US3369793A

US3369793A - Well repair

Info

Publication number: US3369793A
Application number: US583155A
Authority: US
Inventors: John S Boldrick; Jr Henry M Krause
Original assignee: Exxon Production Research Co
Current assignee: ExxonMobil Upstream Research Co
Priority date: 1964-04-27
Filing date: 1966-08-15
Publication date: 1968-02-20
Anticipated expiration: 1985-02-20

Description

Feb. 20, 1968 J; s. BOLDRICK ETAL ,793

WELL REPAIR Original Filed April 27, 1964 S. zozwmmmzoo R nlm z. 255 3 mks.

E m S 35E 2. sum. 05:03:13 NnNu mm United States Patent 3,369,793 WELL REPAIR John S. Boldrick and Henry M. Krause, Jr., Houston, Tex.,

assignors to Esso Production Research Company, Houston, Tex., a corporation of Delaware Original application Apr. 27, 1964, Ser. No. 362,646, now Patent No. 3,316,963. Divided and this application Aug. 15, 1966, Ser. No. 583,155

3 Claims. (Cl. 254-30) ABSTRACT OF THE DISCLOSURE Tension is resorted to surface pipe of a well having a wellhead by employing apparatus involving a hydraulic piston operated arrangement including a hinged clamp which is placed around the surface pipe to engage therewith as clamp means on the piston arms connect to the wellhead to move same when the surface pipe is cut to relieve compression and restore tension.

This application is a division of Ser. No. 362,646, now US. Patent 3,316,963, entitled Repair of Wells, filed Apr. 27, 1964, for John S. Boldrick and Henry M. Krause, Jr.

The present invention is directed to repairing a well. More particularly, the invention is concerned with a well operation wherein there has been subsidence of the ground or movement of the surface casing. In its more specific aspects, the invention is concerned with method and ap paratus for repairing a well.

In the drilling of oil and gas wells, it is common practice to set a surface string of pipe which serves to protect shallow fresh water sands from contamination, provides a means for controlling the well during the deeper drilling operations, and supports the weight of subsequent strings of casing and tubing. If the well is completed, the oil or gas string is set inside this surface pipe. Mostly, the weight of the oil or gas string is supported on the well-head on top of the surface pipe so that the oil or gas string is in tension and the surface pipe is in compression after the well is completed. Subsequent conditions can and have caused these loads to change. For example, subsidence of the surface formations can cause the surface pipe to drop. This is resisted by the oil or gas string which is fixed at its bottom and rigidly connected to the surface pipe at the surface wellhead. The end result is that the surface pipe stress tends to reverse from compression to tension and the stress on the oil or gas string reverses from tension to compression. These stress reversals can cause serious well problem such as leakage of thread connections, obstruction to passage of tools, and may even result in the failure of the casing strings. Heretofore, conditions resulting from earth subsidence and movement of the surface pipe have been corrected by using a conventional workover rig and killing the well. The wellhead was then separated and the oil or gas string pulled into tension, following which the excess oil or gas string pipe was cut and removed and the wellhead then reconnected.

In accordance with the present invention, problems due to subsidence of the earth and surface casing movement may be solved without using a conventional workover rig and without the necessity of removing the wellhead or breaking any of the wellhead seals. Thus, the present invention may be briefly described as a method of providing original stress on a well having a wellhead arranged on a surface pipe and having a pipe string connected to the wellhead wherein original stress on the surface pipe and pipe string is changed such as to be reversed. Thus, instead of the oil string being in tension, it is in compression and rather than the surface casing ICC being in compression, it is in tension. Where such a situation arises, in accordance with the present invention, compressive stress is applied to the surface pipe at a point below the wellhead. The surface pipe is then cut and separated between the wellhead and the point where stress is applied and thereafter the separated surface pipe ends are then sealingly joined whereby original stress is provided on both the surface pipe and the pipe string.

In accordance with the present invention, after the surface pipe has been cut and separated, a section of split surface pipe is placed between the separated ends of the surface pipe, and then the separated ends and the section are welded together to extend the length of the surface pipe and to return the surface pipe to compression and the oil string to tension.

Alternatively, reduction in compressive loading on surface pipe may be performed by removing a section of the surface pipe by cutting same then pulling the ends of the surface pipe together and then sealingly joining them such as by welding. Thus, in accordance with the present invention, the condition of changes in original stress may be corrected by employing apparatus which comprises or consists essentially of at least first and second piston cylinders having a piston in each of the cylinders with a piston arm extending outwardly from the cylinders. A plurality of cylinders may be employed and in one operation four cylinders were actually used. The free end of each of the piston Iarms has a clamp for releasable connection to the wellhead. The opposite end of the piston cylinder has a hinged clamp which is adapted to be placed around the surface pipe, the hinged clamp being provided with means for maintaining it around the surface pipe, and with slip means for engaging with the surface pipe. By connecting the clamp on the piston arms to the wellhead and by placing the hinged clamp around the surface casing, pressure may then be applied to the piston cylinder in either direction, as desired, to control or alter the relative positions of the hinged clamp and the clamp connected to the piston arms. With this assembly installed, in applying pressure to the piston cylinders a compression load may be induced between the Wellhead and the surface pipe so that the pipe may be safely cut by any means, such as with a cutting torch or by a mechanical cutter. -In a tension load on the surface pipe, an excess of that induced by the piston cylinders is transferred to the piston cylinders when the surface pipe is cut. If, on the other hand, it is desired to induce tension loads into the oil string or pipe, fluid pressure is applied so as to move apart the clamp at tached to the wellhead and the clamp attached to the surface pipe until the desired load, as determined by the pressure applied, is obtained.

A split section of surface pipe may be inserted and aligned in the resulting gap in the surface pipe and welded in place or otherwise joined to the separated'ends to become an integral part of the surface pipe string. When the hinged clamp assembly is released, the compression load is then carried by the surface pipe.

The technique of the present invention may also be used to reduce compressive loading in surface pipe if such should be desired and in this instance a section of the surface pipe would be removed after cutting same and pressure applied to pull the separated ends of the pipe together for rejoining, such as by welding.

Thus, the present invention is quite useful and provides a safe and economical means of correcting reverse surface pipe stress in wells where subsidence of the earths surface or movement "has caused a reversal or change in loading on the surface pipe and oil pipe string.

The present invention will be further described by reference to the drawing in which:

FIG. 1 illustrates the apparatus on the well with the stress of the surface pipe and oil string reversed;

FIG. 2 is a showing of the well after cutting the surface pipe, raising the wellhead and inserting a split section of surface pipe between the separated ends of the surface pipe; and

FIG. 3 is a showing of the repaired well.

Referring now to the drawing and specifically to FIG. 1, numeral 11 designates coacting piston cylinders having a piston 12 arranged therein attached to a piston arm 13. The free end of piston arm 13 is connected through a yoke 14 and pin 15 to a C-shaped clamp 16 which is provided with means, such as threaded bolts 17, for attachment to flanges 18 on the wellhead 19. A surface pipe or casing 20 is also connected to the wellhead 19 and the hinged clamp 21, which is attached by yokes 22 and pins 23 to connecting member 24 and piston cylinder 11. The hinged clamp 21 is provided with double slips 25 which bite into the external surface of the surface pipe 20. Hinged clamp 21 is also provided with threaded bolts 26 to maintain the hinged clamp 21 around the surface pipe 20, the threaded bolts being arranged in openings of flanges 27 on the hinged clamp 21.

It is to be noted that an oil or pipe string 28 is arranged concentrically within the surface pipe 20 and a second pipe string 29 is also arranged concentrically within the oil pipe string 28. These strings are connected to and are sealed with the wellhead 19 and ordinarily are suspended therefrom such that the oil string 28 and pipe string 29 are in tension. It is to be noted that the surface pipe or casing 20 is arranged within the well bore 30 drilled from the earths surface 31 and cemented in place with cement 32. The oil pipe string 28 is fixed at the bottom of the well, such as with a packer, or cemented in the well and is rigidly connected to the surface pipe through the wellhead 19.

In FIG. 1, it may be assumed that there has been earth subsidence and the surface pipe 20 is in tension which, in turn, results in the oil pipe string 28 being in compression rather than the opposite, which is normally true. Hydraulic pressure is exerted on the pistons 12 through

hydraulic lines

33 and 34 from a source of hydraulic fluid (not shown) as a safety measure. A pressure gauge 35 is connected to hydraulic line 33 to register the pressure exerted downwardly on pistons 12. In accordance with the present invention, with the apparatus illustrated in place, the surface casing 20 is cut at a point C below the wellhead 19 and between the wellhead and the clamp 21.

The wellhead 19 is then raised, as shown in FIG. 2, by applying force on the pistons 12 from the opposite direction, as will be described, to cause a separation in the surface pipe 20 and to provide a space 39 for insertion of a section 40 of split surface pipe in the space 39.

The raising operation is accomplished by injection of hydraulic fluid under a sufiicient pressure from a source (not shown) below the pistons 12 through

lines

36 and 37, pressure being indicated on pressure gauge 38. This provides for separation of the surface casing 20 and provides a space 39, as has been described, into which the sections 40 of split surface pipe may be inserted. With the surface casing in compression and the oil pipe string in tension, the

clamps

16 and 21 may be removed after the sections 40 have been sealingly joined into the surface pipe 20, such as by welding, with welds 41. The well assembly, in its repaired condition, with the surface pipe 20 in compression and oil string 28 in tension, is shown in FIG. 3.

If it is desired to remove a section of the surface pipe 20, stepwise the procedure would be reversed proceeding from FIG. 3 to FIG. 2 and to FIG. 1, rather than the opposite as has been described. In this instance, with the well in a condition as shown in FIG. 3, the apparatus would be placed on the well as shown in FIG. 2 and cuts would then be made on the lines of the welds 41 in FIG. 3 and the section 40 would be removed as shown in FIG. 2. Then the separated ends of the cut surface pipe 20 would be pulled together with the apparatus, as described, by applying fluid pressure through

lines

33 and 34 against the piston 12. The two ends would then be sealed together by welding at the point C as shown in FIG. l.

It will be seen from the foregoing description taken with the drawing that a mode and apparatus have been provided by way of which oil and/or gas wells may be repaired without requiring the killing of the well and the breaking of the wellhead seals; thus, the present invention is quite advantageous and useful.

The nature and objects of the present invention having been fully described and illustrated and the best mode and embodiment thereof set forth, what we wish to claim as new and useful and secure by Letters Patent is:

1. Apparatus adapted to be arranged on a surface pipe of a well below a wellhead for moving said wellhead relative to said surface pipe which comprises at least first and second coacting piston cylinders, a piston in each of said cylinders having a piston arm extending outwardly from said cylinders, a clamp on each of said piston arms for releasable connection to said wellhead, a hinged clamp connected to said cylinders on the end opposite said piston arms adapted to be placed around said surface pipe, and means carried by said hinged clamp for holdingly engaging with said surface pipe.

2. Apparatus in accordance with claim 1 in which the hinged clamp is C-shaped and the means carried by the hinged clamp comprise slip means.

3. Apparatus in accordance with claim 1 which comprises means for maintaining said hinged clamp around said surface pipe and in which the means carried by said hinged clamp for holdingly engaging with said surface pipe are slip means.

References Cited UNITED STATES PATENTS 870,931 11/ 1907 Claiborne 29-237 1,435,486 11/1922 Leon et a1. 25430 1,895,132 l/1933 Minor l66-77 2,958,125 1l/1960 Nochols 29237 3,096,075 7/1963 Brown 25429 3,180,617 4/1965 Brown 2S430 MILTON S. MEHR, Primary Examiner.