Directional drilling apparatus

[57] ABSTRACT

This invention relates to a directional drilling apparatus. More particularly, the invention is a drilling tool including provisions for changing the direction of drilling of a borehole, the tool including a tubular body having means at the upper end for attachment of a drill string, a drill bit affixed to the lower end of the body by means of a slip clutch drill bit so that the drill bit is rotated when the tubular body is rotated while permitting the drill bit to be rotated independently of the body, means within the tubular body for rotating the drill bit, and means controllable from the surface of the earth of varying the angle of the drilling axis of the drill bit relative to the tubular body.

Claims, 9 Drawing Figures

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PATENTEDJUH 61972

3,667,556

SHEET 1 OF 3

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FIG. IA

ATTORNEYS

PATENTED^ 6 1972

3,667,556

SHEET 2 CF 3

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ATTORNEYS

PATENTEDJUH 6 1972

3.667, 556

SHEET 3 OF 3

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ATTORNEYS

3,667,556

DIRECTIONAL DRILLING APPARATUS

CROSS REFERENCE

This disclosure is not related to any pending United States or foreign patent application.

BACKGROUND AND OBJECTS OF THE INVENTION

In borehole drilling it is frequently necessary to change the direction of drilling. Such procedure is commonly utilized in the petroleum industry to slant wells. By this means a borehole may be started, for instance, adjacent a lake, river or other body of water, with the lower terminus of the borehole being beneath the body of water. Another example of the frequent application for directional drilling is encountered in offshore drilling. Drilling platforms are extremely expensive to move from one location to another. By use of directional drilling techniques it is possible to drill several wells from a drilling platform without moving the platform. In addition to the petroleum industry, the solution mining industry also has requirements for directional drilling, especially high angle drilling, even from vertical to horizontal.

At the present time the most frequently used technique for changing the direction of a drill bit in a borehole is first, removing the drilling string from the borehole, second, lower into the hole a tool known as a whipstock, and third, reinsert the drilling string into the borehole. The function of the whipstock is to divert the direction of drilling and cause the drill bit to drill along a drilling axis at an angle relative to the axis of the prior drilled borehole. Such means of directional drilling is not completely satisfactory since it is time consuming and therefore expensive. Each time it is necessary to change drilling directions the drill string must be removed, the whipstock lowered into position, and the drill string reinserted. When drilling is resumed only a preselected declination from the drilling axis of the original borehole is obtained. Further change in the direction of drilling requires the procedure to be repeated, each time requiring the drill string to be completely removed and reinserted.

The primary object of this invention is to provide an improved directional drilling tool.

More particularly, an object of this invention is to provide an improved drilling tool including provisions for changing the direction of drilling of a borehole by means controllable at the surface of the earth without requiring the drill string having the drilling tool attached thereto to be removed from and reinserted in the borehole each time a drilling direction change is required.

These general objects, as well as more specific objects of the invention, will be understood by reference to the description, taken in conjunction with the attached drawings.

DESCRIPTION OF THE VIEWS

FIGS. 1A, IB and 1C show an embodiment of the drilling tool of this invention in cross section in three segments, FIG. 1A showing the lowermost segment, FIG. IB showing the middle segment, and FIG. 1C showing the topmost segment.

FIGS. 2, 3 and 4 are cross-sectional views taken along the lines 2—2,3—3 and 4—4 respectively, of FIG. 1A.

FIG. 5 is a cross-sectional view taken along the line 5—5 of FIG. IB.

FIG. 6 is a cross-sectional view of the lowermost segment as in FIG. 1A, but showing the relationship of the components of the drilling tool when the tool is set to change the direction of drilling.

FIG. 7 shows a borehole having a high degree of declination and showing means of preventing a drill string from becoming stuck in the borehole.

DETAILED DESCRIPTION

Referring first to FIGS. 1A, IB and 1C, the directional drilling tool includes four attached tubular housing sections, that is, a drill housing 10A shown in FIGS. 1A and IB; a motor housing 10B shown in FIG. IB; an instrument housing IOC shown in FIGS. IB and 1C; and a connector housing 10D shown in FIG. 1C. The housing portions are connected to each other by swivel socket portions generally indicated by the numerals 12A, 12B and 12C.

Supported to the lower end of drill housing portion 10A is a drill bit 14, which may be of the type customarily used in rotary drilling. The drill bit is affixed to a shaft 16 and, although shown integrally formed with the shaft the bit may be detachably affixed to the shaft so as to provide easy removal and replacement. Shaft 16 includes an enlarged diameter ball portion 16A which is spherical in most of its exterior surface and is received in a spherical socket recess 18A in the lower end 18 of drill housing 10A. Formed in the ball portion 16A, in a plane normal to the axis of shaft 16, is a peripheral groove 20, and in like manner, formed in the socket recess 18A is a circumferential groove 22. Positioned between the enlarged ball portion 16A and the socket recess 18A, in grooves 20 and 22, are balls 24A and 24B.

Referring to FIG. 2, groove 20, formed in shaft ball portion 16A, is configured to provide opposed ball engaging projecting portions 26A and 26B. Contrarily, groove 22 formed in housing socket recess 18A has opposed tapered ball recesses 28A and 28B. When the housing 10A is rotated in the direction indicated by the upper arrow at the top of FIG. 2, balls 24A and 24B lock against the projecting portions 26A and 26B to rotate the shaft, and thereby the drill bit 14. However, with the housing 10A held in a stationary position, shaft 16 is free to rotate in the same direction, as indicated by the lower arrow, since the balls 24A and 24B are pushed back into the ball recesses 28A and 28B. The purpose of this ratchet means affording independent rotation of the shaft 16 will be described subsequently.

The upper end of shaft 16 has affixed to it a universal coupling 30 which, in turn, is coupled to a telescoping shaft section 32, and at its upper end is another universal coupling 34. Supported within housing 10A above shaft 16 is a gear reducer 36 having an input shaft 38 and an output shaft 40. The output shaft 40 is secured to the upper universal coupling 34. Gear reducer 36 is supported in housing 10A by plates 42 having openings 44 therein permitting fluid flow within the housing past the gear reducer. Shaft 16, including the ball portion 16A, is tubular, permitting fluid flowing downwardly within the interior of housing 10A to flow out through bit 14.

Above the ball portion 16A is a positioning gear 46 having an eccentric opening 48 therein which rotatably receives shaft 16. Opening 48 is contoured to permit shaft 16 to extend angularly therethrough. Engaging positioning gear 46 is a drive gear 50 affixed to shaft 52 extending from positioning motor 54. A gear reducer portion 54A may be included with positioning motor 54 so that shaft 52 rotates relatively slowly when motor 54 is energized.

Referring to FIG. 6 the drilling tool is shown in an attitude in which the drilling axis 56 (that is, the axis of shaft 16) is at an angle relative to the axis of housing 10A. That is accomplished by energizing positioning motor 54 which rotates gear 50 and thereby positioning gear 46. The eccentric opening 48 in positioning gear 46 causes shaft 16 to be pivoted about ball portion 16A. FIG. 3 shows the relationship of drive gear 50 and positioning gear 56. Spacer 60 affixed to the interior of housing 10A retains gears 46 and 50, each in its rotational position.

The upper end of housing 10A (see FIG. IB) has an integral ball portion 62 which is received in a socket recess 64 formed in the lower end of motor housing 10B. The ball portion 62 and socket recess 64 form swivel socket 12A previously mentioned. The ball portion 62 includes vertical slots 66 in the exterior surface which slidably receives studs 68. The slots 66 and studs 68 permit a pivotal or swivel relationship of housing 10A to 10B while rotationally coupling the housings to each other.

Received in housing 10B is a drill drive motor 70 having a drive shaft 72 extending from the lower end. Drive shaft 72 is

3,667,556 attached to the upper end of gear reducer input shaft 38 by means of a universal coupling 74.

Drill drive motor 70 is supported in housing 10B by means of plates 76 having openings 78 therein permitting the flow of fluid in the housing past the drive motor. The spherical portion 62 at the upper end of drill housing 10A has opening 80 therethrough so that the fluid flow may pass downwardly from housing 10B to housing 10A and ultimately out through the shaft 16 and drill bit 14.

At the upper end of housing 10B and the lower end of housing 10C is swivel socket 12B having the same configuration and serving the same function as previously described with reference to swivel socket 12 A. That is, the upper end of housing 10B includes a ball portion 82 received in a socket recess 84, with slots 86 and studs 88 as above described. OPening 89 in ball portion 82 allows flow of fluid downwardly through socket 12B.

Supported in the lower portion of instrument housing 10C (see FIGS. IB and 1C) is a pressure equalization chamber 90, held in position by plates 92 having openings 94 therein. Extending between the upper end of drill drive motor 70 and the lower end of pressure equalizing chamber 90 is a flexible conduit 96 connecting the interior of motor 70 with that of the pressure equalizing chamber 90. The function of equalizing chamber 90 is to prevent fluid contamination of motor 70 through seals around shaft 72. The use, purpose, and function of a pressure equalizing chamber with a submerged motor operated to drive a pump is well known and such, of and within itself, is not novel to this invention.

Positioned in the upper end of instrument housing 10C (FIG. 1C) is an instrument package 98 supported by plates 100 having apertures 102 therein affording fluid flow externally of the package within the housing. The instrument package 98 may include a variety of instruments but typically houses a dip meter which indicates the angle of declination of the borehole and a magnetic compass or flux gate arrangement which provides means of indicating directional orientation. Basically, a magnetic compass or flux gate arrangement senses the direction of the earth’s magnetic field and indicates the direction of such field to the surface by means of conductors 104. The upper end of instrument housing 10C forms the swivel socket 12C in the same manner as previously described for swivel sockets 12A and 12B and includes ball portion 106, a socket recess 108 formed at the lower end of connector housing 10B, slots 110 and studs 112. Opening 114 through the ball socket 106 provides free fluid flow from connector housing 10D downwardly through instrument housing 10C.

Positioned within housing 10D is a plate 116 having fluid flow apertures 118 therein. Mounted on the plate 116 is a stab connector male portion 120 which provides means for receiving a stab connector female portion (not shown) lowered into the connector housing 10D by means of a cable (not shown). Extending from the connector portion 120, in addition to conductors 104 which communicate with instrument package 98, are conductors 122 and 124 which connect to the positioning motor 54 and drill drive motor 70 respectively. For a description of a submergible electrical connector which includes male portion 120 reference may be had to U.S. Pat. No. 3,398,392. entitled “Submergible Electrical Connector,” issued Aug. 20, 1968.

At the upper end of connector housing 10D are threads 126 by which the housing may be connected to the lower end of a tubular drill string (not shown).

OPERATION

The directional drilling tool of this invention is used with conventional drilling equipment. Prior to the depth at which it is desired to change drilling direction of a borehole, the drill string is brought to the surface and, in place of the regular drill bit, the drilling tool of this invention is secured to the drill string by means of threads 170 at the upper end of the connector housing portion 10D. The tool is then lowered into the borehole. Drilling can be continued in the normal way until the depth at which a deviation in direction of drilling is required. Rotation of the connector housing 10D by means of a drill string rotates the other housing portions 10C, 10B and 10A due to the non-rotatable but flexible connections between housing portions. Rotation of the drill housing 10A, in the direction of the upper arrow as shown in FIG. 2, causes the rotation of the shaft portion 16 and thereby drill bit 14 as previously described.

When it is desired to change drilling direction the drill string is lifted slightly so that pressure is taken off the bit 14. By means of a cable the upper portion of a submergible electrical connector is lowered through the drill string and into the upper end of connector housing 10D where the connector 120 is engaged. This connection provides continuity with conductors 104, 120 and 124 to the earth’s surface. Instruments within package 98 conduct information by way of conductor 104 and connector 120 to the earth’s surface identifying the orientation of the drilling tool relative to the earth’s magnetic field. The drill string and the drilling tool may be rotated to change the orientation as required.

By means of electrical signal from the earth’s surface, conveyed by way of connector 120 and conductor 122, positioning motor 54 is energized rotating drive gear 50 and thereby positioning gear 46. This rotation changes the drilling axis 56 relative to the axis 58 of drill housing 10A. The amount of declination depends on the length of time motor 54 is energized, within the limit of the maximum declination provided by the amount of eccentricity of opening 48 in positioning gear 46.

After the desired drilling declination angle is obtained the drill string may be lowered so that bit 14 engages the bottom of the borehole.

Energy may then be supplied by way of connector 120 and conductor 124 to drill drive motor 70. The rotation of shaft 72, gear reducer input shaft 36, and gear reducer output shaft 40 causes the rotation of shaft 16 and drill bit 14. During this time the drill string and therefore the directional drilling tool housing is held non-rotational but is allowed to move downwardly as bit 14 advances. The drilling operation can continue for a length of time sufficient that the borehole extension is established at the selected angle of deviation. At this time the borehole can be checked for dip and direction to see if the desired angle has been attained.

After the borehole is drilled sufficiently by means of motor 70 to positively establish a new direction of drilling, positioning motor 54 is energized to return shaft 16 to its normal position in which the axis 56 of the shaft is coincident with the axis 58 of body portion 10A. The cable with the removable connector portion is removed, disconnecting from connector 170. Conventional drilling may then be resumed by means of rotation of the drill string causing the rotation of the drilling tool and bit 14. Conventional drilling may continue as long as desired and when it is necessary to again change the direction of drilling the above described procedure is repeated, that is, the rotation of the drill string and thereby the tool is stopped, the drill string is lifted slightly, the cable is run within the drill string to establish connection with connector 120, a new angle of direction of drilling is selected by energization of positioning motor 54, followed by drilling by means of drill drive motor 70 to establish the new drilling direction. Thus, the change of direction of drilling may be repeated as many times as desired, limited only to the life of bit 14, without removing the drill string and drilling device from the borehole and requiring only the running of a cable supported connector into and out of the drill string each time a new direction of drilling is desired.

It can be seen that by use of this invention a borehole may be drilled at a very high degree of declination relative to he vertical, even to the extent of changing drilling from a vertical to a horizontal direction. Only a small degree of angular deviation can achieve an ultimate change from vertical to horizontal. The housing of the directional drilling tool is formed in

3,667,556 sections 10A, 10B, IOC and 10D to permit drilling of much shorter radius curves than would otherwise be possible if all of the elements were housed in a single enclosure.

One problem which has existed in the drilling industry with directional drilling is that continuous wear along the inside curves of a borehole deviation results in the formation of a recess having approximately the same diameter as the drill string. When attempt is made to remove the drill string it is not uncommon for the drill string collars to be caught in this recess and make it difficult, if not occasionally impossible, to remove the drill string. Such phenomena is referred to in the industry as a “key seat.” An arrangement is shown in FIG. 7, which may be utilized, to prevent the formation of a key seat. Casing, in the form of joints 128 held together by couplings 130, is positioned in the curved portion 132 of a borehole. After the casing 128 is in position fluid cement is run through the casing to flow out the lower end and upwardly within the borehole 32, the cement 134 solidifying and serving to hold the casing 128 in position. As the borehole is extended past the portion 132 wherein declination takes place the drill string rotates in the interior of casing 128 which, being much harder and more resistant to abrasion than most earth formations, prevents a key seat from forming. The casing 128 may be regular casing as presently utilized in the petroleum industry if the borehole curve is of a large radius and more flexible casing can be used if the curve is of a smaller radius. “Cement” as used herein means any material which can be pumped in liquid form and which solidifies after a given time.

It is to be understood that the invention has been described by reference to a structural embodiment shown for purposes of exemplifying the invention only. Obviously, many alternate means may be utilized to provide the slip arrangement between the shaft 16 and drill housing 10A. Other devices may be utilized to provide, upon the application of an electrical signal, the declination of the axis of shaft 16 other than by the use of motor 14, gear 50 and gear 46 as shown. The arrangement and placement of the drilling motor 70, gear reducer 36, pressure equalizing chamber 90, instrument package 98, and so forth, may change considerably, all within keeping of the invention. The specific details of construction of the universal couplings 30,34 and 74 are exemplary only of many other types of universal couplings which may be utilized.

Drill drive motor 70 is shown and described as being an electrical motor. An alternate arrangement would include the use of a hydraulic motor. While a male connector portion 120 is shown, adaptable to receive a female connector portion, it can be seen that connector portion 120 may be a female portion adapted to receive a male portion lowered downwardly into the upper end of connector housing 10D.

While the invention has been described with a great degree of particularity it is manifest that many changes may be made in all parts of the apparatus without departing from the spirit and the scope of the invention. The invention is not to be limited to the apparatus described but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element or step thereof is entitled.