Apparatus For Cementing Well Bore Casing

Abstract

There is disclosed an 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.

Parent Case Text

This application is a division of Application Ser. No. 251,191, filed May 8, 1972, now U.S. Pat. No. 3,777,819.

Description

BACKGROUND OF THE INVENTION

In the art of cementing tubular strings in well bores, it is well known to affix scratchers and centralizers to the tubular string in order to abrade the bore hole wall and position the string generally in the center of the bore hole. Scratchers are commercially available in various designs and are of two basic types. The first type is an elongate scratcher which is affixed longitudinally of the tubing string so that rotation of the string causes the scratching elements to abrade the bore hole wall. The other type scratcher is circular and of limited extent in the longitudinal direction of the tubular string. This type scratcher requires reciprocation of the tubular string to abrade the bore hole wall.

The general practice of cementing is to scratch the bore hole wall while circulating clean drilling mud through the hole to remove loose shale particles, excessive mud filter cake and the like from the bore hole wall. After the hole has been circulated for a desired length of time, usually on the order of about 2 to 10 hours, cement is pumped downwardly through the tubular string. The cement exits through a cementing shoe on the bottom of the tubular string and passes upwardly into the annulus between the tubular string and the bore hole wall. Scratching of the bore hole wall generally continues during the placement of cement. Scratching the bore hole wall during placement of the cement aids chiefly in agitating the cement and assuring a generally uniform placement thereof in the annulus. It is accordingly widely practiced to rotate or reciprocate a tubular string while pumping a cement slurry into the well bore.

It has been disclosed in the prior art to "rotate and/or reciprocate" a tubular string during cement as in U.S. Pat. Nos. 2,609,881 and 2,675,082. Upon analysis, the hardware illustrated in these patents allows sequential rotation and reciprocation and is incapable of simultaneous rotation and reciprocation. For example, in U.S. Pat. No. 2,609,881, the tubular string 16 passes through a conventional rotary table 18 and is presumably suspended from a conventional traveling 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 slips received in the top of the rotary table 18. Conventional casing slips are generally wedge-shaped segments of an annulus and are received in a beveled opening in the top 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, that conventional casing slips do not provide a torque transmitting connection unless the weight of the casing string loads the slips against the rotary table. It is accordingly abundantly apparent that the casing string 16 of Warren cannot be rotated as the string 16 is raised since the torque transmitting connection through the rotary table is inoperative. In would appear, at first blush, that the casing slips would transmit rotation to 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 suspended from the rotary and is immobile. The apparatus disclosed in U.S. Pat. No. 2,675,082 is substantially identical and is incapable of simultaneously rotating and reciprocating the tubular string disclosed therein.

In the published prior art of which applicant is aware, there is no disclosure of an approach for simultaneously 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 applicant is not the invention 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 the Kelly to the sub, remove the casing slips and rotary 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. This 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 below ground level when the tubular string sticks, it is impossible 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 be done 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 alternatives 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 makeshaft table fabricated to receive casing slips and thereby suspend the casing in order to break the joint between the sub and the tubular string. It will be appreciated that this can cost many thousands of dollars and leave a very dangerous situation if the well formations are not cemented.

Since the top of the blowout preventer is normally within a few feet of the bottom of the drilling floor, the odds of the casing sticking or the cement setting up when the sub is above the top of the blowout preventer is small. In this event, the casing slips could probably be set in the top of the blowout preventer without incurring 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 casing slips are removed from the rotary table, and the casing string is rotated with the casing tongs while the string is reciprocated with the drawworks. This approach 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 3 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 a 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 soley 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 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 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 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, a torque applier for applying torque to the conduit for rotating the same and means for controlling the torque output of the torque applier; 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

FIG. 1 is a cross section of a portion of a bore hole and drilling rig illustrating the apparatus of this invention;

FIG. 2 is a side elevational view, partly in section, of the swivel illustrated in FIG. 1;

FIG. 3 is a side elevational view, partly in section, illustrating the cementing sub shown in FIG. 1; and

FIG. 4 is a cross sectional view of a portion of a bore hole.

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 substructure 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 are connected 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, Tex. 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 24 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 54.

The rotating tool 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 ten 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 comprises a power sub manufactured by Bowen Tools, Inc., Houston, Tex. This particular device is described in an instruction manual printed December, 1955. 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 a threaded connection 72 conduit 74 and driven by a hydraulic motor 78. The housing 76 includes a bracket 80 apertured to receive a stationary guide 82 therethrough. It will be seen that the rotating tool 34 is constrained for vertical movement by the guide 82 which acts to ensure that the conduit 74 is rotated rather than the housing 76. The motor 78 is provided with suitable hydraulic lines 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 FIG. 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 delivery 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 the tubular 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 swivel unit 32, the bypass manifold 90, 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 80 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 100 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 20 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 FIG. 4. The typical manner in which casing is rotated is to maintain the string 24 in tension during rotation. In this circumstances, 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, rotation of the 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.

Claims

I claim:

1. Apparatus for cementing a tubular string in a well bore comprising

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, a torque applier for applying torque to the conduit and thereby rotating the same, and means for controlling the torque output of the torque applier; 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.

2. The apparatus of claim 1 wherein the power sub conduit is connected in fluid transmitting relation with the swivel fluid outlet and the cementing sub conduit is connected at one end thereof to the power sub conduit and provides means at the other end thereof for securement to the tubular string. 61

3. The apparatus of claim 1 wherein the swivel means defines an axis of rotation, the power sub conduit and the cementing sub conduit being substantially co-axial with the axis of rotation.

4. The apparatus of claim 1 wherein the controlling means includes means for controlling the torque output throughout a range of 0-6,000 foot pounds.