US3570612A

US3570612A - Fluid accelerator for use with an hydraulic jar in a well

Info

Publication number: US3570612A
Application number: US768363A
Authority: US
Inventors: Damon T Slator
Original assignee: Bowen Tools Inc
Current assignee: Bowen Tools Inc
Priority date: 1968-10-17
Filing date: 1968-10-17
Publication date: 1971-03-16
Anticipated expiration: 1988-03-16

Abstract

An accelerator for use with an hydraulic jar in a well for storing energy immediately above the jar and drill collars, including piston means for compressing a fluid on one side thereof to develop stored energy on the jarring stroke, and means for transferring fluid from the other side of the piston means to said one side thereof upon the return stroke of the jar.

Description

United States Patent [111 3,570,612

[72] Inventor Damon T. Slator [56] References Cited H UNITED STATES PATENTS [211 PP 763,363 2,988,147 6/1961 Webb 175/297x [22] Filed Oct. 17, 1968 3,088,533 5/1963 Sutliff 175/297 3 i t f iz 3,251,426 5/1966 LeBourg 175/297 1 sslgnee 3,353,613 11/1967 Harrison 175/293 3,399,741 9/1968 Monroe 175/297 3,405,773 10/1968 Sutliff 175/297 Primary Examiner-Nile C. Byers, Jr. Attorney-Pravel, Wilson & Matthews [54] FLUID ACCELERATOR FOR USE WITH AN ABSTRACT: An accelerator for use with an hydraulic jar in a 25:: {a g well for storing energy immediately above the jar and drill colm a mg g lars, including piston means for compressing a fluid on one U.S.Cl 175/297 side thereof to develop stored energy on the jarring stroke, E2lb1/06 and means for transferring fluid from the other side of the Field of Search 175/297, piston means to said one side thereof upon the return stroke of 293; 267/71 the jar.

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PATENTED MARI 61971 SHEET 2 OF 3 INV EN TOR flTTORNE YS 00700 7. J/a for BY Magda mum! WEIAW & MaHLewA FLUID ACCELERATOR FOR USE WITH AN HYDRAULIC JAR IN A WELL BACKGROUND OF THE INVENTION The field of this invention is accelerators for use with hydraulic jars in a well.

In 1960, U.S. Pat. No. 2,953,352 wasgranted to D. D. Webb for an accelerator wherein a compressible fluid was compressed to store energy on the jarring stroke of an hydraulic jar. Such accelerator served to accumulate tensile energy upon the upstroke of the jar rather than distributing the tensile energy through the full length of the pipe string being pulled. Such localized accumulation of the tensile energy in the accelerator made it possible to develop an adequate jarring blow with the'hydraulic jar in relatively shallow well depths, and also in crooked well bores which prevent a full stretching of the pipe string. Additionally, the accelerator served to isolate the jarring impact so that it was not transmitted to equipment at the surface.

However, such Webb accelerator suffers from the disadvantage that it produces a partial vacuum below the piston in the accelerator as the fluid is compressed during the jarring stroke of the jar; the partial vacuum creates a pressure differential across the piston which induces leakage of fluid to the reduced pressure. Then, upon a return of the piston for another stroke, the fluid trapped below the piston causes excessive pressure which either bursts the fluid seals or prevents a full closing of the tool.

The Harrison U.S. Pat. No. 3,353,613 discloses an accelerator which is an attempt to solve the problems of the Webb accelerator. However, Harrisons accelerator introduces other problems in its attempt to solve the problems of the Webb accelerator. Harrison provided an accelerator wherein one side of the piston is exposed to well pressure so that a partial vacuum is not produced, but the well pressure acts to partially close the accelerator before the jarring stroke. Such partial closing can be extremely detrimental, particularly in deep wells where the well pressure is high, since the force which can be developed in the accelerator is reduced in direct proportion to he well pressure.

SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of the accelerators in both the Webb patent and the Harrison patent. Thus, the accelerator of this invention is unafiected by well depths and pressures as is the Harrison device, but at the same time, the problem of trapping liquid below the piston on the return stroke of the jar as in the Webb device is eliminated. The present invention produces these advantages by means of a floating piston which compresses the liquid on the jarring stroke of the jar therewith, but which moves on the return stroke to permit fluid below the piston to pass above the piston rather than being trapped, whereby damage to the fluid seals is prevented and full closing is not obstructed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view, partly in elevation and partly in section, illustraing the accelerator of this invention;

FIGS. 2A, 2B, 2C and 2D are vertical sectional views of one-half of the accelerator of H6. 1 from substantially the upper portion thereof to the lower portion thereof, and with the piston of the accelerator disposed in position for the upstroke;

FIG. 3 is a view similar to FIG. 2C, but illustrating the piston in the raised position for transferring fluid during the downstroke of the apparatus; and

FIG. 4 is a partial cross-sectional view taken on line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT In .the drawings, the letter A designates generally the accelerator of this invention which a threaded upper end 10 for connection to a conventional pipe string (not shown) in a well, and a lower threaded pin 12 for connection with conventional drill collars (not shown) therebelow in the well. A typical hydraulic jar is then disposed below the drill collars, as is well understood. As will be explained hereinafter, the accelerator A is so constructed that the tensile energy stored therein by the compression of compressible noncombustible liquid is unaffected by the depth of the well and the pressure of the fluid in the well. Additionally, the apparatus A has means for transferring fluid during the return or downstroke of the accelerator A so as to prevent a trapping of liquid by the piston to thereby prevent damage to the seals and to also prevent interference with a full closing of the accelerator A, as will be more evident hereinafter.

The accelerator A includes an outer housing 15, which in the form of the invention illustrated in the drawings, has the threaded pin 12 at its lower end. A hollow mandrel 20 is longitudinally slidably disposed within the bore of the housing 15, and such mandrel 20 has the threaded box 10 formed at its upper end in the preferred form of the invention as illustrated in FIG. 1.

The housing 15 and the mandrel 20 are suitably splined together by splines 15a on the housing 15 and grooves or splines 20a on the mandrel 20 so as to permit relative longitudinal movement therebetween while providing for the transmission of rotational movement from the mandrel to the housing 15 if such is desired.

An upper seal 22 is provided by one or more resilient seal rings which may be formed of rubber or other suitable sealing material and which are preferably disposed between the upper end of the mandrel 20 and the housing 15 (FIGS. 1 and 2A). A lower seal 23 which is essentially the same as the seal 22 is formed at the lower end of the housing I5 for forming a seal between the mandrel 20 and the housing 15 (FIGS. 1 and 2C). It is to be noted that the housing 15 is illustrated as being formed in a plurality of separate parts, and likewise the mandrel 20 is illustrated as being formed in several parts, which is for assembly purposes and it is to be understood that the invention is not limited to having each formed in a plurality of parts since either may be formed in a single part except for assembly purposes.

A piston P (FIGS. 1, 2C and 3) is mounted on the mandrel 20 for limited longitudinal movement relative to such mandrel 20. The piston P is formed of metal and is flared or tapered outwardly at its upper end so that its annular lip 25 is adapted to provide a flexible metal-to-metal seal with the bore 15b of the housing 15. By reason of the externally tapered surface 26, only the lip 25 actually engages the bore 15b so as to minimize the frictional resistance therebetween. The flexibility of the lip 25 assures an adequate seal during the upstroke of the piston P for compressing the liquid which is thereabove. It is to be noted that the external surface of the mandrel 20 is spaced from the internal surface or bore 15b of the housing 15 so as to provide an annular space therebetween which serves as a chamber 30 in which a compressible noncombustible fluid such as silicone liquid is disposed. The upper seal 22 and the lower seal 23 thus confine the compressible liquid within the chamber 30 and prevent any communication with well fluid.

In the preferred form of the invention, a fluid transfer sleeve 35 is mounted on the mandrel 20 between the mandrel 20 and the piston P. Such sleeve 35 is also preferably mounted in conjunction with a seat ring 36. The sleeve 35 and the set ring 36 are assembled on the mandrel 20 between a threaded sleeve 20a which forms a lower part of the mandrel 20, and an upper threaded sleeve 38 which is threaded on the mandrel 20 and which has an upper surface 38a which provides an upper limit to the movement of the mandrel 20 with respect to the housing 15 should such surface 38a ever engage a shoulder on the housing I5.

The sleeve 35 has a lower external surface 350 which has a diameter corresponding substantially to the internal diameter 27 of the piston P. An enlarged external diameter is provided at the upper portion 35b of the sleeve 35 so as toform an annular laterally extending shoulder or stop 350 which is adapted to be engaged by a shoulder 28 on the piston P to limit the upward movement of the piston P relative to the sleeve 35 and the mandrel 20. A plurality of longitudinally extending slots 35d are formed in the external surface of the sleeve 35, but such slots 35d terminate at a lower shoulder 35a (FIG. 2C) so that fluid cannot pass inwardly of the piston P when the piston P is in the seated position of FIG. 2C. The lower annular surface 29 of the piston P may be termed a seating surface since it is adapted to engage the upper lateral surface of the seating ring 36 to form a seal therewith to prevent the flow of fluid from above the piston P to the area in the chamber 30 therebelow during the jarring stroke with the hydraulic jar used with the accelerator A of this invention.

The grooves or recesses 35d serve as pocket means to trap foreign particles such as small pieces of metal, rubber or the like which may be present inadvertently in the compressible liquid in the chamber 30. By trapping the particles in the recesses 35d, they are prevented from passing to the seating surface 29 and the upper surface 36a of the seating ring 36 so as to prevent any obstruction or interference with a proper seating and sealing between such surfaces during the jarring stroke with the hydraulic jar, and thus during the upstroke with the accelerator A.

In the operation or use of the accelerator A of this invention, it is connected in the pipe string (not shown) above the drill collars and the hydraulic jar (not shown). At the beginning of the jarring stroke, the piston P is in the first or lowermost position illustrated in FIG. 2C and is ready for the compression stroke. Thus, as the pipe string is pulled upwardly, the mandrel 20 is moved upwardly, but the housing moves at a slower rate since it is connected to the hy rhulic jar. Thus, there is relative upward-movement of the piston P and the mandrel relative to the housing 15, and since the liquid above the piston P cannot pass therebelow, such liquid is compressed in the known manner to store tensile energy within the accelerator A.

When the hydraulic jar reaches the upper end of its pulling stroke and is released from the restriction, the housing 15 is likewise released and then the stored energy of the compressed fluid within the chamber is transmitted to the housing 15 to cause it to move rapidly upwardly and thus accelerate the jarring action with the hydraulic jar therebelow.

The hydraulic jar and the accelerator A are then returned to their lowermost positions for repeating the jarring stroke with the jar. During such lowering or return movement of the accelerator A, the housing 15 is prevented from moving downwardly by reason of the jar having reached in its lowermost position so that the mandrel 20 may then move downwardly relative to the housing 15. During the downward movement of the mandrel 20 relative to the housing 15, the flexible metal lip 25 of the piston P has sufficient frictional engagement with the bore 15b of the housing 15 to cause the piston P to move to the uppermost position shown in FIG. 3. In that position, any fluid which is below the piston P may pass upwardly through the passages or slots d to the area above the piston P. Thus, any fluid which might have leaked past the piston P during the upstroke thereof may be returned to the area above the piston P to avoid applying excessive pressure to the seals.23 or the other seals in the apparatus A during the return stroke of the piston P to its lowermost position. Also, by allowing the transfer of the fluid, if any, which is below the piston P to the area thereabove during the return stroke of the piston P, the full closing of the piston P, or the full return of the piston P to its lowermost or starting position is unobstructed by any collected fluid below the piston P.

I claim: 1. An accelerator for use with a hydraulic jar in a well, comprising:

a. an outer housing; b. a hollow mandrel disposed in said housing and slidable relative thereto; c. the exterior of said mandrel being spaced from the interror of said housing to form an annular chamber therebetween;

an upper seal between said mandrel and said housing at the upper end of said chamber;

e. a lower seal between said mandrel and said housing at the lower end of said chamber;

f. a piston mounted on said mandrel for longitudinal movement relative thereto and disposed in said chamber between said upper seal and said lower seal;

g. compressible liquid in said chamber adapted to be compressed on one side of said piston during relative movement of said piston in one longitudinal direction with respect to said housing;

b. means for transferring liquid in said chamber from the other side of said piston to said one side thereof upon a relative movement of said piston in the other longitudinal direction with respect to said housing;

h. means on said mandrel and engageable with said piston for limiting longitudinal movement of said piston relative to said mandrel between a first position and a second position; I i

i. said piston and said mandrel having passage means associated therewith for establishing fluid flow from one side of said piston to the other when said piston is in said first position; and

j. means on said mandrel engageable with said piston for closing off fluid flow through said passage means when said piston is in said second position for compressing the liquid as said piston and mandrel move in said one longitudinal direction relative to said housing.

2. The structure set forth in claim 1, including a. pocket means between said mandrel and said piston for collecting foreign particles in the compressible liquid when said piston is in said second position.

3. The structure set forth in claim 1, wherein:

a. said means for closing off fluid flow through said passage means includes 1. a seating element mounted on said mandrel; and

2. a seating surface on said piston adapted to engage said seating element and fonn a seal therewith.

4. The structure set forth in claim 1, wherein:

a. said piston is annular; and

b. said means for transferring liquid includes:

1. a sleeve on said mandrel between said piston and said mandrel; and

2. passage means formed in said sleeve for the flow of the liquid therethrough from said other side to said one side of said piston when said piston moves in said other longitudinal direction. 5. The structure set forth in claim 1, wherein a. said piston is annular and is formed with an annular outwardly flared flexible metal sealing lip for metal-to-metal sealing engagement with the metallic bore of said housing.

6. The structure set forth in claim 1, wherein:

a. said movement of said piston in said one longitudinal direction occurs during the jarring stroke of the hydraulic jar; and

b. the transfer of the liquid with said means for transferring liquid occurs during the return stroke of the hydraulic jar.

Claims

1. An accelerator for use with a hydraulic jar in a well, comprising: a. an outer housing; b. a hollow mandrel disposed in said housing and slidable relative thereto; c. the exterior of said mandrel being spaced from the interior of said housing to form an annular chamber therebetween; an upper seal between said mandrel and said housing at the upper end of said chamber; e. a lower seal between said mandrel and said housing at the lower end of said chamber; f. a piston mounted on said mandrel for longitudinal movement relative thereto and disposed in said chamber between said upper seal and said lower seal; g. compressible liquid in said chamber adapted to be compressed on one side of said piston during relative movement of said piston in one longitudinal direction with respect to said housing; h. means for transferring liquid in said chamber from the other side of said piston to said one side thereof upon a relative movement of said piston in the other longitudinal direction with respect to said housing; h. means on said mandrel and engageable with said piston for limiting longitudinal movement of said piston relative to said mandrel between a first position and a second position; i. said piston and said mandrel having passage means associated therewith for establishing fluid flow from one side of said piston to the other when said piston is in said first position; and j. means on said mandrel engageable with said piston for closing off fluid flow through said passage means when said piston is in said second position for compressing the liquid as said piston and mandrel move in said one longitudinal direction relative to said housing.

2. a seating surface on said piston adapted to engage said seating element and form a seal therewith.

2. passage means formed in said sleeve for the flow of the liquid therethrough from said other side to said one side of said piston when said piston moves in said other longitudinal direction.

3. The structure set forth in claim 1, wherein: a. said means for closing off fluid flow through said passage means includes

4. The structure set forth in claim 1, wherein: a. said piston is annular; and b. said means for transferring liquid includes:

5. The structure set forth in claim 1, wherein a. said piston is annular and is formed with an annular outwardly flared flexible metal sealing lip for metal-to-metal sealing engagement with the metallic bore of said housing.

6. The structure set forth in claim 1, wherein: a. said movement of said piston in said one longitudinal direction occurs during the jarring stroke of the Hydraulic jar; and b. the transfer of the liquid with said means for transferring liquid occurs during the return stroke of the hydraulic jar.