US2126075A

US2126075A - Drill collar

Info

Publication number: US2126075A
Application number: US97507A
Authority: US
Inventors: Martha H Wright
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-08-24
Filing date: 1936-08-24
Publication date: 1938-08-09
Anticipated expiration: 1955-08-09

Description

J. C. WRIGHT Aug. 9, 1938.

DRILL COLLAR Filed Aug. 24, 1936 2 Sheets-Sheet 1 Aug. 9, 1938. J. c. WRIGHT DRILL COLLAR Filed Aug. 24, 1936 2 Sheets-Sheet 2 cor.

.lesse E. Wright, Los Angeles, Calif.; Martha. H. Wright, executrix oi' .lesse Wright, deceased Application August 2d, i936, Serial No. 97,507

23 Claims.

This invention relates to well drilling equipment and relates more particularly to a drilling stem or drill collar for use in a rotary well drilling string. A'general object of this invention is to provide an improved and practical drill collar that materially assists in the rapid drilling of the Well and that aids in the drilling of a straight vertical bore.

lin the rotary method of well drilling it is the usual practice to interpose a drill collar between the drilling too l and the drilling string. A drill collar consists of one or more cylindrical sections oi steel ten feet or more in length and of the saine diameter as the drill pipe or sli'ghtly larger in diameter than the drill pipe. A drill'collar is provided with a fluid conducting bore of less diameter than that of the drill pipe and, therelore, has greater wall thickness than the pipe. Thus a drill collar provides additional weight and rigidity in the drillingv assembly immediately above the drilling tool. llt has been found necessary to employ drill collars to lend rigidity to the otherwise rather flexible drilling string and to furnish weight to feed or force the drilling tool into the earth formation. When a drill stem is employed it is possible to maintain the drille ing string, or a portion of the drilling string in suspension while drilling, utilizing the weight of the drill collar to feed the drilling tool into the earth formation. In the event that hard earth formations are encountered it is necessary to employ a very long drill collar of one hundred ileet or more in a length to provide the necessary weight to ieed the drilling. tool to the formation. if the well bore. is crooked or inclined the drill collar has a tendency to fall over against the wall oi the bore and further increase the deviation of the drill. This is particularly true where a long drill collar is employed.

Another object of this invention is to provide a drill collar Whose weight is concentrated in a minimum vertical zone immediately above the drilling tool to eiiectively odset the forces tending to cause deviation of the drilling tool from the vertical.

Another object of this invention is to provide a drill collar several times greater in weight than a typical drill collar and that is of minimum length whereby a great weight is concentrated i immediately above the drilling tool which weight is imposed on the drilling tool to cause it to drill a vertical bore or to bring it back to a vertical position.

Another object oi this invention is to provide a drill collar of suicient weight that it may conltr dit

a drill collar of minimum length, great weight and maximum diameter that may be readily ilshed or recovered from the well in the event the drilling string parts above the drill collar. It is customary to employ drill collars of a diameter sufficiently small to allow a wash-over pipe to be run over the drill collar in the event that the drilling string is parted and the drill collar and drilling tool are lost in the well. This requirement has limited the diameter of the typicai drill collar and has made it necessary to increase the length of the drill collars when additional weight is required so that drill collars often are one hundred feet or more in length, as described above. The drill collar provided by the present invention may be readily recoveredfrom the well without introducing a wash-over pipe from the surface of the ground and, therefore, the drill collar may be of maximum diameter to operate as a stabilizer or guide and to concentrate its weight immediately above the drilling tool.

Another object of this invention is to provide a drill collar embodying an outer part that constitutes a wash-over pipe for conducting iluid to the bottom portion oi the well when it becomes necessary to free the drill collar and the drilling tool :from sand or caved in earth formation.

Another object ol this invention is to provide a drill collar or the character mentioned in which the inner and outer parts may be rotated relative to one another to assist in freeing `the outer part in the event that it becomes sanded in the well bore.

Another object of this invention is to provide a drill collar oi the character mentioned in which the outer part may be moved vertically relative to the inner part to free it in the event that it becomes sanded in the well bore.

Another object of this invention is to provide a drill collar of the character mentioned in which the outer part carrying the weight blocks or weight elements may be disconnected from the inner part and recovered from the well leaving the inner part so that it may be readily engaged and recovered by a suitable fishing tool.

A further object of this invention is to provide a drill collar of the character mentioned that may be easily assembled in the drilling string and that embodies parts that may be easily replaced when worn.

The various objects and features of my invention will be fully understood from the following detailed description of typical preferred forms and applications of my invention, throughout which description reference is made to the accompanying drawings, in which:

Fig. 1 is a view illustrating one form of drill collar of the present invention connecting a typical drilling tool with a drilling string, illustrating the outer part and the weight elements in longitudinal cross section. Fig. 2 is an enlarged longitudinal detailed sectional view of the drill collar illustrated in Fig. 1 showing the inner part and the sub in side elevation. Fig. 3 is a fragmentary longitudinal detailed sectional View of the upper portions of the drill collar with the inner part in elevation, illustrating the ilshing or recovering member in connected relation with the outer part. Fig. 4 is an enlarged transverse detailed sectional view taken as indicated by line 4-4 on Fig. 1. Fig. 5 is an enlarged transverse detailed sectional view taken as indicated by line 5 5 on Fig. 3 and Fig. 6 is a side elevation of another form of drill collar of the present invention illustrating the lower portion of the outer part in longitudinal cross section.

The drill collar of the present invention illustrated in Figs. 1 to 5, inclusive, of the drawings includes, generally, a body I0 to be interposed between the lower end of a drilling string and a drilling tool T, a shell or outer part I I surrounding the body" I0, weight blocks or weight elements I2 carried by the outer part II and a member I 3 adapted to be run into the well on a fishing string F and connected with the outer part I I to manipulate or recover the outer part and the weight elements I2.

The body II) of the improved drill collar is an elongate member for connecting the drilling string S with the drilling tool T. In accordance with the invention the body Il) has considerable strength and rigidity to dependably connect the string S and the tool T and to withstand the various strains to which it may be subjected. The body I0 may be formed of steel and has a substantial wall thickness to have the required strength and rigidity. In practice the body I0 may be in the nature of a typical or common drill collar. In the structure illustrated in the drawings the body I0 is cylindrical and is of uniform external diameter throughout its length. A. central longitudinal fluid passage I4 extends through the body I0 from one end to the other to conduct the circulation fluid. Suitable connecting means are provided at the opposite ends of the body IIJ. A tapered socket I5 may be provided in the upper end of the body I0 to receive a pin part of the drilling string S and a similar threaded socket I6 may be provided in the lower end of the body I0.

'Ihe invention provides a sub or connecting member I1 at the lower end of the body I0. The member I1 has a pin I8 screw threaded in the socket I6. 'I'he member I'I may be larger in diameter than the body II) and is provided at its lower end with a socket I9. 'I'he socket I9 may receive a threaded pin 20 on the upper end of the drilling tool T. The drilling tool T is in the nature of a typical fish-tail bit it being understood that the drill collar of the present invention is adapted for use with various types of drilling tools. It is to be noted that the lower en d of the body I 0 may be closely coupled with the drilling tool T. It is to be understood, however, that a tool joint or the like may be connected between the body IIJ and the tool T, if desired.y The member I1 is provided with a central longitudinal fluid passage 2l for conducting the circulation fluid downwardly from the passage I4 to the fluid passage of the tool T.KA The above described body I0 in addition to forming a strong rigid connection between the string S and the tool T provides substantial weight or load for the tool T and operates to carry the various other parts of the drill collar.

'I'he shell orouter part II of the drill collar is an elongate tubular member surrounding the major portion of the body I0. The outer part II performs several functions as will behereinafter described. In the preferred construction the outer part II is sufficiently large in internal diameter tosurround the body I0 with substantial clearance. This leaves suicient space within the outer part II to contain the weight elements I2 and provide for the circulation of fluid when necessary.' The outside diameter of the outer part II may be such that the outer part is received in the well bore with only slight clearance so that the outer part may engage the wall of the bore to act as a bearing guide and stabilizer for the tool T. In practice the outer part II may comprise a simple length of tubing as illustrated. However, it may comprise several connected lengths of tubing',y if desired. The lower end of the outer part II is removably supported on the connecting member II in a manner to turn with the body I0 and the drilling string S. In'the embodiment of the invention being described the sub or member I'I is provided with an upwardly facing external shoulder 22. A clutch ring 23 is secured to the lower end of the outer part II and is adapted .to seat downwardly on the shoulder 22 to support the outer part. The ring 23 closely surrounds the member I'I to steady and centralize the lower end portion of the outer part II.

Releasable clutch means normally connects the outer part II and the member I1 so that the outer part turns with the body I0. In the. simple preferred structure illustrated flat .walled notches 24 are provided in the lower end of the ring 23 and correspondingly shaped teeth or lugs 25 project upwardly from the shoulder 22 to cooperate with the notches. The notches 24 and the lugs 25 are such that they are properly engaged when the lower end of the ring 23 rests on the shoulder 22 as illustrated in the drawings. It will be apparent that the ring 23 may be released from the shoulder 22 and its clutch lugs 25 by raising the outer part II relative to the body I0.

The upper end of the outer part II is provided with a head 26. The head 26 may be a tubular or annular member rigidly secured to the upper end of the outer part II. In the particular case illustrated the head 26 has a downwardly facing shoulder 21 welded to the upper end of the outer part II. The invention provides spaced longitudinally extending ribs 28 on the interior of the head 26 to cooperate with the exterior of the body IIJ. The ribs 28 operate to centralize and stabilize the upper portion of the outer II -part Il.

part II. In accordance with the invention a thread 29 is provided on the head 26 to be engaged by a thread on the member I3 as will be subsequently described. In the preferred construction illustrated a tapered pin 30 is provided on the upper end of the head 26 and carries the thread 29. The thread 29 is coarse or heavy and is of a type that may be easily mated with by the thread of the member I3. The ribs 28 cooperating withthe body I centralize the head 26 relative to the body making the thread 29 readily engaged by the thread of the member I3. Set

screws 28a may be threaded through openings in the head 26 for the same purpose.

The weight blocks or weight elements I2 are provided to give the desired weight to the assembly whereby the drill collar is operable to feed or force the drilling tool T into the earth formation during the drilling operation. In the structure illustrated in the drawings the weight elements I2 are within the outer part II and are carried or supported by the outer part. It is a feature of the invention that the elements I2 are formed of a material having a high specific gravity. Where I herein employ the term high speciiic gravity" I mean a specic gravity greater than the specific gravity of steel of which drill collars have heretofore been constructed. In practice the weight elements I2 may be formed of lead which has a specific gravity much greater than that of steel of which drill collars are usually constructed. Owing to the high specific gravity of the material of which the elements I2 are formed, a relatively small number ofelements may be embodied in the drill collar and yet may give the vdrill collar the desired weight. 'Ihe invention contemplates the constructing and supporting of the weight elements I2 in various manners'. weight elements I2 are annular or tubular blocklike parts supported one upon the other in the annular space occurring between the exterior of the body II) and the interior of the outer The tubular elements I2 surround the body I0 and the lowermost element is supported on the upper end of the ring 23. 'I'he number of weight elements I2 employed depends upon the drilling conditions it being understood that any desired number of weight elements I2 may be employed. When it is desired to impose a great weight on the drilling tool T a substantial number of blocks or elements I2 may be provided within the outer part II in which c ase the uppermost element I2 may have its upper end adjacent the head 26, as illustrated in the drawings.

In accordance with the invention a uid passage is` provided through the outer part II to conduct ilushing fluid downwardly to free the outer part in the-event that it becomes sanded or mudded in the well. In the construction illustrated in the drawings the blocks or weight elements I2 surround the body III with substantial clearance leaving an annular passage P. The upper end of the passage P is in communication with the interior of the tubular head 26. Circumferentially spaced uid grooves 3l are provided in the exterior of the member I1 and have their upper ends in communication with the lower end of the iluid passage P. The grooves 3l extend downwardly to the shoulder 22 where they communicate with fluid discharge ports 32. The fluid ports 32 extend through the member Il to its exterior where they discharge the uid into the well.

In the particular case illustrated the Fluid dischargel ports 32a may also be provided in the ring 23 to communicate with the grooves 3|. It will be noted that the fluid passed downwardly through the passage P discharges into the well at the lower end of the outer part II so that its return upwardly through the well may free the outer part for recovery. The blocks or weight elements I2 preferablyt rather closely within the outer part Il so that they do not have excessive lateral or horizontal movement.

It will be observed that the weight elements -at I2 formed of a material having a high specific gravity add materially to the weight of the drill collar so that the drill collar imposes a great weight on the drilling tool T. The elements I2 are housed in the outer part II so that the weight of the drill collar is concentrated directly above the drilling tool T. The heavy weight elements I2 surround the relativelyheavy body I0 and the drill collar is of maximum` length.

The outer part II surrounding and housing the relatively soft weight elements I2 protects thev elements against wear and against contact with the wall of the well bore.

The member I3 is provided to connect with the outer part Il of the drill collar to vfacilitate manipulation of the outer part or recovery of the outer part in the event that it becomes caught' in the well or the drilling string S parts above the drill collar. The member I3 is adapted to be run into the well on a recovering string or shing string F passed downwardly over the drilling stringfS. In practice the member I3 may be a simple tubular part directly threaded on the lower end of the shing'string F. A socket 33 is provided in the lower end of the lmember I3 to'receive the pin 39. A thread 34 is provided on the wall of the socket 33 to mate with the thread 29. The

threads

29 and 34 are such that they maybe easily made up or threaded together to connect the shing string F with the outer part I I. When the member I3 is threaded on the pin 3|] the shing string F connected vwith the outer part II through the medium of the member I3 and may conduct flushing uid to the passage P may also be employed to recoverthe outer part Il and the weight elements I2 from the well in the event that the drill collar is lost in the well.

In operation the drill collar illustrated in Figs. 1 to 5, inclusive, of the drawings may be'connected between the drilling tool T and the drillthe drilling tool T downwardly against the earth formation. Owing to thev presence of the plurality o`f weight elements I2 in addition to the relatively heavy body Ill, the drill collar is very heavy to urge the drilling tool T downwardly with substantial force. It is important to note that the great weight provided by the drill collar is concentrated immediately above the drilling tool to materially assist in feeding the tool to drill a straight vertical bore. The weight provided by the improved drill collar being concentrated immediately above the drilling tool T offsets or resists the forces which may tend to effect deviation of the drilling tool T from the vertical. The heavy drill collar is rigidly and closely coupled to the tool'T and having a center of gravity very close to the tool T urges the tool directly downward even though the earth formation be such that it tends to deviate the tool from the vertical. Further, in the event the well bore is crooked or inclined the heavy compact drill collar immediately above the bit and closely coupled thereto feeds the bit directly downwardly to straighten the bore. The drill collar of the present invention embodying the blocks or weight elements I2 may have a weight two or three times greater than a typical drill collar and yet may have a minimum length so that it has little or no tendency to tilt or fall against the wall of the well bore even though the bore be inclined. The outer part I'I of the drill collar may be proportioned to rather closely fit the well bore so that it engages the wall of the bore to act as a guide bearing and to stabilize the bit. This action of the outer part II further. assists in directing the tool T to drill a straight vertical bore. The outer part II of the drill collar may be proportioned as above described without danger of the drill collar becoming immovably caught 0r sanded in the well. The heavy drill collar absorbs the shocks resulting from the action of the tool T on rough and hard formations.

If for any reason the outer part II becomes caught or sanded in the well bore the member I3 may be secured to the lower end of a wash-over string F and passed downwardly over the drilling string S to the head 26. Circulation fluid or water may then be pumped downwardly through the string F to flow through the head 26, the passage P, the grooves 3l and the ports 32 and 32a into the well at the lower end of the outer part II. After being discharged in the well the iluid passes upwardly around the outer part II and may free the outer part so that operations may be resumed. The outer part II of the drill collar thus serves as a wash-over pipe always conveniently available at the drill collar. The string F may be rotated to thread the member I3 on the pin 30. The string F may then be raised to disengage the notches 24 from the clutch parts 25 whereupon the string F may be moved vertically. or rotated, or both, to free the outer part II.

In the event that the drilling string S parts or breaks above the drill collar and it becomes necessary to fish or recover the drill collar and the tool T from the well the string F carrying the member I3 is run into the well, the member I3 is engaged over the pin 30 so that the

threads

29 and 34 engage, and the string F is rotated to thread the member I3 on the pin 30. The string F may then be manipulated and raised in an attempt to withdraw the lost parts from the well. If this attempt fails it may be found necessary to first loosen or free the outer part I I. Circulation fluid or water may be pumped downwardly through the iishing string F to pass through the passage P, the grooves 3| and the

ports

32 and 32". This iiuid under pressure discharged into the well passes upwardly around the outer part II and loosens or frees it from the accumulated sand, cuttings, etc. If believed necessary or desirable the string F may be manipulated to move the outer part II upwardly whereupon it may be reciprocated or rotated, or both, to free it. When freed the outer part II carrying the weight elements I2 may be withdrawn from the well on the string'F. The removal of the outer part II carrying the weight elements I2 leaves the body I9 exposed for easy engagement by a suitable shing tool so that the body I0, the tool T and any remaining lower portion of the string B may be readily recovered from the well. The

clutch connection between the outer part II and the member I1 is sufficiently loose to prevent the transmission of undesirable vibration between the parts and to prevent strains being set up in the connection. The movement between the parts due to the character and looseness of the clutch connection prevents the circulation passage P from becoming sanded up.

Fig. 6 of the drawings illustrates a slightly modied form of construction in which the ring 23 of the outer part II is threaded to the member I1 on the body I0. The various parts of the drill collar may be constructed and assembled as described above. The notches 24 and the lugs 25 are eliminated, however, and the interior of the ring 23 and the exterior of the member I1 are provided with cooperating threads 40. The

'threads 4U normally rigidly connect the outer part II to the body I0. The threads are prei'- erably left-hand threads so that they may be unthreaded by rotation transmitted through the string F without endangering the threaded joints and connections of the string and without unthreading the

threads

29 and 34. It may be preferred to eliminate the fluid grooves 3l and extend the ports 32a upwardly through the member II to have their upper ends in direct communication with the passage P.

.The operation of the construction illustrated in Fig. 6 of the drawings is substantially the same as the operation of the previously described form of the invention. The threads 40 normally connect the outer part Il with the body I0 but are such that the outer part II may be disconnected from the body I0 for movement relative thereto or for recover from the well. The string F may be connected with the outer part I I by means of the member I3 as described above and rotated to unthread the threads 40 whereupon the member II carrying the weight elements I2 may be moved vertically or rotated to free it or may be withdrawn from the well on the string F.

Having described only typical preferred forms and applications of my invention, I do not wish to be limited or restricted to the specific details herein set forth but wish to reserve to myself any variations or modiiications that may appear to those skilled in the art or fall within the scope of the following claims.

Having described my invention, I claim:

1. A drill collar for use in a rotary drilling string including, a body to be connected in the string and having sufficient strength for the transmission of the forces to which the string is subjected, a tubular part around the body, coupling means on the upper end of the said part for connecting with a washover pipe whereby said part is adapted to operate as a continuation of the wash-over pipe, and means removably connecting the outer part with the body.

2. A drill collar for use in a rotary drilling string including, a body to be connected in the string and having suillcient strength for the transmission of the forces to which the string is subjected, an outer part around the body and removably carried by the body to be removable upwardly from the body when the body is connected in the string means on the outer part for coupling with a wash-over pipe, and an element of high specific gravity carried by the outer part.

3. A drill collar for use in a rotary well drilling string including, a body. means at the ends of the body for facilitating its connection in the string, an outer part around the body rotatable relative to the body to be freed of material imof annular blocks surrounding the body within` -pacted about it, releasable clutch means for holding the outer part against such movement, the outer part being removable upwardly from the body, and coupling means on the outer part for coupling with a wash-over pipe. whereby the outer part may be removed from the well by the wash-over pipe.

4. A drill collar for usein a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, an outer part around the body, means supporting the outer part on the body, said outer part having a longitudinal uid passage whereby it may act as a Wash-over pipe, and means on said outer part for receiving a uid conducting. string to supply iiuidto said passage.

5. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, an outer part around the body, a weight element carried by the outer part, means supporting the outer part on the body, said outer part having a longitudinal iluid passage whereby it mayact' as a wash-over pipe, and means on said outer part for receiving a fluid conducting string to supply uid to said passage.

6. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body i'or facilitating its connection in the string, an outer part around the body, means supporting the outer part on the body, said outer part having a longitudinal iluid passage whereby vit may act as a wash-over pipe, and a member to be run intothe well on a iiushing string to connect with the outer part whereby the said passage receives fluid from the string. 4

7. A drill collar for use in a rotary well drilling string including, a body, means at the endsof the body for facilitating its connection in the string, an outer part, releasable clutch means removably supporting the outer part on the body and connecting the outer part with the body to move therewith, a weight element carried by the outer part, connecting means on the outer part.`

a member to be run into the well on a fishing string, and connecting means on the member to mate with the rst mentioned connecting means .whereby the outer part may be recovered from the well.

8. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, an outer part surrounding the body with clearance and removably carried by the body to be removable upwardly therefrom, coupling means on the outer part for connecting with a .pipe passed downwardly over the string, and

material of higher specic gravity than the body in the space between the bo'dy and outer part.

9. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, an outer part carried by the body and surrounding the body with clearance, and a stack the outer part.

10. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the v gitudinal iluid passage extending from its upper portion to its lower portion, and coupling means on the upper portion of the outer part for connecting with a fluid conducting pipe whereby the outer part may act as a wash-over pipe.

l11. A drill collar for connectionA in a. drilling string including, an nected in the string for the transmission of torque. an outer member oi' steel or the like surrounding and supported on the inner member for longitudinal movement thereon, and coupling means on the upper end oi' the outer member for connecting with a washover pipe.

12. A drill collar for connection in a tubular drilling string including, an inner member to be .connected in the string for the transmission or torque and having a passage for conducting tluid during drilling, an outer me'mber surrounding and supported on the inner member, coupling means on the upper end of the outer member for connecting with a wash-over pipe, the outer member having a longitudinal iluid passage open at the upper end of the outer member to receive fluid from said pipe and discharging adjacent its lower end for handling uid when mentioned passage is obstructed.

13. A device for use in a well drilling string carrying a drilling tool including, an inner member connected in the string, an outer weight member carried by the inner member to be removable upwardly therefrom when the inner member is connected in the string, and releasable clutch means connecting the members against relative rotation and releasable by upward movement oi the outer member relative to the inner member.

14. A device for use in a well drilling string carrying a drilling tool including, an inner member connected in the string, an outer member surrounding the inner member, left hand threads releasably connecting the members, and a lright hand thread on the upper portion of the outer member adapted to be cooperated with by a similar thread on a tool for transmitting rotation to the outer member to unscrew the first mentioned thread.

15. A device for use in a weil drilling string carrying a drilling tool including, an inner member connected in the string, an outermember surrounding and rotatable with respect to the inner member, and releasable means coupling the outer member to the inner member so that it rotates therewith and releasable by upward movement of the inner member relative to the outer member to allow rotation of the outer member relative to the inner member.

16. A drill collar for use in a tubular rotary Well drilling string comprising, an elongate body to be interposed in the string, the body having a longitudinal fluid passage for conducting the drilling fluid during drilling and'having a iluid passage out of communication with the iirst mentioned passage for handling ilushing uid when shing the drill collar from the well, and a coupling part on the body for coupling a wash over pipe with the body to supply ilushing iluid inner member to lbe conthe first nected in the drilling string and having a passage for conducting the circulation fluid handled by the drilling string, means for conducting flushing iiuld longitudinally of the body to discharge from the lower portion thereof, and connecting means carried by the body for connecting with awash over pipe to receive fluid therefrom and deliver it to said means.

19. A device for use in a rotary drilling string including, a drill collar body to be connected in the string and having sufllcient strength for the transmission of the forces to which the string is subjected, a part formed of a material having a higher specific gravity than the body surrounding the body to slide and rotate thereon and removably carried by the body to be removable upwardly from the body when the body is connected in the string, and means connecting the body and said part against relative rotation when in a predetermined relative position.

20. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, a tubular part around the body shiftable relative to the body, there being a longitudinal fluid passage through said part opening into the well whereby the outer part may operate as a.

wash-over pipe, a weight element formed of a material of higher specific gravity than the body and carried by the said part, and clutch means supporting the outer part on the body whereby the weight of said element is imposed on the string.

21. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, an outer part fitting the body for rotation relative to the body and for longitudinal movement relative to the body, clutch means'removably supporting the outer part on the body. and connecting the outer part with the body t turn therewith when in a predetermined longitudinal position relative thereto, a weight element carried by the outer part, and a member to be run into the well on a ilshing string to connect with the outer part to recover the same.

22. A drill collar for use in a rotary well drilling string including, a body, means at the ends of the body for facilitating its connection in the string, an outer part carried by the body to be removable upwardly therefrom when the body is connected in the string, the outer part surrounding the body with clearance, a thread on the upper end of the outer part forming coupling means on the outer part for connecting with a pipe passed downwardly over the string, means connecting the body and the outer part releasable by relative rotation between lthe body and the outer part, and a weight in the outer part.

23. A device for use in a well drilling string carrying a drilling tool including, an inner member connected in the string, a weight rotatable relative to the member and shiftable longitudinally of the member, and parts on the member and weight cooperating when the weight is in a predetermined position longitudinally of the -member to detachabhr couple the weight and the inner member so they rotatetogether, the weight being removable upwardly from the inner member when the said parts are out of cooperating engagement.

JESSE C. WRIGHT.