US2804147A

US2804147A - Sealing leaking tubing couplings without removing the tubing from the well

Info

Publication number: US2804147A
Application number: US468306A
Authority: US
Inventors: Pistole Harry; John G Calvert; Roger J Williams; Joe V Morse; Ike T Pryor; Jr Charles B Corley; Billy W Evans
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1954-11-12
Filing date: 1954-11-12
Publication date: 1957-08-27
Anticipated expiration: 1974-08-27

Description

Aug. 27, 1957 H. PISTOLE ETAL SEALING LEAKING TUBING COUPLINGS WITHOUT REMOVING THE TUBING FROM THE WELL Filed Nov. l2, 1954 ..........n....... .3... .,.uuwnw.v ...wtm25.....

INVENTORS. Harry P/'sd/e, lo/1n G. Ca/Ver, 7 Bil/y W. Evans,

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Roger J. Wi//iams, e, /ke 72 Pr Joe Mors ,Char/es B. Car/ey,J/:,

A TTU/MIE Y United {States Patent SEALING LEAKING TUBING COUPLINGS WIT?- OUT REMOVING THE TUBING FROM THE WELL Harry Pistole and John G. Calvert, Tyler, Roger I. Williams and .loe V. Morse, Overton, Ike T. Pryor III and Charles B. Corley, Jr., Tyler, and Billy W. Evans, Katy, Tex., assignors, by mesne assignments, to Esso Rev search and Engineering Company, Elizabeth, N. J., a corporation of Delaware Application November 12, 1954, Serial No. 468,306

8 Claims. (Cl. 166-14) The present invention is directed to the sealing of one or more points of leakage in a string of pipe in a well without removing the string of pipe from the well.

In the production of petroleum and natural gas, it is` conventional to complete the well by inserting and cementing a string of casing in the well and then placing a string of tubing within the casing through which the well flows. The string of tubing is conventionally made up of lengths of pipe connected together at the end by screwed couplings. It sometimes happens that the string of tubing leaks at one or more couplings interfering with the desired management of the well.

The present invention is directed to a simple eiective procedure for sealing one or more leaking couplings and/ or any similar aperture which might be revealed in the producing string of tubing in a Well.

Further advantages of the present invention will be seen from the following description taken with the drawing in which Fig. 1 is in the form of an elevation, partly in section, showing equipment used in sealing one or more points of leakage in a string of tubing in a well;

Fig. 2 is a fragmentary view showing a portion of the string of tubing of Fig. l;

Fig. 3 is in the form of an elevation, partly in section, illustrating another procedure for sealing one or more points of leakage in a string of tubing in a well;

Fig. 4 is in the form of an elevation partly in section illustrating a tubing stop satisfactory for use in the'present invention and Fig. 5 is a partial sectional view of the pressure regulator valve of Figs. 1 and 3,

Turning now specically to the drawing and first to Fig. l, a well with the producing formation shown at 11 has the borehole lined with a string of casing 12 and cemented in position with cement 13. The upper end of the casing extends above the surface of the earth 14 and terminates in a conventional wellhead H' provided with 'control valves 15. The well is provided with a string of tubing 16 having its upper end secured to Wellhead H. It will be understood that the showing of thewellhead and outlet valves is schematic only and that conventional equipment may be used for this purpose. At the lower end of the string of tubing is a packer 18 which seals the space between the string of tubing and casing in a fluid-tight manner.

The string of tubing 16 is made up of lengths of pipe having their ends terminating in screw threads with the separate lengths held together by screwed joint couplings, This procedure is conventional and in orderto illustrate the invention more fully a short section of tubing is shown in Fig. 2 made up of lengths of tubing 19 with the ends secured together by couplings 2t) provided with threads 20a which mate with threads 19a of the tubing 1 9. It is these threads which are susceptible to leaks.

ItA sometimes happens that leaks develop in the string ICC of tubing and such leaks interfere with the proper operation of the well. In the well shown in Fig. 1, it will be assumed that one or more couplings have developed leaks at their threads and that the present invention is being applied to the well to seal such leaks. It is to be understood that leaks sealed in the practice of the present invention are not limited to leaks in the threads of the couplings but may occur in the wall of a coupling or in the wall of a length of tubing. Further, that the invention may be applied to a string of tubing where joints of pipe, making up the total string of tubing or a part of the tubing are connected by welding.

In carrying out the present invention with the equipment shown in Fig. l, a bottom hole regulator A is placed at a selected level in the tubing of the well, for example,

on landing nipple B, or other suitable supporting or se` curing means such as pipe slips, latching dogs, and the like anchoring means. The regulator A is set so that it maintains the pressure in the interior of the tubing until the pressure becomes substantially greater than the well pressure whereupon it opens to relieve the excess pressure. By way of example, if the well is a gas producing well and the pressure of the gas within producing formation is 3000 pounds, the regulator A may be adjusted to release pressure in the neighborhood of 5000 or 6000 pounds per square inch.

The pressure regulator valve A is comprised of a regulator valve seating member 34 provided with an annular shoulder 35 having a seating surface 36 which communicates with a passageway 37 extending through the member 34. The member 34 is slidably attached in the lower end of the regulator A by means of a collar 38. A helical coil regulator spring 39 bears against the collar 38 and against the underside of the shoulder 35 to bias the member 34 upwardly. Arranged above the regulator seating member 34 in seating arrangement therewith is a regulator Valve 40 provided with spider member 41 having ports 42 for passage of uid therethrough. A plug seating member 43 which is adapted to seat on the surface 36 is slidably arranged within the member 4i) and is biased in a downward position by biasing means such as helical coil spring 44.

Thus, the member 34 is biased upwardly to seat against the seating member 43 and when the pressure exerted through the passageway 45 of the mandrel 47, which forms the upper end of the regulator A, exceeds the pressure differential of the regulator spring 39 the member 34 is forced downwardly, allowing pressure to be released through the passageways 45 and 37.

The mandrel 47, as shown in Figs. 1 and 3, is provided with packing 4S and a retrieving head 49.

When pressure is released from the interior of the tubing string 16 to less than the pressure in the well, then the pressure in the well forces the seating member 43 against the spring 44 and allows well pressure to be exerted through the passageway 42 and the passageway 45 upwardly in the tubing.

In the procedure carried out in Fig. l, the string of tubing' 16 has lubricated or forced into it a body of plastic thread sealing material C. The plastic thread sealing compound is preferably made up of finely divided sized, non-deformable bridging material in a lubricating base. By way of a specific example may be mentioned a thread sealing compound described and claimed in U. S. patent application entitled Thread Sealing Compound, Serial No. 468,532, filed November 12, 1954, now abandoned, in the names of John Beson and Algernon S. Badger which may be described briefly as made up of 10% of equal amounts of 100-140 mesh silica, 140-200 mesh silica and 200 plus mesh silica and of a lubricating.

` base. A suitable thread sealing compound in accordance with the Beson et al. application supra may contain 59% by volume of aluminum stearate, 8% by volume of lubricating oil, 23% by volume of graphite and by volume of silica made up of equal quantities of 100 to 140 mesh silica, of 140 to 200 mesh and of 200+ mesh. In employing sealing compounds of this nature it is believed that the various sizes and ranges of particles employed act to block fluid passageways through threads desired to be sealed by the smaller particles lodging behind the next larger particles which results in a screen so small the viscous carrier cannot ow through. However, it is to be understood that other thread sealing cornpounds of finely divided particles dispersed in a lubrieating base may be used in the practice of the present invention. Descriptions of suitable lubricating bases are found in U. S. Patents 2,205,990, Nelson et al., 2,065,248, Smith and in Abstract 165,377, entitled, Thread Lubricant, 662 O. G. 4, page 1188.

lt may at times be found that one type of thread scal-l ing compound will seal range of sizes of holes in the tubing string more satisfactorily, and another type of thread ysealing compound will seal another range of sizes of holes in the tubing string more satisfactorily. It is within the scope of the present invention to use two different types of thread sealing compounds, for example types with differing average particle sizes in the lubricating vehicle either as two portions making up a single body or as two separate bodies vertically separated as they pass through the string of tubing.

The plastic thread sealing material which is forced as a body in intimate contact with the wall of the tubing from one end of the tubing to the other end of the tubing is quite viscous. The portion of the body of plastic thread sealing material which is not deposited along the walls of said string of tubing must be removed before the well is returned to production. It is a particular advantage of the present invention that the body of thread sealing material employed extends only a small fraction of the total length of said string of tubing and as it passes down the string of tubing has less viscous fluid both below and above it in the string of tubing. For example, the body of thread sealing material may have mud or water above and below it as it is forced down the borehole or gas above and below it, or water below and gas above or gas below and gas above. As previously mentioned, it is preferred to provide a plug above and a plug below said body of plastic thread sealing material as it is forced through the bore of the tubing.

As a practical matter, the body of plastic thread sealing material should occupy as a minimum a length in the neighborhood of 50 feet of the tubing in order t0 assure opportunity for an adequate amount of the thread sealing material to be forced into any leaks in the threads of each coupling as the body of thread sealing material moves across the coupling. However, it is also important that an excessively large amount of thread sealing material not be used since it is quite costly and large amounts particularly are difficult to remove from the tubing when returning the well to production. The desirable way to remove the remainder of the body from the tubing after it has been forced from the top to the bottom of the string of tubing is to employ the well pressure for flowing the body of plastic material out of the well and when this procedure is to be used it is essential that the hydrostatic pressure of the body of thread sealing material be less than the well pressure. By way of example, in a 10,000 foot well a maximum length of 1000 feet of thread sealing material may be used in the tubing. lt may be said that as a minimum the body of thread sealing material should occupy in the neighborhood of 50 feet of the tubing bore and as a maximum approximately 10% of the length of the complete string of tubing and such an amount that its hydrostatic pressure is less than the well pressure if the body is to be removed by flowing it from the well. In anyevent, the body occupies only a small percentage of the total length of the tubing 4 through which it is passed with the body of thread sealing material maintained in intimate contact with the tubing walls at a pressure substantially in excess of the natural pressure in the well.

The body of thread sealing material C is lubricated or forced into the upper end of the well with a plug D placed in the tubing ahead of sealing material C and a plug E placed in the tubing following the body of thread sealing material. The body of material C with plugs D and E is then forced down the tubing by suitable means such as by pumping it down with water, this assembly compressing the gas in the space F in the string of tubing between valve A and plug D, the assembly being forced downwardly until the pressure in space F equals that at which valve A is set to operate. At this point an additional body of thread sealing material C is inserted in the upper end of the string of tubing with plug D' below it and plug E above it. The body of thread scaling compound C is then forced a substantial distance of the length of the string of tubing under the pressure at which valve A is set to operate and thus is forced past each coupling at the predetermined pressure leaving deposits in the spaces of each coupling 20 as it moves downwardly so that the thread sealing compound enters any leaking threads or other point of leakage which the string of tubing may have. As an example, and exemplary only, the sealing body C may span only approximately the upper half of the tubing string 16 under the pressure at which the regulator valve A is set and the body C may span the lower half of the tubing string 16 at the regulator valve A pressure. Body C is normally or usually pumped through approximately half the length of the tubing string 16 before the gas below the body C in space F is compressed to the pressure at which regulator valve A is set to open.

It will be understood that as sealing body C is forced downwardly it forces body C and plugs D and E ahead of it so that eventually that part of the thread sealing material remaining after bodies C and C have been forced through the length of the tubing string plus the plugs D, E, and D', E', reach the bottom of the string of tubing with lower plug D in contact with regulating valve A and landing nipple B. The plugs D, E, and D', E and the remainder of bodies C and C of thread sealing compound may be displaced from the well by releasing the pressure by a suitable valve 15 at the Wellhead H to allow the well pressure to force these units to the surface and thereafter they, as well as pressure regulating valve A, may be removed from the string of tubing and the well returned to production.

Another procedure for carrying out the method of the present invention is shown in Fig. 3. The casing, wellhead and tubing shown in Fig. 3 may be identical to that of Fig. 1 and these parts are for this reason designated with identical reference characters. In the embodiment of Fig. 3 a pressure regulator valve A may be set in the bottom of the string of tubing 16 in the same manner as described in conjunction with Fig. 1. Thereupon the pressure within the string of tubing above valve A may be increased to the pressure at which the valve A is set to release by the use of a suitable means, such as a com pressor G connected through line 21 to the wellhead.

.After the pressure throughout the string of tubing has been increased as described, a body of thread sealing material C" with a plug D" below it and a plug E" above it may be lubricated into the tubing string. The assembly consisting of a body of thread sealing compound C" and plugs D and E is then forced downwardly as by pumping water into the upper end of the tubing to force Vthe assembly down through the entire length of the tubing with the body of thread sealing material C" coming into contact with each coupling and a portion of it remaining as a deposit in each coupling so that any leaking threads in the string of tubing are sealed by the sealing compound. When the assembly consisting of thread sealing material C and` plugs D`fand E reach the regulating valve A, each coupling in the string has been brought ito contact with the thread sealing material. Plugs D and E" and remainder of the body of thread sealing material C may then be displaced by the well pressure to the top of the tubing and removed from the well. Thereupon gas regulating valve A may be removed from the string of tubing and the well returned to production.

It is also possible in the present invention to repair a leaking coupling in a tubing where the location of the leaking couling is known. In this instance, a tubing stop, as shown in Fig. 4, is placed on slips, and the like at a level in he tubing immediately below the leaking coupling. In accordance with this embodiment of the `invention a tubing stop 30 is lubricated or inserted in the tubing 16 and lowered on a wireline, not shown, attached to the shing neck 31 until it is placed at a point below a tubing coupling 20 which has been determined to be leaking. The tubing stop 30 may be a tubing stop such as described at page 3999 of the 1954-55 edition of the Composite Catalog of Oil Field and Pipe Line Equipment and is provided with slips 32 which may be actuated by imposing weight on stop 30 and has a passageway, not shown, for fluid passageway through the stop 30 for discharge by way of ports 33. After the tubing stop 30 has been located at the selected point, a first plug, such as D, is inserted into the tubing 16 and thereafter a body, such as C, of sealing compound is forced into the tubing 16. A second plug, such as E, is then inserted in the tubing 16 and the body of sealing material C between the plugs D and E is then forced down through the tubing 16 to seal off the leaking coupling 20. The thread sealing compound is then pumped down the tubing behind a suitable plug and the sealing compound is squeezed into the leak by applying a preselected pressure when the plug contacts the tubing stop and thus seals off against the tubing stop. Leaking tubing couplings have been successfully sealed or repaired in two gas wells in the East Texas area.

In carrying out the present invention, good results may be obtained by using enough thread sealing material for each body of thread sealing material introduced into the well to occupy a length of from 50 to 1000 feet of the tubing. It is desirable to allow the body of the material at a pressure substantially greater than the natural pressure in the well bore to remain in contact with each coupling in the string of tubing for minutes. That 1s to say, if the body of thread sealing material occupies 100 feet of the tubing it should be forced downwardly through the tubing at such a rate that it requires at least 5 minutes for it to be forced past each of the couplings in the string of tubing.

The present invention having been described and illustrated, what is desired to be claimed is:

l. A method for sealing a point of leakage in a string of tubing arranged in a producing well having a pressure substantially greater than atmospheric including the steps of inser-ting into the bore of said string of tubing a body of plastic thread sealing material in intimate contact with the inner wall of 4said string of tubing and in such an amount that it occupies only -a small fraction of the total length of said string of tubing, exerting a selected pressure above said body substantially greater than the maximum natural pressure exerted in the well bore on the exterior of said string of tubing and thereby forcing said body of thread sealing material into intimate `contact with the inner wall of said string of tubing through said string of tubing with a uid different from said thread sealing material above and below said body from one end of said string of tubing to the other end of said string of tubing while maintaining on said body said selected pressure whereby .said body of thread sealing material comes into intimate contact with the wall of said string of tubing at said selected pressure, reducing the pressure in the in of the string'of tubing, exerting said maximum natural pressure on the interior of the tubing below any remaining portion of said body of plastic thread sealing material which has not been deposited along the wall of said tubing, and thereby forcing any remaining portion of said body of vplastic thread sealing material upwardly in said string lof tubing in intimate contact with the wall thereof and then from the upper end of said string of tubing, and returning the well to production.

2. A method for sealing points of leaking in a string of fluid containing tubing made up of lengths of pipe connected together and arranged in a producing well having a pressure substantially greater than atmospheric including the steps of placing at a selected point in said string of tubing la pressure regulator valve set to release pressure from the interior of -the tubing into the well bore at a pressure substantially greater than the maximum natural pressure exerted on the .string of tubing Within the well bore, exerting on the interior o-f said fluid filled string of tubing a selected fluid pressure great enough to cause said pressure regulator valve to release pressure and while maintaining said selected pressure on said fluid filled string of tubing, inserting a body of plastic thread sealing material with plugs above and below said body into the upper end of said string of tubing with said body of plasticl thread sealing material in intimate contact with the inner wall of said string of tubing and in such an amount that it occupies only a small fraction of the total length of sai-d string of tubing, exertingsaid selected pressure on said tubing above said body and thereby forcing said body of thread sealing material into intimate contact with the inner wall of said string of tubing at said selected pressure downwardly through said string of tubing with fluid diterent from said thread sealing material above and below `said body whereby said body of thread sealing material comes into intimate contact with the interior wall of said string of tubing from the upper end of said string of tubing to said regulator valve while maintaining a pressure no less than said selected pressure, reducing the pressure in the interior of the s-tring of tubing to less than the maximum natural pressure by releasing pressure from the upper end of the string of tubing, exerting said maximum natural pressure below said plugs and against any remaining portion of said body of thread sealing material which has not been deposited along the wall of said tubing and thereby forcing said plugs and any remaining portion yof said body of thread sealing material upwardly in said string of tubing in intimate conta-ct with the wall thereof and then lfrom the upper end of said string of tubing whereby the plugs in their upward passage scrape of excess thread sealing material, retrieving said pressure regulator valve from said string of tubing, and thereafter returning the well to production.

3. A method for sea-ling a leaking coupling at a known level in a string of tubing arranged in a producing well having a pressure substantially greater than atmospheric including the steps of inserting into the bore of said string of tubing a body yot plastic thread sealing material in intimate `contact with the inner wall of said `string of tubing and in such an amount that it occupies only a small fraction `of the total length of said string of tubing, exerting a selected pressure in said string of tubing above said body substantially greater than the maximum natural pressure exerted within the well bore on the exterior of said string of tubing and thereby forcing said thread sealing material in a body into intimate contact with the inner wall of -said string of tubing downwardly through said string of tubing with uid ditferent from said thread sealing material above and below said body at least to said leaking coupling, maintaining on said body said selected pressure whereby said body of thread sealing material comes in-to intimate contact with said leaking coupling at said selected pressure, reducing the pressure in the interior of said string of tubing to less than'th'e maximum natural pressure by releasing pressure from the 'upper end of said string of tubing, exerting 'said maximum natural pressure on the interior of the tubing below any remaining portion of said plastic thread sealing material which has not been deposited along the wall of said tubing and thereby forcing any remaining portion of said body upwardly in said string of tubing in intimate contact with the wall thereof and then from the upper end of sai-d string of tubing, and returning the well to production.

4. A method for sealing a point of leakage in a string of pipe arranged in a well having a pressure substantially greater than atmospheric including the steps of inserting into the bore of said string of pipe a body of thread sealing material, imposing a pressure in said string of pipe above said body of thread sealing material greater than well pressure and thereby forcing said body downwardly through said string of pipe whereby said body of thread sealing material comes into contact with t-he inner wall of said string of pipe, reducing the pressure in the interior of the pipe to less than well pressure by releasing pressure from the upper end of said string of pipe, exerting well pressure on the interior of the string of pipe below any remaining portion of said body of thread sealing material which has not been forced into a point of leakage or deposited along the wall of said pipe and thereby forcing any remaining portion of said body upwardly in said string of pipe in intimate contact with the wall thereof, and then from the upper end of said string of pipe.

5. A method in accordance with claim 4 in which the body of thread sealing material is forced through said string of pipe by uid pressure.

6. A method in accordance with claim 4 in which the body of thread sealing material is forced through said string of pipe by gas pressure.

7. A method in accordance with claim 4 in which the body of thread sealing material is forced through said string of pipe by water pressure. n

, 8. A method for sealing a point ofjleakage in a string of pipe arranged in a producing well having a pressure substantially greater than atmospheric including the steps of inserting into the bore of said string of pipe a body of thread sealing material in such an amount that it occupies only a small fraction of the total length of said string of pipe, imposing a selected pressure in said string of pipe above said body of thread sealing material substantially greater than the maximum natural pressure exerted on the exterior of said string of pipe and thereby forcing said body downwardly into contact with the inner wall of said string of pipe through said string of pipe while maintaining on said body said selente-d pressure whereby said body of thread sealing maerial comes into contact with the Wall at said selected pressure, reducing the pressure in the interior of the string of pipe to less than the maximum natural pressure by releasing pressure from the upper end of the string of pipe, exerting said maximum natural pressure on the interior of the vpipe below any remaining portion of said body of thread sealing material which has not been forced into a point of leakage or deposited along the wall of said pipe and thereby forcing any remaining portion of said body upwardly in said stringv of pipe in intimate contact with the wall thereof and then from the upper end of said string of pipe.

References Cited in the file of this patent UNITEDl STATES PATENTS OTHER REFERENCES Thermo-setting plastics elective in well repair by O. O. Dale, Petroleum Engineer, May 1947, pages 90, 92.