US2865455A

US2865455A - Tubing scraper

Info

Publication number: US2865455A
Application number: US192061A
Authority: US
Inventors: Jr Benjamin J Rhoads
Original assignee: Pan American Petroleum Corp
Current assignee: Pan American Petroleum Corp
Priority date: 1950-10-25
Filing date: 1950-10-25
Publication date: 1958-12-23
Anticipated expiration: 1975-12-23

Description

Dec. 23, 1958 B. J. RHOADS, JR

TUBING SCRAPER Filed Oct. 25, 1950 I III FIG.

B. J. RHOADS JR.

IN V EN TOR.

II III \12 wvk g f ii: 5 6

. "ATTORNEY FIG.

United States Patent TUBING SCRAPER Benjamin J. Rhoads, In,

American Petroleum Delaware Hobbs, N. Mex., assignor to Pan Corporation, a corporation of This invention relates to scrapers for removing deposits from the interior of tubing and the like. More particularly, it relates to a scraper for removing paraflin deposits and the like from the tubing of an oil well.

The paraffin deposition on well tubing, due generally to the cooling of crude oil containing paraffin and the subsequent deposition, has been a problem in the art for many years. Wire-line and rod-actuated scrapers of various design have been proposed. Scrapers which will reciprocate in the tubing automatically also have been proposed. This invention is directed specifically to an improvement in tubing scrapers of the latter type. Previous scrapers which reciprocate automatically in a tubing have relied upon the scraper striking a solid bumper at the lower end of the stroke to cause the scraper to return to the surface. When these scrapers strike the bumper, a valve is closed or the diameter is expanded to form a plug which is forced up the tubing by the well pressure. The main difliculty with the automatic scrapers of this type has been that the scraper will not fall through the rising well fluids with suflicient velocity to trip the mechanism which packs oif or plugs flow through or around the scraper and causes it to be forced to the surface with the well fluid.

It is therefore an object of this invention to provide an improved scraper for removing deposits from the inside of vertical tubes. Another object of this invention is to provide an improved tubing scraper of the type which automatically reciprocates in the tubing. A more specific object of this invention is to provide an automatic tubing scraper which will automatically return to the surface from the bottom of a well or some intermediate point in a well regardless of the velocity at which the scraper descends through the tubing. Other objects of this invention will become apparent as the description thereof proceeds. In this description reference will be made to the accompanying drawings in which:

Figure 1 is a cross-sectional view of a tubing scraper of my improved design; and

Figure 2 is a cross-sectional view of a preferred embodiment of my tubing scraper.

In general, the objects of this invention are accomplished by actuating or tripping the lifting apparatus in a tubing scraper by fluid pressure on the scraper. That is, instead of striking a bumper at the bottom of the stroke to actuate the lifting mechanism of a scraper, as proposed in the prior art, my scraper relies upon the increase in static pressure in a well tubing as the depth increases to actuate the mechanism which raises the scraper through the tubing and removes any deposits from the tubing as the scraper rises.

The scraper herein described and claimed operates in a system similar to that proposed in, for example, S. Patent 2,143,450. In that disclosure, as is typical in the prior art, the lifting mechanism is actuated when the scraper strikes the bumper at the bottom of its, stroke. As will beseen from the following detailed description of certain embodiments of my-invention, the actuation of the 2,865,455 Patented Dec. 23, 1958 liftin g mechanism by the hydrostatic fluid head on the 'scraperhas many advantages over the system previously proposed.

Referring now to Figure 1 of the drawings, the scraper consists of a body 4 which is desirably substantially smaller in diameter than the inside diameter of the tubing in which it operates. The body is divided into two chambers, an upper pressure chamber 5 and a lower gas chamber 6. The pressure chamber is in communication with the atmosphere or well fluids in a well through a port 7. This portis, however, normally closed by check valve 8 which seats against the pressure chamber head ,9 and is held in position by a compression spring 10. A check valve stem 11, which is aflixed to check valve 8, extends through a pressure chamber divider 12. ,This divider has ports 13 which permit communication of fluid between the upper and lower ends of pressure chamber 5. The divider has a recess 14 in which is placed a quickacting mechanism such as a snap ring 15. This snap ring is held in position by a bushing 16, or the like, which is threaded into the divider and limits the vertical movement of snap ring 15. This quick-acting mechanism, i. e., snap ring 15, is resilient and has a normal diameter in a non-stressed state less than the diameter of check valve stem 11. A groove 17 is cut in the valve stem, and the snap ring is adapted to fit into this groove and, once it is closed, hold check valve 8 in a closed position. .Compression spring 10 is placed on the valve stem in a stressed condition, as pointed out hereinafter, to close the check valve when pressure differentials across the valve permit.

Means are provided to release the fluid pressure in pressure chamber 5 when the scraper is at the top of the well. This pressure is normally released when the scraper strikes a bumper (not shown) in the top of the tubing. A pressure release mechanism, such as valve-actuating rod 18 which is attached to check valve 8, may be used for this purpose. Obviously, however, separate check valves and pressure release valves may be provided for admitting fluid to pressure-chamber 5 and releasing fluid therefrom respectively.

A device for transmitting pressure into motion, such as a bellows, a diaphragm, a piston, or the like, is placed in the body 4 between pressure chamber 5 and gas chamber 6. This device, hereinafter, for convenience, designated piston 19, is represented in Figure l as a diaphragm which is sealed around the periphery to the body 4 and thereby prevents fluid communication between pressure chamber 5 and gas chamber 6. A packer 21, which is actuated bypiston 19 through a piston rod 22, is adapted to be expanded to a diameter greater than the diameter of body 4 and substantially restricts flow of fliud in a well tubing past'the body. This packer may be any of a number or designs. For example, it may be a solid rubb'er packer expanded by motion of. piston rod 22, it may be an inflatable packer which is filled and expanded by fluid pumped by the action of piston rod 22, or it may be a double semi-circular flapper packer of the type shown. The hinged diameter of these arcuate flappers is connected by a pin 23 to piston rod 22. This pin and the central portion of the packer is drawn up into a slot 24 in the lower head 25 of body 4 by piston 19 and piston rod 22. Resilient means, such as spring 26, tends to contract packer 21. Obviously, this spring could be replaced by various means, including rubber; or, in some cases, it may be desirable to prepressure gas chamber 6 with an expandable gas. It will also be apparent that in some fcasesas,- for example, where the packer is rubberor some such resilient material-the packer could be placed on the body in a contracted position, and no spring would be required to contract the packer. This packer, whilefit'is employed primarily as a means to seal the tubing so that well 'fluids will not by-pass the body,

differential across piston 19 remains constant.

known types may be placed on the outside of the body or .on a separate core which is carried by the above-described Japparatus.

In operation, the force to be exterted byithe va .springsis predetermined by calculation or by trial and error and set so that the scraper will reciprocate in the tubing between selected elevations or pressure heads.

The scraper is then introduced (in some cases, through a lubricator) into a flowing well, the tubing of which may be equipped at the well head with a resilient bumper. The body 4, being substantially smaller in diameter than the inside diameter of the tubing, the scraper falls relatively-freely through the well tubing. As the scraper falls through the fluid in the tubing, the static fluid head thereon increases as the depth and density of the fluid in the tubing increase. :8 duetothe static head of this fluid in the tubing is greater than the-preset force on the check valve due to compression spring 10 and snap ring 15, check valve 8 is opened,

When theforce on check valve allowing well fluid, including some gas and trapped air, tofill pressure chamber 5. When the pressure in pressure chamber: 5' plus the pressure required to compress spring 26 is greater than the pressure in gas chamber 6,

surface of the tubing when the packer is "expanded. Furthermore, scratchers or cutters of any of the well- 'ious piston 19 will move down sufliciently to expand packer 21 so that it completely fills, or packs off, the tubing. 'At this time, the well fluidflowing upwardly in the tubing carries the scraper to the surface. The packer remains expandedduring the upstroke, since the pressure That is, afterthe scraper starts to rise, there is nofurther increase in the static pressure on the scraper; and, therefore, check valve 8 closes, sealing the body, in general, and pressure chamber 5, in particular, so that'piston19 cannot rise and contract packer 2t.

The fluids in the well which flow at high velocity carry the scraper to the surface where valve-actuatingrod 18 strikes a bumper in the upper end of the tubing. When this valve-actuating rod strikes the bumper, check valve 8 is opened, allowing the pressure in pressure chamber 5 to equalize with wellhead pressure. As the pressure in pressure chamber 5 is thus released, the compressed gas and spring 26 in gas chamber 6 displace piston 19 upwardly. The rise of this pistoncontracts packer 21,

*iaseansa the section 37 of body 4 which has a reduced inside diameter.

Scraper body 4 has a pressure chamber 5 and a gas chamber 6. The head 9 of pressure chamber 5 is fitted with one or more check valves 8 which seat upwardly against head 9 and which are normally held in a closed position by compression springs 10. A valve-actuating rod 18 extends through the chamber head. This rod has a pin 38 aflixed transversely thereto a short distance .above the upper end of check valve stem 11. A packing' gland 39 is provided in head 9 around valve-actuating rod'18 to seal the upper end of the pressure chamber and allow vertical motion of the rod therethrough. A packing gland extension 41 containing slots 42 aligns pin 38 with valve'stem 11 and allows limited vertical movement of the pin. Valve-actuating rod 18 is normally held in the upper position by spring 26 which rests on the lower head 43 of pressure chamber 5. The lower head 43 contains a valve seat 44, or may, in some cases, contain a sleeve valve, which has a diameter substantially smaller than the inside diameter of body 4. Piston 19 .is disposed in gas chamber 6 and contains a packing ring 45 which prevents fluid communication around the piston between the .gas chamber and the pressure chamber, A piston rod 22, having a fluid passage 46 partially therethrough and terminating at the bottom in communication with the lower end of gas chamber 6, is connected to the piston and extends down through the gas chamber andthrough a central bore 47 in the lower gas chamber head 25. The piston contains a largediameter. bore 48 which is in communication, through fluid passage 46,,with gas chamber 6. A piston valve 49 having a cross-sectional area less than the cross-sectional area of pistonlSt is threaded into the large diameter bore 48. This. .piston valve. seats on valve seat 44 when the piston. is in its upwardposition. Valve-actuating rod 18 extends through aport 51 in the piston valve. A valve head,52 on the lower end of the valve actuating rod seats. against the lower face of piston valve 49. .This valve head, also contains ashort cylindrical section 53 which has substantially the same diameter as port 51 and acts as a sleeve valveto permit some motion between valve-actuating rod 18 and piston 19 before opening the valve and permitting fluid communication between gas chamber ,6 and pressure chamber. 5 through fluid passage 46. v

Downward movement of piston 19 and piston rod 22 through body. 4 actuates the packer 21, which prevents flow of well fluids upwardly around the scraper. This allowing thescraperto fall in the tubinglthrough the well fluid. As the scraper thus reciprocates in the tubing, it scrapes any deposit, such as parafiin, ironjoxide, calcium sulfate, or the like, off the ,walls of the tubing and carries it to the surface.

Referring now more particularly to Figure} in which a preferred embodiment is shown, the body 4 may be fitted with cutters 31 for a deposit on the inside surface of the well tubing. One type of such cutter similar to that described in U. S. Patent 2,315,069 is shownh This cutter consists of a knife 32 on 'a'spring 33' which rotates on a shaft 34 that is set in the body. "The cutter operates in a recess 35 in body 4. That is,'as thescraper is descending in the tubing, the cutter rotates upwardly. about shaft 34, thereby decreasing the resistance of the knives and allowing the scraper to fall'freely through the tubing. On the upward stroke of the scrapper, the cutters tall by their own weight into a horizontal position where they are maintained by the 'heel 366 which strikes the bottom of recess 35. Any number of jtheserecesses may be provided along the'bodyflforexample, Ltnay employ ten or'more cutters ,by;extending the ,lengthlof packer may .be any of. a number of types, as discussed above. As one example, I have shown a doublesemicircular. flapper packer which, in a collapsible orv contracted positionas shown, has the two

arcuate sections

54 and 55 drawn upwardly. in.a slot..24 in lowerhead 25. ,The two arcuate sectionsare hinged on pin 23 which is on a diameter of the extended packerand-is. connected to the bottom end of piston rod 22. The sections may be urged apart by torsion springs 56 or the like so that, when the hinged diameter is moved down to below the end of slot 24, these two sections spread apart and substantially fill the cross .section of the tubing, preventing fluid frorn by-passing, and thereby providing a means to lift thescraper in the tubing.

inoperation, this embodiment of "my scraper, in the positionshowmfis introducedinto the top of the tubing with the tubing. open in case'of-a low-pressure vwell or, generally, asin the case of most flowing wells, through a lubricator. As the scraper falls through the fluid in the well, or as the lubricator is opened exposing the scraper to wellhead tubing pressure, the pressure differential across checkvalves 8 is increased, and eventually the valves are opened, fillingpressure chamber 5 with=well fluid.. ,Assuming that the scraper was introduced into the well-with gas. chamber .6 filled -.with air.- on-some iother gas; at substantially atmospheric. pressure,v this. .wellpresv sure in pressure chamber 5 forces piston 19 down against the action of spring 26. As the piston moves downward, piston rod 22 drives pin 23 below slot 24, so that the two

sections

54 and 55 spread apart, plugging the tubing. Any flow of well fluid upwardly in the tubing then urges the scraper up to the top of the tubing. As the scraper hits a bumper (not shown) at the top of the tubing, valve-actuating rod 18 is forced down. The spacing of the parts is so arranged that, when the packer is in an expanded position against the lower end of head 25, the clearance between pin 38 and the upper end of valve stems 11 is very small, for example, less than about 4; inch. The first action of the pin 38 is to open valve 8, equalizing the pressure in pressure chamber 5 with wellhead pressure and then, by continued upward motion of the scraper, to open valve 52. Thus, when the scraper is at the upper limit of its travel, gas chamber 6 is in communication with the well fluids through fluid passage 46, bore 48, port 51 pressure chamber 5, and valve 8. At this position, the pressures being equal on both sides of piston 19, spring 26 urges the piston and piston rod upward in the body, forcing the packer flappers into slot 24. At the same time, spring 26 seats piston valve 49 against seat 44 and closes

valves

8 and 52, thereby sealing pressure chamber 5 and gas chamber 6 and allowing the scraper to fall in the tubing. As the scraper falls through the tubing, the static pressure, i. e., the fluid head, on the scraper increases;.and, after the differential pressure across check valve 8 is suflicient to overcome the force of valve spring 10, the pressure in pressure chamber 5 commences to increase. When the scraper has fallen to a position at which the pressure in pressure chamber 5 multiplied by the area of piston valve 49 is equal to the force of spring 26 plus the total upward force on the piston due to the pressure in gas chamber 6 and the Well pressure on the end of piston rod 22, the piston is moved downwardly, opening piston valve 49 and exposing the total area of the top of the piston to the pressure of pressure chamber 5. This pressure times the top area of piston 19 being substantially greater than the wellhead pressure in gas chamber 6 times the bottom area of piston 19, the piston will be forced downward at high velocity by expansion of the gas in pressure chamber 5, thereby expanding packer 21 with a snap action. By this snap action or instantaneous expansion of the packer, an equilibrium condition at which the scraper merely floats in the well is avoided. When the packer is expanded, the scraper is carried upward in the tubing at the velocity of the well fluids, until it strikes the upper bumper as above described.

Thus, it will be seen that, inmy preferred embodiment, the pressure in gas chamber 6 will be equalized with wellhead pressures each cycle of the scraper, so that gradual changes in well conditions will not unbalance the operation of the scraper. An additional feature of this embodiment is that, since pin 38 opens check valve 8 before short cylindrical section 53 opens port 51, the pressure in pressure chamber 5 is equal to wellhead pressure when port 51 is opened; and, therefore, there is no fluid transfer through fluid passage 46 except when the wellhead pressure changes. By this means, there is substantially no change in the fluid within gas chamber 6, and the scraper can operate for extended periods of time without the chamber becoming contaminated with foreign matter, such as sand or the like.

From the above description of certain embodiments of my invention. it will be apparent that various modifications may be made in the apparatus and that the apparatus is adapted to various uses. For example, the fact that paraffin cutters or the like may be attached does not prevent its use as a gas-lift plunger. Since the packer is expanded automatically by fluid pressure on the apparatus,

it is particularly suited for use as a gas-lift plunger in flowing wells-i. e., wells in which a plunger cannot be actuated by the injection of gas or the like. Such modifir 6 cationsas may be construed to fall within the-scope and meaning of the appended claims are therefore considered to be within the spirit and intent of the invention.

I claim:

1. A scraper for removing deposits from well tubing comprising an elongated body, cutters for said deposit on said body, a pressure chamber in said body, a gas chamber in said body, a piston between said chambers,v a packer on'said body, said packer normally being held in a contracted position by resilient means, a piston rod connecting said packer with said piston, said packer being expanded by a fluid pressure in said pressure chamber greater than the fluid pressure in said gas chamber, quickacting means to expand said packer instantaneously, a check valve in said pressure chamber, said check valve normally allowing fluid to enter said pressure chamber but preventing exhaust thereof, and means to release the pressure in said pressure chamber and contract said packer when said scraper is at the top of said tubing.

2. A scraper for removing deposits from well tubing comprising an elongated body, cutters for said deposit on said body, a pressure chamber in said body, a gas chamber in said body, a piston between said chambers, a packer on said body, said packer normally being held in a contracted position by resilient means, a piston rod connecting said packer with said piston,'a check valve in said pressure chamber, said check valve normally allowing fluid to enter said pressure chamber but preventing exhaust thereof, and means to release the pressure in said pressure chamber and contract said packer, said piston having two sections of different diameter, the smaller diameter section being first exposed to the pressure in said pressure chamber and the larger diameter section being exposed tosaid last-named pressure when the force on said small diameter section is greater than the force of said resilient means whereby said piston is moved with a snap action and said packer is expanded instantaneously.

3. A tubing scraper according to claim 2 in which said gas chamber is in communication 'with said pressure chamber once each cycle of said scraper in said Well to equalize the pressure in said gas chamber with wellhead pressure, whereby variations in well pressure will not materially affect the depth to which said scraper falls in i said Well.

4. An apparatus for automatic reciprocation in a vertical tube in which fluid is rising at high velocity, comprising an elongated body having a cross-sectional area substantially less than the cross-sectional area of said tube, a pressure chamber in said body, a gas chamber in said body, a packer on said body, said packer normally being retained in a contracted position by resilient means, means to release the pressure in' said pressure chamber, a piston between said chambers and connected with said packer, said piston having two sections of different diameter, the smaller diameter section being normally in communication with said pressure chamber and the larger diameter section being normally in communication with said gas chamber, the fluid pressure on said smaller diameter section acting against the fluid pressure on said larger diameter section to expand said packer, a check valve to admit said fluid tosaid pressure chamber whenever the pressure in said tube is greater pressure chamber by a predetermined amount, means to release the pressure in said pressure chamber once each cycle of said apparatus in said tube and contract said packer, a piston valve for exposing the shoulder area of said piston between said smaller diameter section and" said larger diameter section to the fluid pressure said pressure chamber when said last-named pressure multiplied by the cross-sectional area of said piston valve is greater than the total force due to pressure in said gas chamber plus the force due to said resilient means acting on said larger diameter section, whereby said piston will expand said packer instantaneously at a point in said tube having a selected static fluid head.

than the pressure in said 5. An apparatus according to claim 4 having a valved fluid passage between said gas chamber and said pressure chamber and means to open said passage once each cycle of said apparatus to equalize the pressure in said chambers.

6. A plunger apparatus for reciprocation in a vertical conduit within a well comprising an elongated body smaller in cross-sectional area than said conduit, means includinga piston forming an enclosed chamber in said body, an expansible fluid in said chamber, closure means to restrict flow of well fluids from one end of said apparatus to the other when said apparatus is in a first condition in said conduit and to permit flow from one end of said apparatus to the other when said apparatus is in a second condition in said conduit, a piston rodconnecting said piston and said closure means to restrict said flow as said piston moves to compress said expansible fluid and to permit saidflow as said piston moves to expand said fluid, said piston being moved to compress and store energy in said fluid by the application of a high pressure externally of said apparatus, means to prevent release of said energy in said fluid regardless of a decrease in said external pressure and the existence of an excess of energy in said fluid for moving said piston and said closure means from said first position to said second position, and separate means to release said energy only upon contact of said apparatus with a member exterior of said apparatus.

7. A plunger apparatus for reciprocation in a vertical conduit within a well comprising an elongated body smaller in cross-sectional area than said conduit, means including a piston forming an enclosed chamber in said body, an expansible fluid in said chamber, a packer on said body, a piston rod connecting said piston and said packer for expanding said packer as said piston moves to compress said fluid and for contracting said packer as said piston moves to expand said fluid, means to apply well pressure to one side of said piston to compress and store energy in said fluid and to expand said packer when said well pressure is greater than the pressure of said fluid, means to prevent release of said energy and contraction of said packer regardless of said well pressure and the existence of an excess of energy in said fluid for contracting said packer, and separate means to release said energy only upon contact of said apparatus with a member exterior of said apparatus.

8. A plunger apparatus according to claim 7 including quick-acting means to restrain said piston as it moves to compress said fluid in said chamber.

9. A gas liftplunger for automatic vertical reciprocation comprising an elongated body, means including a piston forming an enclosed chamber in said body, an

expansible fluid in said chamber, a packer on said body' adapted to expand to a cross-sectional area greater than the cross-sectional area of said body, a piston rod connecting said piston to said packer to actuate the expansion and contraction of said packer, said packer being expanded when said piston moves to compress said expansible fluid in said chamber and being contracted when said piston moves to expand said expansible fluid in said chamber, said piston being moved to compress and store energy in said fluid by the application of a high pressure externally of said body and to expand and release said energy insaid fluid when said pressure is reduced and when said plunger contacts an exterior member, and snapacting means to prevent movement of said piston and compression of said fluid until the pressure differential across said piston issuflicient to expand said packer completely and to prevent movement of said piston and expansion of said fluid until said plunger contacts said external member.

10. A gas lift plunger according to claim 9 including means to equalize the pressure in said chamber with the external pressure on said plunger when said plunger contacts said external member.

11. In an apparatus for reciprocation in a well tubing, an elongated body, an expansible packer on said body, means forming a gas chamber in said body, a piston exposed on one side to the pressure in said tubing and on the other side to the pressure in said gas chamber, and means connecting said piston to said packer to actuate the expansion. andcontraction of said packer, the improvement comprising a fluid passage between said gas chamberand the outside of said body, normally closed valve means in said passage, and means to open said valve means and equalize the pressure in said gas chamber with the gas pressure in said tubing when said apparatus contacts the upper end of said tubing whereby changes in pressure at the bottom of said tubing will be automatically compensated once each cycle of said apparatus.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,698 Brown Aug. 18, 1953 2,143,450 Pippenger Jan. 10, 1939 2,196,658 Burt Apr. 9, 1940 2,315,069 McKean et al. Mar. 30, 1943 2,334,788 OLeary Nov. 23, 1943 2,372,016 Rockwell Mar. 30, 1945 2,373,006 Baker Apr. 3, 1945 2,458,631 Parks Jan. 11, 1949 2,714,855 Brown Aug. 9, 1955