CA1243663A - Adjustable bent sub - Google Patents
Adjustable bent subInfo
- Publication number
- CA1243663A CA1243663A CA000520506A CA520506A CA1243663A CA 1243663 A CA1243663 A CA 1243663A CA 000520506 A CA000520506 A CA 000520506A CA 520506 A CA520506 A CA 520506A CA 1243663 A CA1243663 A CA 1243663A
- Authority
- CA
- Canada
- Prior art keywords
- bent sub
- mandrel
- respect
- sleeve
- clutch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B7/00—Special methods or apparatus for drilling
- E21B7/04—Directional drilling
- E21B7/06—Deflecting the direction of boreholes
- E21B7/067—Deflecting the direction of boreholes with means for locking sections of a pipe or of a guide for a shaft in angular relation, e.g. adjustable bent sub
Abstract
ABSTRACT OF THE INVENTION
There is disclosed an adjustable bent sub for use in directional drilling in earth formations which is adapted to be placed between the power unit and bearing assembly components of a downhole motor and which can be angularly adjusted without requiring disassembly of the downhole motor unit. The bent sub is comprised of a first member having a primary axis and an external, cylindrical surface defining a secondary axis disposed at a predetermined offset angle with respect to the primary axis; a tubular second member secured to the first member against axial displacement and having a primary axis, an internal, cylindrical surface defining a secondary axis disposed at a predetermined offset angle with respect to the second member primary axis, the internal surface being adapted to telescopically receive the first member external surface in sliding fit relation for rotation about the secondary axis, and a first clutch extending axially from one end thereof; a locking sleeve telescopically receiving and non-rotatably coupled to the external surface of the first member and having a second clutch extending axially of one end thereof toward the second member, the sleeve being axially moveable on the first member between an engaged position whereat the first and second clutch are interengaged and non-rotatably couple the second member and the first member in a predetermined angular position and a disengaged position whereat the locking sleeve is axially displaced from the second member and the first and second clutch are disengaged from one another so as to permit angular adjustment of the second member with respect to the first member; and threads on the external surface of the first member for securing the sleeve in the engaged position thereof.
There is disclosed an adjustable bent sub for use in directional drilling in earth formations which is adapted to be placed between the power unit and bearing assembly components of a downhole motor and which can be angularly adjusted without requiring disassembly of the downhole motor unit. The bent sub is comprised of a first member having a primary axis and an external, cylindrical surface defining a secondary axis disposed at a predetermined offset angle with respect to the primary axis; a tubular second member secured to the first member against axial displacement and having a primary axis, an internal, cylindrical surface defining a secondary axis disposed at a predetermined offset angle with respect to the second member primary axis, the internal surface being adapted to telescopically receive the first member external surface in sliding fit relation for rotation about the secondary axis, and a first clutch extending axially from one end thereof; a locking sleeve telescopically receiving and non-rotatably coupled to the external surface of the first member and having a second clutch extending axially of one end thereof toward the second member, the sleeve being axially moveable on the first member between an engaged position whereat the first and second clutch are interengaged and non-rotatably couple the second member and the first member in a predetermined angular position and a disengaged position whereat the locking sleeve is axially displaced from the second member and the first and second clutch are disengaged from one another so as to permit angular adjustment of the second member with respect to the first member; and threads on the external surface of the first member for securing the sleeve in the engaged position thereof.
Description
~Z~3~i63 The present inverltiorl relates, iII yeneral, to directional drilling in earth formations and, more specifically, to an adjustable bent ~ub for u~e in directional drilling.
~AC~GROU~D OF TEE I~VENTION
"Directional drîlling" is a procedure employed in the ~arth drilliny i~dustry when it is necessary to change the direction of a borehole. In e~sence, 10 directional drilling is achieved by inserting, at the downhole end of a drill striny, a small section of pipe, called as ~ "sub", which has been "bent" such that the longitudinal axis at one end its ends is at a slight angle, ~eferred to herein as the "offset angle" to the 15 lonyitudinal axis at the other end. 5uch a tool is called a "bent sub".
In practice, a vertical borehole is drilled to a predetermined depth. The drill string is then withdrawn and a bent sub having the desired offset angle is 20 inserted between the end of the drill string and the downhole motor. The drill string is then inserted back into the borehole. Since the longitudinal axis of th~
drill bit will now be a-t an angle to the original borehole, the direction of the bore hole will be
~AC~GROU~D OF TEE I~VENTION
"Directional drîlling" is a procedure employed in the ~arth drilliny i~dustry when it is necessary to change the direction of a borehole. In e~sence, 10 directional drilling is achieved by inserting, at the downhole end of a drill striny, a small section of pipe, called as ~ "sub", which has been "bent" such that the longitudinal axis at one end its ends is at a slight angle, ~eferred to herein as the "offset angle" to the 15 lonyitudinal axis at the other end. 5uch a tool is called a "bent sub".
In practice, a vertical borehole is drilled to a predetermined depth. The drill string is then withdrawn and a bent sub having the desired offset angle is 20 inserted between the end of the drill string and the downhole motor. The drill string is then inserted back into the borehole. Since the longitudinal axis of th~
drill bit will now be a-t an angle to the original borehole, the direction of the bore hole will be
2~ altered. The bent sub may be replaced any number of times in order to provide a borehole of the desired angular offset.
The positioning of the bent sub in the drill string has an effect upon the operation of the downhole motor.
30 The more r~mote the bent sub is from the drill bit, within practical limitations for directional drillin~, the more interference there is between the borehole and drill bit, and between the borehole and bent ~ub when inserting the drill string into the bor~hole. When 35 drilling such int~rference causes a loss of power which ~D
~Z4~663 would otherwise be available for drilling, a~ the mo-tor must overcome the interference and the drill bi-t is not desi~ned to drill sideways. It i5 desirable -to be able to rotate the drill string in the borehole. An excessive amount of in-terfererlce will prevent or render difficult such rotation. It has been ascertained, that if the ben-t sub is placed closer -to -the drill bit interference between the borehole and bent sub is reduced. If the bent sub is placed closer to the drill 10 bit, interference between the borehole and the drill bit i5 similarly reduced and the angle of engagement between the drill bit and the side of the borehole is improved.
The optimum positioning o the bent sub is 15 considered to be between the power unit and beariny components of the downhole motor. This creates severe limitations upon the use of conventional bent subs. The angular offset of conventional bent subs is achieved by physically bending the sub or by otherwise modifyiny the 20 longitudinal axis of the sub during the machininy stage of its manufacture. In order to provide for selectivity, it i5 necessary to provide a series of bent subs having offset angles ranging from about 1/4 of one degree in lJ4 increments to about 2 degrees. Once a downhole 2~ motor unit is assembled having a power unit, a bearing assembly, and a bent sub in between, the rig crew will not under ordinary circumstances take the motor unit apart to interchange the bent sub component, such work must be performed in a service shop which is usually at 30 a location remote from the drill site. It is therefore, the practise to have a plurality of downhole motor units on site having incorporated therein bent subs of varying degrees of offset. This practise results in a needless duplication of expense, If the available units do not B
.
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The positioning of the bent sub in the drill string has an effect upon the operation of the downhole motor.
30 The more r~mote the bent sub is from the drill bit, within practical limitations for directional drillin~, the more interference there is between the borehole and drill bit, and between the borehole and bent ~ub when inserting the drill string into the bor~hole. When 35 drilling such int~rference causes a loss of power which ~D
~Z4~663 would otherwise be available for drilling, a~ the mo-tor must overcome the interference and the drill bi-t is not desi~ned to drill sideways. It i5 desirable -to be able to rotate the drill string in the borehole. An excessive amount of in-terfererlce will prevent or render difficult such rotation. It has been ascertained, that if the ben-t sub is placed closer -to -the drill bit interference between the borehole and bent sub is reduced. If the bent sub is placed closer to the drill 10 bit, interference between the borehole and the drill bit i5 similarly reduced and the angle of engagement between the drill bit and the side of the borehole is improved.
The optimum positioning o the bent sub is 15 considered to be between the power unit and beariny components of the downhole motor. This creates severe limitations upon the use of conventional bent subs. The angular offset of conventional bent subs is achieved by physically bending the sub or by otherwise modifyiny the 20 longitudinal axis of the sub during the machininy stage of its manufacture. In order to provide for selectivity, it i5 necessary to provide a series of bent subs having offset angles ranging from about 1/4 of one degree in lJ4 increments to about 2 degrees. Once a downhole 2~ motor unit is assembled having a power unit, a bearing assembly, and a bent sub in between, the rig crew will not under ordinary circumstances take the motor unit apart to interchange the bent sub component, such work must be performed in a service shop which is usually at 30 a location remote from the drill site. It is therefore, the practise to have a plurality of downhole motor units on site having incorporated therein bent subs of varying degrees of offset. This practise results in a needless duplication of expense, If the available units do not B
.
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., . -..
3~
hav~ the correc-t angular offset work must ~top until one is obtained.
S~ARY OF T~ INV~NTION
The present inven-tion seek6 to prov:ide a bent sub which overcomes the above described disadva~tages of the prior art.
Accordingly -to the present inverltiorl, t~ler~ is provided an adjustable bent sub for use in directional 10 drilling in earth formation~ which iY compIi~ed of a first member havin~, a primary axis, and external, cylindrical surface means defining a secondary axi5 disposed at a predetermined offset angle with respect to the primary axis; a tubular second member secured to 15 the first member against axial displacement and having, a primary axis; internal, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to the second member primary a~is, the internal sur~ace being adapted to 20 telescopically receive the first member external surface in sliding fit relation for rotation about the secondary axis, and first clutch means extending axially from one end thereof; locking sleeve means telescopically receiving and non-rotatably coupled to the external 25 surface means cf the first member and having second clutch means extending axially of one end thereof toward the second member, the sleeve means being axially moveable on the first member between an engaged position whereat the first and ~econd clutch means are 30 interengaged and non-rotatably couple the second member and the first member in a predetermined angular position and a disengaged position whereat the locking sleeve is axially displaced from the second member and the first and second clutch means are disengaged from one ~nother 35 so as to permit angular adjustment of the second member ::-.....
,.
~ ~ r~
with respect t~ the first member; and means threaded onto the external surface of the first mernber or securing the sleeve in the engaged position thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the in~en-tion ~ill become more apparen-t from the following de~criptioIl in which reference i~ made to the apperlded drawin0s, wherein:
FIGURE 1 i5 a partially broken view, o~ a drill ~tring in a borehole illustrating a oonventional bent sub arrangement;
FIGURE 2 is a view similar to FIGURE 1 but illustrating an adjustable bent sub assembly according 15 to the preferred embodiment of the present invention;
FIGURE 3a is a partial broken, elevational view of a portion of a drill ~tring illustrating the adjustable bent sub of the present invention at its maximum offset angle;
FIG~RE 3b is a view similar to FIGURE 3a, but illustrating the bent sub of the pre~ent invention at its minimum offset angle;
FIGURE 4 is a view si.milar to FIGURE 3a but in partial section illustrating the internal structure of 25 the adjustable bent sub of the present invention; and FIGUR~ 5 i5 an enlarged view of indi~ia means disposed on the adjustable bent sub of the present invention for facilitating adjustment of the offset angle.
D~TAIL~D D~SCRIPTIO~ OF _R~F~R~D ~MBODIMENT
Figure 1 illu~trates a conventional assembly employed ~or directional drilling in earth formations.
The assembly includes a bent sub 12 threadedly e~gaged at its uphole end to the downhole end of a drill ~tring .~
..
~Z~3663 14 and -threadedly engaged at its lower end to the uphole end of a downhole motor assembly 16. The lower erld o~
the drilling motor assembly i~ secured to a drill bit 18. The bent sub is constructed so that the axis of its 5 dOWllhOle end i8 disposed at an offset angle ran~ g ~rom a fract:ion of one degree to about two degrees to the axis of its uphole end. This i~ typically ac~lieved by machining the threads of the lower threaded cont~ectiort at an offset angle to the a~is of the sub and upper 10 connection. It will be understood that with the axi~
of the drill bit being angularly off~et with resp~c-t to the axis of the drill string, it is then possible to alter the direction of the borehole. The magnitude of the angular deviation from the axis of the drill string 15 may be altered by selecting a bent sub with the proper ang~lar offset, within functional limitations where interference with the borehole becomes too great. Thus, it is conventional to maintain an inventory at the drill site of bent subs 12 having differen-t offset angles so 20 that when a new drilling direction is required, the drill string i5 withdrawn from the borehole and the bent sub is replaced with a bent sub having the appropriate offset angle.
The present invention, generally designated by 25 reference numeral 20, will be now be described with reference to FIGUR~S 2 to 5 where the same reference characters designate similar parts.
With particular reference to FIGURE 2, the bent sub 20 of the present invention is disposed between the 30 power unit and the bearing section of a downhole motor 16. This location permits larger off~et angles and/or reduces interference whils running in the boreh~le. The bent sub of the present invention is constructed in such a manner that the offset angle can be easily adjusted 35 between predetermined limits without removal of the B
: :
`:
.
~Z~36~3 downhole motor from the drill ~trirlg and thus render~
unnecessary the maintenance of a large inventory of downhole motors with bent subs having diff~rent offse-t anyles.
With reference to FIGURES 3 and 4, bent ~ub 20 will be seen to be compri~ed of five componerlt~, namely, a mandrel 22, a bent sub housing 24, a sleeve 26 and a first nut 2a and a ~econd nut 30.
Mandrel 22 is in the ~orm of a pipe section having 10 an externally threaded end 32 adapted to a threadedly engage the bearing assembly 34 of a downhole motor 16.
The mand~el includes a first exterior surface portion 36 whose diameter is the same as that of the beari~g assembly 34 and a second exterior ~urface portion 38 15 having two portions 40 and 42 of reduced di~meter.
Reduced diameter portions 40 and 42 are separated by a conical shoulder 44. The end 46 of mandrel 22 is externally threaded for threaded engagement with nut 30 while end of reduced diameter portion 40 is externally 20 threaded to receive nut 28.
The common axis of the threaded ~nd 32 and the first exterior portion 36 of the mandrel defines a first primary axis 50 which is coaxial with the axis of the bearing assembly 34 of the downhole motor, while the 25 axes of the outer cylindrical surfaces of reduced diameter portions 40 and 42, respectively, are machined such that their longitudinal axis is anyularly off~et from primary axis 50, so as to define a first secondary axis 56. The significance of this will become clear a~
30 the description proceeds. The mandrel defines a central fluid passageway 58 for conveying drill.ing fluid to the drill bit.
Bent sub housing 24 i5 a generally tubular member having an outer ~urface 60, who~e diameter is the same as that of the bearing assembly 34 of -the downhole motor ~' and portion 36 of -the mandrel, and a -threaded end 62 threadedly engageable with the internally threaded power unit section 64 of the downhole motor. Housiny 24 i~
formed with a pair of concentric internal surface 66 and 68 separated by conical shoulder 70 which i5 engageable with conical ~houlder 44 of the mandrel which coop~rate to limit tele~copic movement irl olle axial directiorl v~
th~ bent sub housi~g with respect to th~ mandrel when nut 28 is loosened. Internal surfaces 66 and 6~ of 10 housing 24 are machined to receive the outer surf~ce~ of reduced diameter portion 40 and 42 of the mandrel in sliding fit relation.
The axi~ of concentric cylindrical surfaces 66 and 68 define a ~econd primary axis 72 while the axis of the 15 threaded housing end 62 defines a second secondary axis ~4, which is angular offset from the second primary axis. When housing 24 is assembled upon mandrel 22, the first secondary axis 56 is coaxial with the second primary axis ~2 50 as to define a co~mon axis about 20 which the housing is rotat~ble, when permitted to do so as explais~ed later. The angular offset between the fir~t primary and secondary axe~ is nominally one degree but may range from a fraction of one degree to two degrees if desired. The magnitude of the offs~t angle 25 is not important to the essence of the pre~ent invention. It will be seen, then, that the angular disposition of housin~ 24 with respect to mandrel 22 will determine the angular offset between the drill string and the drill bit. Maximum offset i5 obtained 30 when the oEfset of the mandrel is in the same radial plane and extends in the same direction as that of the housing. This configuration i9 illustrated in ~IG~RE
3a. Thus, if the angular offset is one degree, then the overall angular offset, i.e. between the axis of the 35 drill string and the axis of the drill bit will be -two ~Z~36~3 degrees. This position is referred to as -the "ba~e"
position. Minimum offset is obtained when the offset of the mandrel is in the same radial plane and ex-tends in the opposite direction to that of the hou~in~. This configuration i5 illustrated in FIGURE 3b. This occur~
when the housing i5 angularly displaced from the ba~e position by 180 degrees whereat the off~et anglc ~ the housing cancels the offset angle of the mandrel ~o that the net overall angular offse-t between the axiB of the 10 drill string and the axis of the drill but will be zero degrees. In this position, there will be a slight radial offset of the axis of the drill striny a~d that of the drill bit; however, the two axes will be parallel to one another. This is reflected in FIGUR~ 3b, where 15 fir~t primary axis 50 i5 shown as being parallel to second secondary axis ~4. It will be understood that angular displacements of mandrel 22 with resp~ct to housing 24 will provide overall angular offsets ranging from a maximum of two degrees (~I6~R~ 3a) to a minimum 20 of zero degrees (FIG~R~ 3a).
As already mentioned, nut 30 threadedly engages threaded end 46 of the mandrel and is formed with a first annular shoulder B0 which bears against the end 82 of the mandrel as well as a second annular ~houlder 84 25 which bears against end 86 of the housing. In this manner, nut 30 prevents axial displacement of the housing with respect to the mandrel, while permitting rotational movement of the housing about the mandrel.
Sleeve 26 provides the means by which rotary forces 30 can be transmitted between the mandrel and the housing end, with nut 28, provide the means by which the housing can be angularly adjustea with respect to th~ mandrel as explained hereinbelow. Shoulders 44 and ~0 p~event displacement of the housing with re~pect to the mandrel, 3~ when nut 28 is loosened.
'~
;3663 The end 100 of housing 24 a~d the snd 102 of sleeve 26 are formed with mating teeth 106 forming dog clutch elemen-ts of a dog clutch generally designa-ted by reference numeral 108. When the teeth, and, thus, the clutch are engaged, rotary ~orces can be -transmit-ted between the sleeve and the hou~in~. Conver~ely, when the ~leeve is displacecl axially away from the houslng ~wch that the teeth are no lonyer engaged, the hou~iny will be free to rotate with respect to the mandrel. In this 10 manner, the housing can be set to the desired po~ition.
Nut 28 is formed with a shoulder 110 which is abuttingly engageable with the end 113 of the sleeve 26 80 that when nut 28 is threaded against the sleeve, the 15 dog clutch is maintained in an engaged or locked position. Conversely, whe~ the nut i~ threaded away from the sleeve a sufficient distance, the ~leeve can be slid axially away from the mandrel to allow disengayement of the clutch and angular adjustment of 20 the housing with respeot to the mandrel.
In order to transmit rotary forces between the mandrel and housing, internal surface 120 of the ~leeve is formed with splines 122 arranged to receive keys 124 located in keyways 126 of the mandrel. The splines 2~ extend to both ends of the sleeve to allow the sleeve to clear keys 124 in order to facilitate assembly and adjustment of the assembly.
Advantageously, as best shown in ~I~URE 5, the sleeve and housing are each~ formed with alignable 30 indicia 130 to facilitate po~itioning the housing iIl the proper and desired anyular position with respect to the mandrel. As shown, the indicia may be in increments of 0.25 degrees and extend 180 deyrees about the sleeve housing. Further, the 35 circumferential width of teeth 106 of the doy clutch may ~ ` t .~
~Z~36~3 be arranged ~uch that it correspands w.ith any desired angular increment, such as 0.25 degrees, for example, to facilita-t~ positioning of the housing with re~pect to the mandrel.
The preferred location of bellt ~ub in the drlll string is between the power unit sectio~ arld bearitlg assembly ~ection o the dowrlhole motor. Prior to loweriny the motor a~sembly into the borehole, the bent sub 20 is adjusted to provide the desired an~ular offse-t 10 between the axis of the drill bit and the axi~ of the drill string. This is accomplished by loo~ening lock nut 28 and sliding sleeve 26 along keys 124 until mating dog clutch elements 106 are di~enga~ed. Once the do~ clutch is diaengaged, housing 24 may be an~ularly adjusted with 15 respect to mandrel 22 as previously explained.
Once the housing ha~ been placed in the desired positivn, the dog clutch is re-engaged and nut 28 is threaded against sleeve 26 thereby securing sleeve 26 and mandrel 22 in the selected position.
It will be appreciated that the above de~cribed preferred embodiment of the present inventioI~ overcomes the disadvanta~es, discus ed earlier, oE the prior art.
First, according to the present invention, it is unneces~ary to maintain a large inventory of downhole 25 motors having a bent subs with differing angles oP
offset. 5econd, adjustment of the bent ~ub of the present invention i~ extremely ~imple and does not re~uire the di~a~sembly of the downhole motor.
It will also be apparent to one ~killed in the art 30 that adjustable bent sub can be run in an inverted position with threaded connectior. 32 coupled to power unit ~ection 64 of a downhole motor and threaded connection 62 coupled to bearing assembly 34 of a downhole motor.
B
~2~3~63 It will be apparent to those ~killed in the art that various modifications and alterations may be made to the above de~cribed embodimerlt without departin~ from the spirit of -the invention as defined by the appended claim~.
1~
hav~ the correc-t angular offset work must ~top until one is obtained.
S~ARY OF T~ INV~NTION
The present inven-tion seek6 to prov:ide a bent sub which overcomes the above described disadva~tages of the prior art.
Accordingly -to the present inverltiorl, t~ler~ is provided an adjustable bent sub for use in directional 10 drilling in earth formation~ which iY compIi~ed of a first member havin~, a primary axis, and external, cylindrical surface means defining a secondary axi5 disposed at a predetermined offset angle with respect to the primary axis; a tubular second member secured to 15 the first member against axial displacement and having, a primary axis; internal, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to the second member primary a~is, the internal sur~ace being adapted to 20 telescopically receive the first member external surface in sliding fit relation for rotation about the secondary axis, and first clutch means extending axially from one end thereof; locking sleeve means telescopically receiving and non-rotatably coupled to the external 25 surface means cf the first member and having second clutch means extending axially of one end thereof toward the second member, the sleeve means being axially moveable on the first member between an engaged position whereat the first and ~econd clutch means are 30 interengaged and non-rotatably couple the second member and the first member in a predetermined angular position and a disengaged position whereat the locking sleeve is axially displaced from the second member and the first and second clutch means are disengaged from one ~nother 35 so as to permit angular adjustment of the second member ::-.....
,.
~ ~ r~
with respect t~ the first member; and means threaded onto the external surface of the first mernber or securing the sleeve in the engaged position thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the in~en-tion ~ill become more apparen-t from the following de~criptioIl in which reference i~ made to the apperlded drawin0s, wherein:
FIGURE 1 i5 a partially broken view, o~ a drill ~tring in a borehole illustrating a oonventional bent sub arrangement;
FIGURE 2 is a view similar to FIGURE 1 but illustrating an adjustable bent sub assembly according 15 to the preferred embodiment of the present invention;
FIGURE 3a is a partial broken, elevational view of a portion of a drill ~tring illustrating the adjustable bent sub of the present invention at its maximum offset angle;
FIG~RE 3b is a view similar to FIGURE 3a, but illustrating the bent sub of the pre~ent invention at its minimum offset angle;
FIGURE 4 is a view si.milar to FIGURE 3a but in partial section illustrating the internal structure of 25 the adjustable bent sub of the present invention; and FIGUR~ 5 i5 an enlarged view of indi~ia means disposed on the adjustable bent sub of the present invention for facilitating adjustment of the offset angle.
D~TAIL~D D~SCRIPTIO~ OF _R~F~R~D ~MBODIMENT
Figure 1 illu~trates a conventional assembly employed ~or directional drilling in earth formations.
The assembly includes a bent sub 12 threadedly e~gaged at its uphole end to the downhole end of a drill ~tring .~
..
~Z~3663 14 and -threadedly engaged at its lower end to the uphole end of a downhole motor assembly 16. The lower erld o~
the drilling motor assembly i~ secured to a drill bit 18. The bent sub is constructed so that the axis of its 5 dOWllhOle end i8 disposed at an offset angle ran~ g ~rom a fract:ion of one degree to about two degrees to the axis of its uphole end. This i~ typically ac~lieved by machining the threads of the lower threaded cont~ectiort at an offset angle to the a~is of the sub and upper 10 connection. It will be understood that with the axi~
of the drill bit being angularly off~et with resp~c-t to the axis of the drill string, it is then possible to alter the direction of the borehole. The magnitude of the angular deviation from the axis of the drill string 15 may be altered by selecting a bent sub with the proper ang~lar offset, within functional limitations where interference with the borehole becomes too great. Thus, it is conventional to maintain an inventory at the drill site of bent subs 12 having differen-t offset angles so 20 that when a new drilling direction is required, the drill string i5 withdrawn from the borehole and the bent sub is replaced with a bent sub having the appropriate offset angle.
The present invention, generally designated by 25 reference numeral 20, will be now be described with reference to FIGUR~S 2 to 5 where the same reference characters designate similar parts.
With particular reference to FIGURE 2, the bent sub 20 of the present invention is disposed between the 30 power unit and the bearing section of a downhole motor 16. This location permits larger off~et angles and/or reduces interference whils running in the boreh~le. The bent sub of the present invention is constructed in such a manner that the offset angle can be easily adjusted 35 between predetermined limits without removal of the B
: :
`:
.
~Z~36~3 downhole motor from the drill ~trirlg and thus render~
unnecessary the maintenance of a large inventory of downhole motors with bent subs having diff~rent offse-t anyles.
With reference to FIGURES 3 and 4, bent ~ub 20 will be seen to be compri~ed of five componerlt~, namely, a mandrel 22, a bent sub housing 24, a sleeve 26 and a first nut 2a and a ~econd nut 30.
Mandrel 22 is in the ~orm of a pipe section having 10 an externally threaded end 32 adapted to a threadedly engage the bearing assembly 34 of a downhole motor 16.
The mand~el includes a first exterior surface portion 36 whose diameter is the same as that of the beari~g assembly 34 and a second exterior ~urface portion 38 15 having two portions 40 and 42 of reduced di~meter.
Reduced diameter portions 40 and 42 are separated by a conical shoulder 44. The end 46 of mandrel 22 is externally threaded for threaded engagement with nut 30 while end of reduced diameter portion 40 is externally 20 threaded to receive nut 28.
The common axis of the threaded ~nd 32 and the first exterior portion 36 of the mandrel defines a first primary axis 50 which is coaxial with the axis of the bearing assembly 34 of the downhole motor, while the 25 axes of the outer cylindrical surfaces of reduced diameter portions 40 and 42, respectively, are machined such that their longitudinal axis is anyularly off~et from primary axis 50, so as to define a first secondary axis 56. The significance of this will become clear a~
30 the description proceeds. The mandrel defines a central fluid passageway 58 for conveying drill.ing fluid to the drill bit.
Bent sub housing 24 i5 a generally tubular member having an outer ~urface 60, who~e diameter is the same as that of the bearing assembly 34 of -the downhole motor ~' and portion 36 of -the mandrel, and a -threaded end 62 threadedly engageable with the internally threaded power unit section 64 of the downhole motor. Housiny 24 i~
formed with a pair of concentric internal surface 66 and 68 separated by conical shoulder 70 which i5 engageable with conical ~houlder 44 of the mandrel which coop~rate to limit tele~copic movement irl olle axial directiorl v~
th~ bent sub housi~g with respect to th~ mandrel when nut 28 is loosened. Internal surfaces 66 and 6~ of 10 housing 24 are machined to receive the outer surf~ce~ of reduced diameter portion 40 and 42 of the mandrel in sliding fit relation.
The axi~ of concentric cylindrical surfaces 66 and 68 define a ~econd primary axis 72 while the axis of the 15 threaded housing end 62 defines a second secondary axis ~4, which is angular offset from the second primary axis. When housing 24 is assembled upon mandrel 22, the first secondary axis 56 is coaxial with the second primary axis ~2 50 as to define a co~mon axis about 20 which the housing is rotat~ble, when permitted to do so as explais~ed later. The angular offset between the fir~t primary and secondary axe~ is nominally one degree but may range from a fraction of one degree to two degrees if desired. The magnitude of the offs~t angle 25 is not important to the essence of the pre~ent invention. It will be seen, then, that the angular disposition of housin~ 24 with respect to mandrel 22 will determine the angular offset between the drill string and the drill bit. Maximum offset i5 obtained 30 when the oEfset of the mandrel is in the same radial plane and extends in the same direction as that of the housing. This configuration i9 illustrated in ~IG~RE
3a. Thus, if the angular offset is one degree, then the overall angular offset, i.e. between the axis of the 35 drill string and the axis of the drill bit will be -two ~Z~36~3 degrees. This position is referred to as -the "ba~e"
position. Minimum offset is obtained when the offset of the mandrel is in the same radial plane and ex-tends in the opposite direction to that of the hou~in~. This configuration i5 illustrated in FIGURE 3b. This occur~
when the housing i5 angularly displaced from the ba~e position by 180 degrees whereat the off~et anglc ~ the housing cancels the offset angle of the mandrel ~o that the net overall angular offse-t between the axiB of the 10 drill string and the axis of the drill but will be zero degrees. In this position, there will be a slight radial offset of the axis of the drill striny a~d that of the drill bit; however, the two axes will be parallel to one another. This is reflected in FIGUR~ 3b, where 15 fir~t primary axis 50 i5 shown as being parallel to second secondary axis ~4. It will be understood that angular displacements of mandrel 22 with resp~ct to housing 24 will provide overall angular offsets ranging from a maximum of two degrees (~I6~R~ 3a) to a minimum 20 of zero degrees (FIG~R~ 3a).
As already mentioned, nut 30 threadedly engages threaded end 46 of the mandrel and is formed with a first annular shoulder B0 which bears against the end 82 of the mandrel as well as a second annular ~houlder 84 25 which bears against end 86 of the housing. In this manner, nut 30 prevents axial displacement of the housing with respect to the mandrel, while permitting rotational movement of the housing about the mandrel.
Sleeve 26 provides the means by which rotary forces 30 can be transmitted between the mandrel and the housing end, with nut 28, provide the means by which the housing can be angularly adjustea with respect to th~ mandrel as explained hereinbelow. Shoulders 44 and ~0 p~event displacement of the housing with re~pect to the mandrel, 3~ when nut 28 is loosened.
'~
;3663 The end 100 of housing 24 a~d the snd 102 of sleeve 26 are formed with mating teeth 106 forming dog clutch elemen-ts of a dog clutch generally designa-ted by reference numeral 108. When the teeth, and, thus, the clutch are engaged, rotary ~orces can be -transmit-ted between the sleeve and the hou~in~. Conver~ely, when the ~leeve is displacecl axially away from the houslng ~wch that the teeth are no lonyer engaged, the hou~iny will be free to rotate with respect to the mandrel. In this 10 manner, the housing can be set to the desired po~ition.
Nut 28 is formed with a shoulder 110 which is abuttingly engageable with the end 113 of the sleeve 26 80 that when nut 28 is threaded against the sleeve, the 15 dog clutch is maintained in an engaged or locked position. Conversely, whe~ the nut i~ threaded away from the sleeve a sufficient distance, the ~leeve can be slid axially away from the mandrel to allow disengayement of the clutch and angular adjustment of 20 the housing with respeot to the mandrel.
In order to transmit rotary forces between the mandrel and housing, internal surface 120 of the ~leeve is formed with splines 122 arranged to receive keys 124 located in keyways 126 of the mandrel. The splines 2~ extend to both ends of the sleeve to allow the sleeve to clear keys 124 in order to facilitate assembly and adjustment of the assembly.
Advantageously, as best shown in ~I~URE 5, the sleeve and housing are each~ formed with alignable 30 indicia 130 to facilitate po~itioning the housing iIl the proper and desired anyular position with respect to the mandrel. As shown, the indicia may be in increments of 0.25 degrees and extend 180 deyrees about the sleeve housing. Further, the 35 circumferential width of teeth 106 of the doy clutch may ~ ` t .~
~Z~36~3 be arranged ~uch that it correspands w.ith any desired angular increment, such as 0.25 degrees, for example, to facilita-t~ positioning of the housing with re~pect to the mandrel.
The preferred location of bellt ~ub in the drlll string is between the power unit sectio~ arld bearitlg assembly ~ection o the dowrlhole motor. Prior to loweriny the motor a~sembly into the borehole, the bent sub 20 is adjusted to provide the desired an~ular offse-t 10 between the axis of the drill bit and the axi~ of the drill string. This is accomplished by loo~ening lock nut 28 and sliding sleeve 26 along keys 124 until mating dog clutch elements 106 are di~enga~ed. Once the do~ clutch is diaengaged, housing 24 may be an~ularly adjusted with 15 respect to mandrel 22 as previously explained.
Once the housing ha~ been placed in the desired positivn, the dog clutch is re-engaged and nut 28 is threaded against sleeve 26 thereby securing sleeve 26 and mandrel 22 in the selected position.
It will be appreciated that the above de~cribed preferred embodiment of the present inventioI~ overcomes the disadvanta~es, discus ed earlier, oE the prior art.
First, according to the present invention, it is unneces~ary to maintain a large inventory of downhole 25 motors having a bent subs with differing angles oP
offset. 5econd, adjustment of the bent ~ub of the present invention i~ extremely ~imple and does not re~uire the di~a~sembly of the downhole motor.
It will also be apparent to one ~killed in the art 30 that adjustable bent sub can be run in an inverted position with threaded connectior. 32 coupled to power unit ~ection 64 of a downhole motor and threaded connection 62 coupled to bearing assembly 34 of a downhole motor.
B
~2~3~63 It will be apparent to those ~killed in the art that various modifications and alterations may be made to the above de~cribed embodimerlt without departin~ from the spirit of -the invention as defined by the appended claim~.
1~
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An adjustable bent sub for use in directional drilling in earth formations, comprising:
(a) a first member having:
i. a primary axis; and ii. external, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to said primary axis;
(b) a tubular second member secured to said first member against axial displacement and having;
i. a primary axis;
ii. internal, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to said second member primary axis, said internal surface being adapted to telescopically receive said first member external surface in sliding fit relation for rotation about said secondary axis; and iii. first clutch means extending axially from one end thereof;
(c) locking sleeve means telescopically receiving and non-rotatably coupled to said external surface means extending axially of one end thereof toward said second member, said sleeve means being axially moveable on said first member between an engaged position whereat said first and second clutch means are interengaged and non-rotatably couple said second member and said first member in a predetermined angular position and a disengaged position whereat said locking sleeve is axially displaced from said second member and said first and second clutch means are disengaged from one another so as to permit angular adjustment of said second member with respect to said first member; and (d) means threaded onto said external surface of said first member for securing said sleeve in said engaged position thereof.
(a) a first member having:
i. a primary axis; and ii. external, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to said primary axis;
(b) a tubular second member secured to said first member against axial displacement and having;
i. a primary axis;
ii. internal, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to said second member primary axis, said internal surface being adapted to telescopically receive said first member external surface in sliding fit relation for rotation about said secondary axis; and iii. first clutch means extending axially from one end thereof;
(c) locking sleeve means telescopically receiving and non-rotatably coupled to said external surface means extending axially of one end thereof toward said second member, said sleeve means being axially moveable on said first member between an engaged position whereat said first and second clutch means are interengaged and non-rotatably couple said second member and said first member in a predetermined angular position and a disengaged position whereat said locking sleeve is axially displaced from said second member and said first and second clutch means are disengaged from one another so as to permit angular adjustment of said second member with respect to said first member; and (d) means threaded onto said external surface of said first member for securing said sleeve in said engaged position thereof.
2. An adjustable bent sub as defined in claim 1, said first and second clutch means being dog clutches having interengageable teeth.
3. An adjustable bent sub as defined in claim 2, said interengageable teeth defining a plurality of predetermined angular positions of said second member with respect to said first member.
4. An adjustable bent sub as defined in claim 1, said securing means comprising a tubular nut threaded onto said external, cylindrical surface means.
5. An adjustable bent sub as defined in claim 1, further including spline means for non-rotatably securing said locking sleeve to said external surface while permitting axial displacement of said locking sleeve with respect to said first member.
6. An adjustable bent sub as defined in claim 5, said spline means including alignable keyways formed in said external surface means and an internal surface of said locking sleeve and key means each extending between aligned keyways.
7. An adjustable bent sub as defined in claim 1, further including means for securing said first and second members in a predetermined axial position.
8. An adjustable bent sub as defined in claim 7, said securing means including cooperating shoulder means on said external and internal surface means for preventing axial displacement of said first and second members in one axial direction and nut means threaded onto one of said members and engageable with the other of said members for preventing axial displacement of said members in the opposite axial direction.
9. An adjustable bent sub for use in directional drilling in earth formations; comprising:
(a) a mandrel having:
i. a primary axis; and ii. external, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to said primary axis, said surface means being stepped so as to define a first annular shoulder;
(b) a tubular bent sub housing having:
i. a primary axis;
ii. a stepped bore defining a secondary axis disposed at predetermined offset angle with respect to said bent sub housing primary axis and a second annular shoulder engageable with said first annular shoulder for locating said first and second members in predetermined axial relationship, said bore being adapted to telescopically receive said mandrel external surface means in sliding fit relation for rotation about said secondary axis;
iii. first dog clutch teeth means extending axially from one end thereof; and (c) a first nut threaded onto said external surface means and engageable with an end of the bent sub housing for maintaining said mandrel and said bent sub housing in said predetermined axial relationship;
(d) locking sleeve means telescopically receiving said external surface means, spline means for non-rotatably coupling said locking sleeve means to said external surface while permitting axial displacement of said sleeve means with respect to said mandrel, said sleeve means having second clutch means extending axially of one end thereof toward said first dog clutch means, said sleeve means being axially moveable on said mandrel between an engaged position whereat said first and second clutch means are interengaged and non-rotatably couple said bent sub housing and said mandrel in predetermined angular position and a disengaged position whereat said locking sleeve is axially displaced from said bent sub housing and said first and second clutch means are disengaged from one another so as to permit angular adjustment of said bent sub housing with respect to said mandrel; and (e) a second nut threaded onto said external surface of said mandrel for urging and maintaining said sleeve means in said engaged position.
(a) a mandrel having:
i. a primary axis; and ii. external, cylindrical surface means defining a secondary axis disposed at a predetermined offset angle with respect to said primary axis, said surface means being stepped so as to define a first annular shoulder;
(b) a tubular bent sub housing having:
i. a primary axis;
ii. a stepped bore defining a secondary axis disposed at predetermined offset angle with respect to said bent sub housing primary axis and a second annular shoulder engageable with said first annular shoulder for locating said first and second members in predetermined axial relationship, said bore being adapted to telescopically receive said mandrel external surface means in sliding fit relation for rotation about said secondary axis;
iii. first dog clutch teeth means extending axially from one end thereof; and (c) a first nut threaded onto said external surface means and engageable with an end of the bent sub housing for maintaining said mandrel and said bent sub housing in said predetermined axial relationship;
(d) locking sleeve means telescopically receiving said external surface means, spline means for non-rotatably coupling said locking sleeve means to said external surface while permitting axial displacement of said sleeve means with respect to said mandrel, said sleeve means having second clutch means extending axially of one end thereof toward said first dog clutch means, said sleeve means being axially moveable on said mandrel between an engaged position whereat said first and second clutch means are interengaged and non-rotatably couple said bent sub housing and said mandrel in predetermined angular position and a disengaged position whereat said locking sleeve is axially displaced from said bent sub housing and said first and second clutch means are disengaged from one another so as to permit angular adjustment of said bent sub housing with respect to said mandrel; and (e) a second nut threaded onto said external surface of said mandrel for urging and maintaining said sleeve means in said engaged position.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000520506A CA1243663A (en) | 1986-10-15 | 1986-10-15 | Adjustable bent sub |
| US07/181,648 US4813497A (en) | 1986-10-15 | 1988-04-14 | Adjustable bent sub |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000520506A CA1243663A (en) | 1986-10-15 | 1986-10-15 | Adjustable bent sub |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1243663A true CA1243663A (en) | 1988-10-25 |
Family
ID=4134150
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000520506A Expired CA1243663A (en) | 1986-10-15 | 1986-10-15 | Adjustable bent sub |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1243663A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7104345B2 (en) | 2004-06-22 | 2006-09-12 | Pathfinder Energy Services, Inc. | Downhole rotatable-shaft connector assembly and method |
-
1986
- 1986-10-15 CA CA000520506A patent/CA1243663A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7104345B2 (en) | 2004-06-22 | 2006-09-12 | Pathfinder Energy Services, Inc. | Downhole rotatable-shaft connector assembly and method |
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| Date | Code | Title | Description |
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| MKEX | Expiry |