Abstract:
A rotating blowout preventor of simplified construction which requires no kelly drive bushing, and which has a rotating external housing formed at the upper marginal end thereof within which the main bearings and seals are isolated. The external housing rotates about a fixed washpipe and supports a stripper seal doughnut to which a stripper seal is mounted in underlying relationship thereto. A removal clamp enables the doughnut and stripper rubber to be lifted free of the assembly for service or replacement. The bearing housing is fabricated in a manner to enable servicing the seals and bearings thereof without removing the blowout preventor from the top of a tool string. The bearing housing and seals therefore are arranged respective to the rotating stripper rubber such that should leakage across the stripper rubber and seal occur, the isolated bearing housing will be maintained free of contamination therefrom.

Description:
BACKGROUND OF THE INVENTION 
     Rotating blowout preventors form a critical part of a tool string for the reason that mud is circulated into and out of the borehole in conjunction therewith and accordingly, it is important that the rotating blowout preventor be able to function properly under continuous duty for several weeks while a borehole is being formed. 
     In drilling deep wells it is extremely expensive to shut a rig down and therefore great emphasis is placed upon the ability to field repair or field replace equipment, such as blowout preventors, at the drilling rig with a minimum of down time being involved. 
     Rotating blowout preventors of the prior art generally require that the entire assembly be lifted in a telescoping manner free of the turn table and kelly in order to replace any component parts thereof including the stripper rubber or stripper seal. Should the bearings or seals require servicing, it is generally necessary to carry the rotating blowout preventor into a service shop and accordingly, a considerable amount of down time is involved before the drilling operation can be resumed. 
     Accordingly, it would be desirable to be able to replace the stripper rubber or the stripper seal associated therewith without having to remove the entire rotating blowout preventor from the tool string. It would furthermore be desirable to be able to replace the bearings and bearing seals thereof without having to unbolt the massive blowout preventor and transport the blowout preventor to a service shop. More especially it would be desirable to have a rotating blowout preventor which normally could endure the abuse of drilling an entire borehole before the apparatus requires servicing. 
     It would also be desirable to have made available a rotating blowout preventor which eliminates the troublesome kelly drive bushing. 
     These desirable attributes are the subject of the present invention. 
     SUMMARY OF THE INVENTION 
     A rotating blowout preventor which is driven by a stripper rubber assembly and which can be completely rebuilt without removing the apparatus from a tool string. The stripper rubber assembly of the rotating blowout preventor slidably receives a driving member therethrough which rotates all of the moving parts thereof with respect to a main body, thereby eliminating the kelly drive bushing. The stripper rubber assembly is located at the upper marginal inner end of a fixed washpipe and can be rapidly removed from the main body by merely unbolting a clamp and withdrawing the assembly in an upward direction whereupon a new stripper rubber can be added to the assembly. 
     The rotating blowout preventor includes an external rotating housing within which spaced seals and bearings are located so that the seals and the bearings are completely isolated from high pressure fluids and therefore enjoy an unexpected long life. The seals and bearings can be replaced without removing the main body from the tool string. 
     The rubber stripper assembly is therefore removably received within and forms part of the upper marginal end portion of the rotating blowout preventor. The rotating head includes a downwardly directed, rotating, outer cylindrical skirt which forms part of the rotating housing, and which is spaced from an upwardly directed, inner fixed skirt which forms the fixed washpipe, and which cooperates together to form a bearing and seal chamber therebetween. The bearing and seal chamber is closed at each end by a seal means, and a slinger ring is superimposed over the uppermost of the seal means. The stripper rubber assembly includes a mounting doughnut, and a stripper seal means is interposed between the mounting doughnut and the washpipe so that any leakage across the seal means of the stripper assembly is directed through a series of radial ports located above the slinger ring to cause fluid leakage to flow across the top of the isolated bearing and seal chamber and away from the rotating blowout preventor. 
     A primary object of the present invention is the provision of a rotating blowout preventor which can be completely overhauled without removing the apparatuus from a tool string. 
     Another object of the invention is the provision of a rotating blowout preventor which does not require a kelly bushing drive, and which includes an external bearing and seal chamber completely isolated from drilling fluids which flow through the axial passageway of the apparatus. 
     A further object of this invention is the provision of a rotating blowout preventor in combination with a rubber seal assembly which rotates the apparatus, and which can be easily and rapidly removed from the main body thereof for servicing. 
     Another and still further object of this invention is the provision of a rotating blowout preventor which is efficient in operation, reliable in service, low in cost, and which includes a minimum of parts. 
     An additional object of this invention is the provision of a rotating blowout preventor which is lubricated in a novel manner. 
     These and various other objects and advantages of the invention will become readily apparent to those skilled in the art upon reading the following detailed description and claims and by referring to the accompanying drawings. 
     The above objects are attained in accordance with the present invention by the provision of a combination of elements which are fabricated in a manner substantially as described in the above abstract and summary. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a rotating blowout preventor made in accordance with the present invention; 
     FIG. 2 is an enlarged, longitudinal, cross-sectional view of the rotating blowout preventor disclosed in FIG. 1; 
     FIG. 3 is an exploded view of the rotating blowout preventor disclosed in FIG. 1; 
     FIG. 4 is a detail of part of the apparatus disclosed in the foregoing figures; and, 
     FIG. 5 is a lateral, cross-sectional view of the stripper mount of FIG. 2, with some additional parts being removed to further illustrate some hidden details thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the various figures of the drawings, wherever it is possible or practical to do so, like or similar numerals will refer to like or similar objects. As seen in the various figures of the drawings, the rotating blowout preventor of the present invention is generally denoted by the numeral 10 and includes an uppermost end portion 12, in the form of a removable clamp, with the clamp having an upper face 14. The lower end of the rotating blowout preventor is in the form of a flange 16 having a lowermost end or face 18 and a bolt circle 19 which enables the apparatus of the present invention to be bolted to a tool string, otherwise known as a stack of equipment, with the apparatus of the present invention being the topmost tool of the stack. 
     A main body member 20 has a constant diameter, longitudinal axial passageway at 22 to form the illustrated upwardly directed fixed washpipe which terminates in a free end 24. The upper, outer marginal end of the washpipe is provided with a threaded surface 26. The threaded surface is right handed at the upper marginal end and left handed at the lower marginal end thereof for a purpose which will be better appreciated later on as this disclosure is more fully digested. 
     A main outlet 27 conducts fluid flow away from the borehole annulus while an auxiliary connection 28 is provided for whatever purpose one may wish to use it for. 
     A rotating head assembly 30 is grooved circumferentially for 320° at 32 and outwardly extends into a boss or flange 33 before turning downward into a bell-like circumferentially extending skirt member. A circumferentially extending lip 34 is received within the complementary groove of the before mentioned clamp 12, while the lower lip of the clamp is received within groove 32. 
     A stripper rubber assembly 36, which forms a subcombination of the present invention, includes a doughnut 38 by which the entire stripper assembly, which includes the doughnut and rubber, is removably mounted in fixed relationship respective to the rotating head assembly. The doughnut is provided with a circular boss 40 which inwardly tapers in a cone-like manner at 41 so that it is tightly and easily received in seated and aligned relationship respective to the remainder of the rotating head assembly. 
     In FIG. 2, a lug 42 is seen to be an extension of the doughnut. The lug engages the clamp gap of the two co-acting clamp halves to further prevent rotation of the stripper assembly. A stripper adaptor in the form of a bolt flange 11 is provided with an annular shoulder 45 which receives the doughnut in close tolerance relationship therewithin with bolts 45&#39; extending downwardly through the doughnut and into the adaptor so that the stripper rubber can be easily removed from the doughnut. A female hinge element 46 is provided with a cavity 47 which outwardly opens at 48 so that a number of radially spaced apart pairs of fingers can be hingedly mounted within the cavity 47 with the fingers and the stripper adaptor all being vulcanized to the stripper rubber 50. 
     As seen in FIGS. 2 and 5, the fingers 52 are provided in pairs with the number of pairs being equal to the number of sides employed on the kelly. The fingers have a male hinge end 53 which is captured in a journaled manner within the before mentioned cavity 47 with the neck 54 being received in a cutout formed through portion 46 so that the enlargement at 55&#39; bears against the lower curved circumferentially extending member at 46. 
     The finger extends down into and is vulcanized within the rubber, with the fingers terminating at free end 56. Ribs 57 are formed on either side of the finger while voids 58 and 59 form lightening holes so that rubber compound fills the voids thereby more efficiently bonding the fingers within the main annular body of rubber. 
     As seen in FIG. 5, the fingers are arranged in radially spaced pairs placed about the stripper bolt flange in close proximity to the inside surface of the stripper rubber. 
     The outturned rubber piece 60 sealingly engages the inside peripheral wall surface 62 of the washpipe 22, thereby forming a debris barrier which prevents ingress of debris into the area 61 located between the washpipe and stripper bolt flange. 
     The inside diameter of the stripper rubber sealingly engages a drive member in an unusual manner as indicated in FIG. 5, so that sufficient force can be transferred from the kelly into the rotating head. The stripper rubber terminates at 64. 
     The skirt member includes an upper marginal portion having a lower edge 65. The upper marginal portion threadedly engages the lower marginal end portion at 66. Hence, the threaded area 66 enables the two members 30 and 68 of the rotating head assembly to be assembled. 
     Upper bearing 69 and lower bearing 70 abuttingly engage one another at interface 72 and are loated within the located bearing and seal chamber 71. The lower bearing inner race is supported by an annular bearing support member 73 which is spaced from an inwardly directed circumferentially extending boss 74 formed on the inner marginal end portion of the skirt 68. Annular plate member 75 forms a keeper and is removably affixed to the boss 74 for properly positioning the lower seal assembly 76 and 78 within the illustrated lower seal chamber. The boss includes an inwardly directed lip 79 against which the upper seal 76 is abuttingly received thereby capturing the two seals 76 and 78 between members 75 and 79. 
     Stationary annular ramada 80 forms a slinger ring and is located in overlying relationship respective to the upper end portion of the bearing and seal chamber and is spaced from the rotating head assembly to form annular chamber 81. The ramada has a polished surface 82 which forms part of a cavity 83. The ramada outwardly and downwardly slopes at 84 and terminates at 85 in close proximity to a plurality of radial outlet ports 90. An upper, outer nut 88 is provided with a seal receiving annular groove 89 within which an upper seal assembly 91 is mounted. Lower, inner nut 92 is provided with a left hand thread for engaging the lower left hand threaded portion of the threaded surface 26. Lower, outer, left hand nut 93 is similarly provided with a left hand thread for engaging the lower left hand threaded portion of a threaded area at 95. 
     Clamp hinge 94 provides a pivot for the two clamp halves, and when the clamp halves are brought together by the illustrated tension adjusting fastener means, a clamp gap 96 is left between the adjacent co-acting clamp halves. 
     A stripper seal 98 is interposed between the doughnut and adapter and wears against wear fixed sleeve 67. A grease fitting 100 provides lubricant for the stripper seal. Numeral 102 indicates a driving member, also called a kelly, which can be square, hexagon, or any other known configuration, as long as it conforms to the geometry of the spaced pairs of fingers of FIG. 5. 
     In operation, the rotating blowout preventor of the present invention is bolted to a stack of other tools located on top of a surface casing during the borehole forming operation, although the bolt flange 18 can equally well be utilized by being bolted directly to the casing if such an expedient be desired. The kelly 102 is run down through the axial passageway in the illustrated manner of FIG. 2 so that drilling mud flows down through the rotating kelly, through the drill string, to the bit, back up the casing annulus, through the outlet 27, and on to the mud bit. 
     As the kelly rotates, the rubber 50 accommodates the driving member in the unusual manner of FIGS. 2 and 5 with the rubber stripper assembly rotating therewith and driving the rotating head assembly. Threaded surface 66 is a right handed thread and tends to be tightened during the drilling operation. The loads imposed upon the stripper assembly are transferred into the rotating head assembly with the upper bearing 69 normally taking most of the load while going into the hole unless the pressure in proximity of the stripper rubber is unduly high, whereupon the lower bearing would carry most of the reversed load. 
     Should leakage occur across debris barrier 60 and stripper seal 98, flow of contaminates will continue into the annular passageway 81 and out through ports 90, with the relative movement between member 88 and the slinger ring 80 preventing debris from entering the close tolerance interface at 86. Hence, the chamber 71, which houses the bearings and seals, is maintained free of contaminates. Lubricant at 103 is added to the chamber from time to time with the excess lubricant flowing past the upper seal 91 due to the assembled configuration of the upper and lower seal assemblies. 
     Should it become necessary to replace either the rubber or the primary seal, the clamp 12 is unfastened and the two halves pivoted away from one another, whereupon the entire seal assembly can be withdrawn from the rotating head assembly and repairs effected as may be required. Hence, it is unnecessary to remove the massive rotating head assembly from the stack. 
     Should a bearing or seal associated with the bearing chamber become doubtful, the entire rotating head assembly can be easily entered for repairs and maintenance by locking the cylinder 68 and rotating the upper end of the rotating head assembly, thereby unthreading the surface 66, whereupon the stripper rubber assembly, along with the clamp and upper end of the rotating head assembly, can be lifted free of the main body, thereby exposing the slinger ring. 
     Next, the slinger ring, which has a left handed thread, is removed, thereby gaining access to nut 88 which is a right handed nut. Nut 88 is removed, thereby gaining access to seal 91. The left handed nut 92 and left handed nut 93 are next removed, whereupon the bearing and lower seal assembly may be replaced as might be required. 
     The rubber of the present seal assembly is affixed to the stripper bolt flange or adaptor in a novel and improved manner by the provision of the before mentioned fingers which individually extend down into the massive rubber body and transmit loads between the rubber and the stripper bolt flange in a new and improved manner so that the combination enjoys a long and satisfactory service life, and provides a novel means by which the low friction rotating head is turned by the kelly. 
     The number of pairs of fingers 52 of FIG. 5 are equal to the number of sides presented by the driving member. Four pairs of fingers are shown for illustrative purposes in FIG. 5, with the driving member 102 having four corresponding corners at 104 which resistingly turn towards an adjacent pair of fingers, with the resisting force provided by the fingers being adequate for imparting rotation into the head. Stated differently, the corners 104 of kelly 102 cannot pass beyond the pairs of fingers and therefore develop a torque which imparts rotational motion into the rotating parts of the rotating blowout preventor.