US3180437A

US3180437A - Force applicator for drill bit

Info

Publication number: US3180437A
Application number: US114278A
Authority: US
Inventors: Jackson M Kellner; Thomas O Allen
Original assignee: Jersey Production Research Co
Current assignee: Jersey Production Research Co
Priority date: 1961-05-22
Filing date: 1961-05-22
Publication date: 1965-04-27
Anticipated expiration: 1982-04-27
Also published as: GB951287A; FR1323927A

Description

April 7; 1965 J. M. KELLNER ETAL 3,180,437

FORCE APPLICATOR FOR DRILL BIT 4 Sheets-Sheet 1 Filed May 22. 1961 Jackson M. Keli ner LNVENTORS Thomas 0. Allen ATTORNEY April 27', 1965 J. M. KELLNER ETAL 3,180,437

FORCE APPLICATOR FOR DRILL BIT Filed May 22, 1961 4 Sheets-Sheet 3 1 a use 4 as 6 [93$ IO :0 P J FIG. 8A

HG- 8B Jackson'M. Kellner INVENTORS Thomas 0. Allen QA&M

ATTORNEY April 27, 1965 J. M. KELLNER ETAL FORCE APPLICATOR FOR DRILL BIT 4 Sheets-Sheet 4 Filed May 22. 1961 IIIIII rill!- IIII! l!!! Thomas 0. Allen Jackson M. Kellner INVENTORS BYM IQM FIG. HA

A T TORNE Y United States Patent 0 3,188,437 FGRQE AEPLKIATQP. FGR DRZLL BIT Jackson M. Kellner and Thomas 0. Allen, Tulsa, Okla, assignors to Jersey Production Research Company, a corporation of Delaware Filed May 22, 1961, Ser. No. 114,273 16 jlainis. (6!. 175-239) This invention relates to apparatus for applying weight to a bit that is used for drilling wells or boreholes into the earth. More particularly it relates to a bottom hole assembly for applying force to a drill bit thereby forcing the bit against the bottom of a borehole. This application is a continuation-impart of co-pending application Serial No. 77,049, now abandoned, filed December 20, 1966.

In the art of drilling wells for the production of oil and gas the most commonly used method is the so-called rotary drilling method. In the rotary drilling method, a drill bit is suspended at the lower end of a string of drill pipe which is supported from the surface of the earth. A drilling fluid is forced down through the drill string through the drill bit and back up to the surface through the annulus between the drill pipe and the walls of the borehole. The purpose of the drilling fluid includes cooling the bit, carrying cuttings out of the well and also to impose hydrostatic pressure upon high-pressure formations penetrated by the drill bit to prevent the uncontrolled escape of oil, gas or water during drilling operations. Rotary drilling practice has found the rate of penetration of a drilling bit through subterranean formations is increased by increasing the force of a drill bit against the bottom of the well. It has been found further that the drilling of a more nearly straight hole is accomplished by creating a localized force in the area immediately adjacent the drill bit. In the latter instance, the twisting and rotative movement of lengthy strings of relatively flexible drill pipe is straightened immediately adjacent the drill bit by the application of such force.

The usual method that has been tried for increasing the pressure of a bit on the borehole is by the addition of several heavy drill collars between the drill bit and the drill string. Modern drilling practice has indicated that a trend toward even higher bit Weight resulted in maximum drilling rates and accordingly minimum footage cost. The use of heavy drill collars has not been completely satisfactory. While the addition of drill collars has aided the penetration rate, this advantage is ofifset by the need for heavier surface equipment. Also more horsepower and rig time are required in pulling the drill pipe, drill collars and drill bit during normal operations of drilling such as are required when the drill bit becomes worn and needs replacing.

Accordingly it is the object of this invention to provide an apparatus for use in the drilling of wells wherein a drilling fluid is utilized to apply force upon the drill bit thereby eliminating handling of long drill collars.

Briefly, a preferred embodiment of this invention concerns upper and lower hydraulic bit loading units. An inner mandrel or arbor extends through each loading unit and fluidly connects the interior of a drill string with the bit. A lower case or section of an elongated housing surrounds the lower part of the mandrel immediately above the drill bit and a second or upper case or section of a housing surrounds the mandrel and is just above the lower case. The upper case and the lower case each contain thrust or pushdown means positioned between the mandrcl and the case for exerting force on the mandrel longitudinally thereof in the direction of the bit, and anchor means attached to each case operable upon actuation to transfer reaction thrust of the pushdown means to the borehole wall. Thus an upper and a lower bit loading units are provided. Control means are provided such that when the anchor means and pushdown means of one unit is being reset deeper down the hole, the other bit loading unit is operative. Differential pressure of drilling fluid which exists across a drill bit attached to the mandrel is utilized (1) to anchor the case of the unit (being operative) to the borehole Wall, and (2) to apply force to the drill bit. A snap-acting valve arrangement operable by movement of the inner mandrel with respect to one of the cases controls the sequences of actuation of the upper and lower bit loading units. While one bit loading unit is being reset, the other is operative thus permitting force to be applied to the drill bit at substantially all times.

Other objects and a better understanding of the invention will become more apparent from the following description taken in conjunction with the drawing in which:

FIG. 1A is an upper and FIG. 1B is a lower elevational view partially in section which when taken together illustrates one embodiment of this invention;

FIG. 2 is a sectional view taken along the line 22 of P16. 1A;

FIG. 3 is a sectional view taken along the line 33 of FIG. 13;

FIGS. 4, 5, 6 and 7 are enlarged fragmentary sectional views of the valve mechanism representing various operational positions of the valve used in this invention;

FIGS. 8A and 8B are elevation views partially in secion which when taken together illustrates another and preferred embodiment of the invention;

FIG. 9 is a sectional view taken along the line 9-9 of FIG. 8B;

IG. 10 is a sectional view taken along the line ill-d6 of FIG. 83;

FIG. 11A is a lower, FIG. 11B is an intermediate, and FIG. 11C is an upper elevational view, in section, which when taken together illustrate another embodiment of this invention; and,

FIG. 12 is a sectional view taken along the line 12-42 of FIG. 118.

In the drawing in FIGS. 1A and 1B in particular, mandrel It is a hollow cylindrical member or arbor which is supported from and connected to a conventional tubular drill pipe, not shown, through drill tool joint 13. The lower end of mandrel ll) i connected to a bit 12. Thus, as shown in the drawing, mandrel 1% provides a rigid connection between drill bit 12 and the drill string. The particular advantage of such a connection will be discussed in greater detail hereinafter. Mounted about the upper portion of mandrel 14B is upper bit loading unit 14 and about the lower portion of mandrel 10 is a lower bit loading unit 16. The apparatus is shown suspended in borehole 18.

Upper bit loading unit includes case or housing 20 having an anchor section 22 and a thrust or pushdown section 24. Upper case 2th is supported from mandrel lit) by lower bearing 26 and upper bearing 28. These bearings may be of the fluted rubber type. An anchor pressure chamber Ell is formed between the upper case 2%) and the exterior of mandrel it Seals for pressure chamber are provided by sealing means 34 at the lower end of the pressure chamber and seal 32 at the upper end of the case preferably above bearing 28. Mounting details of the various seals and bearings illustrated in the drawing will not be shown, as means for mounting such seals and bearings are known. Mounted in ports in the wall of case 20 adjacentpressure chamber 3% are a plurality of anchor shoes 36 which preferably is a metal element 38 mounted in rubber 4% which seals it with the periphery of the port. Shoes 36 thus are a type which expands outwardly against the borehole wall whenpressure is applied in pressure chamberfitl and retracts to the position shown when pressure is released.

Below anchor section 22 is cylinder 42 defined between the outer surface of mandrel 10 and the inner surface of upper housing 20. Seal 34 is at the upper end of cylinder 42 between mandrel 10 and housing 24} and seal 44 is similarly at the lower end of cylinder 42. Mounted within cylinder 42 ispiston 46 which can be made an integral part of mandrel it or can be otherwise secured thereto. Mounted around the lower part of piston 46 is a fluted rubber. bearing 4-3 which prevents excessive lateral movement to piston seal ifia within cylinder 42. Mounted in the wall of cylinder 4-2 at its lower end is plug 50 which as will be seen hereinafter is used to chargethe portion of cylinder 42 below piston 46.

Mounted about the lower portion of mandrel 10 is lower housing 52. The upper end of lower housing 52 is reduced in diameter from the remaining portion of the housing and into a splined section 54-. Section 54 is insertable into the lower end of upper housing 2t which is splined internally to match the outer splines. This'is shown clearly in FIG. 2. The splined connection between upper housing 29 and lower housing 52 results in the upper housing and the lower housing being connected in. a non-rotatable but longitudinally slidable relationship with each other.

'Lower housing 52 is supported from mandrel l t} by lower bearing 56 and upper bearing 58 which maybe fiuted'rubber bearings. A seal 62 is above fluted bearing 56 and seals the exterior of mandrel It with the interior of lower housing '52. V

An a'nch'or'section is provided in the lower part of lower bit loading unit 16. This includes a pressure chamber 60 defined between the exterior wall ofmandrel 1d and the interior wall of lower housing 52. Pressure chamber 6% has a lower seal 62 and an upper seal 64 which forms a seal between mandrel it and the interior part of lower housing 52. Mounted in the wall of lower housing 52 opposite pressurechamber '69 are a pluralityof anchor shoes '66 which are similar to anchor shoes '36.

Mounted above the anchor section in the lower housing is a pushdown or thrust section 68 which is. similar to thrust section 24 of the upper bit loading unit; A cylinder 70 is defined between the exterior wall of mandrel 149 and the internal wallof lower housing 52. In the lower part of cylinder 70 is charging plug 84. Cylinder 70 is of slightly greater length in its longitudinal dimen:

sion masts chamber Ill l. A'piston '78 is attached to'or made partof mandrel'ltl. The upper face of'piston' 78 is preferably the same size in area'as the upper face of 1 piston de so as to have the same downward thrust from each loading unit. The ends of the etfective'stroke of housing 52. When in the position shown inFIGS. 1A' and 15, upper supply conduit 1% is in fluid communica- 82 upon which lower housing 52 can rest when in its lowermost position.

Mounted within mandrel It) is a resetting fluid conduit 86 which through ports 83 in the wall of mandrel it) below piston 78 and through port 90 in mandrel ll) below piston 46 fluidly connects cylinder 4-2 below piston 46 with cylinder 70 below piston 78.

A lower power conduit 92 is provided within the lower part of mandrel It). At the upper end of lower power conduit 92 is port 94 in the wall of mandrel 16. Intermediate the ends of conduit )2 is a throttle port 95 in the wall of mandrel 10 which establishes fluid communication between theinterior of conduit 92 and the-interior of cylinder 76 above piston '78. Positioned at the lower end of power conduit 92 is inflation port 98 in the wall of mandrel 1:) which establishes fluid communication between the'interior of power conduit 92 and the interior of pressure chamber 6%.

An upper power supply conduit 1% for supplying power to upper bit loading unit 14 is provided in mandrel 10 and extends from-just above lower power conduit 92 to sufficiently close together to permit convenient operation of D-slide valve or valve ring 118 which surrounds mandrel 10.

Preferably 'in'lower housing 52 above section 63 is valve operating chamber (shown in enlarged views in FIGS. 4, 5, 6 and 7) which is vented at 112 to the relatively lower differential pressure existing during drilling conditions within'annulus 19 between the, apparatus and the borehole Wall. The valve itself operatively surrounds inner. mandrel ltl and includes annular valve release cage or tube 114 which has vertical move'n'ie'n't about man'dr'el 10 within chamber llltl. Release tube 114 has a multiplicity of portsillo formed in itswall. D-type -slide valve 118 is longitudinally sealed in a slidable relationship with inner mandrel 10 using upper and lower shaft seals such asO-Iings 12E) andl22. Slide valve 118 is connected to valve release 'tube li l by a resilient spring means lld,

typically a resilient ela's'tomer materialbonded to the valve 138 a'ndrelea'se tube' 114. Attachedto slide valve I118 are a multiplicity of spring loaded la tch fingers, 128

and llotl which are adapted to be latched or unlatched to or from respective upper shoulder 132 and lower shoulder- 134 a'ttached to or :made "integral with inner mandrel 149. Positive stops 13601" 133 on mandrel it] limits the vertical I dreiia; 3. p v I s Slide valve lifiis operable toalternately connect the upper and lowersupply conduits with the pressure-fluid. supply port 140. which is midway between shoulders 132 and shoulder 1542- andextends through the wall ofv mandrel it). Whenin theposition shown inFIG. 1B, the interior of mandrel ltl is fiuidly incomrnunicaiton with lower power conduit 92 which in turn is in fluid communication with cylinder. 70. above piston .78 and the pressure chamber 69 of the anchor section of the lower bit loading unit. Inflation port '98 oi pressure chamber 6! is made larger thanthrottle port' o above piston '78,

In operation; this permits anchor shoes 66 to be expanded against the borehole wall. before the reaction thrust in cylinder-70 can cause substantial upward movement of tion with annulus w through port 106 and mandrel 14?, port 116 in valve release tube 114 and vent 112. When travel of valve ll's with respect to manalso ls? valve 118 is in its alternate position, it fluidly connects the interior of mandrel it with upper power supply conduit 109, which supplies power for anchor section 22 and pushdown or thrust section When valve 13% is in its upper position against stop 135, port 94 is uncovered and thus the interior of lower power conduit 2 i in fluid communication with annulus 19 through ports 116 and release tube 114 and vent 112.

The operation of the apparatus shown in FIGS. 1A and IE will now be described, with attention also being directed to the views of FIGS. i, 5, 6 and 7 which illustrate in greater detail the valve operating mechanism while taken in combination with the views of FIGS. 1A and 13.

Before the device is lowered into the well bore resetting fluid, which may be a lightweight oil, for example, is injected through either plug 84 or plug to fill cylinder it? below piston '78, the interior of resetting fluid conduit 86 and that portion of cylinder 42 below piston 46. To obtain optimum operation, the stroke of piston 78 in the lower unit is approximately equal to the stroke of piston 46 in the upper bit loading unit. The stroke of valve release tube 314 within valve operating chamber iii) is preferably slightly less than the stroke of piston '7? to prevent bumping of the pistons 73 against the shoul ders of cylinder 7% and also prevents the bumping of piston 4-5 against the shoulders of cylinder $2. A rotary drill pipe, not shown, is attached through coupling 13 to inner mandrel l0 and bit 12. Drilling fluid is pumped down through the interior of the rotary drill pipe and the interior of inner mandrel it to the bit where it passes through the bit and is circulated to the surface through the annulus E9. The pressure drop through the bit then results in a relatively high pressure within the interior of mandrel 13 in a relative lower pressure in annular space 1?. Assume that in the initial operation the inner mandrel and valve mechanism is in the position shown in FIGS. 1A and 1B and EEG. 4. A small portion of the drilling fluid passes through supply ports 14%) into the confined portion of slide valve 118 and thence through port 94 into lower power conduit $2. Substantially instantaneously this pressure is transferred into pressure chamber 6% forcing anchor shoes as into anchor contact with the borehole wall. Since throttling port 95 is smaller than inflation port $8, thrust force is delayed until the anchor shoes have been positioned. Thereafter full pressure is applied to the upper part of power piston 78 tending to force it downwardly with respect to lower housing 52.

Rotary drilling imparted to mandrel it to bit 12 continues with slide valve 118 traveling therewith as drilling progresse until such time as the lower part or face 142 of valve release tube 114 engages the lowermost position of upward face 72 of valve operating chamber 113. Rotary drilling continues under the applied pressure force of lower bit loading unit 16 until the lower valve latch fingers 136 are released from latch shoulder E34 by engagement with lower release finger 2 36 as a part of release tube or cage 11 The continued downward movement of slide valve 113 creates tension in spring means 124. (See FIG. 5.) Upon its release slide valve 113 is snapped upward, causing engagement of upper latch fingers 123 with latch shoulder 132 as shown in FIG. 6. In that position, pressure supply fluid is now diverted through port 146 into or through port 186 into upper power supply conduit During the drilling operation just described in which the lower bit loading unit was operative; that is, anchor shoes 65 were enga ed in th wall of the well bore and pushdown piston 78 were exerting a force on the bit, resetting fluid was being forced from beneath piston 78 to port 83, resetting fluid conduit 36 and port 96 to beneath piston 46 thus driving upper housing downwardly with respect to piston 46. During this process anchor shoe are in a relaxed position and are not enga ing the well bore wall. Also during this period, the area above piston 45 and cylinder 42 is not in communication with the high pressure fluid within mandrel 10 but rather is in communication through the valve control means to annulus 19. It is thus seen that as piston '78 reaches the lower part of its stroke within cylinder 759, piston 46 is driven to its uppermost position in cylinder 42.

Due to the snap-action of valve 118 power supply is fed to upper supply conduit 1599 nearly instantaneously with the stopping of the power supply to the lower power supply cool 2. As the power supply is cut off to the lower bit loading unit pressure is immediately released from pressure chamber 6d and cylinder '76 thus allowing the immediate retraction of anchor shoes 66 and stopping the downward thrust of thrust section 63. When piston 78, the lower bit loading unit 16, is at its lowermost position, piston 4-6 in the upper bit loading unit is at its uppermost position in cylinder 42. Nearly instantaneous with slide valve 113 being in its uppermost position, power is supplied through port res, upper supply conduit illa'l through valve port tea to (a) cylinder 42 above piston 45 and through port Hi2 (b) to anchor pressure chamber 351 Anchor section 22 is anchored securely to the borehole wall before there is any substantial downward movement of piston 46 with respect to upper housing This can be accomplished by making throttle port res smaller than port and it is also effected by the throttle, in effect, of the resetting fluid beneath piston it can also be done by using resetting ports and fill as throttle ports.

Drilling continues by rotating mandrel all and this time the downward thrust is supplied by thrust section 24 of the upper bit loading unit and the reaction thrust is transferred to borehole wall by shoes 36 in the upper part of upper housing 2% During this time the lower bit loading unit is being reset; that is, lower housing 52 is being forced downwardly with respect to piston 78 by resetting fluid being forced from beneath piston 35 downwardly through resetting supply conduit 8:5 to the underside of piston 78 in the lower loading unit. During this itme anchor shoes tit? are in a retracted position and tile lower unit moves readily downward. Lower unit housing 52 continues to move downwardly at twice the rate as piston 46 moves through its stroke in cylinder of the upper bit loading unit. As drilling progresses and as shown in FIG. 7, contact of valve release cage lid with the upper portion of chamber ill forces release finger I127 into engagement with valve latch fingers 12%, moving them from contact with latch shoulder 3%2. Similarly, due to the potential tension created in spring means 124, valve 118 is snapactingly forced dow wardly. Latch fingers 136 are engaged with latch shoulder 134 to assume the starting position as shown in FIG. 4 when the cycle above described is repeated.

Referring now to FIGS. 8A and 83, there is illustrated another embodiment and the best mode contemplated for carrying out the present invention. The apparatus shown in FIGS. 8A and 8B is similar to that shown in FIGS. 1A and 1B, for example, it has an upper bit loading unit and a lower bit loading unit. However, the resetting of the loading units is different. These differences are incorporated in FIGS. 8A and 8B and will now be discussed. More particularly, the resetting fluid conduit 86 and the port arrangement of the unit control section illustrated in FIG. 18 have been changed. A first fluid channel 15% extends from beneath piston 78 of the lower unit to above piston 46 of the upper loading unit. This fluid channel fluidly communicates with the lower portion of cylinder 7%) beneath piston 78 to port 152. A port 154 in mandrel 1 fluidly connects fluid channel 159 with the interior of slide valve 118 when in the position shown in FIG. 8B. When the valve is in its lowermost position the interior of fluid channel is in fluid communication through port 116, valve release tube 114 and through vent 112 to annulus 19. The upper end of fluid channel 15 3 is in fluid anchor pressure chamber 60 in thelower loading unit to.

approximately piston 46 in the upper loading unit. Se ond fluid channel 156 fluidly communicates with the under side of piston 46 into cylinder 42 through port 158. Second conduit 156 fluidly connects with pressure chamber 69 of the lower anchor section through port 16h and to the upper side of piston 78 in cylinder 70 through port 162. When in the position illustrated in FIG. 8B, second fluid conduit 156 is in fluid communication through port 164 to 116 and vent 112 to the annulus 19.

When slide valve 118 is in its lower position the interior of conduit 156 is in fluid communication with the interior of mandrel 10 and the interior of conduit is in fluid drill pipe and is then lowered into the bottom of a well bore. Drilling fluid under pressure is forced downwardly through mandrel 10. When the valve mechanism is in the position shown in FIG. 8B, fluid conduit 15% is in fluid communication with the high pressure fluid in mandrel 1t). Anchor section 22 is anchored to the borehole wall and downward pressure is exerted on piston 46 through mandrel 10 to hit 12. The anchor shoes of section 22 are anchored securely to the borehole wall before suflicient fluid is passed through port 1194 above piston 46 to cause piston 46 to move substantially. High pressure fluid is also in fluid communication with the under side of piston 78 of the lower bit loading unit and drives the lower outer housing 52 rapidly downwardly. When valve 118 is in the position shown in FIG. 8B, fluidconduit 156 is in fluid communication with the lower pressure annulus 19. This permits the lower anchor section to be relaxed as shown while the upper loading unit is anchored to the borehole wall and is supplying thrust to the bit. The upper portion of cylinder it! above piston 73 of the lower unit is also in fluid communication with the exterior of the housing. This permits the outer housing to be pushed rapidly downwardly by the high pressure fluid entering cylinder beneath piston 78. The lower portion of cylinder 42 beneath piston 46 in the upper loading unit is also fluidly connected to the low pressure exterior of the units.

with the high pressure fluid within mandrel 1t} and fluid conduit is in fluid communication with the relatively low pressure annulus 19 exterior of the units.. When in this position, the lower'anchor shoes 66 are nearly instantaneously expanded against the wall of the borehole and high pressure fluid enters cylinder 70 above piston 78 and begins toexert a downward force on the mandrel. The slight throttling effect of fluid through port 162 permits shoes 66 to be anchored securely before substantial movement is obtained between the lower housingahd the mandrel. W hen valve 118is in its lower position, the anchor section of the upper loading'unit is relaxed as pressure chamberfifl is in fluid communication with the low pressure area asis also the portion of cylinder 42 above piston 46. However, the lower part of cylinder" 42 below piston 46 is in fluid communication with the high pressure fluid in fluid conduit 156 and the high pressure fluid acts on face or shoulder of the lower parrot cylinder 42 driving upper housing 20 downwardly. and resetting it where it remains reset until drill 1-2'is drilled the length of the stroke of piston 78 at which point valve 118 is snap-actinglymovedto its upper position and the cycle is repeated. In the apparatus shown in FIGS. 8A and 8B, the weight is applied most of the time to the lower unit. This is desirableas it is preferred to load the bit as close to the bit itself as is possible. In this embodiment, the length of the stroke of the upper unit compared to the lower unit is preferably rather short. In fact, the stroke of piston 46 may be as small as onefourth or less of the stroke of piston 78 of the lower unit. This is possible as the upper unit is in operation only the length of time it takes the lower unit to be reset. This resetting time will depend upon such factors as the length of the stroke of piston 78, the weight of the lower housing, the viscosity of the drilling fluid, the diiferehtial pressure existing across the bit, diameter and length of the fluid conduits, etc. However, for a unit in which the stroke of piston 78 is about 10 ft. and under normal drilling conditions the time for the lower unit to reset is in the range of about 20 to 30 seconds or less. It is thus seen that in the system shown in FIGS. 8A'and 82 that the anchor shoes closer to the bit 12 are in operation all the time except for this brief resetting period. This tends to permit a'straighter hole to be drilled during the drilling operations.

Also shown in FIG. 8B is a spiraling preventer which is added about the mandrel 10 just above bit 12. The spiraling preventer may be made an integral part of mandrellfl and includes a series of spaced-apart hard surface skates or shoes 171 spaced about the circumference of the mandrel. The face 172 of each skate 171 is preferably a hard surface. spiraling preventer 17% as shown in FIG. 10 is approximately equal or slightly greater than the relaxed diameter of the anchor shoes and less than the gage diameter of the bit. This spiraling preventer 17% stops or reduces spiraling (bit walking) and prevents substantial reduction of the drift diameter of the hole. This permits more readily advancement of the outer case after resetting of the tool.

Turning now to FIGS. 11A, 11B and 11C there is illustrated still another embodiment of the invention. In this embodiment both the upper and the lower loading units are operative to exert a force on the bit at all times except for a brief resetting time for each bit loading unit. Controls are provided such that theunits are reset at diflerent times. Illustrated thereon is an upper loading unit 189 and lower loading unit 182. Mandrel 188 is connectable at its upper end to a string of drill pipe not shown and at its lower end to a; bit 1%. Mounted about mandrel 188 is upper housing 184 and lower housing 186. The upper housing and the lower housing are interconnected in a nonrotatable, longitudi nally slidable relationship through spline joint 192 which includes external splines on an upper reduced portion of the lower housing and internal splines 1% in the bore of the lower end of upper housing 189. The splined connection between the upper housing and the lower housing prevents rotation of a housing as it is being reset. This feature protects the anchor shoes as they cannot be rotated when retracted. Upper housing 186) is rotatably supported from mandrel by upper bearing 198, intermediate bearing 200, and lower bearing 262, which are supported withininte'rnal'recesses in the housing in a known manner These bearings can be of the fluted rubber type similarly as hearing 26.

An annular cylinder 211i is formed between the outer wall of mandrel 188 and the interior of' housing 184. Upper seal 204 and intermediate seal 2% disposed between housing 184 and mandrel 138 aid in making annular cylinder 21%) relatively fluid tight. Mounted in annular cylinder 210 is an annular piston 214 which is carried by or made integral with m'andrellSS. A seal 216 is provided between piston 214 and the interior of I cylinder 21h. Piston 214 carries bearing .218 to prevent excessive lateral deformation of seal 216. Immediately. below annular cylinder 21% is pressure chamber 212 7 formed in a recessed portion of housing 184 and the interior of mandrel 188. 'A'lower seal ZZilis provided just The diameter D of the ensues? above bearing 2% between housing 184 and mandrel 188. Thus, seals 22% and 2% aid in making chamber 212 relatively fluid ti ht. Resiliently and sealingly mounted in ports in the wall of housing 184 adjacent pressure chamber 212 are a plurality of anchor shoes 222 which are similar to anchor shoes 35 described above in relation to PBS. 1A.

As shown in t e upper portion of housing 134 is valve operating chamber 224 which is vented at 225 to the relatively lower pressure existing during drilling conditions within the annulus between the apparatus and the borehole wall. Operating in valve operating chamber 224- is a D-slide valve 228 and its component parts which are similar to the valve shown in FIG. 1B as operating within valve operating chamber lit The valve operatively surrounds mandrel 188 and includes annular release cage 23% which has a plurality of ports 232,. Slide valve 228 is connected to valve release cage 239 by resilient spring loans 23%. Attached to slide valve 228 are a plurality of spring loaded latch fingers 235 which are adapted to be latched or unlatched to or from respective upper shoulder 23% and lower shoulder 24%. Positive stops and on mandrel 1E3 lhnits the vertical travel of val e 228 with respect to the mandrel.

Stops n42 and 245 on mandrel 318?: are so designed in relation to slide valve 228 that power port 2&6 in the wall of mandrel 223 is in fluid communication with the interior of annular valve 223 in any position of the valve between upper stop 242 and lower stop 244. Mounted adjacent the wall of the interior mandrel 133 is a power supply conduit 24%. This conduit is in fluid communication with pressure chamber 212 and annular cylinder 21d above piston 21 3.- through ports 2 3' and 252. Port 25%) can be slightly larger than port 252 and thus when fluid pressure is applied, the anchor section is secured to the borehole wall prior to any substantial movement of housing 184 with respect to piston 214. Port 254 is provided in the wall of mandrel 3.85 below port 246. When slide valve 228 is in its uppermost position against stop 242 as shown in FIG. US, power supply conduit 24-3 is in fluid communication through

ports

232 and 2 26 with the annulus between the tool and the borehole wall. However, when valve 228 is in its lowermost position as against stop 244, port 254 is in fluid communication with the interior or" the valve; thus power conduit 243 is in rluid communication with the interior or" mandrel Also shown is a resetting conduit 256 which is in fluid communication with the part of annulus cylinder 218 below piston 2 14. The interior of conduit 255 is also in fluid communication with port 253 and in the posit on shown resetting conduit 256 is in fluid communication with the interior of mandrel 138. However, when slide valve 22.8 is in its lower position against stop 244-, port 2 58 is not covered by valve 223 and thus the part of cylinder below piston 214 is in iluid communication through conduit 25%,

ports

232 and 226 with the annulus between the tool and the borehole.

Attention will now be directed toward lower loading unit 182. Lower loading unit 382 contains a pushdown section and wall anchor section similarly as upper loading unit 139. The pushdown section includes annular cylinder 26d and piston 262 which is mounted on the mandrel E33. Below annular cylinder 26% is pressure chamber 264 in which anchor shoes 265 are mounted in the wall of housing 185 similarly as shoes 222 in the upper loading unit. The lower housing 186 is rotatably and longitudinally movable, in relation to mandrel ldfi and is supported therefrom by upper bearings 268, intermediate bearings 27%, and lower bearing 27?). Associated with these hearings are upper seal 2%, intermediate seal 2%, and lower seal 278. These seals and bearings are carried in grooves or otherwise by the housing in a known manner. Piston 262 is also provided with a seal 28% and bearing 2232 similarly as seals 21% and bearing 21% of piston 214.

The valve control mechanism for actuating and resetting the lower unit will now be discussed. A valve operating chamber 284- is provided between the interior of the lower end of upper housing 13 and the exterior of reduced portion 2%. The valve mechanism in valve operating chamber 284 is similar to D-slide valve 228 and its associated parts, except the slide valve 286 and its associated parts are actuated by a relative movement between upper housing 134 and lower housing 186, whereas slide valve 28 is actuated by a relative movement between mandrel and upper housing 184. Extending upwardly into valve operating chamber 284- is an upper reduced portion 2% of lower housing 186 which is decreased in size and has an internal bore approximately the size of the external diameter of the mandrel 188. An annular power supply conduit 288 is provided in a recessed portion of upper reduced portion The longitudinal length of annular conduit 28% is such that the port 2% is in communication with the power conduit 238 during the entire stroke of piston 262. Upper seal 292 above annular conduit 238 and lower seal 2% below annular conduit 28% are carried by reduced portion 296 of the lower housing. Slide valve zss is resiliently supported from annular release cage 2% in which is provided relief port A port 3%2 is provided in the wall of upper housing 134 to vent valve operating chamber 284 to the annulus between the apparatus and the borehole wall.

Slide valve 2% has longitudinal movement between upper step 394 and lower stop 5%. The interior of annu lar slide valve 286 is in fluid communication with power conduit 23% through port 388. Port 363 is arranged in relation to the annular slide valve and stops 334 and 3th: such that it is always in fluid communication with the interior of annular slide valve ass; thus the interior of slide valve 286 is always in fluid communication with the interior of mandrel 1%. In the position shown a power fluid conduit 31% is in fluid communication with interior of annular valve 285 through port 312 and witr annular cylinder 26% above piston 262 and with pressure chamber 254 of the anchor section of the lower loading unit. In the position of the valve as shown annular cylinder 25? below piston 262 is in fluid communication through relief conduit 314 through ports 3% and 392 to the annulus.

Above stop is upper shoulder 316 and below lowe stop 3% is lower shoulder 31%. These

shoulders

318 and 315 function with respect to the valve operating mechanism similarly as stops 238 and 2d!) of the upper valve arrangement in relation to the slide valve 228. The upper part of valve operating chamber 284- has a downwardly facing shoulder 32h which is arranged to contact the upwardly facing shoulder 322 of relief cage 29%. Likewise, the lower part of relief cage 2% forms a shoulder 32% which is arranged to contact the upwardly facing shoulder 326 or" the lower portion of valve operating chamber 284.

Port 312 and port 315 are arranged to contact the upwardly facing shoulder 326 of the lower portion of valve operating chamber 284.

Port 3212 and port 315 are arranged such that when slide valve 286 is in the position shown, port 312 is in fluid communication with the interior of the slide valve and 315 is exterior or" the slide valve. However, when the slide valve Zild is in its lower position, that is against stop 3%, port 312 is above the annular slide valve and port 315 is in communication with the interior of the slide valve. in other words, in the position shown pressure chamber 26% of the anchor section and the upper part of cylinder 26% of the pushdown section is in fluid communication through conduit 330 through port 3E2 and the valve with the interior of mandrel and the lower side of chamber 26% below piston 262 is in fluid communication through conduit 3M and 315 to the exterior of tool.

The stroke of pistons 21d and 252 are preferably about the same length. The stroke of piston 214 is preferably fing surface of annular cylinder 210. The stroke, or

movement ofthe upwardhousing with respect to the lower housing necessary to actuate valve 286 from either position, is preferably about the same as the stroke re- "quiredto actuate valve 228. 7 Having described the structural features of the embodiment on FIGS. 11A, 11B and 11C, attention will now be directed briefly toward its operational features. Thetool is connected-in a conventional manner to the lower end of a string of drillpipe by connecting mandrel 188 to a tool joint not shown. -The tool is lowered to the bottom of .a drill hole. Drilling fluid is then circulated downwardly through-mandrel 188 under pressure and bit 1% is rotated by-rotating the drill pipe at the surface which in turn rotates mandrel 188. The particular relative position of upper housing 184 and'lower housing 186 when operation is initiated does not matter as the two units of the tool automatically assume their proper relationship upon initial actuation of one or both control valve means by the upper loading unit. It will further be assumed for purpose of description'of operation of the tool that initially lower '-valve 286 is in the position shown in FIG..

11B and the valve 228 isin its lowermost position against stop 244. In this position fluid under pressure-is anchoring both the upper loading unit andthe lower loading unit to the borehole wall by

anchor shoes

222 and 266 respectively. Fluid under pressure is also urging pistons 214 and 252' downwardly thus forcing the drill bit against the bottom of the borehole and the reaction thrust is being transferredto the walls of the borehole being drilled. As drilling progresses, mandrel 183 is moved downwardly through-the upper and lower loading'units. As it moves downwardly, it takes with it annular valve release cage 23@ similarly as described above in relation to valve 118. When the mandrel reaches a downward position relative to upper housing 184, slide valve 228' is snap-actingly moved to its upperposition againststop 24-2 thus assuming the position shown in FIG. l'lC ina-manner similarly described above in relation to the snap-acting movement of a similar D-type-slide valve in operating chamber 110. L

interior of mandrel 183. When-in this position, cylinder a 210 below piston 214 is in fluid communication through annular valve 228 with interior of mandrel 188. The

upper loading unit housing, with its anchor section retra'c-ted, is forced downwardly. The downward'move ment of upper housing 134 causes lower shoulder 225 a of the'upper part of operating chamber 224 to strike the upwardly facing shoulder 22 7 of release cage 230, thus forcing the slide valve to its lower position, that is against stop 24-4 at which time the anchor shoes 222 engage the wall of the borehole and'power is applied to the upper side of piston 214. It will be noted here'that port 252 is designed such that flow is restricted sufliciently so that the anchor section is anchored before a great deal'of forceis applied against piston 214.

The downward movement of upper housing 134 causes shoulder 320 of-the lower valve operating chamber 284 to strike the uppershoulder 322 of the lower release cage 298. This continued downward movement of the upper housing then causes valve 286m be snap-actingly moved downwardly suchthat pressure chamber 2654 of the anchor sectionof the lower loading unit 182 and cylinder 260 above piston 262 are in fluid communication with.

V the annulus. At the same time cylinder 2430 beneath pis ton 262 is indirect fluid communication with the interior of the mandrel 183 through ports 3:15 and 308. Fluid unease? pressure thus forces the lower housing 1% downwardly to the end of its stroke, valve 236 is snap-actingly moved back to the position as shown in FlG.'11C. In this'position the anchor shoes are driven outwardly against the borehole wall and fluid pressure 'is applied against the .upper side ofpiston 262, 'thus exerting a downward force on the mandrel, thus forcing the bit .190 downwardly against the bottom of the borehole.

In the operation of the apparatus shown in FIGS. 11A, 11B and 11C upper loading'lfitland the lower loading unit 182 are both in operation and exerting a downward force on the drill bit at all times'except when being reset.

. However, the upper loading unit is reset at a different its lower position at'about thesame time that valve 2% is moved to its lower position. The anchor section of the upper unit is nearly instantaneously anchored when valve 223 gets in its lowermost positionand is anchored approximately as fast 'as'the' anchor sectionshoes 266 of the lower unit are retracted; Likewise, the pushdown section of the upper loading unit is actuated immediately as the anchor sectionis anchored to the borehole. Thus, for all practical purposes one of the loading units is operative at all't irnes during the resetting'period. of the tool. Except forits resetting time, each unitis operative at all times during d'rillingoperations. The'resetting time for each unitis rather brief, being only a matter of a few seconds. a p

' in using the tool'of this invention, drill pipe above the tool-will normally be held in tension inorder to prevent buckling and undue wearing of the tool joints. In cases Where it is desired to apply less force to the 'bit than is normally furnished by the tool, the tension in the drill string can be'increas ed by applyingupward time to the drill string at the surface with the rig equipment to lessen the eiiectiveforce of the bit. One instance where it is frequently desirable to'do this is in reaming operations.

The ability to'control the force applied to the bit inthis manner is a particular advantage of the tool of this iii vention. Furthen'this'reduction of force on the bit is accomplished by'reduction-of the flow rate of the drilling fluid. A reduction'in the quantity ofthe fluid circulated reduces the fluid availablefor cooling and'lubricatlng the bit and lifting cuttingsfrom the boreholeandis therefore to be avoided. The use of a mandrel which extends through the tool and furnishes a rigid connection between the drill string and the bit as disclosed herein readily per-v mits control of the force on the bit.

While there are above described but alimited number of'cmbodiments of the process and system of the invention herein presented, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed. It is therefore desired that only such limitations be imposed. on the appending claims as are stated therein.

V first pushdown means positioned between said mandrel and said lower case for exerting a force on said mandrel longitudinally thereof in the direction of said'bit and for eXerting'the reaction thrust of such load on said lower case; first anchor means attached to said lower case and operable upon actuation to transfer said reaction thrust to the borehole wall; an upper case mounted around said mandrel longitudinally above-said lower case and in a a longitudinally slidable and rotatable relationship'with said mandrel; second anchor means attached to said upper case' andoperable upon actuation to engage the borehole wall;

means operable in a first condition to de-actuate said first alarms? i 3 anchor means and said first pushdown means and to actuate said second anchor means and in a second condition to actuate said first pushdown means and said first anchor means and (ls-actuate said second anchor means.

2. In a rotary drilling apparatus for drilling a borehole including a drill bit and a drill string assembly and means for circulating fiuid through said assembly and said borehole, the improvement which comprises: a rigid mandrel connectable within said drill string and having a conduit for the flow of fluids therethrough, a first housing surrounding said mandrel and rotatable and longitudinally movable therewith between upper and lower positions, first thrust transfer means interposed between said mandrel and said first housing and actuatable to thrust said mandrel downward relative to said first housing, first wall anchor means on said first housing actuatable to lock said first housing to the wall of said borehole, a second housing surrounding said mandrel and spaced longitudinally from said first housing and rotatable and longitudinally movable between upper and lower positions on said mandrel, second thrust transfer means interposed between said mandrel and said second housing and actuatable to thrust said mandrel downward relative to said second housing, second wall anchor means in said second housing actuatable to lock said second housing to the wall of said borehole, control means operable upon said first housing reaching said lower position to sequentially actuate said first wall anchor means and said first thrust transfer means, said control means being further operable upon said first housing reaching its upper position to de-actuate said first wall anchor means and said first thrust transfer means and to actuate said second transfer means and said second wall anchor means.

3. An apparatus as defined in claim 2 in which the first and second housing are telescopically connected in a nonrotatable manner.

4. An apparatus for forcing a bit against the bottom of a borehole comprising in combination: a mandrel atachable at its lower end to a drill bit, a first case mounted around said mandrel in a longitudinally slidable and rotatable relationship therewith; first pushdown means positioned between said mandrel and said first case for exerting a force on said mandrel longitudinally thereof in the direction of said bit and for exerting the reaction thrust of such force on said first case, first anchor means attached to said first case and operable upon actuation to transfer said reaction thrust to the borehole wall; a second case mounted longitudinally from said first case around said mandrel in a longitudinally slidable and rotatable rel tionship with said mandrel; second pushdown means positioned between said mandrel and said second case for exerting a force on said mandrel longitudinally thereof in the direction of said bit and for exerting the reaction thrust of such force on said second case; second anchor means attached to said second case and operable upon actuation to transfer reaction thrust to the borehole wall; control means operable in a first condition to actuate said first pushdown means and said first anchor means and to deactuate said second anchor means and said second pushdown means and in a second condition to de-actuate said first anchor means and to actuate said second anchor means and said second pushdown means.

5. An apparatus as defined in claim 4 with the improvement of providing positioning means such that when said first case moves in one longitudinal direction with respect to said mandrel the second case moves in the opposite longitudinal direction.

6. An apparatus as defined in claim 4 in which the two cases are telescopically connected in a non-rotatable mannor.

7. An apparatus as defined in claim 4 in which the mandrel is enlarged near its connection to the bit to a diameter substantially equal to the diameter of the first anchor means when such anchor means are in a retracted position.

8. In a rotary drilling apparatus for drilling a borehole including a drill bit and a drill string and means for circulating fluid through said assembly and said borehole, the improvement which comprises: a mandrel rigidly connecting said bit to said drill string and having a conduit for the flow of fluids therethrough; a first housing surrounding said mandrel and rotatable and longitudinally movable therewith between upper and lowerpositions; first thrust transfer means interposed between said mandrel and said first housing and actuatable to thrust said mandrel downwardly relative to said first housing; first wall anchor means on said first housing actuatable to lock said first housing to the wall of said borehole; a second housing surrounding said mandrel and spaced longitudinally above said first housing and rotatably and longitudinally movable between upper and lower positions on said mandrel; second thrust transfer means interposed between said mandrel and said second housing and actuatable to thrust said mandrel downwardly relative to said second housing; second wall anchor means in said second housing actuatable to anchor said second housing to the wall or" said borehole; said first housing and said second housing telescopically connected in a non-rotatable manner; control means being operable upon said first housing reaching its lower position to sequentially actuate said first wall anchor means and said first thrust transfer means and to de-actuate said second anchor means and said second thrust transfer means; said control means being further operable upon said first housing reaching its upper position to de-actuate said first wall anchor means and said first thrust transfer means and to actuate said second ransfer means and said second Wall anchor means; housing positioning means operable such that when said first housing moves in one longitudinal direction with respect to said mandrel the second housing moves in the opposite longitudinal direction with respect to said mandrel.

9. In a rotary drilling system for drilling a borehole, including a drill string and a bit, the improvement which comprises: a hollow mandrel rigidly connecting said drill string to said oh and of a character to convey fluid from said drill string to said bit through its interior, the exterior surface of said mandrel defining a lower piston and an upper piston; a lower case surrounding said mandrel in a rotatable and longitudinally slidable relationship therewith and defining a lower cylinder for said lower piston, said lower case having an upper and a lower position with respect to said mandrel, said lower case further defining a valve operating chamber, such chamber being in fluid communication with the exterior of said lower case; a lower pressure chamber formed between said lower case and said mandrel; an upper case above said lower case and surrounding said mandrel in a rotatable and longitudinally slidable relationship therewith and defining an upper cylinder for said upper piston; an upper pressure chamber formed between the Wall of said mandrel and said upper case; lower hydraulically expansible wall anchor means mounted in said lower case, the interior of said lower anchor means being exposed to said lower pressure chamber; upper hydraulically operated wall anchor means mounted in the wall or": said upper case, the interior of said upper anchor means being exposed to said upper pressure chamber; a lower supply conduit within said mandrel extending from near the upper end of said lower case to within said lower cylinder above said lower pis ton and to within said lower pressure chamber; a first port means in the wall of said mandrel extending from the upper end of said lower supply conduit to the exterior of said mandrel; an upper supply conduit within said mandrel extending from about the upper end of said lower supply conduit to within said upper pressure chamber and the upper cylinder above said upper piston; a second port means in said mandrel spaced above said first port means and fluidly connecting the interior of said upper supply conduit with the exterior of said mandrel; a supply port in said mandrel spaced longitudinally intermediate be- J3 tween said first and said second ports; a sliding valve mounted in said valve operating chamber and having an upper and a lowerpo'sition and alternately actuat'able between its upper and lower positions by movement of said lower case to its upper position and its lower position respectively, said valve when in an upper position 'fluidly connects said supply port with said second port and fluidly connects the lower port with the exterior of the lower case, said valve when in a lower position fluidly connects said supply port with the lower port and fluidly oonnectsthe upper port with the exterior of said lower case; and a resetting fiuid conduit establishingfiuid communication between said lower cylinder below said lower -pist-on and said upper cylinder'below said upperpiston.

10. An apparatus for forcing a bit against thetbottoni of the borehole cornprising in combination: a mandrel attachablcat its lowe r end to a drill bit, a first outer case mounted around'said mandrel in a longitudinally slidable and rotatable relationship therewith; first pushdo'wn 7 means positioned between said mandrel and said first case I -means'p'ositioned between said mandrel and said second case for exerting a force on said mandrel longitudinally thereof in the direction of said bit and for exerting the reaction thrust of such force on said second case; second anchor means attached to said second case and operable upon actuation to transfer reaction thrust to the borehole Wall; and control means operable to sequentially deactuate said (a) first pushdown means and said first anchor means and (b) said second pushdown means and said second anchor means when in a first condition and to sequentially actuate said (a) first pushdown means and said first anchor means and (b) said second pushdown means and said second anchorrmeaus when in a second condition. a

11. In 'a'rotary drilling apparatus for drilling a borehole including a drill bit and a drill string assembly and means for circulating fluid through "said assembly and said borehole, the improvementwhich comprises: a mandrel connectable within said drill string and including a conduit for the flow of fluids therethrough; afirst housing surrounding said mandrel and rotatably and longitudinally movabletherewith between upper and lower positions; first thrust transfer means interposed between said mandrel andsaid firsthousing; first wall anchor means carried by said first housing actuatable to lock said first housing to the wall of said'borehole; a second housing surrounding said mandrel rotat'ablyand longitudinally movable therewith between'upper and lower positions and spaced longitudinally below said first housing in a non-rotatable and longitudinally movable relationship therewith; second thrust transfer means interposed between said mandrel and said second housing and actuatable to thrust said mandrel downwardly relative to said second housing; second wall anchor'means carried by said second'housing and actuatable .to lock said secondhousing to the 'wall of said borehole; first valvecontrol means operable when said first housing is in its upper position with respect to said mandrel to de-actuate said first thrust transfer means andsaid first wall anchor means and to 'driv'e said first housing downwardly with respect to said mandrel, and in transfer means and said second wall anchor means when thrust transfer means and said second wall anchor means upon said'second housing reaching its lowermost position.

12; An apparatus for forcing a bit against the bottom of a borehole comprising in combination: a mandrel attachable ,at its lower end to a drill bit, a lower case mounted around one portionof said mandrel in a longitudinally slidable and rotatable relationship therewith, first pushdown means positioned between said-mandrel and said lower ,c'asefor exerting a force on said mandrel longitudinally thereof in the direction of said bit and for exerting the reaction-thrust ofsuch load onrsaid lower casegfirst anchor means attached vto said lower case and operable upon actuation tetransfer saidreaction thrust tothe borehole wall; means to prevent substantial longitudinal movement of'saidlower casewith respectto said mandrel prior to the actuation of said first anchor means; an upper case mounted around said mandrel longitudinally above said lower case and in a longitudinally slidable and rotatable relationship with said mandrel; second anchor means attached to said upper case and operable upon actuation to engage the borehole wall; means operable in a first condition to de-actuate said first anchor means and said'first pushdown means and to actuate said second anchor means and in a-second condition to actuatesaid' first pushdown means and said first anchor means and de actuate said second anchor means.

13. An apparatus for forcing a bit against the bottom of a bore hole comprising in combination: a mandrel attachable at its lower end to a drill bit, a first case mounted around said mandrel in a longitudinally slidable and rotatable relationship therewith; first pushdown means positioned between said mandrel and said first case for exerting aforce on said rnandrel longitudinally thereof in the direction of said bit and for exerting the reaction thrust of such force-on said first case; first anchor means attached to said first case and operable upon actuation to transfer said reaction thrust to the borehole wall; a second case mounted longitudinally from said first case around said" mandrel in a longitudinally slidable and rotatable relationship with said mandrel; second pushdown means positioned between said mandrel and said second case for exerting a force on said mandrel longitudiiially thereof in the direction of said bit and for exerting the reaction thrust of such force on said second case;

second anchor means attached tos'aidsecond case and 'operableupon actuation to transfer reaction thrust to the borehole wall; control m ans operable in a first conchor means and said second pushdown means and in a second condition to de actuate said first anchor means and to actuate said second anchor means and said sec- 7 of a borehole which comprises :-a mandrel provided with means near the lower'end thereof for connecting said mandrel to abit; an upper loading and anchoring unit mounted on said mandrel, said upper unit including means for exerting'a downward'thrust on said mandrel and means for transferring-the reaction thrust to the wall of the borehole when said upper unit is actuated;

5a lower loading and anchoring unit mounted on said i mandrel, said lower unit including meanst for exerting a downward thrust'on. said mandrel and means for trans- 7 -ferring the reaction thrust to-the wall of the borehole said first housing is in its lower position and to move said lower housing longitudinally from said first housinn andbeing further operable to actuatesaidsecond when said lower unit is actuated; and control means ."for alternately-actuating said upper umtand ,SfilddQWeI' unit.

15. Apparatus as-defined in claim 14 wherein said upper and lower loadingand, anchoring units are telescopically interconnected in a nonfr'otatable manner.

16. Apparatus as defined in claim 14 including positioning means for applying force to said lower loading and anchoring unit to move said unit in one longitudinal direction with respect to said mandrel in response to the application of force tending to move said upper loading and anchoring unit in the opposite direction with respect to said mandrel.

References Cited by the Examiner UNITED STATES PATENTS 556,718 3/96 Semmer 175-118 X 1,549,168 8/25 Townsend 166-187 2,223,645 12/40 Solomen 175-94 2,474,453 6/49 Armitage 166-98 2,537,413 1/51 Lawrence 166-98 2,589,534 3/52 Buttolph 175-325 X 2,643,860 6/53 Koch 175-99 18 2,684,835 7/54 Moore 175-321 2,807,326 9/57 Church 166-120 2,827,263 3/58 Scott et a1. 175-99 X 2,877,822 3/59 Buck 175-98 X 5 2,937,007 5/60 Whittle 175-321 X 2,946,587 7/60 De Smaele 175-99 X 3,105,561 10/63 Kellner 175-230 FOREIGN PATENTS 1,084,380 1/55 France.

OTHER REFERENCES Hydraulic Wall-Anchored Drill Collar Promises Lower Drilling Costs, J. M. Kellner and A. D. Roberts, vol. 58, 15 Oil and Gas Journal, No. 40, Oct. 3, 1960, pp. 87-89.

CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner.

Claims

14. APPARATUS FOR FORCING A BIT AGAINST THE BOTTOM OF A BOREHOLE WHICH COMPRISES: A MANDREL PROVIDED WITH MEANS NEAR THE LOWER END THEREOF FOR CONNECTING SAID MANDREL TO A BIT; AN UPPER LOADING AND ANCHORING UNIT MOUNTED ON SAID MANDREL, SAID UPPER UNIT INCLUDING MEANS FOR EXERTING A DOWNWARD THRUST ON SAID MANDREL AND MEANS FOR TRANSFERRING THE REACTION THRUST TO THE WALL OF THE BOREHOLE WHEN SAID UPPER UNIT IS ACTUATED;