US3311180A

US3311180A - Hydrostatically balanced bumper sub

Info

Publication number: US3311180A
Application number: US355836A
Authority: US
Inventors: Lafayette E Gilreath; Eddie C Mcgarrahan
Original assignee: Houston Oil Field Material Co Inc
Current assignee: Houston Oil Field Material Co Inc
Priority date: 1964-03-30
Filing date: 1964-03-30
Publication date: 1967-03-28
Anticipated expiration: 1984-03-28

Description

March 28, 1967 L. E. GILREATH ETAL 3,311,180

HYDROSTATICALLY BALANCED BUMPER SUB Filed March 30, 1964 2 Sheets-Sheet l United States Patent 3 311 180 HYnRosTATrcALLYBAiANcEn BUMPER SUB Lafayette E. Giireath and Eddie C. McGarrahan, Houston, Tex., assignors to Houston Oil Field Material Company, Inc., Houston, Tex., a corporation of Delaware Filed Mar. 30, 1964, Ser. No. 355,836 9 Claims. (Cl. 175-293) The present invention relates to a hydrostatically balanced bumper sub, and more particularly, relates to a bumper sub for use in a drilling string for drilling a well bore in which the sub, when connected in the drill string, and subjected to the high pressure fluids both in the drilling string and in the well bore provides a structure in which the vertical hydrostatic forces acting on the sub are balanced.

Generally, a bumper sub is a tool which is connected in the drilling string which is used to drill a well bore. A drilling type bumper sub is generally placed immediately above the drill bit or drill collars. The bumper sub is used to affect a bumping action to prevent the drill string from becoming stuck in the well bore. However, since the usual drilling fluids are pumped down the drill string, out the drilling bit, and up the annulus between the drilling string and well bore the bumper sub will be subjected to the usual hydrostatic pressures of the fluid in the string and in the well bore. Because of the great depths to which wells are now being drilled, these hydrostatic pressures are considerable and act against any unbalanced areas of the surfaces of the drilling string including the bumper sub and create tremendous forces which may adversely affect the drilling operation. For instance, it is desirable in drilling operations to keep the drill string as straight as possible so as to drill straight holes and to accomplish this result the drill string is generally kept in tension. Therefore, if the bumper sub provides a downwardly directed horizontal surface area in excess of the area of its upwardly directed horizontal surfaces, an upwardly directed hydrostatic force may result, particularly in deep wells, which will act on and place the drilling string in compression and cause it to bow or cork screw. Furthermore, unbalanced hydrostatic forces may act on the movable or bumper section of the bumper sub and cause the sub to be locked in position and prevent its operation.

Therefore, it is a general object of the present invention to provide a bumper sub in which all of the vertical hydrostatic forces acting on the bumper sub are balanced.

A still further object of the present invention is the provision of a bumper sub having a housing, a wash pipe connected thereto, and a telescoping supporting stem connected to the lower end of the drill string in which the areas of the horizontally directed surfaces on the housing and wash pipe which are exposed to the well fluid are balanced to prevent any vertical hydrostatic pressure acting on the drill string.

Yet a further object of the present invention is the provision of a bumper sub having the usual housing and wash pipe for connection at its upper end in a drill string, and a telescoping supporting stem which is adapted to support the lower portion of the drill string in which the exposed horizontal areas of the housing and wash pipe are substantially equal, and the hydrostatic pressure acting in an upward direction on the supporting stem is balanced or overcome by adding drill collars having a suflicient weight to the lower end of the stem.

Yet a still further object of the present invention is the provision of a hydrostatically balanced bumper sub having a housing adapted to be connected at its upper end to a drilling string, a wash pipe connected to and forming an annulus with the housing, and a supporting stem the 3,3l L Patented Mar. 28, 167

upper end of which telescopes into the annulus and is nonrotative relative to the housing, and in which the annulus is sealed from the fluid in the drill string and well bore whereby the jarring and contact surfaces are enclosed in a suitable lubricant.

A still further object of the present invention is the provision of a hydrostatically balanced bumper sub having a housing, a wash pipe, at supporting stern telescoping in an annulus between the wash pipe and housing and sealin ly engaging the wash pipe and annulus and wherein an annular lubricant divider is connected to the top end of the stem to insure adequate lubrication on the engaging surfaces and wherein bearings having spiral helical grooves are provided to cause the hearings to rotate and prevent grooving of the bearing surfaces.

Yet a further object of the present invention is the provision of a hydrostatically balanced bumper sub having a housing and a wash pipe forming an annulus, a supporting stem, the upper end of which is telescopically slidable in said annulus, said annulus including a gas and a lubricant, but sealing the upper end of said stem from hydrostatic forces and in which the horizontal surfaces of the housing and wash pipe, when the sub is positioned in a drilling string, are balanced.

Other and further objects, features and advantages will be apparent from the following description of a presently preferred embodiment of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings, where like character references designate like parts throughout the several views, and where,

FIGURE 1A is a fragmentary elevational view, partly in cross-section, illustrating the top portion of the bumper sub of the present invention,

FIGURE 2 is an enlarged cross-sectional view taken along the line Z2 of FIGURE 1A,

FIGURE 3 is an enlarged cross-sectional view taken along the line 33 of FIGURE 1A,

FIGURE 13 is a fragmentary elevational view, partly in cross-section, and is a continuation of FIGURE 1A,

FIGURE 1C is a fragmentary elevational view, partly in cross-section, and is a continuation of FIGURE 1B, and

FIGURE 4 is an enlarged perspective view of one of the spirally grooved bearings of the present invention.

Referring now to the drawings, the reference numeral 10 generally indicates the hydrostatically balanced bumper sub of the present invention and generally includes a housing 12 and a wash pipe 14 which are connected together and adapted to be connected at their upper ends to the upper portion 15 of a conventional drill string, and includes a supporting stem 16 which slidably telescopes within the housing 12 and at its lower end (FIG- URE 1C) is adapted to be connected to and support the lower portion 18 of the drilling string.

The housing 12 may include, as best seen from FIG- URE 1A, an upper sub 20 having conventional threads 21 for connection to the upper portion 15 of the drill string, and as best seen in FIGURES 1B and 1C, respectively, upper cylinder 22 and lower cylinder 24. And between the upper and lower cylinders a hexagonal guide sub 26 is provided, which as will be more fully described hereinafter engages the hexagonal portion 32 of the supporting stem 16 to provide rotative movement between the housing 12 and the stem 15.

Referring again to FIGURE 1A, the wash pipe 14 is secured such as by threads to upper sub 24} and in addition to serving to direct the drill string fluid downwardly through the Wash pipe is spaced from the upper cylinder 22 to provide an annulus 30 in which the upper end of the supporting stem 16 moves.

The supporting stem 16 slidingly telescopes with the upper and

lower cylinders

22 and 24 as best seen in FIG- URES 1A and 1B and as best seen in FIGURE 3 includes a hexagonal section 32 for engagement with the hexagonal sub 26 (FIGURE 1B) whereby rotative movement may be transmitted from the housing 12 to the supporting stem 16 and thus .to the lower portion of the drilling string 18 (FIGURE 1C). Furthermore, the supporting stem 16 includes upper engaging shoulder 34 (FIGURE 1A) and lower engaging shoulder 36 (FIGURE 1B) which on upward or downward movement of the housing 12 and of the hexagonal sub 26 will cause a bump or jar against the

shoulders

34 and 36 to provide a conventional bumping action to the lower portion 18 of the drilling string as may be desired.

However, as has previously been mentioned, in the present day practice of drilling deep oil and gas wells the fluid pressures encountered in the drill string and well bore have become increasingly large. For example in a 10,000 foot well the normal drilling pressure may be as high as 6,000 pounds per square inch. Therefore, it becomes important to insure that any horizontally disposed surfaces on the well string which are exposed to Well fluids are suitably compensated or balanced; otherwise tremendous forces will act against those surfaces with adverse results. And, of course, if the movable stem 16 and the lower portion 18 of the drill string are unbalanced the supporting stem 16 could become locked in position and thus be inoperable.

Therefore, it is important that all of vertical hydrostatic forces on the bumper sub be balanced. Referring now to FIGURE 1A, it is noted that the outside diameter of the upper portion of the drill string has a diameter of A. And referring to FIGURE 1C it is to be noted that the internal diameter of the cylinder 24 is also equal to A. Since the outside areas or outside diameter of the housing 12, that is, sub 20,

cylinders

22 and 24, and sub 26, are the same, it is therefore apparent that the horizontally disposed surfaces on the housing 12 which are exposed to the drilling fluid, when the housing 12 is in position in the drilling string, are equal in an upward and downward direction and therefore the vertical hydrostatic forces on the outside of the housing 12 are equal and thus balanced. That is, the upwardly directed horizontal component of the surface 40 isequal to the downwardly directed horizontal component of surface 42. Similarly, and referring to wash pipe 14 the upwardly directed horizontal component of exposed surface 44 (FIGURE 1A) is balanced by the downwardly directed horizontal component of the surface 46 (FIGURE 1B). Therefore, the

hydrostatic forces acting on the housing 12 and the wash pipe 14 are balanced and thus will not adversely affect the upper portion 15 of the drilling string to which they are connected.

Referring again to FIGURE 1A it is to be noted that the annulus 30 between the housing 12 and the wash pipe 14 includes a plug 48 through which a suitable lubricant may be inserted for lubricating the engaging surfaces between the movable supporting stem 16 and the housing 12, and the wash pipe 14.

Suitable seals

50 and 52 are provided between the stem 16 and the wash pipe 14. Similarly, suitable seals 54 and 56 are provided between the stem 16 and the housing 12 (FIGURE 1B). Thus, it is to be noted that the annulus 30 is sealed and is not exposed to hydrostatic pressures from the fluid in the drilling string and well bore. Because of this, there will be no hydrostatic force acting against the upper end of the movable stem 16. Referring again to FIGURE 1A, the lubricant is filled through the plug 48 to a level 58 when the apparatus 10 is in an extended position. This leaves the remainder of the annulus 30 filled with air at atmospheric pressure of 14.7 pounds per square inch. The volumetric change of air may be, for example, in the ratio of three to one so that the maximum air pressure in the annulus 30 when the bumper sub is fully closed will be less than 45 pounds per square inch. Thus, after the movable stem 16 is moved upwardly in the annulus 30, there will be an unbalanced pressure of 45 pounds per square inch acting downwardly on the upper end of the stem 16, and upwardly on the upper sub 20. However, this pressure is insignificant in comparison with the other forces acting on the sub 10 and will have no adverse effects on the drill string or on the operation of the sub 10. Nevertheless, the use of a gas in the closed and sealed annulus 30 prevents the presence of well fluids and their extremely high pressures and adverse consequences, and yet does not provide a hydraulic block as would be the case if the entire annulus were filled with lubricant.

Referring now to FIGURES 1A, 1B, and 1C, it is to be noted that the exposed horizontal components of the downwardly directed faces of .the movable stem 16 are not balanced by the horizontal components of any upwardly directed faces on the movable stem which are exposed to the tremendous hydrostatic pressures in the well bore. This is because the upper end of the movable stem 16 is positioned in the annulus 30 and sealedoff from the hydrostatic pressures in the well bore by the

seals

50 and 54. Thus, an upwardiforce acts on t-he'stem 16 having antagnitude of the hydrostatic pressure. times the cross sectional area between the, outer diameter of the washpipe 14 and the inner diameter of theupper and

lower cylinders

22 and 24. Therefore, suitable drill collars (not shown) must be connected to the lower portion 18 of the drill string with a sufficient weight to balance the upwardly directed hydrostatic pressures acting on the movable stem 16.

Referring now to FIGURES lA and.2, it is to be noted that an annular lubricant divider 68' is provided connected to the upper end of the stem 16 sothat lubricant will remain in 'a cup 7 0. regardless of the position of the stem 16 relative to the housing 12 so as to provide suflicient lubrication for the contact surfaces between the. wash pipe 14 and the stem 16. Otherwise, if the lubricant level falls below the top of the stem. 16, only the surfaces between the stem 16 and the housing 12 would be lubricated.

And referring to FIGURES 1A and 1B, suitable bearings. 72 are provided about the movable stem 16 andengaging the upper and

lower cylinders

22 and 24. Referring to FIGURE 4 it is noted that the bearings 72 include spiraling grooves74 which will cause the bearing 72 to rotate and prevent grooving of the bearing surfaces.

In operation, the bumper sub 10 of the present invention is connected into a conventional drilling string. In the case of using the bumper subas a drilling-type bumper sub, it is run immediately above the bit or drill collars (not shown). Since the housing 12' is threadably connected to the upper portion of the drill string 15v (FIG- URE 1A), the rotative movement of the drill string will be transmitted by hexagonal sub 26 through hexagonal surfaces 32 on the telescoping stem. 16 to the lower portion of the drilling string 18 (FIGURE 1C) and to the drill hit. As is convention the bumper sub may provide a bumping or jarring-action. 15 of the drill stn'ng may be raisedand lowered thereby raising and lowering the hexagonal sub-26 to alternately contact or jar engaging shoulders34 and 36 on the sup porting stem 16. to alternately jar the lower portion 18 of the drilling string upwardly and downwardly. However, it is to be noted that the areas of the horizontally directed surfaces on the housing 12 and the wash pipe 14, which are exposed to well fluids, are balanced in an upward and downward direction. That is, the areas directed upwardly are substantially equal to the areas di-- rected downwardly thereby balancing the vertical hydrostatic pressures acting on these elements. The unbalanced upwardly directed force acting on the supporting stem 16 is balanced by the weight of drill collars (not shown) connected tothe lower portion of the drilling string 18. It is to be noted that the upper end of the supporting stem 16 is positioned in the annulus 30 (FIG- That is, the upper portion- URE 1A) between the housing 12 and the wash pipe 14 and thus is not subjected to any hydrostatic pressures in the well bore. As previously mentioned, the air in the annulus 38 may vary for example from 14.7 pounds per square inch to approximately 45 pounds per square inch as the jar is operated but this will not be sufiicient to cause any adverse effects on the drilling string or bumper sub ill.

The present invention, therefore, is well suited and adapted to attain the ends and objects mentioned herein as well as others inherent therein. While a presently preferred embodiment of the invention is given for the purpose of disclosure numerous changes in the details of construction and arrangement of parts may be made which are within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A hydrostatically balanced bumper sub for use in a drilling string comprising,

a housing adapted to be connected in the drilling string,

a washpipe connected to and positioned inside of the housing,

a supporting stern telescoping in and nonrotatably engaging the housing and the lower end of which is adapted to be connected in the drilling string,

the horizontally disposed surfaces of said housing, and wash pipe, when the sub is connected in a drilling string, and which are exposed to hydrostatic pressures inside and outside of the drilling string, having areas which are substantially equal in an upward and a downward direction whereby the forces generated by the pressures acting thereon would be substantially balanced.

2. The invention or" claim 1 wherein,

the horizontally disposed upwardly and downwardly directed surfaces on said wash pipe have areas which are substantially equal, and

the horizontally disposed upwardly and downwardly directed surfaces on the housing have areas which are substantially equal.

3. A hydrostatically balanced bumper sub for use in a drilling string in a well bore comprising,

a housing adapted to be connected at its upper end to the drilling string,

a wash pipe connected to and positioned inside of and forming an annulus with said housing, said annulus being sealed from the well bore and including a gas,

a supporting stem, the upper end of which telescopes in said annulus and non-rotatably engages said housing, and the lower end of which is adapted to be connected in the drilling string, and

the upwardly and downwardly directed horizontally disposed surface areas of the housing and wash pipe, when the sub is positioned in a drilling string, are substantially equal, thereby balancing the vertical hydrostatic forces on said housing.

A hydrostatically balanced bumper sub for use in a drilling string in a well bore comprising,

a housing adapted to be connected at its upper end in the drilling string,

a wash pipe connected to and positioned inside of and forming an annulus with said housing,

a supporting stem, the upper end of which telescopes in said annulus and non-rotatably engages said housing, and the lower end of which is adapted to support a lower portion of the drill string,

said annulus being sealed from fluids in the well bore and including a gas,

the upwardly and downwardly directed horizontally disposed surfaces of the housing and the wash pipe, when the bumper sub is positioned in a drilling string, having areas which are substantially equal whereby the forces generated by the ressures acting thereon would be substantially balanced.

5. The invention of claim 4 including,

a weight connected to the lower end of the supporting stern sufiicient to balance the upwardly directed hydrostatic force acting on the supporting stem.

6. A hydrostatically balanced bumper sub for use in a drilling string in a well bore comprising,

a housing adapted to be connected at its upper end in the drilling string,

a supporting stem, the upper end of which telescopes in said annulus and is nonrotative relative to said housing, and the lower end of which is adapted to be connected in the drilling string,

sealing means between the supporting stem and said housing,

sealing means between said supporting stem and said wash pipe,

said annulus being sealed from the well fluid in a drilling string and well bore,

gaseous means in said annulus,

a scalable opening in said annulus for supplying lubricating oil to the telescopically engaging surfaces between the supporting stern and said housing and wash pipe,

hammer engaging surfaces on said supporting stern and housing for supplying a jar when engaged, and

the upwardly and downwardly directed horizontally disposed surfaces of the housing and wash pipe, when positioned in a drilling string, having areas which are substantially equal whereby the forces generated by the pressures acting thereon would be substantially balanced.

7. The invention of claim 6 including,

annular bearings between the supporting stern and said housing,

the face of said bearings including helically spiraling grooves.

3. The invention of claim 6 including,

an annular lubricant divider connected to the upper end of said supporting stem to supply lubricant on both sides of said supporting stem.

9. The invention of claim 6 including,

a weight connected to the lower end of the supporting stein suflicient to counterbalance the hydrostatic upwardly directed force created by the well bore pressures acting on the downwardly directed surfaces of the supporting stern.

References Cited by the Examiner J. A. LEPPINK, Assistant Examiner.

Claims

1. A HYDROSTATICALLY BALANCED BUMPER SUB FOR USE IN A DRILLING STRING COMPRISING, A HOUSING ADAPTED TO BE CONNECTED IN THE DRILLING STRING, A WASHPIPE CONNECTED TO AND POSITIONED INSIDE OF THE HOUSING, A SUPPORTING STEM TELESCOPING IN AND NONROTATABLY ENGAGING THE HOUSING AND THE LOWER END OF WHICH IS ADAPTED TO BE CONNECTED IN THE DRILLING STRING, THE HORIZONTALLY DISPOSED SURFACES OF SAID HOUSING, AND WASH PIPE, WHEN THE SUB IS CONNECTED IN A DRILLING STRING, AND WHICH ARE EXPOSED TO HYDROSTATIC PRESSURES INSIDE AND OUTSIDE OF THE DRILLING STRING, HAVING AREAS WHICH ARE SUBSTANTIALLY EQUAL IN AN UPWARD