US3777819A

US3777819A - Cementing well bore casing

Info

Publication number: US3777819A
Application number: US00251191A
Authority: US
Inventors: C Delano
Original assignee: MUSTANG OIL TOOLS Inc
Current assignee: MUSTANG OIL TOOLS Inc
Priority date: 1972-05-08
Filing date: 1972-05-08
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11
Also published as: BE808513A

Abstract

There is disclosed a method and apparatus for cementing a tubular string in a well bore wherein the tubular string is simultaneously rotated and reciprocated while passing a cementing slurry into the well bore.

Description

United States Patent 11 1 Delano Dec. 11, 1973 CEMENTING WELL BORE CASING Inventor: Charles G. Delano, Corpus Christi,

Tex.

Assignee: Mustang Oil Tools, Inc., Corpus Christi, Tex.

Filed: May 8, 1972 Appl. No.: 251,191

US. Cl. 166/285, 166/78 Int. Cl E2lb 33/14, E2lb 19/00 Field of Search 166/285, 286, 78;

References Cited UNITED STATES PATENTS 2,609,881 9/1952 Warren 166/285 2,613,060 10/1952 Trahan.... 2,675,082 4/1954 Hall 166/285 3,205,945 9/1965 Holt .l 166/286 OTHER PUBLICATIONS Bowen Tools, Inc., Bowen Power Sub, Instruction Manual, Houston, Texas, Dec. 1965, pp. 2-23. American Petroleum lnstitute, Oil Well Cementing Practices in the United States," A.P.l., New York, N.Y., 1959, pp. 104-107 and 124.

- Mills, Rotating While Cementing Proves Economical," The Oil Weekly, Dec. 4, 1939, pp. 14 and 15.

Primary Examiner-Stephen J. Novosad AttorneyG. Turner Mo'ller [57] ABSTRACT There is disclosed a method and apparatus for cementing a tubular string in a well bore wherein the tubular string is simultaneously rotated and reciprocated while passing a cementing slurry into the well bore.

8 Claims, 4 Drawing Figures 1 cEMENTrNo-wumonr: cxsmc BACKGROUND OF THE INVENTION In the art of cementing tubular Strings in 'well' bores, it is well known to affix scratchers and eentralizers to the tubular string in orderto abrade thebore hole wall and positionthe stringgenerally in the center of the bore hole. Scratchers are commercially available in various designs and are of two basic types. Thefirst type is an elongate scratcher which isaffixed longitudinally of the tubing string so that rotation of the string causes the scratching elements to abrade' the borehole wall. .The other type scratcher is circularandof limited extent in the longitudinal direction of the tubular string. This type scratcher'requires reciprocation of. the tubular string toabrade the bore hole wall.

The generalpractice of cementing is to-scratch-the bore hole wall while circulating clean drilling mud through the hole to remove loose shale particles, excessive mudfilter cakeand the like from'the" bore hole wall. After the'holehas been circulated-for a desired length of time, usually on the order of about two toten hours, cementispumped downwardly through the tubular string. The'cement exits through a cementing shoe on the bottomofthe tubular string andpasses upwardly into the annulus between the: tubular string and the bore hole wall.1'Scratching o'fithe'tbore hole wall generally continues during the :placement 'of cement.

Scratching the bore hole' -wall'duringpplacement of. the

cement aids chiefly in agitating the cement. and 'assuring a generally uniformplacement thereof in the-annulus. It is accordingly widely practiced to rotate orrreciprocate a tubular string while .pumping acement slurry into the well bore.

'there is no disclosure of an approach'for simultaably suspended from a conventionaltraveling block and elevator arrangement. The conventional traveling block is presumably operatively connected to a conventional drawworks for raising and lowering the tubular string 16. The tubular string 16 presumably rests in a set of conventional casing slipsreceived'in'the top of the rotary table l8. Conventionalcasingslips are generally wedge-shaped segments of anannulus and are received in a beveled opening in thetop of the rotary table. When the wedge-shaped segments are loaded against the rotary table, driving of the rotary causes the slips to rotate and consequently to rotate the casing string. It is apparent, however, thatconventional casing slips do not provide a torque transmitting connection unless the weight of the casing string loads the slips against the rotary table. Itis accordingly abundantly apparent thatthe casingstring 16 of Warren cannot be rotated as the string.16 israised'since the torque transmitting connection through'the rotary table is inoperative. It would appear, at first blush, that the casing slips would transmit rotationto the casing string if the casing string were moving downwardly into the well bore. In fact, this is not the case since conventional casing slips grip the exterior casing wall, as opposed to the collar.

Accordingly, if the slips are loaded, the casing string is neously rotating and reciprocating a tubular string in a well bore while passing a cementing slurry into the well bore. There are two approaches'for simultaneously rotating and reciprocating a tubular string which have been the subject of conversation. Applicant is unable to state whether these approaches have ever been published or publicly used to bring these approaches within the purview of the prior art. It will suffice for present purposes to state that applicantis not the inventor of the approaches hereinafter described.

One approach is to run the tubular string through the rotary table into the well bore, set the casing slips on the string, attach a sub to the female coupling at the top of the tubular string, attach'theKelly to the sub, remove the casing slipsandrotary bushing, lower the string such that the Kelly. extends through the rotary table, place the Kelly bushing in the rotary table and then simultaneously rotate and reciprocate the tubular string. 1' his approach presents two primary disadvantages, either of which is so severe as to preclude serious consideration of this approach for use in a cementing process. The "first disadvantage occurs if the casing string becomes stuck in the well bore. In this event, the 'Kelly must'be'removed from the casing string in order to attach suitable fishing tools, for example. jars, wireline tools or the like. If the sub is belowground level when the tubular string sticks, it isimpossible to remove the 'Kelly from the tubular string in order to attach suitable fishing tools thereto. In the vernacular, the operator is up a creek with no'paddle. The only thing that can bedorie is to rotate the Kelly to the left to unscrew one of the joints, pull the freed part of the string out of the well bore, and then go in the hole with a spear or overshot. Since the joint that unscrewed bears no relation to the location where the string is stuck, the probability is that the string will have to be milled up or the well plugged. Either of these alterna tives is expensive and under many circumstances is enormously so. The disastrous results of this situation are substantially duplicated if the cement sets up when the connection between the sub and the tubular string is below ground level.

Another disadvantage which is not quite so severe but still substantial occurs when the tubular string is stuck or the cement sets up and the connection between the sub and the tubular string is below the top of the blowout preventer. In this event, the blowout preventer could presumably be cut off with an acetylene torch and a makeshift table fabricated to receive casing slips and thereby suspend the casing in order to break 7 the joint between the sub and the tubular string. It will curring tremendous expense. Since the odds of this happening are small, it will be readily apparent that no serious consideration is given to simultaneously rotating and reciprocating a tubular string while cementing by using the Kelly.

The second approach discussed in conversation but which is not known to applicant'to be within the purview of the prior art, is to rotate the casing string with a set of power casing tongs while reciprocating the casing string with the drawworks. In this situation, the casing is run into the well bore, the casing slips are set in the rotary table, the casing tongs are attached to that part of the casing string extending above the rotary table, a cementing head is attached to the tubular string, the elevators are attached to the casing string, the casing tongs are tied off against a leg of the derrick the easing slips are removed from the rotary table, and the easing string is rotated with the casing tongs while the string is reciprocated with the drawworks. This ap proach avoids sticking the casing or setting up the cement and not being able to attach suitable fishing tools to the casing string. One prime disadvantage of this approach is that the casing string can be reciprocated through a stroke of less than about three feet since the tie-off to the derrick leg allows only very limited reciprocating travel. Another prime disadvantage of this approach is that power casing tongs presently available are incapable of applying substantial torque to the casing string at substantial rotational speeds. In other words, this approach does not allow the tubular string to be rotated fast enough nor reciprocated through av sufficient stroke to scratch the bore hole wall to any extent. Thus, this approach is less satisfactory than either solely reciprocating the tubular string with the drawworks or solely rotating the string with the rotary table. Accordingly, no serious consideration has been given this approach for cementing a tubular string in a well bore.

SUMMARY OF THE INVENTION It is an object of this invention to provide a cementing technique and apparatus for simultaneously rotating and reciprocating a tubular string in a well bore and passing a cementing slurry into the well bore.

Another object of this invention is to provide a cementing technique and apparatus for simultaneously rotating and reciprocating a tubular string while maintaining the rotating tool above the derrick floor and passing a cementing slurry into the well bore.

In summary, the cementing method of this invention comprises rotating a tubular string; reciprocating the string up and down for a stroke of at least feet while rotating the string and maintaining the tool above the floor; and passing a cementing slurry into the well bore during rotation and reciprocation of the string.

In summary, the apparatus of this invention comprises swivel means having a stationary portion including a fluid inlet and means for attaching the swivel means to hoist means for raising and lowering the apparatus, and a rotatable portion including a fluid outlet in communication with the fluid inlet; a power sub having a conduit and means for rotating the conduit; and a cementing sub comprising a conduit and means for launching at least one cementing plug into the tubular string, the power sub conduit and the cementing sub conduit being in torque transmitting relation and in fluid transmitting relation between the swivel fluid outlet and the tubular string.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is illustrated a drilling rig 10 comprising a floor 12 elevated above a ground surface 14 by a structure 16. The drilling rig 10 includes a rotary table 18, a derrick (not shown), a drawworks (not shown) and other typical equipment. A bore hole 20 is illustrated as extending into the earth and penetrating a formation 22. A tubular string 24 is illustrated as extending into the bore hole 20 and is comprised of a plurality of joints of pipe of any desired size. In a conventional manner, the tubular string 24 carries a plurality of scratchers 26, a cementing shoe 28 and such other cementing equipment, for example centralizers, float equipment and the like, as may be desired during the cementing of the string 24 in the bore hole 20.

As mentioned previously, it is highly desirable to simultaneously reciprocate and rotate the string 24 during cementing. To this end there is provided equipment 30 comprising as major components a swivel unit 32, a rotating tool 34 and a cementing sub 36. The swivel unit 32 is illustrated as suspended from elevators 38 which areconnected by bails 40 to the traveling block (not shown) and drawworks (not shown) which are customarily part of the drilling rig 10; In summary, the equipment 30 accomplishes simultaneous rotation and reciprocation of the string 24 by energizing the rotating tool 34 simultaneously with raising and lowering of the elevators 38.

Referring to FIG. 2, the swivel unit 32 is illustrated in greater detail. The swivel unit may be any desired type and is illustrated as a fishing tool swivel manufactured by Texas Iron Works of Houston, Texas. The swivel unit 32 comprises a stationary portion 42 and a rotatable portion 44. The stationary portion 42 is illustrated as comprising a solid shank 46 having a shoulder 48 thereon received in the elevators 38. The shank 48 is conveniently threaded into the top of a sleeve 50 which also comprises part of the stationary portion 42. The sleeve 50 includes a fluid inlet 52, a fluid passage 54 for transmitting liquids or slurries pumped into the well bore 20 during the course of operation.

The rotatable portion 24 is conveniently made in two

parts

56, 58 which are threaded together. Suitable bearings 60 mount the portion 44 for rotation about the centerline of the swivel 32.

Suitable seals

62, 64 and

grease fittings

66, 68 may be provided as desired as will be recognized by those skilled in the art. The part 58 comprises a fluid outlet 70 in communication with the fluid inlet 52 and also provides a threaded connection 72 for securement to the rotating tool 34.

The rotating tool 34 may be of any desired type so long as it has operating characteristics commensurate with its desired functions. As will be more fully apparent hereinafter, the rotating tool 34 transmits liquids or slurries pumped into the swivel unit 32 to the cementing sub 36, allows reciprocation of the equipment 30 through a stroke of at least feet and rotates the string 26 at desired torque and speed levels. The desired torque level is, of course, less than the collapse strength of the screw couplings which connect the joints of the string 24 together. In a prototype of the invention which has operated satisfactorily, the rotating tool 34 comprised a power sub manufactured by Bowen Tools, Inc., Houston, Texas. This particular device is described in an instruction manual printed December, 1965. As reported on page 23 of this manual, the maximum torque of such devices is 6,000 foot pounds.

The rotating tool 34 is illustrated as comprising a conduit 74 attached at the upper end thereof to the threaded connection 72 and at the lower end therof to the cementing sub 36. A housing 76 encloses a gear wheel operatively connected to the conduit 74 and driven by a hydraulic motor 78. The housing 76 includes a bracket 80 apertured to receive astationary guide 82 therethrough. It will be seen that the rotating tool 34 is constrained for vertical movement by the guide 82 which actsto ensure that the conduit 74 is rotated rather than the housing 76. The motor 78 is provided with

suitable hydrauliclines

84, 86 for delivering and returning power fluid from the motor 78 to a suitable pump (not shown). Suitable controls and pressure gauges are provided as desired. As will be apparent to those skilled in the art, pressure readings from the

lines

84, 86 may be used to determine the torque and speed delivered by the motor- 78.

The cementing sub 36 may be of any suitable type and is illustrated in F IG. 3 as comprising a coupling 88 connected to the conduit 74, a bypass manifold 90, a conduit 92 connected to the coupling 88 at one end thereof and to a coupling 94 at the other end thereof.

Suitable valves

96, 98, 100 are provided to deliver fluid from the manifold 90 to selected locations along the conduit 92. Cement plug

gates

102, 104 are provided for delivering at least one and preferably at least two cementing plugs into the string 24.

During the cementing process, a clean drilling mud slurry is initially circulated through the well bore by closing the

valves

98, 100 and opening the valve 96. It will be seen that the clean drilling mud passes through the cementing sub 36 without disturbing the cement plugs 106, 108 respectively positioned above the

gates

102, 104. When it is desired to commence delivery of cement into the string 24, cement is pumped into the fluid inlet 52 while the valve 96 is closed, the valve 98 is opened and the cement plug gate 102 is open. It will be seen that cement passes through the swivel unit 32, the bypass manifold 90, the valve 98 and the conduit 92 to force the cement plug 106 from its resting position above the gate 102 into the tubular string 24. When the desired column of cement has been injected into thetubular string 24, drilling mud is again pumped into the fluid inlet 52, the valve 98 is closed, the valve 100 is opened and the cement plug gate 104 is opened. It will be seen that drilling mud will pass through the swivelunit 32, the bypass manifold90, the valve 100 and the conduit 92 to force the cementing plug 108 downwardly into the tubular string 24. As the cementing plug 108 reaches the cement shoe 28, the fluid passage therethrough is closed and no further liquid can be injected into the well bore 20.

It will be apparent that the swivel unit 32 provides an attachment to the hoist means of the drilling rig 10, provides for the injection of drilling mud and cement slurry into the well bore 20 and allows rotation of the components suspended therefrom. The rotating tool 34 causes rotation of the string 24 and does not interfere with reciprocation of the string 24 throughout a stroke of substantial length. The cementing sub 36 provides for the launching of one or more cementing plugs.

In operation, the tubular string 24 is run through the rotary table 18 into the well bore 20 in a conventional manner. After the last joint comprising the string 24 is run into the well bore 20, the cementing sub 36 is attached thereto. The rotating tool 34 is then threaded into the top of the cementing sub 36 and the threaded connection between the swivel 32 and' the rotating tool 34 is made up. The guide 82 is operatively connected to the bracket and a suitable flexible hose is connected to the fluid inlet 52. The mechanism 30 is accordingly ready to commence simultaneous rotation and reciprocation of the string 24.

To reciprocate the string 42, the driller manipulates the drawworks in a conventional manner to raise the elevators 38 and thereby raise the string 24. Power hydraulic fluid is delivered through the line 84 to drive the motor 78 and thereby rotate the string 24. Reciprocation of the string 24 for a stroke less than about 10 feet'is not contemplated. Accordingly, the driller continues to raise the elevators 38 until the desired stroke is achieved. By slacking off on the drawworks brake, the weight of the string 24 causes the string 24 and the equipment 30 to fall into the well bore 20. The rate of descent of the equipment 30 is controlled by the drawworks brake in a conventional manner. Rotating and reciprocating the string 24 in this fashion causes the scratchers 26 to abrade the wall of the bore hole 20 and thereby remove cuttings embedded in the bore hole wall, excess filter cake and the like. During initial rotation and reciprocation, clean drilling fluid is pumped into the inlet 52, down the string 24, through the cementing shoe 28 and upwardly through the annulus and is returned to the mudpits in a conventional manner.

After the bore hole 20 has been scratched for some time, the decision is made that the bore hole 20 has been conditioned sufficiently for cementing. Rotating and reciprocation of the string 24 is temporarily halted in order to close the valve 96, open the valve 98 and open the cement plug gate 102. The cementing trucks then connect to the flexible hose attached to the fluid inlet 52 and commence pumping a cementing slurry into the equipment 30. contemporaneously with the delivery of cementing slurry into the string 24, rotation and reciprocation of the string 24 is commenced. When sufficient cementing slurry has been introduced into the string 24, rotation and reciprocation of the equipment 30 is temporarily halted, the valve 98 is closed, the valve is opened, the cementing plug gate 104 is opened and connections are made to pump drilling mud into the fluid inlet 92. Rotation and reciprocation of the string 24 is again commenced and drilling mud is pumped into the inlet 52.

When the first cementing plug 106 comes to rest in the cementing shoe 28, larger ports are usually opened therein and cementing slurry passes into the annulus defined between the well bore 20 and the casing string 24. Pumping of drilling mud through the inlet 52 continues until the second cementing plug 108 contacts the cementing shoe 28. Flow through the cementing shoe 28 is thereupon halted and upward travel of the cementing slurry through the annulus ceases. Rotation and reciprocation of the string 24 continues and results in substantially uniform dispersion of the cementing slurry throughout the bottom part of the annulus.

Rotating and reciprocating the casing string 24 after the second cementing plug 108 is down causes kneading or working of the cement in the annulus to ensure that the cement completely fills the annulus from the bottom of the well bore 20 to a predetermined level above the formation 22. It will be appreciated that the well bore 20 may have washouts or enlargements that need to be completely filled with cement. Rotation of the string 24 aids in complete dispersion of the cement since the scratchers 26 and the centralizers (not shown) act to some extent as paddles. Simultaneous reciprocation of the string 24 acts to some extent-as a plunger to propel cementing slurry laterally into washouts and the like.

It is well known in the art that a typical hole is not plumb or perpendicular to the ground surface 14 but instead meanders downwardly into the earth and often assumes a generally corkscrew shape trace. This is illustrated in exaggerated fashion in P16. 4. The typical manner in which casing is rotated is to maintain the string 24 in tension during rotation. In this circumstance, the string'24 tends to reside along the centerline 110 of the bore hole. Since the string 24 tends to be generally centrally in the bore hole 20, particularly under the influence of conventional centralizers, rota- -tion ofthe string 24 is not a particularly efficient means of churning the cement in the annulus.

in contrast to this conventional technique, the elevators 38 may be lowered so that at least a substantial part of the weight of the string 24 is borne by the cementing shoe 28 and by frictional engagement of the string 24 with the bore hole wall. This condition is illustrated in FIG. 4 where the string 24 is offset with respect to the bore hole centerline 110. Since the casing string 24 is offset, rotation thereof churns the cement in the annulus to a substantially greater extent than the conventional approach.

Since the cementing shoe 28 is carrying a load in the situation shown in FIG. 4, it is highly desirable to provide a swivel 112 above the cementing shoe 28 to allow relative rotation between the string 24 and the shoe 28. The provision of the swivel 112 substantially reduces the possibility of twisting the string 24 off at the bottom thereof.

1 claim:

l. A method of cementing a tubular string, comprised of a plurality of threadably connected joints having thereon means for frictionally engaging a bore hole wall, in a well bore from the floor of a rig with a tool including a hydraulic torque applier and means for controlling the applier for varying the torque output of the tool, the method comprising the steps of rotating the tubular string with the tool;

manipulating the control means for controlling the torque output of the tool so that the torque output thereof can never exceed the strength of the joint couplings;

reciprocating the string up and down for a stroke of at least ten feet while rotating the string and maintaining the tool above the floor; and

passing a cementing slurry into the well bore during rotation and reciprocation of the string.

2. The method of claim 1 wherein the reciprocating step comprises alternately pulling upwardly on the string while rotating the same and allowing the string to move downwardly while rotating the same.

3. The method of claim 1 further comprising the steps of simultaneously rotating the reciprocating the string after delivery of cementing slurry into the well bore.

4. A method of cementing a tubular string, comprised of a plurality of threadably connected joints having thereon means for frictionally engaging a bore hole wall, in a well bore from the floor of a drilling rig spaced above an underlying surface, the method comprising the steps of running the tubular string through a table on the rig into the well bore;

attaching onto the upper end of the string a tool ineluding a hydraulic torque applier for rotating the string during reciprocation thereof and means for controlling the hydraulic torque applier for varying the torque output of the tool;

rotating the tubular string with the tools;

manipulating the control means for controlling the torque output of the tool so that the torque output thereof can never exceed 6,000 foot pounds;

reciprocating the tubular string up and down for a stroke sufficient to reciprocate the lower string end while rotating the string, the lowermost point of travel of the tool being above the table; and passing a cementing slurry into the well bore.

5. A method of cementing a tubular string in a larger bore hole comprising the steps of delivering cementing slurry into a bottom part of the annulus between the string and the well bore; placing the string in compression; and

rotating the tubular string and maintaining the same in compression while cementing slurry is in the annulus. 6. The method of claim 5 further comprising the step of installing a swivel in the tubular string adjacent the lower end thereof and wherein the placing step comprises the steps of suspending the string in a well bore with hoist means; manipulating the hoist means to place the lower string end on the bottom of the well bore; and

manipulating the hoist means to insufficiently support the string therefrom thereby immobilizing the lower end of the string below the swivel and placing the string off center in the well bore.

7. A method of cementing a tubular string, comprised of a plurality of threadably connected joints having thereon means for frictionally engaging a bore hole wall, in a well bore from the floor of a rig with a tool including a torque applier and means for controlling the torque applier for varying the torque output of the tool, the method comprising the steps of running the tubular string into the well bore;

placing a cementing slurry into the well bore;

rotating the tubular string with the tool;

manipulating the control means for controlling the torque output of the tool so that the torque output thereof can never exceed 6,000 foot pounds; and

running the tubular string into the well bore; immobilizing the lower end of the string below the swivel;

rotating the tubular string with the tool;

passing a cementing slurry into the well bore; and rotating the upper end of the string after the delivery of cementing slurry into the well bore.

* i I k

Claims

1. A method of cementing a tubular string, comprised of a plurality of threadably connected joints having thereon means for frictionally engaging a bore hole wall, in a well bore from the floor of a rig with a tool including a hydraulic torque applier and means for controlling the applier for varying the torque output of the tool, the method comprising the steps of rotating the tubular string with the tool; manipulating the control means for controlling the torque output of the tool so that the torque output thereof can never exceed the strength of the joint couplings; reciprocating the string up and down for a stroke of at least ten feet while rotating the string and maintaining the tool above the floor; and passing a cementing slurry into the well bore during rotation and reciprocation of the string.

4. A method of cementing a tubular string, comprised of a plurality of threadably connected joints having thereon means for frictionally engaging a bore hole wall, in a well bore from the floor of a drilling rig spaced above an underlying surface, the method comprising the steps of running the tubular string through a table on the rig into the well bore; attaching onto the upper end of the string a tool including a hydraulic torque applier for rotating the string during reciprocation thereof and means for controlling the hydraulic torque applier for varying the torque output of the tool; rotating the tubular string with the tools; manipulating the control means for controlling the torque output of the tool so that the torque output thereof can never exceed 6,000 foot pounds; reciprocating the tubular string up and down for a stroke sufficient to reciprocate the lower string end while rotating the string, the lowermost point of travel of the tool being above the table; and passing a cementing slurry into the well bore.

5. A method of cementing a tubular string in a larger bore hole comprising the steps of delivering cementing slurry into a bottom part of the annulus between the string and the well bore; placing the string in compression; and rotating the tubular string and maintaining the same in compression while cementing slurry is in the annulus.

6. The method of claim 5 further comprising the step of installing a swivel in the tubular string adjacent the lower end thereof and wherein the placing step comprises the steps of suspending the string in a well bore with hoist means; manipulating the hoist means to place the lower string end on the bottom of the well bore; and manipulating the hoist means to insufficiently support the string therefrom thereby immobilizing the lower end of the string below the swivel and Placing the string off center in the well bore.

7. A method of cementing a tubular string, comprised of a plurality of threadably connected joints having thereon means for frictionally engaging a bore hole wall, in a well bore from the floor of a rig with a tool including a torque applier and means for controlling the torque applier for varying the torque output of the tool, the method comprising the steps of running the tubular string into the well bore; placing a cementing slurry into the well bore; rotating the tubular string with the tool; manipulating the control means for controlling the torque output of the tool so that the torque output thereof can never exceed 6,000 foot pounds; and reciprocating the string up and down for a stroke of at least ten feet while rotating the string and maintaining the tool above the floor.

8. A method of cementing a tubular string in a well bore from the floor of a rig with a tool comprising the steps of installing a swivel in the tubular string adjacent the lower end thereof; running the tubular string into the well bore; immobilizing the lower end of the string below the swivel; rotating the tubular string with the tool; passing a cementing slurry into the well bore; and rotating the upper end of the string after the delivery of cementing slurry into the well bore.