US2621894A - Apparatus for initiating the drilling of a deviating bore from an existing vertical well bore - Google Patents

Description

Dec. 16, 1952 J. A.2UB1 |N 621,894

APPARATUS FOR INITIATING THE DRILLING OF A DEVIATING BORE FROM AN EXISTING VERTICAL WELL BORE 2 SHEETS-SHEET l Filed Aug. 22, 1950 ATTORNEYS Dec. 16, 1952 J, A ZUBLIN 2,621,894

APPARATUS'FOR INITIATING THE DRILLING A DEVIATING BORE FROM AN EXISTING VERTICAL L BORE 2 sIiEETs-SHEET 2 Filed Aug. 22, 1950 Patented Dec. 16, 1952 APPARATUS FOR INITIATIN G THE DRILLIN G OF A DEVIATING BORE FROM AN EXIST- ING VERTICAL WELL BORE John A. Zublin, Los Angeles, Calif.

Application August 22, 1950, Serial No. 180,856

The present invention relates to an improved method and apparatus for initiating the drilling of a deviating bore from an existing vertical well bore. The provision of drain holes deviating laterally from the vertical oil well have proved their eflicacy in the recovery of oil from the oil bearing strata.

It is not broadly new to provide methods and apparatus for drilling deviating bores from existing vertical well bores, and examples of such practice will be found in my own prior United States Patents Nos. 2,336,338; 2,344,277 and 2,382,933. The present invention has as its purposes and objects the provision of specific iml provements, more particularly in respect to the introduction of the drilling apparatus to the well and in initiating the drilling laterally from the wall of the vertical well bore of a deviated bore.

The employment of a normally curved, exible, resilient drill guide positioned immediately above the drill bit to impose pressure on the drill bit so as to cause the same to be deected laterally from the existing well bore, has been heretofore discussed in some detail in the above-identified United States patents.

In the employment of such a normally curved, flexible, resilient drill guide a premature imposition of too great a bit pressure in the course of initiating the drilling of a deviating bore, gives rise to the chipping-olf of the formation from the wall of the vertical bore immediately below the drill bit and makes it difficult if not impossible to initiate the drilling of a lateral bore at such a point. It then becomes necessary to move the bit to a diierent location along the vertical bore and to exercise great caution to the end that the bit will properly initiate the drilling of and enter the deviating bore. Additionally, the moving of a drill bit carried at the lower end of a normally curved, flexible, resilient drill guide in the interconnected portion of the vertical well bore has in the past occasioned excessive scraping on the side wall of the well bore due to the fact that the bit is forced thereagainst under from 400 to 700 pounds pressure, due to the fact that the curved, resilient guide has been flexed to a lesser curvature than its normal curvature by introduction to the well bore. This scraping action sometimes removes the mud layer from the wall surface and precipitates cave-ins to say nothing of imposing undesirable and excessive wear on the bit, the primary purpose of which it is to drill the deviating bore.

It is the purpose and object of the present 1 Claim. (Cl. Z55-1.6)

invention to overcome the foregoing diiTlculties and to generally improve and facilitate the drilling of deviating bores by greatly increasing the eicacy with which the drilling of such bores is initiated at the pre-selected point along the vertical well bore.

Further and more detailed objects and advantages of the invention will be made apparent from the following detailed description which is here given with reference to the accompanying drawings wherein:

Figure 1 is a view in side elevation of th lower end of a drill string and associated elements illustrative of the invention.

Figure 2 is an enlarged detailed view of the lower portion of the normally curved, exible, resilient drill guide and bit showing the bit at right angles to the position which it occupies in Figure 1.

Figure 3 is a cross-sectional view through the bit and the lower end of a drill guide illustrating the inner ilexible drive member in the manner of connection of the bit thereto.

Figure 4 is a fragmentary View partly in crosssection illustrating the upper end of the normally curved, flexible, resilient drill guide together with the inner bit driving member and illustrating the manner in which the bit driving member is connected to the drill string.

Figure 5 is a bottom plan view looking upwardly at the bit when in the position shown in Figure 1, and

Figure 6 is a similar bottom plan View looking up at the bit when in the position shown in Figure 2.

Referring to Figure 1, the entire mechanism there shown is suspended from the surface of the well by a drill string only the lower end portion I0 of which appears at the top of the iigure. The drill string above the lower end portion l0 thereof is of conventional construction and it will be understood that it is made up of sections of drill pipe. In conformity with the present invention, there is directly connected to the lower end I0 of the lowermost section of the substantially rigid drill string a non-resilient, flexible drill pipe Il which may suitably take the form of the non-resilient exible drill pipe, more particularly disclosed in my prior United States Patent No. 2,515,366, issued July 18, 1950. Depending upon the overall length of the deviating bore to be drilled, one or more sections of non-resilient flexible drill pipe Il may be interposed between the lower end l0 of the substantially rigid drill string and the normally curved, flexible, resilient drill guide I2. The normally curved, flexible, resilient drill guide I2 is preferably of the type disclosed in my prior United States patent, 2,515,365, issued July 18, 1950. It will be observed that this drill guide consists of a tubular metal pipe having a slot through its wall extending in a generally helical path along and around the path. The sides of the slot are however provided with intermeshing and interlocking dovetail teeth. It will be appreciated that in its normal unstressed condition the drill guide I2 has a curvature approximately equal to the curvature at which .thel deviating drain hole is to deviate from the existing vertical well bore.

For efciency in practicing the method of the present invention, it is recommended that the flexible curved resilient drill guide I2 should have an over-all length of about 16 feet and a curvature in its unstressed condition that lies on a radius of about 16 feet so that the height of the arc formed when the guide is in unstressed condition is about 30 inches. When such a. drill guide .is inserted into a well bore, the btcarried at the lower end thereof will be forced against the side wall of the vertical bore at a pressure of the order of from 100 to 700 pounds.

The non-resilientilexible drill pipe section II is not directly connected to the normally curved resilient drill guide I2, but is connected to a, coupling member I3 by screw-threads I4 (see Fig. 4), and the coupling member I3 is connected at its lower end through screw-threads I5 to an interior flexible non-resilient tubular drive member I6. The drive member I6, except for the fact that it is of lesser diameter, may take the form of thev non-resilient flexible drill pipe section II. The drive member I3 thus rotates in unison with the flexible drill pipe section I I and the substantially rigid drill string extending to the surface of thev well, To facilitate the free rotation of the drive member I6 within the curved drill guide I2, suitabler roller-bearings Il' and I8 are provided in appropriately machined bearing races and disposed between the. inner face of the drill guide I2 and the outerface of the drive member I6, as shown in Figures 3.and 4. The lower end of the drive member I6 isv connected through the screw-threads I9 with the hollow bit coupling shank 20 to the lower end of which the bit indicated generally at 2l is threadedly connected at 22. It will thus be observed that when the drill string is rotated at the surface of the well, the flexible drill string section II, the drive member I6, and the bit 2| are directly driven, while the curved, resilient drill guide I2 can be held against rotation to drill a deviating bore in any desired azimuth.

It will be appreciated that the exible drill pipe section II and the flexiblev drive member IG, whichA have slotted walls, is each provided with a exible impervious liner tube such, asshown at 23 in Figures 3 and 4, through whichthe circulating drilling fluid passes downwardly to the bit.

By reference to Figure 3, it wil-l be noted that the tubular bit coupling member 23 has an enlarged lower end 24 on which ball-bearings 25 ride and are arranged to receive both radial and thrust loads. The bit couplingv 20 is held in vpo*- sition. by means of thrust ball-bearings 26 positioned between the upper end of a .bearing member 21 and a bearing race member 28 which is screw-threaded to the upper end of the bit coupling member 20, the bearing member 2T being threadedly connected at 29 to the lower end of the curved resilient drill guide I2. A set of rollerbearings 30 may be positioned between the bearing member 2'I and the bit coupling member 20, all shown in Figure 3.

As shown at the upper end of Figure 4, a similar arrangement is provided at the upper end of the flexible, resilient curved guide I2 at the point of coupling of drive member I6 to the flexible drill string section II.

Coming now to the details of the bit 2I and their relationship to the other elements of the combination, it will be observed that bit 2I is provided with two conical cutters 3I and 32, the axes 33 and`34 of which lie in the same vertical plane bisecting the entire bit 2I. The body of the bit 2I is cut-away above the conical cutters 3| and 32 as indicated in Figure 3, so as to provide a substantial clearance between the bit body 2I and the wall of the existing vertical well bore when the bit is in position to initiate the drilling of a deviating bore. This feature of the invention can vbe appreciated by reference to Figure 2, where the wall of the bit 2I is shown as lying in the vertical plane a, designated in the drawing body plane.r The clearance between this'plane and the vertical wall of the well is designated by the legend clearance in Figure 2.

A further important feature of the invention resides in the fact that the teeth 35 ofthe coni'- cal cutters 3| and 32 project beyond the body of the bit 2I, a distance equal to the designated clearance in Figure 2; The teeth 35 of the bit 2I are furthermore so formed that at the largest diameter of each of the conical cutters-the teeth terminatek in sharpened formation cutting and penetrating points. It will be observed that-this is quite contrary to conventional conical cutter construction, wherein at the point of maximum diameter of the conical cutter they terminate in flattened surfaces deliberately designed to prevent' cutting intoV the side wall of thevertical bore.

By reference to Figure 2, it will be' noted that the bit 2I rotates about the axis designated b. When the bit 2I and the conical cutters 3l and 32 are in the position shown in Figure 5, the axis b of the bit is at its maximum distance from the point lof contact A of thev cutter teeth 35 with the formation. This maximum distance is desighated X in Figure 5. When the bit 2'I and the cutters 3I and 32' have moved to the position shown in Figurev 6, the distancebetween the axis bf of the bitv and the formation at the points of contact of the teeth 35 of the cutters therewith is at a minimum. rlhis minimum distance is designated Y in Figure 6. As the bit 2I rotates, it will be observed that its axis of rotation b shifts from a position shown in Figure 5', to the position shown in Figure 6. This shifting of the axis of rotation of the bit is broughtA about by the difference inl the transversedimensionsv of the cutting face of the bit in planes at right angles to the axis thereof. Therefore, as the bit 2I rotates at high speed, i. e., from 75 to 200 R. P. M., the lowerV end of the resilient curved guide I2 is causedy to vibratel and the amplitude of itsv vibration is represented bythe difference between the distances designated X in Figure 5 and Y in Figure 6. The vibration of the lower portion of the curved drill guide I2 causes the cutter teeth 35 ofthe conical cutters 3I and 32 to strike the vertical wall of the existing well bore twice with each revolution of the bit with a rapid succession of hammer-like blows Vand since a substantial clearance is provided between the plane of the bit body 2| and the vertical wall of the well bore, the sharpened ends of the teeth 35 are driven into the wall of the vertical bore under the force imposed on the bit by the normally curved flexible resilient drill guide I2 which has been exed to a lesser curvature than its normally unilexed configuration.

The sideward pressure of the bit against the wall of the vertical bore in the position occupied by the bit in Figure 5 is represented by P and in the position shown in Figure 6 by P2.

It will be observed that through this action the drilling of a deviating bore is initiated by a radial cutting into the wall of the vertical bore which is accomplished without any substantial downward thrust on the bit. This feature is highly important since when too great a downward thrust is imposed upon the bit in the initial stages of the drilling of a deviating bore, it causes the bit to break out that portion of the wall of the vertical bore immediately below the point at which drilling of the deviating bore is being initiated. When this happens, the bit must be moved to a new location where reinitiation of the drilling of the deviating bore must be started.

The method of the present invention is thus characterized in that the drilling of a deviating bore is initiated through the vibration of the lower portion of a normally curved flexible resilient drill guide which has been flexed to a lesser curvature and the eifecting of initial lateral drilling without substantial downward thrust on the bit.

It is a further feature of the invention to insure against deleterious action on the wall of the vertical well bore and destructive wear on the bit during the insertion of the flexed normally curved resilient drill guide and bit into the uncased well bore. As is well recognized in the art, the well bore often extends a substantial distance below the cased portion of the hole and the wall of the well bore is plastered over by adhering portions of the drilling mud. Bearing in mind that the bit carried at the lower end of a ilexed normally curved resilient drill guide bears against the wall of the well bore with a pressure of from 400 to 700 pounds, it will be appreciated that it frequently gouges into the side wall of the well bore, scrapes along the side thereof removing the plastered wall and frequently causing cave-ins. The conical cutters 3| and 32 of the bit 2| of the present invention are so formed that when the bit is moved to the position that it occupies in Figure 2, the cutters will roll on the wall of the vertical bore as the drill string carrying the curved resilient drill guide bit is lowered into the well bore. This rolling action of the cutters 3| and 32 on the wall of the well bore greatly facilitates introduction of the bit and the associated elements of the drilling mechanism into the well.

From the foregoing, it will be appreciated that the method and apparatus of the present application constitutes a marked improvement, both in facilitating the introduction of a normally curved resilient drill guide when ilexed to a lesser curvature into an existing well bore and the initiating of the drilling of a laterally deviating drain hole, all of which advantages are achieved through practices wholly compatible with normal rotary drilling procedure.

The foregoing description has been given by way of exemplication and is not to be considered a limitation of the invention which is dened by the subjoined claim.

Having thus described my invention what I claim is:

What I claim is:

A rotary drilling bit for initiating the drilling of a deviating bore from an existing vertical well bore, comprising a bit body having a substantially cylindrical upper end portion and diverging leg portions projecting downwardly therefrom, said leg portions having a. maximum transverse dimension substantially less than the diameter of said upper portion, a conical cutter mounted on the inner Wall of each leg portion, the axes of said conical cutters lying in a common plane intersecting the axis of the bit body, the diameter of the base of each of said conical cutters being greater than the transverse dimension through that leg of the bit body on which said conical cutter is mounted, the maximum dimension of said bit body being substantially less than the distance between the laterally projecting ends of the teeth carried by said conical cutters when said teeth are in their lowermost position, the teeth of said cutters at their point of maximum diameter terminating in sharpened points for penetrating the side wall of a well bore when said bit is moved in a horizontal plane at substantially right angles to the axis of the bit.

JOHN A. ZUBLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,325,944 Hughes 1 Dec. 23, 1919 2,336,338 Zublin Dec. 7, 1943 2,344,277 Zublin Mar. 14, 1944 2,516,421 Robertson July 25, 1950 2,585,207 Zublin Feb. 12, 1952

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