US 3239005 A
Description (OCR text may contain errors)
March 1966 A. G. BODINE, JR
METHOD OF MOLDING WELL LINERS AND THE LIKE Filed Jan. 28, 1964 I v Q United States Patent 3,239,005 METHOD OF MOLDING WELL LINERS AND THE LIKE Albert G. Bodine, Jr., Los Angeles, Calif. (7877 Woodiey Ave., Van Nuys, Calif.) Filed Jan. 28, 1964, Ser. No. 340,745 11 Claims. (Cl. 166-23) The present invention employs apparatus of a type disclosed in my co-pending application Serial No. 98,801, filed Mar. 28, 1961, now Patent No. 3,130,552 entitled Method and Apparatus for Creating a Load Bearing Region in Earthen Material, and is a continuation-in-part of said application.
This invention relates generally to the art of molding longitudinally extended forms from fluent materials which set and harden upon standing, such as concrete, and certain plastics, and more particularly, and in an illustrative application, to methods of molding from such materials a tubular well casing, or other products to which the invention may be applicable. The invention involves and is characterized by the use, with a forming mold, in a slip form process, of sonic vibration of the mold, or at the interface between the mold and the molded product, to prevent adhesion between the set material and the mold.
An object of the present invention is the provision of an improved process for forming such representative products as a concrete or cement liner or casing for a well.
The invention, in an illustrative application to wells, and the lining thereof with a cement casing, employs an elongated stem or mandrel, which is inserted into the ground, either in a previously prepared bore hole, or by setting up in the mandrel longitudinal standing wave vibrations, which causes the mandrel to sink into the soil by a self-driving vibratory action. This stern has a longitudinal feed bore therethrough, through which a cement slurry, for example, may be fed and discharged into the earth bore at the lower end of the latter. The mandrel is elevated a short distance from the bottom of the earth bore, whether preliminarily bored, or formed by self-driving, to give room for the discharge of the cement. Also, particularly in the case of preliminarily boring, the earth bore is made somewhat larger in diameter than the outside diameter of the mandrel, so as to afford good space for the formation of a cement wall between the outside of the mandrel and the inside of the well bore.
With the mandrel in position in the bore hole, a longitudinal sonic standing wave vibration is set up in the mandrel by means of a sonic vibration generator coupled to the upper end thereof, and the cement slurry is fed to the upper end of the feed passage in the mandrel, and is discharged from the lower end thereof into the bottom of the bore hole. This injected material first fills in the space between the mandrel and the bottom of the bore hole, and then rises in the annulus between the mandrel and the defining surface of the bore hole until ground level is reached. The injected slurry is cyclically driven against the walls of the bore hole by the sonic wave vibration of the mandrel as sonic waves are radiated from the mandrel, and transmitted through the injected cement to the surrounding soil. This sonic wave action results in compaction of the cement, and also an impacting action of the cement against the soil. The cement slurry is thereby highly compacted, and helps match the moderate impedance of the surrounding soil to the higher impedance of the mandrel, so that a considerable degree of sound wave transmission takes place from the vibratory mandrel through the slurry and into the soil. The effect of the sonic waves so transmitted to and into the soil is to fluidize it and impart to it a quality of mobility, and the injected cement slurry, under the sonic Wave and vibration conditions established, is cyclically driven against the thusfluidized soil and drives the soil back and compacts it. Thus voids within the original soil structure are filled by the fluidized soil and by penetrating cement slurry, and a general consolidation and compaction is accomplished. A tubular cement liner for the well bore is thus formed which extends from the bottom of the bore to the ground surface. The vibratory standing wave action in the mandrel imparts, by virtue of a shear coupling effect, a sonic vibration to the cement thus formed into the shape and position of a tubular liner or casing surrounding the mandrel, thus promoting compaction all the way to the ground surface. The cement slurry, under sonic vibration drive as described, tends to penetrate or finger its way into the surrounding soil, filling voids therein, contributing to further compaction, and eventually, after setting and hardening, forming keys with or into the soil.
The above described highly effective fiuidizing action apparently is due to the mandrel undergoing sonic elastic vibrations with the unique sonic property of having vibratory mass reactance substantially neutralized by the elastic compliance reactance of the mandrel. This means then that the earthen material functions primar ily as a resistive impedance since the earth does not have to provide reactance provided by this mandrel action. Therefore, the individual particles making up the adjacent earthen material do not tend to vibrate reactively in unison, but rather vibrate more randomly relative to each other, and thus become very fluid and adaptive near the mandrel. This sonic system provides a unique action in the introduced material, and in the adjacent soil into which the material is introduced, even in firm earth structure.
The sonic vibration of the mandrel is continued while the material sets and hardens, thereby preventing adhesion of the cement to the mandrel as the cement sets up. The cement is thus allowed to set up while the mandrel is still in the well, so as to form the internal bore of the well.
As indicated above, the sonic vibratory action causes the cement or concrete to compact and become very dense and free of voids and cracks. This makes possible the formation of a liquid-tight liner or casing for the well. It is of course of essential importance, and a feature of the invention, that the mandrel be vibrated while the cement or concrete is setting up, so as to prevent adhesion between the two and thus to permit easy retrieval of the mandrel after the cement has set. The continued sonic vibratory action as the cement is setting up thus prevents the otherwise tight adhesive contact between the cement and the mandrel at the interface between the two, and in place of such a condition, there will exist at the interface, after setting up and hardening, a soft, crumbly or chalky layer of material between the mandrel and the cement. This very weak layer offers no material frictional resistance to withdrawal of the mandrel, and any interfering portions of the layer readily fail and permit easy withdrawal of the mandrel. However, the withdrawal of the mandrel can be still further facilitated by setting up a degree of longitudinal vibration thereof during the withdrawing procedure, and such is a further but optional feature of the invention.
It will of course be understood that, in case the casing is to become a water or oil well, the lower end portion of the casing may be opened to the surrounding productive formation by any perforating techniques common to the well industry, such as gun perforating for example.
It has been mentioned above that the mandrel may be driven into the ground by its own vibratory action, without making a preliminary bore hole. The principles by which this may be accomplished are taught in my prior Patent No. 2,975,846. In this case, the cement slurry has to 'be forced up between the mandrel and the wall surface of the surrounding soil. This can be accomplished by suitable pressure on the cement slurry, aiding by the driving effect of the sonic vibrations radiated from the vibratory mandrel and transmitted through the slurry. In addition, or alternatively, a loose cap piece, of larger diameter than the mandrel, can be driven down by the bottom of the mandrel, so as to enlarge the hole around the mandrel. Such a cap piece can be frictionally fitted onto the lower end of the mandrel, and may subsequently be disengaged by elevating the mandrel from the bottom of the hole, and setting it into its vibratory action.
The invention will be more fully understood from the following detailed description of an illustrative embodiment thereof, reference for this purpose being had to the accompanying drawings, in which:
FIG. 1 is a longitudinal sectional view showing an apparatus in accordance with the invention, in course of forming a well casing;
FIG. 2 is a view taken in accordance with line 2-2 of FIG. 1;
FIG. 3 is a detail section taken on line 33 of FIG. 1; and
FIG. 4 is a view similar to the lower end portion of FIG. 1, but showing a modification.
In the drawings, numeral designates generally an earth bore which has been made in the ground, using any suitable boring apparatus. In an alternative procedure, referred to hereinafter, the earth bore may be made by simply driving the mandrel to be presently described into the earth, though in such case the bore may be of 21 normal diameter substantially that of the bottom of the mandrel itself, as will later become understood, unless some enlarged 'head or cap piece is placed on the bottom of the mandrel.
Numeral 11 designates generally a tubular elastic injector stem or mandrel, composed of a good elastic material such as steel, and which has been lowered into bore 10. The mandrel is preferably of somewhat smaller diameter than the bore 10 so as to leave an annulus space of good thickness to be filled with the cement casing to be formed. The mandrel 11 may be of considerable length, and wherever the depth of the well to be cased is so great that a single-piece mandrel would be impracticable, the mandrel may be made up in a number of sections screwthreadedly joined to one another as will be understood without necessity of illustration herein.
A central feed bore 12 extends longitudinally through mandrel 11, and mounted therein are one or more check valves 13, arranged to pass fluid in a downward direction. As here shown, each check valve comprises a valve ball 14 adapted to seat upwardly on a seat ring 15 and confined by suitable cage means, here in the form of a cross pin 16 fitted across valve sleeve 17.
A material feed hose 20 is coupled to the upper end of mandrel 11, so as to feed the bore 12, and will be understood to lead from a suitable source of fluid material, such as a materials pump, not shown.
Near its upper end, mandrel 11 is provided with an external piston 22, which works in an air cylinder 23, having a bottom wall 24 slidably surrounding and pressure sealed, as at 25, to the mandrel 11. The piston 22 is airsealed to cylinder 23, as at 26. The cylinder space 27 below piston 22 is supplied with air under pressure via an air hose 28. The air pressure maintained in space 27 is sufiicient to act as an air spring for support of the mandrel 11 and auxiliary equipment connected thereto.
Cylinder 23 has a pair of eyes 30 suspended through links 31 from the arms of a hanger 32 hung, in turn, by means of a cable 33, from any suitable lowering and hoisting gear such as is conventionally used in connection with derricks, cranes, etc., not shown.
A sonic wave generator 40 is coupled to the upper end of the mandrel 11. In this instance, the generator 40 is in two parts 40a and 40b secured rigidly against opposite sides of the upper end of the mandrel 11 by bolts 41. It will be understood that these parts 40a and 40b co-act through the upper end of mandrel 11 so as to act as a unitary wave generator. The type of wave generator used and its operation are disclosed in my prior Patent No. 2,960,314. Each of members 40a and 40b comprises a housing embodying a cylindrical wall 44 forming a circular raceway 45. Two side plates 48 engage opposite edges of each circular side wall 44, and form with wall 44 a cylindrical chamber in which is confined a generally cylindrical inertia rotor 49. The rotor 49 is of a diameter substantially smaller than that of the raceway 45, and is adapted to roll therearound in an orbital path, exerting a centrifugal force on the wall 44. The rotor 49 is driven in this fashion by a jet of air under pressure introduced tangentially of the raceway via a nozzle bore 54] supplied by pressure air hose 51. Spent air escapes via ports 54 in side plates 48.
It will be seen from FIG. 1 that the two inertia rotors are driven in opposite directions of rotation. As will presently be described, the two rotors are phased to run in synchronism with one another. That is to say, they are always at corresponding points of their respective orbital paths. Thus they move up and down together and, by virtue of their opposite directions of orbital motion, they move laterally in opposition to one another. Accordingly, the vertical components of the force exerted by the rotors on the generator housings, and thence on the mandrel 11, are in phase and additive; while the horizontal force components are equal and opposite and cancel. The air pressure driving the rotors is made such that the number of circuits per second taken by the rotors around their raceways is in the range of the resonant frequency of the mandrel 11 for a mode of longitudinal standing wave vibration of the mandrel, usually the halfwavelength mode. Assuming the half-wavelength mode, a standing Wave is characterized by the two half-length portions of the mandrel alternately elastically elongating and contracting with the mid-point of the mandrel experiencing a velocity node or pseudo-node of the standing wave, i.e., having minimum vibration amplitude, and the two end portions experiencing velocity antinodes, i.e., vibrating in directions longitudinal of the rod at maximum amplitude.
At first, the two rotors 49 have random phase relations. Very shortly, they chance to come into such phase relations as to cooperate, or be additive, to a degree in vertical motion (longitudinally of the rod). When that occurs, a component of vertically oscillating force is exerted on the generator housing, and therefore on the upper end of mandrel 11, and if the frequency is in the range of fundamental resonance, the mandrel will vibrate, possibly only feebly at first, in an approximation to the desired half-wave standing wave mode. Once this process is started, the resonantly vibrating mandrel tends to vibrate at a frequency just under peak resonance frequency for the mandrel; and this controlled vibration of the mandrel back-reacts on the rotors to hold them both at the frequency of vibration of the mandrel, and to bring them into synchronism with each other. As they synchonize, the amplitude of the standing wave increases to maximum.
Operation is as follows: The bore 10 is formed in the ground, as by use of any suitable earth boring apparatus. The mandrel 11 is then lowered into this bore, in a centralized position therein, to a position a short distance above the lower end of the bore, as shown in example in FIG. 1. A pump, not shown, preferably a continuous flow pump, is connected on its intake side to a source of cement slurry, and on its discharge side to feed hose 20, and pressurized air is delivered through hose 51 to sonic wave generator 40, with pressure regulated so as to drive the generator at a frequency setting mandrel 11 into resonant half-wave standing wave vibration as earlier explained.
The check valves 13 in the bore 12 of vibrating mandrel 11 then act to pump the cement slurry downwardly through said bore 12 to be discharged at the lower end of mandrel 11 into the lower end portion of earth bore 10. The pumping action occurs in accordance with a sonic pumping process disclosed in my Patent No. 2,444,- 912, the only difference being that in the patent, the check valves open upwardly, and the liquid is pumped upwardly. Here, the check valves open downwardly, and pumping is in the downward direction. Briefly, on each upward movement of a check valve ball seat ring, fluid immediately above the ring is displaced by the latter, and moves through the ring by momentary suction from below the ring owing to the elevation of the ring. The ball is at this time unseated. In other words, a void created below the ring as the ring rises is filled with fluid owing to fluid above the ring being displaced by the ring. Gn the downstroke, the ring, moving with an acceleration greater than gravity, seats against the check valve ball, and the fluid is propelled downwardly. Springs, not shown, may be used to bias the check valve balls to seat normally on the seat rings.
The cement slurry thus pumped down through mandrel 11 fills in the bore below the mandrel, as at 60, and rises in the annulus between the mandrel and the wall of the bore hole, finally filling in the latter to the ground surface to provide the tubular liner 61, as illustrated in FIG. 1. The portions of the vibrating mandrel 11 contacting the injected body 60 of cement slurry underneath the mandrel and the inner surface of the tubular body of cement slurry 61 surrounding the mandrel 11 for the full length of the underground portion of the mandrel radiate sonic waves or vibrations which travel through the cement slurry to and into the surrounding soil. The cement slurry has an impedance intermediate that of the mandrel and that of the soil, and helps match the two for effective transmission of sonic energy from the mandrel through the slurry and into the soil.
It will be seen that the cement slurry is injected into the bore 10 in sonic frequency pulses. These pulses generate intermittent sonic or compressional waves which are transmitted through the cement slurry to the soil, and cause intermittent compactions of both slurry and soil which result in desirably densifying the cement and the surrounding soil. In addition, the piston-like action of the lower end of the mandrel operates, on each downstroke, to compact the slurry in the bore hole, to force it cyclically outward against the wall surfaces of the bore hole, and to pump the slurry up the annulus around the mandrel. The vibratory piston-like action of the lower end of the mandrel also radiates sonic vibrations which are transmitted around the lower end of the mandrel and up the tubular column of slurry around the mandrel, thus compacting this slurry, and, by ultimate transmission on into the soil, acts also to compact the soil. Still further, the standing wave vibration in the mandrel results in an acoustic shear coupling between the side surfaces of the mandrel and the cement slurry, by which acoustic vibrations are radiated into the slurry. This vibratory action will be seen to occur directly at the interface between the mandrel and the slurry.
The various sonic actions described'cooperate to compact the slurry, and to drive it cyclically against the soil, accompanied by transmission of sonic vibrations to and into the soil, with the effect of fluidizing and then compacting the soil as well as the slurry. The sonic action involves the additional effect of driving the slurry into the fluidized and compacting soil, so that the latter receives fingers or runners of the slurry, such as well illustrated in FIG. 1. These aid in anchoring the casing in the soil when the cement has set and hardened.
The mandrel is maintained in its condition of sonic standing wave vibration while the cement sets and hardens around it, and thereby the hardened cement liner or casing 61 is prevented from adhering to the mandrel, so that the latter can be readily removed from the casing.
The final step, after setting and hardening of the cement casing, is to elevate the mandrel therefrom by means of its hoisting equipment. FIG. 4 shows the mandrel hoisted a short distance oif bottom, leaving the cement casing or liner 61 in the bore hole. If desired, or necessary in any case, the process may include as a final step, the vibration of the mandrel, as before, though not necessarily to the same amplitude, while it is being elevated. This final step facilitates withdrawal of the mandrel by reducing surface friction with the casing.
The vibratory actions described while the casing is being formed, and while it is setting, compact and densify the cement so that the completed casing is very dense and free of voids and cracks. The well can be brought into production by any known or desired casing perforating operation, such as gun perforating.
One additional advantageous step is to sonically activate or vibrate the mandrel and lift it off bottom a short distance, after it has been driven to full depth, and the full amount of cement has been injected in the hole, and then to inject a quantity of water down the central bore so as to clean the cement out of the mandrel. There will then be a water filled cavity at the very bottom, as the cement is setting up. It is then unnecessary to clean the cement out of the bore of the mandrel after the well has been established, and the mandrel subsequently removed.
A further advantageous step is to fluctuate the pressure of the air entering the pipe 51 to drive the vibration generator, so as to cause a fluctuation in frequency. This can be accomplished by use, in line 61, of any cyclically operated throttle valve, unnecessary here to illustrate. Only a relatively small fluctuation in frequency need thereby be effected, but sufficient to cause a small amount of lateral vibration to appear in the mandrel along with the longitudinal vibration. This added lateral vibration further assures that the mandrel will remain loose in the cement as the cement is setting up. There are of course other known ways of modifying the sonic vibration generator, or its operation, so as to induce a degree of lateral vibration along with the longitudinal wave pattern, and any of these may be resorted to within the broad scope of the present invention to accomplish the effect described.
It is also to be understood that there are many materials in addition to cement or concrete which can be applied and utilized in the practice of the invention. Thus, plastics are now becoming known which are effective in forming surfaces and re-inforcing structures, and are suitable to the present purpose. Because of the efficiency of the sonic process, and because of the savings effected through its use, it becomes feasible to utilize some of the more expensive hardening agents now available for use with these materials.
It has been mentioned in the foregoing that the process may be practiced either by first forming a bore hole, and then lowering the mandrel therein, the mandrel being of a diameter to leave an annular spacing between its outer surface and the inside surface of the bore hole, so as to afford room for the casing which is to be constructed. It has also been described that the mandrel may form its own bore hole in the ground, simply by setting it into its resonant longitudinal standing wave mode of operation, and then engaging its lower end with the ground. This process has been described fully in my United States Patent No. 2,975,846, to which reference may be had for a description of the phenomena employed in the upper end of the mandrel 11, around the feed pipe 10 20. Of course, after such a self-driving operation, the mandrel will fit fairly snugly within the soil. A cement liner or casing can still be formed around such a closefitting mandrel, however, in view of the pressure with which the cement is injected from the mandrel, and the sonic action inherent in the process, which compacts the soil and drives it back to a degree, so as to permit a tubular column of cement to be forced upwardly around the mandrel. As an alternative an enlarged head or cap 62 can be frictionally fitted on to the lower end of the mandrel during the self-driving operation (see FIG. 4, where however the cap is shown as having been already dislodged from the mandrel). This cap, in place on the mandrel, forms a bore hole of somewhat larger diameter than the mandrel. Following the driving operation, the mandrel can then be lifted a short distance ofl bottom, and then set into sonic vibration, which will shortly shake the head or cap olf the mandrel. The cap may then fall a short distance, but is likely to be caught and held in the well bore just below the mandrel. The cement is thereafter ejected from the mandrel with the bottom of the mandrel just above the cap; and the cap is furnished with an orifice 63 to pass the cement to the bottom of the bore hole. FIG. 4 actually shows the mandrel after having been elevated somewhat above its cement discharging position, which would be immediately above the cap stuck or lodged in the bore. The position of FIG. 4 thus actually shows the mandrel 11 on its way out subsequent to hardening of the tubular wall 61.
The invention has been particularly described in its Well casing exemplification. -It will be understood that the cement well casing or liner might also serve the purpose of a load-supporting pile, and the expressions well casing or liner are therefore to be read in a broad sense such as to include such a use of the casing or liner as a pile. The process of the invention is applicable not only to vertical wells, but to horizontal wells and holes also. Thus, it is possible to utilize the process for forming a tunnel or conduit horizontally in the ground. Other cavities such as cisterns and various storage rooms can be formed in this manner. The process is also broadly applicable to the forming of large concrete castings in the structural industry. In other words, broadly, the present invention may be considered as a sonic process for activating the forming mold in any slip form process. As a further example, the process could be applied to laying down strips or ribbons of concrete, as in forming a highway. It will be seen that in these broad aspects, the mandrel of FIGS. 1-4 constitutes, in effect, a linearly extended slip form die, and the bore hole constitutes a fixed die. From these illustrations, the broad field of application of the invention will be understood.
1. The method of forming a well casing or the like in the earth from a fluent, hardening material, that comprises:
introducing an elastic mandrel longitudinally in the earth,
creating continuous sonic standing wave elastic vibrations in and along said mandrel, whereby said mandrel acts as a radiator of sonic vibrations into fluent media in contact therewith,
simultaneously therewith introducing into the earth,
around and in contact with said mandrel, a stream of said material in its fluent state, whereby sonic 8 vibrations are radiated into said material from said mandrel.
maintaining said vibrations in said mandrel for a time period during hardening of said fluent material, whereby to prevent tight adhesion of the hardened material to the mandrel,
and subsequently withdrawing the mandrel from the hardened material.
2. The method of claim 1, including also the step of vibrating said mandrel during withdrawal thereof from the hardened material.
3. The method of forming a well casing or the like in the earth from a fluent, hardening material, that comprises:
introducing a tubular elastic mandrel longitudinally into the earth,
creating continuous sonic standing wave elastic vibrations in and along said mandrel, whereby said man drel acts as a radiator of sonic vibrations into fluent media in contact therewith,
simultaneously therewith introducing said fluent material into the earth through said tubular mandrel, so that said material is ejected from the lower end of said mandrel and then forced upwardly to the ground surface in a tubular form around and in contact with the exterior surface of said mandrel and between said mandrel and the surrounding soil, and so that sonic vibrations are radiated into said material from said mandrel,
maintaining said vibrations in said mandrel for a time period during hardening of said fluent material, whereby to prevent tight adhesion of the hardened tubular form to the mandrel,
and subsequently withdrawing the mandrel from the hardened tubular form.
4-. The method of claim 3, including also the step of vibrating said mandrel during withdrawal thereof from the hardened tubular form.
5. The method of claim 3, including additionally the preliminary step of forming a bore hole in the earth for reception of said mandrel on a diameter exceeding the diameter of the mandrel.
6. The subject matter of claim 3, wherein the step of introducing the mandrel into the earth comprises setting up in the mandrel longitudinal elastic vibrations while causing the mandrel to be biased against the earth in the direction of desired penetration.
7. The method of claim 6, including the step of removably fitting onto the lower end of the mandrel, prior to introduction into the earth, a drive cap of larger diameter than the mandrel, and
removing said cap from the mandrel prior to ejection of the fluent material from the mandrel.
3. The method of claim 3, including the step of introducing to the tubular mandrel a purging liquid to displace the last portion of the hardening material from within said mandrel.
9. The method of claim 8, wherein said purging liquid is filled into said mandrel until a portion thereof comes out the bottom of the mandrel, so as to assure purging the hardening material from within the mandrel.
10. The method of forming a well casing or the like in the earth from a fluent, hardening material, that comprises:
forming a well bore in the earth,
introducing into said bore an elastic material-guiding mandrel that is of smaller size than said bore, so as to leave a space between the mandrel and the wall of the bore,
creating continuous sonic elastic standing wave vibrations in and along said mandrel, whereby said mandrel acts as a radiator of sonic vibrations into fluent media in contact therewith,
simultaneously therewith filling said space with said material in its fluent state, with said material in contact with and guided by and between the exterior surface of said mandrel and the wall of said bore, whereby sonic vibrations are radiated into said material from said mandrel,
maintaining said vibrations in said mandrel for a time period during hardening of said fluent material, whereby to prevent tight adhesion of the hardened material to the mandrel,
and subsequently withdrawing the mandrel from the hardened material.
11. The method of forming an extended body from a fluent, hardening material, that comprises:
positioning an extended body of the fluent material between a fixed die and the forming surface of a slip form die which is linearly extended parallel to said forming surface and which is subsequently to be re moved from said body, after hardening of the material, in the direction of its linear extension,
setting up sonic standing wave vibrations in said slip for-m die during hardening of said fluent material, whereby adhesion between the hardened material and said slip form die is prevented,
and finally, after hardening of the material, removing said slip form die from the hardened body by sliding movement thereover in said direction of linear extension.
References Cited by the Examiner UNITED STATES PATENTS 1,313,013 8/1919 Polysu.
1,867,837 7/1932 Jackson 254-71 X 2,072,982 3/1937 Dale 166-l77 X 2,080,406 5/1937 Allen 16624 2,229,912 1/ 1941 Baily 173--49 X 2,264,948 12/ 1941 McKenzie 264-69 2,356,852 8/1944 Hutchinson 264-72 2,614,312 10/1952 Rankin et al. 264-23 2,942,849 6/1960 B-od-ine 175-55 OTHER REFERENCES Mill, Brad: Rotating While cementing Proves Economical. In The Oil Weekly, Dec. 4, 1939, pp. 14, 15.
CHARLES E. OCONNELL, Primary Examiner.