US3365202A - Downhole drilling motor having an improved shaft seal - Google Patents

Description

Jan. 23,l 1968 M. D. CARLETON 3,365,202

DOWNHOLE DRILLING MOTOR HAVING AN IMPROVED SHAFT SEAL Filed June l5, 1965 2 Sheets-Sheet 1 Zik W i W M il, WfmRP .,mam/ wr Z fw., f a ,m 5.@ f, v www //W 7 //A////////// ////K i v \CXC m \w M www s 4 s FLM Arrow/w Jan. 23, 1968 M, D. CARU-:TON

DOWNHOLE DRILLING MOTOR HAVING AN IMPROVED SHAFT SEAL 2 Sheets-Sheet 2 Filed June 1 5, 1965 United States Patent O 3,35,2tl2 DGWNHLE DRlLLlNG MOTR HAVING AN IMPRUVED SHAFT SEAL Mike D. Carleton, deceased, late of Franklin, Tex., by Ida H. Carleton, administratriur, Franklin, Tex., assigner to Dresser Industries, Inc., Dallas, Tex.

Filed .lune 15, 1965, Ser. No. 464,244 6 Claims. (Cl. 277-73) ABSTRACT F THE DISCLOSURE The seal disclosed herein is adapted uniquely for a fluid driven motor to prevent the flow of fluid past the motor in the tubular means within which such motor usually is positioned. An annular piston-like member is moveable between two surfaces and having a surface exposed to the driving fluid within such tubular means to urge the annular piston against one of the surfaces. For fluid flow in the opposite direction, the annular piston is moveable against the opposite surface to permit the fluid to flow therepast readily.

This invention relates to a downhole drilling motor having an improved fluid flow seal that substantially prevents escape of power fluid from the lower end of the motor housing which surrounds the rotating output shaft.

This invention is adaptable to a variety of fluid driven downhole drilling motors wherein a shaft carrying the bit is rotated by means of hydraulic energy supplied to it from the well surface. The most commonly used form of hydraulically driven downhole motor is the turbodrill and for the purpose of illustrating this invention, the drawings and descriptive matter relate to turbodrills although the invention is adaptable to other forms of downhole motors.

Conventional fluid driven downhole motors utilize a lower radial bearing to absorb lateral forces between the rotating output shaft and the motor housing during drilling operations. The bearing frequently includes an elastomer sleeve element carried by the housing and engaging the shaft. The sleeve is provided with a plurality of longitudinal grooves on its inner surface to permit circulation fluid to flow through the bearing to lubricate and cool the bearing contact surfaces and prevent seizure. It is important to prevent this circulation fluid from flowing out into the bore hole from the annulus between the output shaft and the motor housing. Any fluid which thus escapes does not pass downwardly through the output shaft to be Vdischarged through the bit thereby reducing the amount of fluid available to remove formation cuttings away from the `working edges of the bit and prevent a build-up of cuttings in the bottom of the hole. Also, the escape of this fluid through the lower radial bearing into the bore hole appreciably reduces the available pressure differential across the bit which it is important to maintain for drilling efficiency.

Various devices have been suggested in the past for sealing between the rotating output shaft and the relatively stationary motor housing at a point below the radial bearing. These have not been altogether successful for various reasons including the failure to meet two requirements for creating and maintaining an effective seal during drilling operations. One requirement is that the seal must be maintained regardless of the degree of wear on the vertical thrust bearings in the motor. Not only do the vertical thrust bearings have a certain degree of assembly clearance which permits relative longitudinal movement between the shaft and the housing but also as they wear, additional clearance is created permitting an even greater degree of longitudinal movement. Second, the seal must be maintained regardless of the clearance and radial wear on the lower radial bearing.

3,365,202 Patented Jan. 23, 1968 ice It is an object of this invention to provide a fluid operated downhole drilling motor with an improved seal for the output shaft of the motor.

It is another object to provide such a motor with a seal that can accommodate the lateral `and longitudinal movement of the shaft that results from the wear of the thrust and radial bearings of the motor.

It is another object to provide such a seal that will bypass fluid as the motor is being lowered into the well bore and which can do so without being damage-d by the forces exerted thereon by the fluid when the motor is being lowered rapidly.

It is another object to provide such a seal that has a minimum of cavities in which cuttings and other solid ma. terial can collect and interfere with the operation of the seal.

These and other objects, advantages, and features of the invention will be apparent to those skilled in the art from a consideration of this specification, the claims and the attached drawings.

In the drawings:

FIG. 1 is a view, partly in vertical section and partly in elevation, of the lower portion of a turbodrill equipped with the preferred embodiment of the shaft seal of this invention;

FIG. 2 is `an enlarged view in vertical section of the shaft seal s-hown in FIG. l; and

FIGS. 3 and 4 are vertical sectional views showing alternate arrangements of shaft seals.

Turbodrill 10 is arranged to drive bit 11 attached to its hollow output shaft 12. The illustrated turbodrill contains a plurality of turbine stages 14 (only the lower portion of one stage is shown), vertical thrust bearings 15, lower radial bearing 16, and shaft seal 17, various sections of the turbodrill housing, the latter generally being numbered 18. It is the purpose of the thrust bearings 1S to resist the downward force imposed on the rotor shaft by the drilling fluid acting against the turbine rotor blades. The thrust bearings v15 also transmit to the shaft and the bit the drilling weight imposed on the housing by the drill string (not shown).

Below the thrust bearings is located radial bearing subassembly -16 which supports the output shaft in the lower end of housing 18. In the embodiment shown in FIG. 2, this radial bearing subassembly includes bearing bushing 19 located inhousing section 18a and engaging bearing sleeve 20 carried by the hollow shaft and keyed thereto by key 21. The bearing bushing is formed of an elastomer such as rubber 16a and is reinforced with steel backing 16h. The bearing Ebushing has longitudinally extending grooves 16C on its inner surface to allow the passage of fluid across the face of the bearing. Seal 22 prevents the flow of drilling fluid between sleeve 20 and shaft 12.

For a more complete description of a turbodrill of this type shown, see U.S. Patent No. 3,519,222.

Both the lantern ring 23 and shaft are provided with an opening 24 through which the drilling fluid can enter the output shaft after it has passed through the turbine sections and thrust lbearings 1S. The fluid then flows through the output shaft to bit 11. Unless prevented from doing so, at least a portion of this fluid would flow through the grooves 16e across radial bearing 16 and out of the turbodrill through the annulus defined by the output shaft and the tubular means comprising housing sections 18a and 18b. A substantial amount of the fluid would follow this path because normally there is a substantial pressure drop across the bit. The loss of a substantial amount of this fluid into the bore hole annulus at this point would greatly reduce the ability of the drilling fluid to cool the bit and to remove the cuttings therefrom.

Therefore, in accordance with this invention, an irnproved shaft seal 17 is provided to prevent the drilling fluid from flowing from the turbodrill through the aforesaid annulus. As shown in FIG. 2, the seal comprises a first annular member 25 mounted on the output shaft. This annular member is provided with an annular groove in which is located an annular ring of elastomeric material 26 to provide an upwardly facing sealing surface. The annular member 25 is prevented from moving longitudinally of the shaft by shoulder 2'7 on shaft l2 and the lower end of bearing sleeve 2@ which is held against rotation relative to the shaft by key 2l which also locks member 2S to shaft 12.

Also encircling the shaft is a second annular member or piston 28 which has a downwardly facing sealing surface formed by annular ring 29 of hard, abrasive, resistant material, such as Stellite. The piston is spaced from shaft 12 to permit the shaft to move laterally or to wobble to the extent allowed by any wear which may occur in the radial bearings supporting the shaft. Also, the piston is movable longitudinally so it can follow any longitudinal movement of sealing face 26 relative to housing member 18b due to thrust bearing wear. The piston is keyed to housing section 18b by key 3l) so it is held against rotation relative thereto. Seal means, comprising in this embodiment O-rings 31, are positioned between the piston and housing section 18a. With this arrangement, the upper end of the piston provides an upwardly facing surface against which the fiuid in the annulus 32 can act to urge the piston downwardly to in turn urge the sealing surfaces 26 and 29 together to effect a seal. As the pressure in the annulus increases, the force urging the two sealing surfaces together likewise increases. The upwardly facing area of the piston should be suiiiciently large that the two sealing surfaces are engaged tightly enough to substantially prevent flow therebetween. On the other hand, the area should not be so large as to press the two sealing surfaces together so tightly that excessive wear results. In this connection, a small amount of leakage may be desirable to not only permit some flow past the radial bearing 16 but also to lubricate and cool the sealing surfaces 26 and 29. In case additional flow is desired past the radial bearings, an opening 33 can be provided in the bearing sleeve and hollow shaft.

It is desirable to be able to lower the turbodrill into a well bore filled with drilling mud at a reasonable rate. This causes force to be exerted upwardly upon the piston and, therefore, the piston must Ibe designed to resist this force without being damaged. In the embodiment shown in FIG. 2, the piston being movable longitudinally, will move upwardly away from the seal member 25 when subjected to an upward surge of pressure. Thus, the seal will open and allow iluid to flow through the annulus between the outside diameter of the bearing sleeve and the inner diameter of the piston 28 and thence upwardly into the turbodrill. This is desirable since it provides another path for the fluid being displaced thereby tending to reduce the upward force exerted on the piston. The upward movement of the piston must be limited however. Therefore housing section 18a is provided with downwardly facing shoulder 34 and piston 23 is provided with an upwardly facing annular shoulder 3S which engages shoulder 34 to limit the upward travel of the piston. By this arrangement, the key 3l) is not placed in shear in an upward direction and the shoulders 34 and 35, being on the outside of the piston, can be made of relatively large area so as to distribute the forces exerted on them.

Since there is relative rotation between the seal surfaces 26 and 29, they will wear. As explained above, one sealing surface is provided by a resilient sealing ring 26 and the other sealing surface by a hard wear resistant material 29, such as Stellite. In this way the rubber suffers the major portion of wear, but it can be quickly, easily, and economically replaced when necessary.

FIGS. 3 and 4 show alternate ways of assembling the seal. In both embodiments, the construction of the components of the seal are modified somewhat. However, the operating principle and function of the components are the same as described above.

FIG. 3 illustrates the arrangement where the housing for the seal and the radial bearing are integrally connected together. This is done when the radial bearing comprises a one piece body 36 of rubber bonded to the inner surface of the housing. Also, in this embodiment, the first annular mem-ber 25 is held in position on output shaft l2 by a plurality of set screws 42, only one of which is shown, rather than a shoulder on the shaft, as was the case in the first embodiment` Thus to change the seal 26', all that is necessary is to take out the set screws 42 and then slide member 25' off the lower end of shaft 12. This eliminates the need to remove all of the parts of the turbodrill above the seal as must be done when the meinber 25 of FIG. 2 is to be replaced.

In the embodiment shown in FIG. 4, lower housing section 13b is threaded to the outside of housing section 18a. Since the same type radial bearing 36 is used in this embodiment as in FIG. 3, housing section 18h does not need to hold the bearing against longitudinal movement within the housing 18a and therefore it can be threadedly connected to the housing by threads provided on the eX- terior of the housing as shown. The construction of the seal otherwise is the same as shown in FIGS. 1 and 2.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which lare obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. In a downhole drilling motor having an output shaft rotated by a drilling fluid driven motor and tubular means connected to the motor and extending down to surround said shaft thereby forming a fluid passage between said tubular means and said output shaft, seal means for substantially preventing flow of fluid out of the motor through said iiuid passage, said seal means comprising means on one of the output shaft and tubular means providing a first endwise facing annular sealing surface, an annular member carried by and longitudinally movable with respect to the other of the output shaft and tubular means and providing a second endwise facing annular sealing surface opposing and slidingly engageable with the first sealing surface, said annular member being of a size so as to provide a radial space to permit the shaft to move laterally, said annular member having an upwardly facing surface exposed to fluid within said tubular means and of an area sufficient that the pressure 0f such fluid is effective to urge the annular member longitudinally toward the first sealing surface to thereby cause said sealing surfaces to engage and substantially prevent the flow of fluid from the motor through said fluid passage, and interengageable stop means on the annular member and tubular means to limit the distance said member can move longitudinally away from said first sealing surface.

2. In a downhole drilling motor having an output shaft rotated by a drilling fluid driven motor and tubular means connected to the motor and extending down to surround said shaft thereby forming a fluid passage between said tubular means and said output shaft, seal means for substantialiy preventing flow of fluid out of the motor through said fluid passage, said seal means comprising means on the output shaft providing an endwise facing annular sealing surface, and an annular member carried by and longitudinally movable with respect to the tubular means and having an endwise facing annular sealing surface opposing and slidingly engageable with the sealing surface on the output shaft, said annular member being larger than the output shaft so as to be spaced radially therefrom to permit the shaft to move late-rally, said annular member having an upwardly facing surface exposed to fluid within said tubular means and of an area sufficient that the pressure of such fluid is effective to urge the annular member longitudinally toward the sealing surface on the output shaft to thereby cause said sealing surfaces to engage and substantially prevent the flow of fluid from the motor through said fluid passage.

3. In a downhole drilling motor having a hollow output shaft rotated by a drilling fluid driven motor and tubular means connected to the motor and extending down to surround said shaft thereby forming a fluid passage between said tubular means and said output shaft, seal means for substantially preventing flow of fluid out of the motor through said fluid passage, said seal means comprising a first annular member encircling the output shaft and attached thereto and having an endwise facing annular sealing surface, a second annular member carried by the tubular means for longitudinal movement relative thereto and provided with an endwise facing annular sealing surface opposing the sealing surface on the first member, said second member being larger than the output shaft so as to be spaced radially therefrom to permit the shaft to move laterally, said second member having an upwardly facing surface exposed to fluid within said tubular means and of an area sufficient that the pressure of such fluid is effective to urge the second member longitudinally toward the first member to thereby cause their sealing surfaces to engage and substantially prevent the flow of fluid from the motor through said fluid passage, and interengageable stop means on the second member and tubular means to limit the distance said second member can move longitudinally away from the first member.

4. In a downhole drilling motor having a hollow output shaft rotated by a drilling fluid driven motor and tubular means connected to the motor and extending down to surround said shaft thereby forming a fluid passage between said tubular means and said output shaft, seal means for substantially preventing flow of fluid out of the motor through said fluid passage, said seal means comprising an annular member encircling the output shaft and attached thereto and having an upwardly facing sealing surface, an annular piston disposed within the tubular means and surrounding the output shaft, means carried by the tubular means mounting the piston for longitudinal movement relative thereto but limiting relative rotation, said piston having a downwardly facing annular sealing surface opposing the sealing surface on the first member, said piston being larger than the output shaft so as to be spaced radially therefrom to permit the shaft to move laterally, said piston having its upper end exposed to fluid within said tubular means and of an area sufficient that the pressure of such fluid is effective to urge the piston longitudinally toward the first member to thereby cause said sealing surfaces to engage and substantially prevent the flow of fluid from the motor through said fluid passage, and interengageable stop means on the piston and tubular means to limit the distance said piston can move longitudinally away from the first member.

5. In a downhole drilling motor having an output shaft rotated by a drilling fluid driven motor and tubular means connected to the motor and extending down to surround said shaft thereby forming a fluid passage between said tubular means and said output shaft, seal means for substantially preventing flow of fluid out of the motor through said fluid passage, said seal means comprising a first annular member having a bore of such size that the first member can be slid over the output shaft toward said tubular means, means releasably connecting the first member to the output shaft, said first member having an endwise facing annular sealing surface, and a second annular member carried by the tubular means for longitudinal movement relative thereto and provided with an endwise facing annular sealing surface opposing the sealing surface on the first member, said second member being larger than the output shaft so as to be spaced radially therefrom to permit the shaft to move laterally, said second member having an upwardly facing surface eX- posed to fluid within said tubular means and of an area sufficient that the pressure of such fluid is effective to urge the second member longitudinally toward the first member to thereby cause their sealing surfaces to engage and substantially prevent the flow of fluid from the motor through said fluid passage.

6. The apparatus of claim 5 wherein said first members sealing surface comprises a replaceable ring having a resilient surface whereby such ring can be replaced by releasing the connecting means and sliding the rst member off the output shaft.

References Cited UNITED STATES PATENTS SAMUEL ROTHBERG, Primary Examiner.

UNITED STATES PATENT OFFICE CERTUHCATE 0F CORRECT1ON Patent No. 3,365,202 January Z3, 1968 Mike D. Carleton, deceased by Ida H. Carleton,

adminstratrx It s certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

column 2, line 55, for "3,519,222" read 3,159,222

Signed and sealed this 29th day of July 1969.

(SEAlJ ttestz Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR.

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