CA1181739A - Thrust generator for boring tools - Google Patents
Thrust generator for boring toolsInfo
- Publication number
- CA1181739A CA1181739A CA000423180A CA423180A CA1181739A CA 1181739 A CA1181739 A CA 1181739A CA 000423180 A CA000423180 A CA 000423180A CA 423180 A CA423180 A CA 423180A CA 1181739 A CA1181739 A CA 1181739A
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- CA
- Canada
- Prior art keywords
- shaft
- propeller
- drilling
- housing
- conduit
- 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.)
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Abstract
ABSTRACT OF THE DISCLOSURE
The present invention relates to the provision of a system for providing forward thrust for a fluid immersed boring tool. More particularly, the invention provides the necessary thrust, a dynamic force, for the operation of a rotary boring tool in situations, such as the drilling of generally horizontal bore holes, where the force of gravity does not act effectively to provide forward thrust. The invention is especially efficaceous with flexible drill pipe or conduit such as may be used in drilling bore holes having a small radius of curvature. Thus this specification discloses a rotary drilling tool which includes a fluid passage extending through a boring means mounted at the end of a hollow shaft for discharge of fluid and a marine screw propeller fixed to the shaft in a manner such that rotation of the propeller generates forward thrust along the axis of the shaft. The arrangement is such that the energy carried by the fluid in the passage is converted to a force causing rotation of the shaft carrying the propeller, whereby the propeller causes forward motion of the conduit and boring means.
The present invention relates to the provision of a system for providing forward thrust for a fluid immersed boring tool. More particularly, the invention provides the necessary thrust, a dynamic force, for the operation of a rotary boring tool in situations, such as the drilling of generally horizontal bore holes, where the force of gravity does not act effectively to provide forward thrust. The invention is especially efficaceous with flexible drill pipe or conduit such as may be used in drilling bore holes having a small radius of curvature. Thus this specification discloses a rotary drilling tool which includes a fluid passage extending through a boring means mounted at the end of a hollow shaft for discharge of fluid and a marine screw propeller fixed to the shaft in a manner such that rotation of the propeller generates forward thrust along the axis of the shaft. The arrangement is such that the energy carried by the fluid in the passage is converted to a force causing rotation of the shaft carrying the propeller, whereby the propeller causes forward motion of the conduit and boring means.
Description
~ ~8~3~
'I'l-ll\US'I' C;l';;~ r~l\ rol~ )r~ L~oi\-r NG rl~OO[.IS
IiACK~,RG ID OF r~E m~:'J.'`~rrION
FIELD OF INVENTION
The present invention ;elates to the provision oE a system for providing forward thrust for a fluid im~ersed boring tool. More particularly, the invention provicles the necessary thrust, a dynamic force, for the operation o-f a rotary boring tool in situations, such as th~ drilling of generally horizon-tal bore holes, where the force of gravity does not ac-t eEfec-tively to provide forward tnrust. The invention is especially efflcaceous with flexible drill pipe or conduit such as may be used in drilling bore holes havlng a small radius of curvature.
ESCRIPTION OF THE PRIOR AR~
~ ecently, Esso Resources Canada L-td., ln seeking to re-cover heavy oil Lrom the deposits at Cold Lake, Alberta drilled what it claimed to be "the first horizontal well to be drilled in North America" using conven,lonal drilling equipment in a special manner described in Oilweek, November 12, 1979, pages 68 to 70. A milled tooth bit rotated by a Dyna-Drill, offered by the Dyna-Drill Company, a division of Smith International, Inc., of Irvine, California, was used 'c make hole. Bent subs provided the angle build up. 'l'he drill collars, rather than being positioned just above thc- bit, were located in the "more vertical portlon of the hole to provide weight on bit." Special "Hevi-wate pipe was used betwee.. collars and bi-t assembly be-cause ordinary drill pipe cannot be used in compression". Oil base mud was used to minimize the tendenc~ of the drill pipe to drag and to reduce the tendency of the curved pipe to stick against the sicle oE the hole.
7~9 The technology emplo~ l, however, was time-consuming and costly. Also, there would appear to be limitations as to how far one could proceed in a hori~ontal direction after it had been obtained by pushiny a heavv drill:;ng assembly with heavy drill pipe.
~ Iydraulic power has been used to rotate boring tools in drilling vertical and devia~ing bore holes Eor many years.
Typical of such tools is the Dyna-Drill. The power generated by the Dyna-Drill is used, and only used, to rotate the drilling bit. The system is used with conventional drill pipe and drill collars to provide the desired weight on bit or thrust.
In U. S. Patent No. 2,251,916 there is disclosed a system for solution mining of salts occurring in thin layers where forced circulation of the solvent is necessary to effec~
tively contact and dissolve th. material to be mined. Generally, the patentee, Roy Cross, discloses the use of horizontally directed nozzles to direct a stream of fresh solvent, specificall~, water, against the face of the materiai to be mined, specifically potash salts. In one form of i,is invention, shown in his Figure 5, Cross schematically shows an electrically driven device which purportedly will produce horizontal circulation and at the same time cut away residue salts not dissolved by the solvent.
Rotation of an electric motor shaft is supposed to rotate a drill bit on one end thereof and a propeller generating forward thrust on the other end. Since the motor housing is freely sus-pended and has no resistance to ro-tation, as soon as any torque is imposed on the shaft by the ;~ropeller or the drill bit, the housing rather than the shaft wo~ld rotate. Thus, the device shown is inoperative.
In U. S. Patent 3,~ o2 there is disclosed a device for cleaning conduits or boriny holes having a rotatably mounted boring head and containing ports ~ro~ which f~uicl is ejectecl to LJro~Jide ~orward thrust and to p;ovid~ rota~.ve torque.
I ~81~39 SU~iARY OF T~IE INVE~rrIO~
The instant inventior ~tilize~ ~he principles of a marine screw propeller to derive thrust forces for the operation of an earth boring tool. The rnarine screw propeller is normally used to de~elop the thrust needed to move a -vessel through water.
According to "Principles of ~aval Architecture", Vol. II, edited by ~ossell and Chapman, and pub,ished by the Society of Naval Architects and Marine Engineering, "propellers derive the propul-sive thrust by accelerating the fluid in which they work". The term "marine screw propeller" as used herein includes any device rotation of which develops thrust relative to the axis of rotation by accelerating the fluid in which it works.
Thrust derived from a marine screw propeller in accord-ance with my invention provides the 'weight on bit' necessary for earth boring. This thrust ma~ also provide the force required to advance a conduit, preferably neutrally buoyant in the drilling fluicd, through which drilling fluids and energy needed for the boring operation are supplied.
In accordance with the present invention the shaft or shafts upon which the propeller or propellers are mounted are caused to rotate either by an electric motor or by hydraulic 'corce derived from the circulating drilling mud. The electric motor may be either an alternating or a direct current motor.
Either the field or the armature or both of the motor may rotate and be fixed to a hollow rotating shaft. In the simplest form of my invention where a single shaft is employed and rotated by an electric ~iotor, the drilling bit will be fixed to the forward end of the shaft. Where a plurality of shafts are employecl, the bit will be fixed to the forw,rd end of the innermost and longest shaft which usually, though not necessarily, will carry a marine ~crewpropcll~r to c~enerate ad-~-tiorlal tnL~St. Where the rotative 7 3 ~
~orce is hydraulically generat~d a mud ~,otor, such as the Dyna-Drill, may be used or a portiG-~ oE thc- circulating drilling fluid may be discharged through jet nozzles ne,ar the propeller blacle tips to provide rotative torc~ue through the reactive Eorce oE
the fluid ejected at high velocity.
The shaft to which the bit is attached is hollow to allow the passage of drilling Eluid therethrough to the bit for discharge therefrom. The drilling fluid serves -to cool the bit and remove cuttings from the newly formed bore hole. The amount of drilling fluid circulated should be sufficient to discharge the functions oE bit cooling and cutting removal but not so great as to significantly nhibit bit advance. However, the reaction force of the ejected fluid will be c~reat enough to push the bit backward if rotation, and hence thrust, ceases. Where bit and propeller or propellers dre mounted on a single shaft, the bit is self non-stalling, since as the bit tends to stall forward thrust rapidly approaches zero and the reactive forces of the discharged drilling fluid retract the bit. In cases wnere the thrust gener-ating propeller is on a diEferent shaft than the bit, the rotation of the bit may be monitored from the surface and, should the bit stall, the flow of power to the motor may be adjusted to reduce or terminate propeller rotation and to allow the reactive forces generated by the dischar~ing drLlling fluid to retract the bit.
Since the drilling system of my invention is primarily intended for use in drilling substantially horizontal holes, the conduit for conducting drilling fluid dnd electric power to the motor and bit combination is so constructed as to be flexible and capabl~ of conforming to the curvatures of the well bore. On the other hand it must have sufi-icien-t resis-tance to twisting so that it will resist and substantially prevent free rotation oE
the motor housing. The use oi ~ neu~ral1v L~uoyant drillinq system 173~
is taught and claimed in my co,~ellding application Serial ~
371,274, filed February 19, l~il. The ~erm "neutrally buo~ant"
as used herein means that the UtillSi ty of a mass immersed in the drilling fluid is from 70 to 133 per cent oE the density of the fluid.
BRIEF DF RIPI`ION OF THE D~AWl~GS
Figure 1 is a view, partly in cross-section and partly schematic, of a hydraulically powerec; propeller bit form of the invention.
Figure 2 is a frontal view of the propeller bit of Figure 1 showing the fluid conduits and jet nozzles carried by the propeller blades in phantom.
Figure 3 is an enlarged cross-sectional view of a pro-peller blade tal<en on the line 3-3 of Figure 2.
Figure 4 is an enlarged view of the fluid conduit in a propeller blade in cross-section showing the jet nozzle and the fluid inlet port in the wall of the hollow shaft on which the propeller blade is mounted.
Figure 5 shows another form of hydraulically powered propeller bit, partly in cross-section and partly schematic, in position for drilling a horizontally deviated well bore with separate means for rotating the propeller and drilling bit.
Figure 6 shows the details of the spline connection shown in Figure 5 linking the propeller shaft and the motor shaft.
Figure 7 shows a form of electric motor driven pro-peller bit, partly in cross section and partly schematic, in position for drilling a horizontal extens:ion of a deviated well bore.
Figure 5 is an enlarged view OL- ~he motor, propeller and drill bit of FiguLe / showir~ decal;s oE the hollow motor shat and the mounting of the blt ancl propeller thereon.
i 73~
Figure 9 shows anoth-L- Eorm oE motor, propeLler and bit combination employincJ ~wo co-axial motor driven shafts wherein ~he motor field s a~Eixed to one shaft, the armature to the other shaft and the two shafts rotate in opposite direc-tions.
Figure 10 shows a form of my invention w~erein both the inner shaft and the housing are fixedly connected to a ro-tating flexible conduit carrying the drilling fluid and electric power and the rotor of the motor drives the outer shaft carrying the propeller in a direction independent of the direction of rot~tion of the conduit and inner shaft.
Figure 11 is a graphic illustration of the relationship between the speed of rotation of the propeller and the delivered thrust and useful torque.
In the various figures of the drawings, like parts are designated by like reference characters.
DESCRIPTION OF P~EFERRED EMBODIMENTS
One form of hydraulically advanced and rotated boring tool indicated in general by the numeral 11 is shown in Figure 1. The tool has the general shape of a multibladed marine screw propeller.
Blades 13 and blade tips 15 are connec-ted by a circular tubular ring 17. Blades and ring are fitted wi~h hardened cutting elements 19 as is the surface around water course 21. Blades 13 may have the usual marine propeller conEiguration or may be formed into an asymmetrical hydrofoil shape as indicated in Figure 3, which in-creases lift/drag ratio. Dri:Lling Eluid passes through hollow conduit shaEt 23 having fluid passage 25 and through rotary union 27 to propeller shaft33 to which blades 13 are fi~ed, thence into 1 ~8~73~
passaye 29, I;iguLe 2, ~o be eJ~ eci tanc~entially at high velocity through jet nozzle 31 to impar~ rotational Eorce to propeller bit 11. Ejected fluid is preventecl fro~ i~pinging upon, and possibly damaging, ring 17 by anglincJ je-, no~zl~s 31 slightly toward the rear or by making appropriate notches in ring 17.
Figure ~ shows a cross-sectioll of a fluicl passage ~9 con-tained in a hydrofoil shaped propeller blade 13, shown in cross-section in Figure 3. Nozzle 31 is replaceable as is common practice in oil well drilling. The propeller blade 13 is Eastened to pro-peller shaft 33, which, as described above, is connected to the con-duit shaft 23 by rotary union 27, permitting relative rotation therebetween. Drilling fluid flowing ~hrough passage 25 into the hollow propeller shaft flows in part throùgh ports 35 into the fluid passages 29 and exits as a jet stream through nozzles 31.
The remaining porlion of the drilling fluid exits through water course 21 where it func~ions to lubricate the cutting elements and wash away the cuttings.
The propeller bit illustrated in Figure~l may be con-structed from any suitable material. For example, the blades 13 and ring 17 may be of alloy steel while the cutting elements 19 and water courses 21 may be made of a hardened material such as one of the carbides.
In the form of my invention shown in Figure 5 the rotative force for propeller blades 13 is derived from a hydraulically powered motor 61. Flow of pressurized drilling fluid from conduit shaft 23 through hydraulic -turbine motor 61 causes the turbine blades 63 and power shaft 65 to rotate, rotating the propeller blades and drilling bit 67. Suitable hydraulic turbodrill motors are manufactured and marketed by Neyrfor Alsthom - Atlantique, Grenoble, France. Thrust generated by the propeller forces the bit against formation 69 extending the well bore. Drilling flui{l exits the turbine throuc3h port 7:L ii the turbine shaft wher,ce it flows forward through the turbine an~l propeller shaft and exits througr, water courses 21 in the bit. ~esirabl~y, the propeller shaft 33 and power shaft 65 are joinecl by a splined connection 73, shown in detail in ~igure 6. The male spline 75 àt the end of shaft 65 mates with the female splinecl yrooves 77 in the rear end of pro-peller shaft 33. Stop 79 at the forward end of the turbine shaft will engage stop 81 on the aft end of the propeller shaft holdin~
the spline connection together as the propeller advances. Shoul~
the bit 67 and propeller 13 stall, drilling Eluid jetted from the forward facing water courses 21 will drive the bit and propeller back until the rear side of stop 81 rests against stop 83. Suf-ficient retraction of the bit ~o allow it to resume rotation will thus be obtained without requiring the backing up of the entire system.
As stated above, one way to overcome a downward trend o.
a well bore being drilled with the drilling sys-tem of the present invention is to employ a tool and fluid conduit neutrally buoyant in the drilling fluid. For use in a 10 pounds per gallon drilling fluid boring tool 11 may be cast from a mix comprised of cycloali-phatic epoxy 61 parts, ceramic microballoons 31 parts and glass fibers 5 parts by volume with s-teel trim, additional epoxy cement and tungsten carbide or other hard material comprising the re-maining 3 parts by volume. Ring 17 is essentially neutrally buoyant when made from a length of aluminum tubing hermetically sealed against fluid entry. Eor example, a one-inch outside diarneter, round, aluminum tubing, closed at the ends, weighing 0.28 pounds per foot would have a density of 0.83 grams per milli-liter. ~ 1.5-inch tube weighing 0.635 pounds per foot would have the same density. Such tubular rings may be roughened and coatecl with an epoxy with a hard surEace material added to Eorm a cutting eleMent 19. Other cutting elements 19 are set into small dlameter 1 ~8~3~
holes bored into the epoxy casling a~ter it has hardened using an epoxy cement. Such neutrally buoy-int tools ~end to be fragile and mainly are suited to boring sol~ L, shallow strata.
A suitable, low density drilliny fluicl sha~t conduit may be formed from a glass reinforced polyethylene plastic, having, for example, a density of 1.20 grams pec milliliter, a tensile modulus of 25,000 pounds per square inch and a tensile strength, determined in burst, of 3,600 pounds per square inch.
One form oE electrically powered thrust generator and boring tool is shown in F~igure 7. Thc- tool is shown in position to drill a horizontal extension oE well bore 91 in earth formation 93. As shown weli bore 91 is deviated Erom vertical portion 95, which may be drilled in the conventional manner and, as shown, is provided with the usual casing 97, generally throughout its vertical depth, and an upper surface casing 99.
F'lexible conduit 23 provides communication betweer. the surface and the electric motor, generally indicated by the numeral 24, for -the transmission of drilling fluid and electric power.
Conduit 23 must have flexibility to conform to the curved well bore, must withstand the pressure differential between the drilling fluid within it and the returns on the outside, and must be re-sistant to twisting. It is also desirable that it be neutrally buoyant in the drilling fluid circulating in the well bore so that it is essentially weightless and its advance offers minimum impedance to the thrust generated by the motor-driven propeller as described hereinafter~ A polyoleEin sucn as polyethylene or other plastic material, such as epoxy resins or polyamides, re-inforced with glass, steel or carbon Eibers may be used. Flexible conduit 23 need not extend all the way to ~he surface but rather it may be connected to the lower encl o~ conventional drill pipe 26 ~nd lowerecl into the well bo;e ~sing ~ coilventional drilling 7.'~
rig, not shown. The drill pi~e and the conduit are provic]ed internally with electrlcal con~ ctors 28, as shown in Figure 8, Eor the transmission of electr1c power from the surEace to motor 24. In operation motor 2~ rotates propeller 13 and drill bit ll which are mounted on the forward end of ho]low shaft 33. ~lollow motor shaEt 33 transmits the drilling fluid from conduit 23 through mo-tor 24 to bit ll from whence it elxits via ports 21.
Bit ll is shown as being prov:ided with hardened abrasive inserts l9, such as tungsten carbide or polycrystaline diamonds to facili-tate the drilling action, especially in hard earth formations.
Figure 8 shows in more detail the arrangement of the components that comprise the drilling system of Figure 7 of my invention. The electric motor comprises a housing 39 which encloses the field or stator ~l of the motor and within which the armature or rotor 43 is affi~ed to and rotates shaft 33 in operation.
Annular extensions at the forwdrd end 45 and rear end ~17 of the housing serve as journal boxes for the hollow shaf-t 33. Rotary seals 49 and bearings 51 permit the shaft to rotate freely while preventing drilling fl~id introduced through conduit 23 and surrounding the motor housing fLom entering the mo~or housing.
~ear housing extension ~7 is externally threaded to receive in-ternally threaded female coupling 53 fixed to the end of conduit 23- Thus, conduit 23 will resist the tendency of the stator and motor housing to rotate in a direction counter to the rotation of shaft 33 as a tor~ue load is imposed throuyh the action of the drill bit and the propeller. Electrical conductor 28 which is carried by conduit 23 passes through coupling 53 and is connected to the motor by means of fluid-proof connectors 550 Thrust bear-ings 57 transmit the forward thrust of propeller 29 to housing 39 which, in turn, transmits a pu11ing Eorce on conduit 21 via coup-ling 53.
1 ~173~
In the form of my inv~l,tion shown in F`iyures 7 ancl ~3 the drilling bit and pLopeller rotate at the same speed. The forward thrust generated by roL~.ti~n o. the marine screw propeller provides weight on bit and via l:hrust bearing 57 provides the necessary forward thrust to aclvance the motor and concluit as drilling progresses.
Another form oE my invention employing concentric hollow rotating shafts is shown in Fiqure 9. In this embodiment the field 41 of the motor is fi~ed to one shaft and the armature 43 to the other. Both field and armature are Eree to rotate within the outer casing 39 of t'le motor housing. The field and the armature will rotate in opposite directions and hence inner shaft 33 and outer shaft 59 will likewise rotate in opposite directions. The absolute speecl of rotation of field and armature will be dependent upon the load imposed upon shafts 33 and 59.
since it is usually desirable that more horsepower be utilized for generating thrust than for rotating the bit, it is desirable that each shaEt carry a propeller. As shown propeller 13 is mounted on shaft 33 and propeller 113 on shaft 59 with rotary seal 69 preventing leakage of drilling fluid into the annulus between the shafts and bearings 71 maintaining alignment. Since shaft 33 and shaft 59 will rotate in opposite directions and since it is desired that the rotation of each generate forward thrust, the pitch of the blades on the two propellers will necessarily be opposite in direction.
One form of motor wherein both field and armature rotate in opposite directions is disclosed in U. S. Patent No. 2,462,182 to D. A. Guerdan et al assigned to Westinghouse Electric Corporation.
Forward thrust generated by the rotation of propeller 113 is transmitted to housing 39 via thrust bearing 57 for advancing the housin~; allcl conduit and will be availa~le to s~lppLe-ment the thrus~ ~ener~ted by ~ropel:Ler 13 to provide adclitional weight on the bit 11. The rei~tive amounts of forward thrust generated by propellers :L3 and 113 will be dependent upon the absolute speed of rotation of each, which in turn will depend upon the load imposed restraining rotation of each shaft. Because of variations in the loacl imposed on t}~le drill bit and turbulence of the fluids in which the pro2ellers are operating, the relation-ship between the thrust generated by each will vary. In view of this, collar 65 on inner shaft 59 is suitably recessed to receive thrust bearings 73 Eor receiving thrust Erom housing 39 and thrust bearings 75 for transmitting thrust to outer shaft 59 and hence to housing 39~
Several advantages are obtained by using the embodiment of Figure 9. Counter rotation oE ~he propellers, particularly where closely spaced, results in more eEEicient generation of forward thrust. Also, importantly, counter rotation of the motor parts and shaft~, which are linked to the motor housing only via rotating seals and bearings, results in the transmittal of mini-mal rotative torque to the housing and hence to the conduit. This, in turn, reduces the amount of twist resistance that must be built into the conduit.
A form of my inventior wherein the electric motor is used only to provide the Eorward thrust ~or the system is dis-clo~ed in Figure 10. In this embodiment the conduit 23 is rotated at the speed at which it is desired to rotate shaft 33 and bit 11.
Referring back to Figure 7, the drill pipe 26 may be rotated from the surface by the rotary table on a convent:ional drilling rig.
This, in turn, will rotate concluit 23. In this form the conduit is fixedly connected not only to motor housing 39 but also to shaEt 33 and bit 11 will rotate with the conduit. As shown the ~ ~1739 end o~ shaEt 33 extencls slicJiltLy beyond the rear end of motor housing 3~ and is welded 73 th Le~o. Rear housing extension is externally threaded to receive ,nt~Lnally threaded female coup-ling 53 and fixed to the end ol conduit 23. Sealing rubber ring 75 may be inserted between the mating faces of coupling 53 ancl the end of the shaft. Electriccll conductor 2~, shown as carried externally of conduit 23, is connected to connector 55 on the coupling and thence through the coupling to a connector 55 on the motor housing.
The field or stator ~1 of the electric motor is fixed to the housing and rotates with it. Rotor armature ~3 is fixed to the outer concentric shaft wnich carries propeller 13, rota-tion of which generates the necessary forward thrust to provide weight on bit-and to advance the system. As in the embodiment shown in Figure 9, thrust bearings 57 transmit the forward thrust to the housing, inner shaft and oit and conduit. The embodiment of Figure 10 is particularly suitable where the drilling characteristics are such that a high weight on bit is desired along with a relatively low speed of bit rotation.
Figure 11 illustrates the relationship between propeller RPM, useful torque and thrust. At zero RPM thrust is zero and torque is a maximum. Thrust increases with increasing rate of rotation while torque available to rotate the propeller and the bit where both are on the same shaft decreases. Factors affecting the speed of rotation and hence, the balance between torque and thrust delivered by a rotating marine screw propeller include the density and viscosity of the drilling fluid in which it is immersed.
Also where propeller and bit are on the same shaft, the nature of the formation being drilled will affect the speed of rotation.
~13-Where p~rt or all oE l-he torque Eor rotating the bit is derived from a propeLler o~ th~ same shaft as the bit the system o~
my invention has the inherent a~ility ~o acljust the balance between torque and thrust. When the L"~ount oE torque required to rotate the bit increases, the bit slows clown, and the thrust deliverecl by the propeller decreases, sl~,wing the rate of penetration unti.
the system comes into balance. Conversely, when the ~orque required diminishes, the resultant decrease in rotational load allows the bit and propeller to speed up increasing the thrust and the rate oE drilling, again until the system comes into balance. ~lso, and importantly, should the bit tend to stall, as, for example, caused by suddenly entering a difficult to drill Eormation, the concurrent slowing oE the propeller would rapidly reduce the thrust to or substantiaily to ~ero allowing the reactive forces generated by the clischarge of fl~lid from the fluid courses in the drill bit tc, retract the bit typically as shown in Figures 5 and 6.
In lateral boring operations the power required may be divided into two parts: first, the power needed to rotate the drilling tool, and second, the power needed to generate the advancing force, or thrust, required to cause the system to move forward which, of course, inclucles the "weight on bit" necessary to achieve penetration. Studies of rotary drilling practive show that relatively little power is required at the bit to rotate it, usually in the range of from a few horsepower up to one hundred or more depending upon the diameter of the hole, the kind of bit, the type of formation being drilled, the weight on the bit or forward thrust and the speed of rotation. In normal drilling practice the weight on bit, which results from the mass of drill dollars used, may vary from a thousand pounds up to fiEty thousancl pounds or more. To translate weiyht on bit, a static gravity force, ~ ~8~'~3~
into horsepower, marine practic. shows that bollard pull of a tuc3-boat amounts to 15 to 40 or more pouncls per shaft horsepower.
Using a figure o~ 30 pounds o~ tilrust per horsepower, 300 horse-power would deliver a penetratlng Eorce of 9,000 pounds (weight on bit) on the bit. Rotative power required could be of the order of lO horsepower. The ratio of dynamic, advanc;ng thrust to rotative power in this example is 30. This ratio may vary as noted above. In consideration of the above factors it has been found that the ratio of dynamic thrust horsepower to rotative horsepower may vary from as low as one to 220. Additionally, since the dynamic thrust must not only provide the equivalent of weight on bit but also the force for advancing the drilling system through the horizontal portion of the well bore, the ratio is usually greater than one. Speeds of propeller rotation in excess of the speed of bit rotation are especially useful for attaining the higher ratios of dynamic thrust horsepower to rota-tive horsepower. ~he more easily penetrated, softer formations would utilize the :Lower ratios while the harder formations would require the higher ratios.
The forms of my invention shown in Figures 9 and 10 are especially suitable where the higher ratios of dynamic thrust horsepower to rotative horsepower are desiredO
In drilling ordinary earth formations using conventional drilling bit, the bit rotation speed is preferably of the order of from 40 to 400 r.p.m. To ob-tain optimum thrust in such situa-tions, the propeller or propellers preferably should rotate at considerably higher speeds. In such situations a plurality of shafts are required with the outer shaft or shafts rotating at the higher speeds. Any marine screw propeller on the innermost shaft, of course, would rotate at the same speed as the bit.
~ ~73~1 In the case oE the so:E~er ancl ea.sier to clri:Ll ~ormations sufEicient thrust may be oh~ained :i.rom a single propeller rotating at the same speed and on the same s~.aft as ~..he bit. Also, and especial.ly where drilling is hard formatl~,ns using speci.al bits such as poly~
crystalline diamond compact ('~) bits, also known as Stratapax bits, incorporating Stratapa~ crystals manufacturecl by the General Electric Company or regular diamond bits, high bit rotation speeds, a thousand or more rpm, are employed and again aclequate thrust may be obtained from a single propeller.
As stated previously, since my invention is in-tended for use in the non-vertical portions of bore holes where thrust forces other than or in addition to the force of gravity are needed to provide adequate weight on bit, the conduits for ^onducting drill-ing fluid and power should be flexible. On the other hand, since there is provided some form of motor Eor generating rotative force at the end of the conduit, it must have some resistance to twisting.
Such resistance may be providecl by suitable design of the reinforc-ing fibers.
In the Eorm of invention shown in Figures 1 to 4, where the hydraulic motor resembles a turboprop, very little rota-tive force is transmitted to conduit 23 via bearing 27. On the other hand, in the forms of the invention shown in Figure 5 and in Figure 7 the conduit must develop sufficient resistance to further twisting without kinking to balance the rotative torque generated by the motor. Similarly, in the form oE my invention shown in Figure 10, since the rotative torque for the bit is transmitted by the conduit directly, it must be highly resistant to twisting~ As mentioned previously, relative low twist resistance is required for the conduit where the form oE motor shown in Figure 9 is usecl.
-L~-~ 1~17~
Since r"~lny mociifications and possible embocliments anduses may be macle of the apparatus oE this invention without de-parting from the scope thereof, it i5 to be understood that all matter herein set forth or shown is to be interpretecl as .i11us-trative not as limit1n~.
'I'l-ll\US'I' C;l';;~ r~l\ rol~ )r~ L~oi\-r NG rl~OO[.IS
IiACK~,RG ID OF r~E m~:'J.'`~rrION
FIELD OF INVENTION
The present invention ;elates to the provision oE a system for providing forward thrust for a fluid im~ersed boring tool. More particularly, the invention provicles the necessary thrust, a dynamic force, for the operation o-f a rotary boring tool in situations, such as th~ drilling of generally horizon-tal bore holes, where the force of gravity does not ac-t eEfec-tively to provide forward tnrust. The invention is especially efflcaceous with flexible drill pipe or conduit such as may be used in drilling bore holes havlng a small radius of curvature.
ESCRIPTION OF THE PRIOR AR~
~ ecently, Esso Resources Canada L-td., ln seeking to re-cover heavy oil Lrom the deposits at Cold Lake, Alberta drilled what it claimed to be "the first horizontal well to be drilled in North America" using conven,lonal drilling equipment in a special manner described in Oilweek, November 12, 1979, pages 68 to 70. A milled tooth bit rotated by a Dyna-Drill, offered by the Dyna-Drill Company, a division of Smith International, Inc., of Irvine, California, was used 'c make hole. Bent subs provided the angle build up. 'l'he drill collars, rather than being positioned just above thc- bit, were located in the "more vertical portlon of the hole to provide weight on bit." Special "Hevi-wate pipe was used betwee.. collars and bi-t assembly be-cause ordinary drill pipe cannot be used in compression". Oil base mud was used to minimize the tendenc~ of the drill pipe to drag and to reduce the tendency of the curved pipe to stick against the sicle oE the hole.
7~9 The technology emplo~ l, however, was time-consuming and costly. Also, there would appear to be limitations as to how far one could proceed in a hori~ontal direction after it had been obtained by pushiny a heavv drill:;ng assembly with heavy drill pipe.
~ Iydraulic power has been used to rotate boring tools in drilling vertical and devia~ing bore holes Eor many years.
Typical of such tools is the Dyna-Drill. The power generated by the Dyna-Drill is used, and only used, to rotate the drilling bit. The system is used with conventional drill pipe and drill collars to provide the desired weight on bit or thrust.
In U. S. Patent No. 2,251,916 there is disclosed a system for solution mining of salts occurring in thin layers where forced circulation of the solvent is necessary to effec~
tively contact and dissolve th. material to be mined. Generally, the patentee, Roy Cross, discloses the use of horizontally directed nozzles to direct a stream of fresh solvent, specificall~, water, against the face of the materiai to be mined, specifically potash salts. In one form of i,is invention, shown in his Figure 5, Cross schematically shows an electrically driven device which purportedly will produce horizontal circulation and at the same time cut away residue salts not dissolved by the solvent.
Rotation of an electric motor shaft is supposed to rotate a drill bit on one end thereof and a propeller generating forward thrust on the other end. Since the motor housing is freely sus-pended and has no resistance to ro-tation, as soon as any torque is imposed on the shaft by the ;~ropeller or the drill bit, the housing rather than the shaft wo~ld rotate. Thus, the device shown is inoperative.
In U. S. Patent 3,~ o2 there is disclosed a device for cleaning conduits or boriny holes having a rotatably mounted boring head and containing ports ~ro~ which f~uicl is ejectecl to LJro~Jide ~orward thrust and to p;ovid~ rota~.ve torque.
I ~81~39 SU~iARY OF T~IE INVE~rrIO~
The instant inventior ~tilize~ ~he principles of a marine screw propeller to derive thrust forces for the operation of an earth boring tool. The rnarine screw propeller is normally used to de~elop the thrust needed to move a -vessel through water.
According to "Principles of ~aval Architecture", Vol. II, edited by ~ossell and Chapman, and pub,ished by the Society of Naval Architects and Marine Engineering, "propellers derive the propul-sive thrust by accelerating the fluid in which they work". The term "marine screw propeller" as used herein includes any device rotation of which develops thrust relative to the axis of rotation by accelerating the fluid in which it works.
Thrust derived from a marine screw propeller in accord-ance with my invention provides the 'weight on bit' necessary for earth boring. This thrust ma~ also provide the force required to advance a conduit, preferably neutrally buoyant in the drilling fluicd, through which drilling fluids and energy needed for the boring operation are supplied.
In accordance with the present invention the shaft or shafts upon which the propeller or propellers are mounted are caused to rotate either by an electric motor or by hydraulic 'corce derived from the circulating drilling mud. The electric motor may be either an alternating or a direct current motor.
Either the field or the armature or both of the motor may rotate and be fixed to a hollow rotating shaft. In the simplest form of my invention where a single shaft is employed and rotated by an electric ~iotor, the drilling bit will be fixed to the forward end of the shaft. Where a plurality of shafts are employecl, the bit will be fixed to the forw,rd end of the innermost and longest shaft which usually, though not necessarily, will carry a marine ~crewpropcll~r to c~enerate ad-~-tiorlal tnL~St. Where the rotative 7 3 ~
~orce is hydraulically generat~d a mud ~,otor, such as the Dyna-Drill, may be used or a portiG-~ oE thc- circulating drilling fluid may be discharged through jet nozzles ne,ar the propeller blacle tips to provide rotative torc~ue through the reactive Eorce oE
the fluid ejected at high velocity.
The shaft to which the bit is attached is hollow to allow the passage of drilling Eluid therethrough to the bit for discharge therefrom. The drilling fluid serves -to cool the bit and remove cuttings from the newly formed bore hole. The amount of drilling fluid circulated should be sufficient to discharge the functions oE bit cooling and cutting removal but not so great as to significantly nhibit bit advance. However, the reaction force of the ejected fluid will be c~reat enough to push the bit backward if rotation, and hence thrust, ceases. Where bit and propeller or propellers dre mounted on a single shaft, the bit is self non-stalling, since as the bit tends to stall forward thrust rapidly approaches zero and the reactive forces of the discharged drilling fluid retract the bit. In cases wnere the thrust gener-ating propeller is on a diEferent shaft than the bit, the rotation of the bit may be monitored from the surface and, should the bit stall, the flow of power to the motor may be adjusted to reduce or terminate propeller rotation and to allow the reactive forces generated by the dischar~ing drLlling fluid to retract the bit.
Since the drilling system of my invention is primarily intended for use in drilling substantially horizontal holes, the conduit for conducting drilling fluid dnd electric power to the motor and bit combination is so constructed as to be flexible and capabl~ of conforming to the curvatures of the well bore. On the other hand it must have sufi-icien-t resis-tance to twisting so that it will resist and substantially prevent free rotation oE
the motor housing. The use oi ~ neu~ral1v L~uoyant drillinq system 173~
is taught and claimed in my co,~ellding application Serial ~
371,274, filed February 19, l~il. The ~erm "neutrally buo~ant"
as used herein means that the UtillSi ty of a mass immersed in the drilling fluid is from 70 to 133 per cent oE the density of the fluid.
BRIEF DF RIPI`ION OF THE D~AWl~GS
Figure 1 is a view, partly in cross-section and partly schematic, of a hydraulically powerec; propeller bit form of the invention.
Figure 2 is a frontal view of the propeller bit of Figure 1 showing the fluid conduits and jet nozzles carried by the propeller blades in phantom.
Figure 3 is an enlarged cross-sectional view of a pro-peller blade tal<en on the line 3-3 of Figure 2.
Figure 4 is an enlarged view of the fluid conduit in a propeller blade in cross-section showing the jet nozzle and the fluid inlet port in the wall of the hollow shaft on which the propeller blade is mounted.
Figure 5 shows another form of hydraulically powered propeller bit, partly in cross-section and partly schematic, in position for drilling a horizontally deviated well bore with separate means for rotating the propeller and drilling bit.
Figure 6 shows the details of the spline connection shown in Figure 5 linking the propeller shaft and the motor shaft.
Figure 7 shows a form of electric motor driven pro-peller bit, partly in cross section and partly schematic, in position for drilling a horizontal extens:ion of a deviated well bore.
Figure 5 is an enlarged view OL- ~he motor, propeller and drill bit of FiguLe / showir~ decal;s oE the hollow motor shat and the mounting of the blt ancl propeller thereon.
i 73~
Figure 9 shows anoth-L- Eorm oE motor, propeLler and bit combination employincJ ~wo co-axial motor driven shafts wherein ~he motor field s a~Eixed to one shaft, the armature to the other shaft and the two shafts rotate in opposite direc-tions.
Figure 10 shows a form of my invention w~erein both the inner shaft and the housing are fixedly connected to a ro-tating flexible conduit carrying the drilling fluid and electric power and the rotor of the motor drives the outer shaft carrying the propeller in a direction independent of the direction of rot~tion of the conduit and inner shaft.
Figure 11 is a graphic illustration of the relationship between the speed of rotation of the propeller and the delivered thrust and useful torque.
In the various figures of the drawings, like parts are designated by like reference characters.
DESCRIPTION OF P~EFERRED EMBODIMENTS
One form of hydraulically advanced and rotated boring tool indicated in general by the numeral 11 is shown in Figure 1. The tool has the general shape of a multibladed marine screw propeller.
Blades 13 and blade tips 15 are connec-ted by a circular tubular ring 17. Blades and ring are fitted wi~h hardened cutting elements 19 as is the surface around water course 21. Blades 13 may have the usual marine propeller conEiguration or may be formed into an asymmetrical hydrofoil shape as indicated in Figure 3, which in-creases lift/drag ratio. Dri:Lling Eluid passes through hollow conduit shaEt 23 having fluid passage 25 and through rotary union 27 to propeller shaft33 to which blades 13 are fi~ed, thence into 1 ~8~73~
passaye 29, I;iguLe 2, ~o be eJ~ eci tanc~entially at high velocity through jet nozzle 31 to impar~ rotational Eorce to propeller bit 11. Ejected fluid is preventecl fro~ i~pinging upon, and possibly damaging, ring 17 by anglincJ je-, no~zl~s 31 slightly toward the rear or by making appropriate notches in ring 17.
Figure ~ shows a cross-sectioll of a fluicl passage ~9 con-tained in a hydrofoil shaped propeller blade 13, shown in cross-section in Figure 3. Nozzle 31 is replaceable as is common practice in oil well drilling. The propeller blade 13 is Eastened to pro-peller shaft 33, which, as described above, is connected to the con-duit shaft 23 by rotary union 27, permitting relative rotation therebetween. Drilling fluid flowing ~hrough passage 25 into the hollow propeller shaft flows in part throùgh ports 35 into the fluid passages 29 and exits as a jet stream through nozzles 31.
The remaining porlion of the drilling fluid exits through water course 21 where it func~ions to lubricate the cutting elements and wash away the cuttings.
The propeller bit illustrated in Figure~l may be con-structed from any suitable material. For example, the blades 13 and ring 17 may be of alloy steel while the cutting elements 19 and water courses 21 may be made of a hardened material such as one of the carbides.
In the form of my invention shown in Figure 5 the rotative force for propeller blades 13 is derived from a hydraulically powered motor 61. Flow of pressurized drilling fluid from conduit shaft 23 through hydraulic -turbine motor 61 causes the turbine blades 63 and power shaft 65 to rotate, rotating the propeller blades and drilling bit 67. Suitable hydraulic turbodrill motors are manufactured and marketed by Neyrfor Alsthom - Atlantique, Grenoble, France. Thrust generated by the propeller forces the bit against formation 69 extending the well bore. Drilling flui{l exits the turbine throuc3h port 7:L ii the turbine shaft wher,ce it flows forward through the turbine an~l propeller shaft and exits througr, water courses 21 in the bit. ~esirabl~y, the propeller shaft 33 and power shaft 65 are joinecl by a splined connection 73, shown in detail in ~igure 6. The male spline 75 àt the end of shaft 65 mates with the female splinecl yrooves 77 in the rear end of pro-peller shaft 33. Stop 79 at the forward end of the turbine shaft will engage stop 81 on the aft end of the propeller shaft holdin~
the spline connection together as the propeller advances. Shoul~
the bit 67 and propeller 13 stall, drilling Eluid jetted from the forward facing water courses 21 will drive the bit and propeller back until the rear side of stop 81 rests against stop 83. Suf-ficient retraction of the bit ~o allow it to resume rotation will thus be obtained without requiring the backing up of the entire system.
As stated above, one way to overcome a downward trend o.
a well bore being drilled with the drilling sys-tem of the present invention is to employ a tool and fluid conduit neutrally buoyant in the drilling fluid. For use in a 10 pounds per gallon drilling fluid boring tool 11 may be cast from a mix comprised of cycloali-phatic epoxy 61 parts, ceramic microballoons 31 parts and glass fibers 5 parts by volume with s-teel trim, additional epoxy cement and tungsten carbide or other hard material comprising the re-maining 3 parts by volume. Ring 17 is essentially neutrally buoyant when made from a length of aluminum tubing hermetically sealed against fluid entry. Eor example, a one-inch outside diarneter, round, aluminum tubing, closed at the ends, weighing 0.28 pounds per foot would have a density of 0.83 grams per milli-liter. ~ 1.5-inch tube weighing 0.635 pounds per foot would have the same density. Such tubular rings may be roughened and coatecl with an epoxy with a hard surEace material added to Eorm a cutting eleMent 19. Other cutting elements 19 are set into small dlameter 1 ~8~3~
holes bored into the epoxy casling a~ter it has hardened using an epoxy cement. Such neutrally buoy-int tools ~end to be fragile and mainly are suited to boring sol~ L, shallow strata.
A suitable, low density drilliny fluicl sha~t conduit may be formed from a glass reinforced polyethylene plastic, having, for example, a density of 1.20 grams pec milliliter, a tensile modulus of 25,000 pounds per square inch and a tensile strength, determined in burst, of 3,600 pounds per square inch.
One form oE electrically powered thrust generator and boring tool is shown in F~igure 7. Thc- tool is shown in position to drill a horizontal extension oE well bore 91 in earth formation 93. As shown weli bore 91 is deviated Erom vertical portion 95, which may be drilled in the conventional manner and, as shown, is provided with the usual casing 97, generally throughout its vertical depth, and an upper surface casing 99.
F'lexible conduit 23 provides communication betweer. the surface and the electric motor, generally indicated by the numeral 24, for -the transmission of drilling fluid and electric power.
Conduit 23 must have flexibility to conform to the curved well bore, must withstand the pressure differential between the drilling fluid within it and the returns on the outside, and must be re-sistant to twisting. It is also desirable that it be neutrally buoyant in the drilling fluid circulating in the well bore so that it is essentially weightless and its advance offers minimum impedance to the thrust generated by the motor-driven propeller as described hereinafter~ A polyoleEin sucn as polyethylene or other plastic material, such as epoxy resins or polyamides, re-inforced with glass, steel or carbon Eibers may be used. Flexible conduit 23 need not extend all the way to ~he surface but rather it may be connected to the lower encl o~ conventional drill pipe 26 ~nd lowerecl into the well bo;e ~sing ~ coilventional drilling 7.'~
rig, not shown. The drill pi~e and the conduit are provic]ed internally with electrlcal con~ ctors 28, as shown in Figure 8, Eor the transmission of electr1c power from the surEace to motor 24. In operation motor 2~ rotates propeller 13 and drill bit ll which are mounted on the forward end of ho]low shaft 33. ~lollow motor shaEt 33 transmits the drilling fluid from conduit 23 through mo-tor 24 to bit ll from whence it elxits via ports 21.
Bit ll is shown as being prov:ided with hardened abrasive inserts l9, such as tungsten carbide or polycrystaline diamonds to facili-tate the drilling action, especially in hard earth formations.
Figure 8 shows in more detail the arrangement of the components that comprise the drilling system of Figure 7 of my invention. The electric motor comprises a housing 39 which encloses the field or stator ~l of the motor and within which the armature or rotor 43 is affi~ed to and rotates shaft 33 in operation.
Annular extensions at the forwdrd end 45 and rear end ~17 of the housing serve as journal boxes for the hollow shaf-t 33. Rotary seals 49 and bearings 51 permit the shaft to rotate freely while preventing drilling fl~id introduced through conduit 23 and surrounding the motor housing fLom entering the mo~or housing.
~ear housing extension ~7 is externally threaded to receive in-ternally threaded female coupling 53 fixed to the end of conduit 23- Thus, conduit 23 will resist the tendency of the stator and motor housing to rotate in a direction counter to the rotation of shaft 33 as a tor~ue load is imposed throuyh the action of the drill bit and the propeller. Electrical conductor 28 which is carried by conduit 23 passes through coupling 53 and is connected to the motor by means of fluid-proof connectors 550 Thrust bear-ings 57 transmit the forward thrust of propeller 29 to housing 39 which, in turn, transmits a pu11ing Eorce on conduit 21 via coup-ling 53.
1 ~173~
In the form of my inv~l,tion shown in F`iyures 7 ancl ~3 the drilling bit and pLopeller rotate at the same speed. The forward thrust generated by roL~.ti~n o. the marine screw propeller provides weight on bit and via l:hrust bearing 57 provides the necessary forward thrust to aclvance the motor and concluit as drilling progresses.
Another form oE my invention employing concentric hollow rotating shafts is shown in Fiqure 9. In this embodiment the field 41 of the motor is fi~ed to one shaft and the armature 43 to the other. Both field and armature are Eree to rotate within the outer casing 39 of t'le motor housing. The field and the armature will rotate in opposite directions and hence inner shaft 33 and outer shaft 59 will likewise rotate in opposite directions. The absolute speecl of rotation of field and armature will be dependent upon the load imposed upon shafts 33 and 59.
since it is usually desirable that more horsepower be utilized for generating thrust than for rotating the bit, it is desirable that each shaEt carry a propeller. As shown propeller 13 is mounted on shaft 33 and propeller 113 on shaft 59 with rotary seal 69 preventing leakage of drilling fluid into the annulus between the shafts and bearings 71 maintaining alignment. Since shaft 33 and shaft 59 will rotate in opposite directions and since it is desired that the rotation of each generate forward thrust, the pitch of the blades on the two propellers will necessarily be opposite in direction.
One form of motor wherein both field and armature rotate in opposite directions is disclosed in U. S. Patent No. 2,462,182 to D. A. Guerdan et al assigned to Westinghouse Electric Corporation.
Forward thrust generated by the rotation of propeller 113 is transmitted to housing 39 via thrust bearing 57 for advancing the housin~; allcl conduit and will be availa~le to s~lppLe-ment the thrus~ ~ener~ted by ~ropel:Ler 13 to provide adclitional weight on the bit 11. The rei~tive amounts of forward thrust generated by propellers :L3 and 113 will be dependent upon the absolute speed of rotation of each, which in turn will depend upon the load imposed restraining rotation of each shaft. Because of variations in the loacl imposed on t}~le drill bit and turbulence of the fluids in which the pro2ellers are operating, the relation-ship between the thrust generated by each will vary. In view of this, collar 65 on inner shaft 59 is suitably recessed to receive thrust bearings 73 Eor receiving thrust Erom housing 39 and thrust bearings 75 for transmitting thrust to outer shaft 59 and hence to housing 39~
Several advantages are obtained by using the embodiment of Figure 9. Counter rotation oE ~he propellers, particularly where closely spaced, results in more eEEicient generation of forward thrust. Also, importantly, counter rotation of the motor parts and shaft~, which are linked to the motor housing only via rotating seals and bearings, results in the transmittal of mini-mal rotative torque to the housing and hence to the conduit. This, in turn, reduces the amount of twist resistance that must be built into the conduit.
A form of my inventior wherein the electric motor is used only to provide the Eorward thrust ~or the system is dis-clo~ed in Figure 10. In this embodiment the conduit 23 is rotated at the speed at which it is desired to rotate shaft 33 and bit 11.
Referring back to Figure 7, the drill pipe 26 may be rotated from the surface by the rotary table on a convent:ional drilling rig.
This, in turn, will rotate concluit 23. In this form the conduit is fixedly connected not only to motor housing 39 but also to shaEt 33 and bit 11 will rotate with the conduit. As shown the ~ ~1739 end o~ shaEt 33 extencls slicJiltLy beyond the rear end of motor housing 3~ and is welded 73 th Le~o. Rear housing extension is externally threaded to receive ,nt~Lnally threaded female coup-ling 53 and fixed to the end ol conduit 23. Sealing rubber ring 75 may be inserted between the mating faces of coupling 53 ancl the end of the shaft. Electriccll conductor 2~, shown as carried externally of conduit 23, is connected to connector 55 on the coupling and thence through the coupling to a connector 55 on the motor housing.
The field or stator ~1 of the electric motor is fixed to the housing and rotates with it. Rotor armature ~3 is fixed to the outer concentric shaft wnich carries propeller 13, rota-tion of which generates the necessary forward thrust to provide weight on bit-and to advance the system. As in the embodiment shown in Figure 9, thrust bearings 57 transmit the forward thrust to the housing, inner shaft and oit and conduit. The embodiment of Figure 10 is particularly suitable where the drilling characteristics are such that a high weight on bit is desired along with a relatively low speed of bit rotation.
Figure 11 illustrates the relationship between propeller RPM, useful torque and thrust. At zero RPM thrust is zero and torque is a maximum. Thrust increases with increasing rate of rotation while torque available to rotate the propeller and the bit where both are on the same shaft decreases. Factors affecting the speed of rotation and hence, the balance between torque and thrust delivered by a rotating marine screw propeller include the density and viscosity of the drilling fluid in which it is immersed.
Also where propeller and bit are on the same shaft, the nature of the formation being drilled will affect the speed of rotation.
~13-Where p~rt or all oE l-he torque Eor rotating the bit is derived from a propeLler o~ th~ same shaft as the bit the system o~
my invention has the inherent a~ility ~o acljust the balance between torque and thrust. When the L"~ount oE torque required to rotate the bit increases, the bit slows clown, and the thrust deliverecl by the propeller decreases, sl~,wing the rate of penetration unti.
the system comes into balance. Conversely, when the ~orque required diminishes, the resultant decrease in rotational load allows the bit and propeller to speed up increasing the thrust and the rate oE drilling, again until the system comes into balance. ~lso, and importantly, should the bit tend to stall, as, for example, caused by suddenly entering a difficult to drill Eormation, the concurrent slowing oE the propeller would rapidly reduce the thrust to or substantiaily to ~ero allowing the reactive forces generated by the clischarge of fl~lid from the fluid courses in the drill bit tc, retract the bit typically as shown in Figures 5 and 6.
In lateral boring operations the power required may be divided into two parts: first, the power needed to rotate the drilling tool, and second, the power needed to generate the advancing force, or thrust, required to cause the system to move forward which, of course, inclucles the "weight on bit" necessary to achieve penetration. Studies of rotary drilling practive show that relatively little power is required at the bit to rotate it, usually in the range of from a few horsepower up to one hundred or more depending upon the diameter of the hole, the kind of bit, the type of formation being drilled, the weight on the bit or forward thrust and the speed of rotation. In normal drilling practice the weight on bit, which results from the mass of drill dollars used, may vary from a thousand pounds up to fiEty thousancl pounds or more. To translate weiyht on bit, a static gravity force, ~ ~8~'~3~
into horsepower, marine practic. shows that bollard pull of a tuc3-boat amounts to 15 to 40 or more pouncls per shaft horsepower.
Using a figure o~ 30 pounds o~ tilrust per horsepower, 300 horse-power would deliver a penetratlng Eorce of 9,000 pounds (weight on bit) on the bit. Rotative power required could be of the order of lO horsepower. The ratio of dynamic, advanc;ng thrust to rotative power in this example is 30. This ratio may vary as noted above. In consideration of the above factors it has been found that the ratio of dynamic thrust horsepower to rotative horsepower may vary from as low as one to 220. Additionally, since the dynamic thrust must not only provide the equivalent of weight on bit but also the force for advancing the drilling system through the horizontal portion of the well bore, the ratio is usually greater than one. Speeds of propeller rotation in excess of the speed of bit rotation are especially useful for attaining the higher ratios of dynamic thrust horsepower to rota-tive horsepower. ~he more easily penetrated, softer formations would utilize the :Lower ratios while the harder formations would require the higher ratios.
The forms of my invention shown in Figures 9 and 10 are especially suitable where the higher ratios of dynamic thrust horsepower to rotative horsepower are desiredO
In drilling ordinary earth formations using conventional drilling bit, the bit rotation speed is preferably of the order of from 40 to 400 r.p.m. To ob-tain optimum thrust in such situa-tions, the propeller or propellers preferably should rotate at considerably higher speeds. In such situations a plurality of shafts are required with the outer shaft or shafts rotating at the higher speeds. Any marine screw propeller on the innermost shaft, of course, would rotate at the same speed as the bit.
~ ~73~1 In the case oE the so:E~er ancl ea.sier to clri:Ll ~ormations sufEicient thrust may be oh~ained :i.rom a single propeller rotating at the same speed and on the same s~.aft as ~..he bit. Also, and especial.ly where drilling is hard formatl~,ns using speci.al bits such as poly~
crystalline diamond compact ('~) bits, also known as Stratapax bits, incorporating Stratapa~ crystals manufacturecl by the General Electric Company or regular diamond bits, high bit rotation speeds, a thousand or more rpm, are employed and again aclequate thrust may be obtained from a single propeller.
As stated previously, since my invention is in-tended for use in the non-vertical portions of bore holes where thrust forces other than or in addition to the force of gravity are needed to provide adequate weight on bit, the conduits for ^onducting drill-ing fluid and power should be flexible. On the other hand, since there is provided some form of motor Eor generating rotative force at the end of the conduit, it must have some resistance to twisting.
Such resistance may be providecl by suitable design of the reinforc-ing fibers.
In the Eorm of invention shown in Figures 1 to 4, where the hydraulic motor resembles a turboprop, very little rota-tive force is transmitted to conduit 23 via bearing 27. On the other hand, in the forms of the invention shown in Figure 5 and in Figure 7 the conduit must develop sufficient resistance to further twisting without kinking to balance the rotative torque generated by the motor. Similarly, in the form oE my invention shown in Figure 10, since the rotative torque for the bit is transmitted by the conduit directly, it must be highly resistant to twisting~ As mentioned previously, relative low twist resistance is required for the conduit where the form oE motor shown in Figure 9 is usecl.
-L~-~ 1~17~
Since r"~lny mociifications and possible embocliments anduses may be macle of the apparatus oE this invention without de-parting from the scope thereof, it i5 to be understood that all matter herein set forth or shown is to be interpretecl as .i11us-trative not as limit1n~.
Claims (23)
1. A rotary drilling tool for drilling a well bore in the earth comprising in combination:
a. a boring means mounted at the end of a hollow shaft;
b. at least one fluid passage extending through said boring means for discharge of fluid conducted through said hollow shaft from the forward face of said boring means;
c. a flexible conduit adapted to conduct drilling fluid and energy;
d. means connecting the forward end of said flexible conduit to said shaft carrying said boring means for conducting drilling fluid to said shaft;
e. a marine screw propeller fixed to a shaft in a manner such that rotation of said propeller generates forward thrust along the axis of said shaft;
f. means for converting the energy carried by said conduit to a force causing rotation of the shaft carrying said propeller; and g. means for transmitting the forward thrust generated by the rotation of said propeller from said shaft carrying said propeller to said conduit and said boring means.
a. a boring means mounted at the end of a hollow shaft;
b. at least one fluid passage extending through said boring means for discharge of fluid conducted through said hollow shaft from the forward face of said boring means;
c. a flexible conduit adapted to conduct drilling fluid and energy;
d. means connecting the forward end of said flexible conduit to said shaft carrying said boring means for conducting drilling fluid to said shaft;
e. a marine screw propeller fixed to a shaft in a manner such that rotation of said propeller generates forward thrust along the axis of said shaft;
f. means for converting the energy carried by said conduit to a force causing rotation of the shaft carrying said propeller; and g. means for transmitting the forward thrust generated by the rotation of said propeller from said shaft carrying said propeller to said conduit and said boring means.
2. The drilling tool of Claim 1 in which the means connecting the shaft and the flexible conduit permits relative rotation between them.
3. the drilling tool of Claim 1 in which the energy is electric and the means for converting the energy to a force causing rotation of the shaft carrying said propeller is an electric motor comprising a rotor and a housing, which housing is fixedly connected to the forward end of the flexible conduit.
4. The drilling tool of Claim 1 in which the energy is elevated pressure applied to said drilling fluid and the force causing rotation of the shaft carrying the propeller is generated by means actuated by a drop in pressure of a fluid passing there-through.
5. The drilling tool of Claim 4 in which the means for converting the drop in pressure of the drilling fluid to a force causing rotation of the shaft carrying the propeller is at least one jet nozzle adjacent the tip of a blade of said propeller and a passageway to conduct pressurized drilling fluid from the interior of said hollow shaft to said jet nozzle.
6. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. an electric motor comprising a housing and at least one rotor;
b. a twist resistant flexible conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
c. at least one rotor driven hollow shaft pro-jecting from the other end of said housing;
d. hollow shaft driven bit means;
e. marine screw propeller means mounted on said rotor driven shaft rotation of which generates forward thrust along the axis of said shaft; and f. means for transmitting the forward thrust generated by said propeller to said bit means, said housing and said conduit.
a. an electric motor comprising a housing and at least one rotor;
b. a twist resistant flexible conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
c. at least one rotor driven hollow shaft pro-jecting from the other end of said housing;
d. hollow shaft driven bit means;
e. marine screw propeller means mounted on said rotor driven shaft rotation of which generates forward thrust along the axis of said shaft; and f. means for transmitting the forward thrust generated by said propeller to said bit means, said housing and said conduit.
7. The drilling system of Claim 6 in which there is a single rotor driven hollow shaft projecting from said housing and in which the propeller means and the bit means are both mounted on said shaft.
8. The rotary drilling system of Claim 6 in which there are two concentric rotor driven hollow shafts the inner of which extends beyond the outer hollow shaft and the bit means are mounted at the end of the inner hollow shaft and the pro-peller means are fixed to the outer hollow shaft.
9. The rotary drilling system of Claim 6 in which there are two concentric hollow shafts projecting from the other end of the housing, the inner of which extends beyond the outer and the bit means are mounted on the end thereof, and the outer shaft is driven by the rotor and has propeller means fixed thereon.
10. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. an electric motor comprising a field and an armature each mounted on separate, hollow concentric shafts and capable of independent rotation;
b. a twist resistant flexible conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
c. projections of the concentric hollow shafts ex-tending from the other end of said housing with the inner extending the farther and having bit means affixed to the end thereof;
d. bearing and sealing means for conducting drilling fluid from said conduit to the inner shaft while permitting relative rotation therebetween;
e. marine screw propeller means mounted on the outer shaft for generating forward thrust along the axis thereof; and f. means for transmitting the forward thrust from said outer shaft to said housing and the inner shaft.
a. an electric motor comprising a field and an armature each mounted on separate, hollow concentric shafts and capable of independent rotation;
b. a twist resistant flexible conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
c. projections of the concentric hollow shafts ex-tending from the other end of said housing with the inner extending the farther and having bit means affixed to the end thereof;
d. bearing and sealing means for conducting drilling fluid from said conduit to the inner shaft while permitting relative rotation therebetween;
e. marine screw propeller means mounted on the outer shaft for generating forward thrust along the axis thereof; and f. means for transmitting the forward thrust from said outer shaft to said housing and the inner shaft.
11. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. an electric motor comprising a housing, a stator affixed to said housing and a rotor;
b. a rotatable, twist resistant, flexible conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
c. a pair of concentric hollow shafts projecting from the other end of said housing the inner of which projects beyond the outer shaft and drilling bit means affixed to the forward projecting end thereof;
d. means for connecting said rotor to said outer hollow shaft;
e. marine screw propeller means mounted on said outer hollow shaft for generating forward thrust along the axis of said shaft;
f. means for transmitting forward thrust from said outer shaft to said housing and said inner shaft; and g. means for interconnecting the rear end of said inner shaft and said conduit for the passage of drilling fluid therethrough to said bit means.
a. an electric motor comprising a housing, a stator affixed to said housing and a rotor;
b. a rotatable, twist resistant, flexible conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
c. a pair of concentric hollow shafts projecting from the other end of said housing the inner of which projects beyond the outer shaft and drilling bit means affixed to the forward projecting end thereof;
d. means for connecting said rotor to said outer hollow shaft;
e. marine screw propeller means mounted on said outer hollow shaft for generating forward thrust along the axis of said shaft;
f. means for transmitting forward thrust from said outer shaft to said housing and said inner shaft; and g. means for interconnecting the rear end of said inner shaft and said conduit for the passage of drilling fluid therethrough to said bit means.
12. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. a pair of concentric hollow shafts, the inner of which projects at one end beyond the outer and has drilling bit means affixed to the projecting end thereof;
b. a housing supporting said shafts in axial alignment and surrounding at least a portion thereof;
c. a twist resistant flexible conduit adapted to conduct drilling fluid and power fixedly connected to said housing and in fluid communication with the inner hollow shaft;
d. marine screw propeller means mounted on the outer hollow shaft in a manner such that rotation of said propeller means generates thrust in a direction toward the bit carrying end of the inner shaft;
e. means for transforming power carried by said conduit to a force causing said outer shaft to rotate;
and f. means for transmitting the thrust in said outer shaft generated by rotation of said propeller means to said housing, said inner shaft and said conduit.
a. a pair of concentric hollow shafts, the inner of which projects at one end beyond the outer and has drilling bit means affixed to the projecting end thereof;
b. a housing supporting said shafts in axial alignment and surrounding at least a portion thereof;
c. a twist resistant flexible conduit adapted to conduct drilling fluid and power fixedly connected to said housing and in fluid communication with the inner hollow shaft;
d. marine screw propeller means mounted on the outer hollow shaft in a manner such that rotation of said propeller means generates thrust in a direction toward the bit carrying end of the inner shaft;
e. means for transforming power carried by said conduit to a force causing said outer shaft to rotate;
and f. means for transmitting the thrust in said outer shaft generated by rotation of said propeller means to said housing, said inner shaft and said conduit.
13. The drilling system of Claim 12 in which means are provided adjacent the extremities of the outer shaft for preventing the ingress of fluids into the annular space between the shafts.
14. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. a rotary boring tool affixed to the end of a hollow shaft;
b. an electric motor comprising a housing and a rotor;
c. a twist resistant flexible, conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
d. marine screw propeller means for generating thrust connected to said rotor;
e. means for conducting drilling fluid from said conduit to said hollow shaft; and f. means for transmitting the thrust generated by said propeller means to said housing and said hollow shaft.
a. a rotary boring tool affixed to the end of a hollow shaft;
b. an electric motor comprising a housing and a rotor;
c. a twist resistant flexible, conduit fixedly connected to one end of the housing of said electric motor for conducting drilling fluid and electric power thereto;
d. marine screw propeller means for generating thrust connected to said rotor;
e. means for conducting drilling fluid from said conduit to said hollow shaft; and f. means for transmitting the thrust generated by said propeller means to said housing and said hollow shaft.
15. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. a pair of concentric hollow shafts the inner of which projects at one end beyond the outer;
b. drilling bit means affixed to the projecting end of the outer shaft;
c. marine screw propeller means rotation of which generates thrust along the axis of said shafts in a direction toward said drilling bit means mounted on said outer shaft;
d. a housing supporting said shafts on axial alignment;
e. a twist resistant flexible conduit adapted to conduct drilling fluid and power fixedly connected to said housing and in fluid communication with the inner hollow shaft;
f. means for converting the power conducted by said conduit into a force causing rotation of said outer shaft and propeller means and rotation of said inner shaft and bit means; and g. means for transmitting the thrust generated by said propeller means to said housing and said inner shaft.
a. a pair of concentric hollow shafts the inner of which projects at one end beyond the outer;
b. drilling bit means affixed to the projecting end of the outer shaft;
c. marine screw propeller means rotation of which generates thrust along the axis of said shafts in a direction toward said drilling bit means mounted on said outer shaft;
d. a housing supporting said shafts on axial alignment;
e. a twist resistant flexible conduit adapted to conduct drilling fluid and power fixedly connected to said housing and in fluid communication with the inner hollow shaft;
f. means for converting the power conducted by said conduit into a force causing rotation of said outer shaft and propeller means and rotation of said inner shaft and bit means; and g. means for transmitting the thrust generated by said propeller means to said housing and said inner shaft.
16. A rotary drilling tool for drilling a well bore in the earth comprising in combination:
a. a hollow shaft;
b. a marine screw propeller affixed to said shaft in a manner such that rotation of said propeller generates forward thrust along the axis of said shaft;
c. boring means fixed to the forward end of said shaft, said boring means having an external diameter at least as great as the diameter of said propeller means;
d. a twist resistant flexible conduit adapted to conduct pressurized drilling fluid to said hollow shaft;
e. means connecting the rear end of said hollow shaft and said conduit to permit relative rotation therebetween;
f. at least one fluid passage extending through said boring means for the discharge of drilling fluid conducted through said hollow shaft from the forward face of said boring means; and g. means connected to said shaft and actuated by the flow of drilling fluid therethrough to cause rotation of said shaft.
a. a hollow shaft;
b. a marine screw propeller affixed to said shaft in a manner such that rotation of said propeller generates forward thrust along the axis of said shaft;
c. boring means fixed to the forward end of said shaft, said boring means having an external diameter at least as great as the diameter of said propeller means;
d. a twist resistant flexible conduit adapted to conduct pressurized drilling fluid to said hollow shaft;
e. means connecting the rear end of said hollow shaft and said conduit to permit relative rotation therebetween;
f. at least one fluid passage extending through said boring means for the discharge of drilling fluid conducted through said hollow shaft from the forward face of said boring means; and g. means connected to said shaft and actuated by the flow of drilling fluid therethrough to cause rotation of said shaft.
17. A rotary drilling tool for drilling a well bore in the earth comprising in combination:
a. a hollow shaft;
b. a marine screw propeller affixed to said shaft in a manner such that rotation of said propeller generates forward thrust along the axis of said shaft;
c. boring means fixed to the forward end of said shaft said boring means having an external diameter at least as great as the diameter of said propeller means;
d. hydraulically powered means for rotating said shaft;
e. a hollow conduit for conducting drilling fluid from the earth's surface to said hollow shaft and to said means for rotating said shaft;
f. means connecting said shaft and said conduit for permitting relative rotation therebetween; and g. at least one fluid passage extending through said boring means for discharging drilling fluid conducted through said hollow shaft from the forward face of said boring means.
a. a hollow shaft;
b. a marine screw propeller affixed to said shaft in a manner such that rotation of said propeller generates forward thrust along the axis of said shaft;
c. boring means fixed to the forward end of said shaft said boring means having an external diameter at least as great as the diameter of said propeller means;
d. hydraulically powered means for rotating said shaft;
e. a hollow conduit for conducting drilling fluid from the earth's surface to said hollow shaft and to said means for rotating said shaft;
f. means connecting said shaft and said conduit for permitting relative rotation therebetween; and g. at least one fluid passage extending through said boring means for discharging drilling fluid conducted through said hollow shaft from the forward face of said boring means.
18. A rotary drilling tool comprising in combination:
a. a hollow shaft;
b. a marine screw propeller comprising a plurality of propeller blades affixed to said shaft in a manner such that rotation of said propeller generates thrust along the axis of said shaft;
c. drilling bit means fixed to the forward end of said shaft, said bit means having an external diameter at least as great as the diameter of said propeller;
d. fluid discharge nozzle means positioned on at least one blade of said propeller in a manner such that discharge of fluid therefrom will exert a force in a direction tending to cause said propeller to rotate;
e. fluid passage means carried by said at least one propeller blade adapted to conduct fluid from the interior of said hollow shaft to said discharge nozzle;
f. conduit means for conducting fluid to said rotary drilling tool; and g. bearing means connecting said hollow shaft and said conduit to permit relative rotation therebetween.
a. a hollow shaft;
b. a marine screw propeller comprising a plurality of propeller blades affixed to said shaft in a manner such that rotation of said propeller generates thrust along the axis of said shaft;
c. drilling bit means fixed to the forward end of said shaft, said bit means having an external diameter at least as great as the diameter of said propeller;
d. fluid discharge nozzle means positioned on at least one blade of said propeller in a manner such that discharge of fluid therefrom will exert a force in a direction tending to cause said propeller to rotate;
e. fluid passage means carried by said at least one propeller blade adapted to conduct fluid from the interior of said hollow shaft to said discharge nozzle;
f. conduit means for conducting fluid to said rotary drilling tool; and g. bearing means connecting said hollow shaft and said conduit to permit relative rotation therebetween.
19. The drilling tool according to Claim 18 wherein the marine propeller blades have an asymmetric hydrofoil shape.
20. A rotary drilling system for drilling a well bore in the earth comprising in combination:
a. an electric motor comprising a housing and at least one rotor;
b. a twist resistant flexible conduit for conducting drilling fluid and electric power to one end of said housing of said electric motor;
c. at least one rotor driven hollow shaft projecting from the other end of said housing;
d. hollow shaft driven bit means;
e. marine screw propeller means mounted on said rotor driven shaft rotation of which generates forward thrust along the axis of said shaft;
f. means for transmitting the forward thrust generated by said propeller to said bit means, said housing and said conduit; and g. coupling means connecting the end of said conduit and said motor housing, said coupling means trans-mitting torque from the motor housing to the con-duit to resist the tendency of the motor housing to rotate in a direction counter to the rotation of said hollow shaft as torque is imposed to the housing through the action of the drill bit and the propeller.
a. an electric motor comprising a housing and at least one rotor;
b. a twist resistant flexible conduit for conducting drilling fluid and electric power to one end of said housing of said electric motor;
c. at least one rotor driven hollow shaft projecting from the other end of said housing;
d. hollow shaft driven bit means;
e. marine screw propeller means mounted on said rotor driven shaft rotation of which generates forward thrust along the axis of said shaft;
f. means for transmitting the forward thrust generated by said propeller to said bit means, said housing and said conduit; and g. coupling means connecting the end of said conduit and said motor housing, said coupling means trans-mitting torque from the motor housing to the con-duit to resist the tendency of the motor housing to rotate in a direction counter to the rotation of said hollow shaft as torque is imposed to the housing through the action of the drill bit and the propeller.
21. The rotary drilling system of Claim 15 in which the means actuated by power conducted by the conduit cause the outer shaft and propeller means to rotate at a higher speed than the inner shaft and bit means.
22. The rotary drilling system of Claim l in which the flexible conduit is substantially neutrally buoyant in the drilling fluid.
23. A rotary drilling system for drilling a well bore in the earth com-prising in combination:
a. a boring tool affixed to the end of a hollow shaft;
b. at least one fluid passage extending through said boring tool for discharge of fluid conducted through said hollow shaft from the forward face of said boring tool;
c. a twist resistant, flexible conduit adapted to conduct drilling fluid and energy;
d. means for converting the energy carried by said conduit to a force causing rotation of said hollow shaft;
e. a housing for said energy converting means;
f. a marine screw propeller fixed to the hollow shaft in a manner such that the rotation of said propeller generates forward thrust along the axis of the shaft;
g. means for transmitting the forward thrust generated by rotation of said propeller to said housing and said conduit; and h. hollow coupling means for conducting drilling fluid and energy between the housing and the conduit, said coupling means limiting rotation of the housing relative to the conduit whereby torque will be transferred between said energy converting means and the conduit.
a. a boring tool affixed to the end of a hollow shaft;
b. at least one fluid passage extending through said boring tool for discharge of fluid conducted through said hollow shaft from the forward face of said boring tool;
c. a twist resistant, flexible conduit adapted to conduct drilling fluid and energy;
d. means for converting the energy carried by said conduit to a force causing rotation of said hollow shaft;
e. a housing for said energy converting means;
f. a marine screw propeller fixed to the hollow shaft in a manner such that the rotation of said propeller generates forward thrust along the axis of the shaft;
g. means for transmitting the forward thrust generated by rotation of said propeller to said housing and said conduit; and h. hollow coupling means for conducting drilling fluid and energy between the housing and the conduit, said coupling means limiting rotation of the housing relative to the conduit whereby torque will be transferred between said energy converting means and the conduit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000423180A CA1181739A (en) | 1983-03-09 | 1983-03-09 | Thrust generator for boring tools |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000423180A CA1181739A (en) | 1983-03-09 | 1983-03-09 | Thrust generator for boring tools |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1181739A true CA1181739A (en) | 1985-01-29 |
Family
ID=4124742
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000423180A Expired CA1181739A (en) | 1983-03-09 | 1983-03-09 | Thrust generator for boring tools |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1181739A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010037992A1 (en) | 2008-09-30 | 2010-04-08 | Futuretec Limited | An apparatus and method for cutting a wellbore |
-
1983
- 1983-03-09 CA CA000423180A patent/CA1181739A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2010037992A1 (en) | 2008-09-30 | 2010-04-08 | Futuretec Limited | An apparatus and method for cutting a wellbore |
| US8074742B2 (en) | 2008-09-30 | 2011-12-13 | Deep Casing Tools, Ltd. | Apparatus and method for cutting a wellbore |
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