid jet cutting tool lowered within the tubular string. Where the cutting tool does not cut a full kerf “hangers” are formed which may impede the down hole operation.

All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art.

BRIEF SUMMARY OF THE INVENTION

A method and apparatus for verifying the complete cut through of a tubular member by a fluid cut through device. A follower runs in the kerf created in the tubular member by the fluid cut through device until the follower encounters an incomplete cut, or hanger. The follower rotates away from the fluid cut through device when the follower encounters a hanger, thereby disengaging a switch to interrupt the fluid cut through device.

Other objects, features, and advantages of the present invention will become apparent with reference to the drawings and detailed description that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cutaway view of an abrasive fluid jet cutting device in use;

FIG. 2A is a close-up view of an abrasive fluid jet cutting device showing a clean cut;

FIG. 2B is a close-up view of an abrasive fluid jet cutting device showing a hanger;

FIG. 2C is a close-up view of an abrasive fluid jet cutting device showing a follower engaging the hanger;

FIG. 2D is a close-up view of a follower as shown in FIGS. 2A-2C;

FIG. 2E is a close-up view of the removal of the blade of the follower shown in FIG. 2D;

FIG. 2F is a close-up view of the blade removed;

FIG. 3 is a close up view of an alternatively mounted blade follower;

FIG. 4A is a close-up view of an abrasive fluid jet cutting device showing a clean cut and a loop-type second alternative follower;

FIG. 4B is a close-up view of an abrasive fluid jet cutting device showing a hanger;

FIG. 4C is a close-up view of an abrasive fluid jet cutting device showing the alternative follower engaging the hanger;

FIG. 4D is a close-up view of a follower as shown in FIGS. 4A-4C;

FIG. 4E is a close-up view of the removal of the loop of the follower shown in FIG. 4D;

FIG. 4F is a close-up view of the loop removed;

FIG. 5 is a cutaway view of an abrasive jet cutting head in use; and

FIG. 6 is a side view of a complete abrasive jet cutting apparatus in use.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical mechanical and electrical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

Referring to FIG. 1, an abrasive fluid jet cutting device 10 forms a through-cut 12 in a tubular 14. The direction of the movement of the abrasive fluid jet cutting device 10 is indicated by the arrow 16.

The abrasive fluid jet cutting device 10 is provided with a follower 20. The purpose of the follower 20 is to detect portions of the through-cut 12 which were not properly completed. When the follower 20 detects a “hanger,” the term used by those in the industry to denote a section of the through-cut 12 that was not properly completed, the follower 20 pivots away from the abrasive fluid jet cutting device 10 thereby signaling the need for remedial action.

FIG. 2A illustrates the abrasive fluid jet cutting device 10 and the follower 20 in greater detail. The follower 20 is pivotally supported at 22 and a switch 24 is actuated whenever the follower 20 is pivoted away from its nominal orientation.

Referring to FIGS. 2B and 2C, the abrasive fluid jet cutting device 10 is forming the through-cut kerf 12 in the tubular 14. The abrasive fluid jet cutting device 10 has previously failed to function properly thereby resulting in a “hanger” 26.

When the follower 20 engages the hanger 26 the switch 24 is activated thereby discontinuing the operation of the abrasive fluid jet cutting device 10. The abrasive fluid jet cutting device 10 is then moved in a direction of that opposite to that of the arrow 16 to a location beyond the hanger. The abrasive fluid jet cutting device 20 is operated either during reverse movement thereof, or during subsequent forward movement thereof, or both, in order to remove the hanger and resume normal cutting operations.

FIGS. 2D, 2E and 2F illustrate the “break-away” construction feature of the follower 20. This feature has been designed to ensure that the abrasive fluid jet cutting device is not trapped in tubular if the kerf closes and traps the follower due to axial compressive loads in the tubular. In the specific case of offshore platform decommissioning, the axial compressive force is often a result of structure dead weight. FIG. 2D shows the follower 20 mounted in the support structure 30. In the case where the blade 28 is trapped in the kerf 12, cutting operations will be discontinued when the follower 20 is pivoted away from its nominal orientation. Reversing the cutting head direction would not result in de-energizing switch 24 as would be the case if a hanger had been encountered. In such a situation, the operator would retract the fluid jet cutting apparatus 10 and the verification arm 20 on parallel arms 50 initiating the break-away of the follower 20 from the support structure 30.

This is illustrated in FIG. 2E where the cutting head retraction is prying the follower grip “fingers” away from the support structure. FIG. 2F shows the follower configuration after break-way.

FIG. 3 illustrates an alternative follower support structure. Those skilled in the art will appreciate the fact that follower 20 may comprise a variety of types and kinds of blades which are removable from the associated support structure utilizing various well-known techniques.

FIGS. 4A through 4F, inclusive, illustrate an alternative embodiment of the invention. In accordance with the alternate embodiment the follower 20 of FIGS. 1 through 3 is replaced by a wire loop 40. Otherwise, the embodiment of the invention shown in FIGS. 4A through 4F functions identically to the embodiment shown in FIGS. 1 through 3 and described hereinabove in conjunction therewith. FIG. 4D illustrates the engagement of the loop 40 with its support structure 42. FIGS. 4E and 4F illustrate the disengagement of the loop 40 from the support structure 42 if the loop 40 were to be trapped in the kerf.

FIGS. 5 and 6 illustrate the supporting and positioning mechanism for the through-cut verification system of the present invention. Referring particularly to FIG. 5, the abrasive fluid jet cutting apparatus 10 and the verification arm 20 are supported by spaced apart pairs of parallel arms 50. The arms 50 function to move the abrasive fluid jet cutting apparatus 10 and the verification arm 20 perpendicular to the axis of the tubular 14. Referring to FIG. 6, the parallel arms 50 and its support structure are, in turn, supported on a structure 52 which assures that the axis of rotation of the abrasive fluid jet cutting device 10 and the follower 20 is exactly aligned with the centerline of the tubular 14 that is being through-cut.

Claims

1. A method for verifying complete cut-through in a tubular member, the method comprising:

providing a fluid jet cut through device that cuts a kerf in the tubular member as it is rotated;

providing a switch attached to the jet cut through device;

providing a follower, the follower swively mounted near the switch such that the follower may extend into the kerf created by the fluid cut through device while also engaging the switch; and

rotating the fluid jet cut through device in a direction to create a kerf.

2. The method of claim 1 further comprising:

discontinuing the operation of the fluid cut through device when the follower engages a section of kerf that is incompletely cut.

3. The method of claim 1 further comprising:

disengaging the switch when the follower engages a section of kerf that is incompletely cut.

4. The method of claim 1 further comprising:

disengaging the switch when the follower engages a section of kerf that is incompletely cut; and

discontinuing the operation of the fluid cut through device when the switch is disengaged.

5. The method of claim 4 further comprising:

reversing the direction of the fluid cut through device.

6. The method of claim 4 further comprising:

reversing the rotation of the fluid cut through device until the follower engages the switch;

restarting rotation in the direction of the cut through device.

7. The method of claim 4 further comprising:

reversing the rotation of the fluid cut through device such that the follower does not engage the switch;

retrieving the fluid cut through device; and

replacing the follower.

8. A device for verifying complete cut-through in a tubular member, the device comprising:

a fluid jet cut through device that cuts a kerf in the tubular member as it is rotated;

a switch attached to the jet cut through device; and

a follower, the follower swively mounted near the switch such that the follower may extend into the kerf created by the fluid cut through device while also engaging the switch.

9. The device of claim 8 wherein:

the follower is a removable member.

10. The device of claim 9 wherein:

the removable member is a blade

11. The device of claim 9 wherein:

the removable member is a loop.

12. The device of claim 8 wherein:

the follower engages the switch while rotating freely in the kerf and disengages the switch when encountering an incompletely cut kerf.

13. The device of claim 8 wherein:

the fluid cut through device is mounted on parallel arms to a structure allowing the deployment and retrieval of the fluid cut through device.