US2279287A - Apparatus for cementing wells - Google Patents

Description

April 7, 1942 J. D. CHESTNUT ETAL 2,279,287

APPARATUS` FOR CEMENTING WELLS Filed Feb. 4, 1939 5 Sheets- Sheet 2 John D. Chenui' Rober J/l. C0061 fir/@.4 A I INVENTORS ATTORNEY J. D. CHESTNUT ETVAL 2,279,287.v APPARATUS FOR GEMENTING WELLS April 7, 1942.

Filed Feb. 4, 19:59'

3 Sheets-Sheet 5 Johln Chenu Robezf' M. C0026 ATTORN EY ldistinguished from a batch process, and the vol- Patentec Apr. 7, 1942 iTED STATES PATENT GFFICE 5 Claims. "(91. 259'154) This invention relates generally to oil well d cementing, and is directed particularly to improvements in apparatus of mixing cement slurry orV for preparing an aqueous mixture of cement and sand for cementing oil wells.

Because of the unusual conditions encountered in cementing oil wells, a cement mixer must fulfill certain exacting requirements not ordinarily present, in order to meet with success in this field. The time element is an important factor in cementing oil wells, inasmuch as the mixture must be pumped a considerable distance, usually several thousand feet, and the relatively high temperatures often encountered accelerate setting of the cement. Consequently, the mixer must be capable of handling a large volume in-a short period* of time, and the volume must be capable of being varied to suit varying conditions. The capacity of a successful mixer should be variable between 300 yand 1800 sacks of cement per hour.

Of major importance, however, is the control of Well-cementing practice requires that the mixing be a continuous process, as

7urne requirements per unit of time are so high that if the control of the cement-water ratio is different cement-water ratios, and at a single wel] the ratio may be changed progressively through a lrange from approximately 0.4 to 1 cubic foot of water per cubic foot of dry material. In order to obtain predetermined cement-Water ratios, the .y

rate of feed of both the dry material and water to the vmixer should be measured while supplying continuous streams of both.

:It is a principal object of this invention to provide-a cement mixer for Well-cementing operations in which the rate of feed of both dry material and watervmay be accurately controlled and in which each may be controllably varied to provide a wide range of cement-waterratios, while supplying continuous, measured quantities of each to the mixer. A further object is to provide a mechanical cement mixer having, in addition to power-operated mixing means, a power-operated measuring and feeding means for the dry material and a metering device for the water supply,v so

`arranged that the rates of feed of dry material and :of water may be varied independently of each Asuitably varied in accordance f with conditions existing at individual Wells, and the rates of feed of dry material and of Water may be correlated to provide the desired cement-Water ratios.

A still further object is to provide a, mechanical cement mixer capable of delivering large volumes of properly mixed cement slurry in a Wide range of predetermined consistencies.

An additional limitation imposed by the operating conditions is the height of the feed hopper above the Working level. Itis customary'to stack the required number of sacks of cement for the particular job in close proximty to the mixer, and to feed them by hand to the feed hopper. The rapid mixing rate, oftentimes as high as 25 to 35 sacks per minute, requires very rapid handling of thesacks, and inasmuch as the standard sack of cement weighs 94 pounds itis wholly impracticable to locate the top of the feed hopper morethan 3 feet abovethe working level. The time element as weil asthe manual exertion required thus impose, for all practical purposes, a height limitation of not more than 3 feet. Mechanical cement mixers best adapted to well-cementing are either of the vertical cylinder or the horizontal cylinder type, each having rotatable paddles or other agitating and mixing means therein. In the vertical type the open upper end of the mixer serves as a hopper, and, if accurate control of the rateof delivery of cement is not required, the sacks may be emptied directly into the mixer, a preferred embodiment of which is approximately 30 inches high. However, if accurate control of the rate of delivery is desired, it is necessary to provide a storage hopper and a metering device between the hopper and the mixer to constantly feed the cement at a uniform rate, Vthe capacity of the hopper being sufficiently large to insure that the metering device is constantly supplied with cement in spite of irregularities in the rateof emptying the sacks into the hopper. obviously, it would be impracticable to superimpose a metering device and a hopper of sufficient capacity above a vertical mixer, because of the aforementioned height limitation. Consequently, the discharge ,of the hopper is necessarily located below the 'top of themixer, requiring elevating means theree between.

It is a further object of this invention toy provide a mixer having a storage hopper delivering Yto a combined metering and elevating `device i i y 2,279,287

common to the mixer drive, but controllably variable independently of the mixer drive, whereby the metering and elevating device may be driven at any one of a plurality of speeds from the power source Vused to drive the mixer and while the 5 latter is driven thereby at a constant speed.

Although it is well known .that an aqueous mixture of cement and sand when set has a much higher strength than a straight cement grout, up until the present time it has been im-` 10,-

possible to use a cement-sand mixture in ce# menting oil wells chiey because of the lack of equipment capable of properly mixing cement, sand, and water under the conditions encounteredin oil well cementing.y Itis a'still further object of this invention to provide a method and f apparatus for thoroughly mixing large quantities of cement, sand, and water within a short space of time While maintaining the proportionso thejf ingredients within closebut controllably variable 20 limits. a y.

Our novel method comprises essentially the steps of` introducing drymaterials `in suitable proportions into'a dry mixing zone wherein three important vsteps are'performed simultaneously- 25 that is, the dry materials are thoroughly mixed While being transported'and vmetered to a wet mixing Vzone wherein the dry mixture is mixed with water which is also metered to the zone.

VBy combining the dry mixing, conveying, and 30 parent from the following description, taken in conjunction with `the accompanying drawings wherein there is illustrated an apparatus capable of being used forv mixing either cement grout or a mixture of cement, sand', and water. -45

Fig. lis a partial vertical sectional View of one form ofthe mixing apparatus showingthe mixing chamber andthe Ydischarge end of the conveyor;

Fig. 2 is a view, partly in vertical section "and 50 partly in elevation,showing the hopper and the intake end of the conveyor;

Fig.` 3 is a plan view of the apparatus of Fig. l; Fig. 4 is a vertical sectional view throughthe plural speed transmission, taken substantially on 55 line 4-4-of Fig. 3;v l s Fig. 5 illustrates.diagrammatically theV gear train from the power take-off sprocket to the conveyorv drive sprocket, as viewed from line 5,,5 of Fig. 1;- l

Fig. 6 is a vertical section taken substantially online '6-6 .of Fig. 3, showing the water inlet pipe and the vertically adjustable slurry dis- I charge pipe; A

Fig. '7. isa view in elevation ofra modication '65 1 :a superposed throat piece or funnel 2 through which` dry material is fed to the mixing cham- 75 f ber by an inclined screw conveyor 3, the discharge end of which overlies the throat piece. The conveyor extends downwardly to merge with f a storage and feed hopper 4, into which dry materials are dumped by members of the cementing crew. In Fig. 3 there are shown two sack-cutting platforms 5 and 5 attached to opposite sides of the hopper 4 and having sack cutters 6 and 6" mounted near their inner ends. The cutters are illustrated as disk cuttersfreely rotatable on the platforms and projecting slightly above the upper surfaces thereof to engage the sacks and rip them open as the latter are slid along the platforms toward the hopper. It will be understood that when mixing only cement and Water, only a single platform may be used if desired,and in this case it is preferably attached y to the sideV of fthe hopper opposite the conveyor 3.

The mixing chamber I comprises a vertically `disposed cylinder supported on legs I0 to which are welded a pair of skids II. Rotatably mount- "ed-within=thecylinder are a plurality of paddles IZJattached-to -a sleeve Vv'I3 journaled, as diagrammatically illustrated in Fig. 1, on an up- 4standing hub I4'secured in-fluid-tight relation to the baselof the cylinder andcoaxial therewith. In order to rotate the sleeve I3, the upper-kend thereof hasl Ya I noncircular opening therein throu'ghwhichextends a similarly shaped stud `I5I formed integral with a -shaft I6 rotatably mountedwithin the hub I4 and projecting downwardly `through a central opening in the base of 'the cylinder. `A ring gear 2I keyed to the lower end of .the shaft meshes with a pinion 22 i keyed -to-I a -shaft f 23 having -keyed thereon Aa drive sprocket adapted to be connected to any suitable power source.` The hub I4v extends upwardly abovethe level of the mixture ofcement andwateror of cement, sand, and water in the chamber, whereby `leakage through the opening inthe base is-avoided. i

l The -throat piece 2 comprises a cylindrical sleeve portion 30 snugly fitting over the upper portion of'the' mixing chamber, and a funnel 3l integral therewith extending downwardly within the mixing chamber and confining the stream of dry! materialtothe central` portion thereof. As s hown in Fig. .6, a water inlet pipe 35 is secured to"an1elbow -36 welded tothe top of the throat piece incommunicationwith a conduit 31 extending downwardly along the inner surface -of the funnel 3|.; The conduit may be a short section of pipe welded to the funnel, as shown, or it `may be formed as an integral part of the funnel. `The-.lower discharge end of the conduit is preferably-bent slightly outwardly as at 38, so as to direct the stream of watereaway from the axis'of the chamber. Wateris supplied to the pipe 35 from -asuitable source, `the rate of flow being vregulated-to supply a-constant, measured supply. Forthis lpurpose any suitable regulating means maybe provided, such f as a graduated valve 33, as shown inFig. 3, or afdisplacement pump, as shown in'Fig's. 7- to 9,\or a gravity meter.

v 1 -*he rotationof the paddles I2 thoroughly Ymixes',the@waterandl dry material and also exertsa slight 4downward force on the mixture, due to qtljie `slight; inclination of the paddles from their planes foff-rotation'. The slurry is discharged tiirougiran-opefning 40 in the wall of the chamiber adacent'thebase thereof, into a tank 4I from which-litA Ais1 drav'vn4 bya pump (not4 shown) and fored-'intthewell- In'forder to regulate the frate ofdischargefrom lthe mixing chamber, Vthe ldischarge pipe'leading from the opening 4I) to Ymixing chamber.

rear edge of the hopper 4, andimay be readilydethe vtank 4| comprises two sections 42 and 43, the section 42- being swiveled tothe chamber outlet 'tof swing in `a vertical plane, and the section 43 being swivelly mounted/on sectionA 42 on a parallel axis. In Fig. 6 the discharge pipe is shown in two alternative positions, but it is apparent that it may be adjusted to any position within the range of adjustment. By this arrangement the eective height -of the outlet may be varied to provide the desired rateof discharge from the A 4predetermined back pressure is provided by reducing the diameter of the discharge pipe at 44.

The screw conveyor 3 is driven from the shaft 23 at any-one of a pluralityof speeds. purpose, a sprocket 45km/'ed to the vend of 'shaft 23 is connected to a sprocket 46 on the input shaft of a variable speed transmission 41. A unit known as the Link-Belt P. I. V. gear (positive infinitely variable) Ihas been found suitable for this purpose, although it will be understood that any other positive drive transmission providing a wide range of speeds may be used. y

A sprocket 48 is keyed on the output shaft of the transmission and is connected by a chain 49 to the larger of two sprockets 5D and 5I constituting a speed reduction unit, the sprockets being connected togetherand journaled on a stub shaft 52 carried by a supporting bracket 53. The small sprocket 5l is connected by a chain 54 to a sprocket 55 loosely journaled on a shaft 56 journaled in a'beari-ng 51 mounted on a bracket 58 secured to the top of the funnel 2. In order to selectively connect the sprocket 55 in driving relation with the shaft, suitable clutch mechanism is provided. As shown in Fig. 1, a jaw clutch member 6E)v is keyed to the hub of the sprocket and is adapted to be interengaged with a clutch member 6| splined to the shaft. The clutch member 6| is shifted into or out ofengagement with clutch member 5l] byV a thrust collar 52 engaged by a shipper lever 63'pivoted at 64 to a bracket 65. Suitable linkage 66, 61, 58 connects the shipper lever to an operating lever-69.

The shaft 5B is'connected through a universal joint 1G to the shaft 1| of a screw12 constituting the impeller of the conveyor 3. kA combined rae dial and thrust bearing 14 supports the shaft 1| at-its upper end, the lower end being journaled in a radial bearing 15 in the end plate of the conveyor housing. The inclination of the conveyor tube 3 is so correlated to the pitch-of the conveyor screw 12 thatduring the travel of material up the tube it is thoroughly admixed, producing an intim-atemixture of the ingredients thereof.

The mixing devicev is so constructed as to be separable into units convenient to transport, and capablevof being quickly set up andA connected together. The transmission 41 is mounted on a base adapted to be bolted to the adjacent skid H. By removing the chain-connecting sprockets 45 and 46, and also cha-in 54, the transmission unit may be detached. The upper end ofthe conveyor Vhousing is bolted at8^0 to the top of the funnel 2' so as to be detachable therefrom, and the conveyor shaft 1I has a splined upper end portion slidable within Yan internally splined sleeve 84 integral with the universal vjoint 10. The conveyor 3 and hopper 4 are thus detachable from the funnel 2, the-bracket 58Y and shaft 56 remaining on the funnel'. The funnel is also detachable from the mixing-drum. The platform 5 is provided with a lip 85 which engagesV over the ForA this tached therefrom. .l

'Iniorder to confine within the mixer thecloud of cement .dust whichmay form as the cement discharges from theconveyonthe upper end-of .the mixer and conveyor .are wholly enclosed.

to the end plate toprovide access to the interior of the mixer after the' conveyor unit has been connected thereto, and to permit inspection duringV the mixing operation. i

The transmission 41 comprises generally-two pairs of opposed conical wheels and 96 (Fig. 4) splined to parallel shafts 91V and 98. A chain 99 connects the pairs of wheels, the effective diameter of each pair being changeable underload to ychange the speed ratio by varying the distance between the opposed conical faces of each pair ofwheels. A pair of pivoted levers |09, HH are oppositely threaded on an adjusting screw |62 and engage pairs of thrust collars |f3, |04 journaled on the wheels 95 and 96 to effect adjustg ment of the latter. vided on the adjusting screw, and an indicator |06 indicates the speed ratio. This type of transmission is `particularly adapted for the present purpose because of the capability of changing the speed ratio under load without nterruptinghe drive.

Referring now to Fig. '1, a modification ofthe water metering means is shown in the-form of a variable capacity, positive displacement pump H0. The apparatus is otherwise similar to the form shown in Figs. 1 to 3', and hence is shown only in dotted outline. The pump l5 is mounted on a bracket I I secured to the plate 9| vof Fig. `1, and is driven in synchronism with the conveyor by means of a sprocket H2 keyed to the ccnveyor drive shaft 5S', a chainl |3 and asprocket H4 keyed to the pump impeller shaft. A water inlet pipe H6 is connected to a source of supply, and a discharge pipe H1 communicates with the conduit 31 of Fig. 6. The pump may be of any type having variable capacity at constant speed, such as the adjustable swash-plate type or one having an eccentric axis, t the Veccentricity of which may be varied. Manipulation of hand wheel '|20 varies ythe output capacity of "the pump. Y Fig. 8 illustrates diagrammatically a modification of Fig. '1, using a positive displacement pump |25 wherein the outputv capacityis varied'by varying the speed. `For this purpose, a change speed mechanism |26 is interposed between the drive sprocket H2" on the conveyor shaft 56" and the pump impeller. The change speed mechanism |26 may be of the same type as the transmission 41 of Figs. V1 to 3, the driving sprocket |21 Aon the input shaft being connected to sprocket H2 by a'chain |28, and the driven sprocket |29 on the output shaft being connected by a chain |30 to a sprocket |3| on the pump impeller shaft. For convenience', the pump |25 and the transmission |26 may be mounted on the top of the mixing chamber on opposite sides of the upstandingbrackets 58 supporting the conveyor drive shaft 56".

' The two forms ofthe invention shown in Figs. '1 andhave theadvantage of synchronizing the A hand wheel H35 is pro` conveyor spe'ed and the pump vspeed while also providing for variation of thepump speed relative to "that'of the conveyor.

be ,iobtainedby adjustment-of the variable capacity pump I I0 of Fig. 7for of the variable speed transmission of Fig.A 8, andzsubsequent manipulations of the variable speed transmission 4'|,for the purpose of correlating the conveyor speed to 4the rate of lling the hopper 4 will have no effect on the cement-water ratio. c

Figure `9 illustrates `diagrammatically a still further modification employing a variable .capacity pump |32 as in Fig. 7. In this case, however, the pump is driven at a constant speed by an Y electric motor |33.A The pump and motor may be obtainable with the forms of the invention shown 'in Figs. 7 and 8. In this respect the form shown in Fig. 9 is quite similar to that shown in Figs. 1 to 3, using a graduated valve, although with With these arrangements `the desired cement-water ratio may the use of a pump closer control over the water rate is obtainable.y c f The mode of operation of the mixing device will be apparent from the foregoing description.

When the sprocket 24 is rotated by a suitable power source, such as the propelling motor of the cementing truck, the paddles |2Awi1l rotate. It will be observed that the paddles are inclined slightly from their planes of rotation, and preferably are rotated in a direction to exert a slight downward propelling I force on the mixture. Water is admitted through the inlet pipe 35 at -a predetermined rate,`and dry material is fed to the mixer by the screw conveyor, the rate of feed and consequently the cement-water ratio being determined by the setting of the variablespeed transmission. Alternatively, the cement-water ratio may be varied by varying the rate of delivery of water while maintaining a constant de- I, n The variable speed 4transmissionvmay be used to obtain the proper livery rate of dry material.

c orrelation between the conveyor speed and the rateat which dry material is dumped into the hopper, and after this is properly adjusted Vthe cement-water ratio may be controlled through the water control means. `Suiicient dry material is maintained in the hopper 4 tofinsure that the conveyor will always be full, thus providing a uniform rate of delivery to the mixer.

As the cementing operation progresses, it is frequently necessary or desirable to vary the cement-water ratiol progressively through the entire `range from 0.4 to 1 cubic foot of water per cubic foot of dry material. 1 'I'his may be accomplished with the mixer shown by simply adjusting the variable speed transmission 4l, without stopping the mixer and without so much as interrupting the conveyor drive,for alternatively by varying the water delivery rate. In View of the high speeds at which well cementing operations are often'necessarilycarried on, mixing as high as 2400 sacks of cement per hour, the advantages derived from avoiding any interruption in the successful completion of a well cementing job depends'on maintaining` close correlation of the `various steps being performed simultaneouslythat is,;the delivery of water and of dry material to the mixer at the proper rates, the rotation of the agitating means, the feeding of dry material to the hopper 4, and pumping theslurry down the well. The ability to providevarious predetermined cement-Water ratios with the elimination o f all guess-work, and without interrupting the cementing operation while changing the ratio, marks an outstanding contribution to the well-cementing art.

When mixing cement, sand, and water, a practical and convenient method of supplying cement and sand to the hopper 4 in the desired proportions consists in providing a supply of sand in sacks each of the proper weight to produce the desiredcement-sand y ratio when one sack of sand to each sack of cement.is dumped into the hopper. For example, a mixture having a 35% sand content may be produced by providing 50-pound sacks of sand and feeding one sack into the hopper for each of the standard 94-pound sacks of cement.

Prior to the start of an oil well cementing operation the required number of Isacks of cement and of sand are stacked near the well, the sand being placed as close to one of the platforms 5 or 5' as possible, and the sacks of cement being stacked adjacent the other platform. Members of the crew feed the material to the hopper by sliding the sacks along 4the platform and over the cutters 6, 6 whereby thepaper sacks are ripped open and their contents dumped into the hopper. By opening sacks of sand and of cement in unison, the desired ratio "of sand to cement is established in the hopper 4. It will be understood, of course, that any other desired procedure may be followed for accomplishing this result.

As long as an adequate supply of material is maintained in theA hopper 4, the screw conveyor 12 will operate at full capacity and will transport the'mixture to the mixing drum at a predetermined constant rate whereby the desired consistency of the final mixy may be accurately controlled byl controlling the delivery of Water to the mixing drum. i A feature` of decided importance in oil Well cementing is that during the conveying and metering steps the cement and sand are also intimately mixed as they travel through the conveyor tube 3. For this reason the time required for mixing a given quantity of cement, sand, and water is no greater than that required to mix a straight mixture of cement and water. Furthermore, by performing these steps Within a single element of the apparatus, the number of pieces of equipment is greatly reduced and the overall weight and size of the apparatus is kept within'limits of easy portability.

- The arrangement disclosed presents a compact unit occupying a minimum of space and consequentlycapable of being mounted on a truck or on a trailer as an adjunct to the main cementing truck on which the pumps, power units, and Water tank aremounted. The unit is. composed of sub assemblies readily detachable from each other if itis preferred to transport them dismantled and to assemble them at the site of each operation. Furthermore, an arrangement has been provided whereby accurate control of the rate of feed of the dry material is attained With the preferred vertical type of mechanical mixer, While at the mixing process will be readily,- apparent. The 'Z5 v521111@ time the #Op of the feed hODDeI' is maintained at a low level convenient for handling the sacks.

This application is a continuation-impart of our earlier-led application for Cement mixer Serial No. 180,816, led December 20, 1937.

We claim:

l. Apparatus for cementing oil wells comprising, in combination: a hopper adapted to receive dry cement and an added dry ingredient in predetermined proportions and having a discharge opening in the lower portion thereof; a closed conveyor tube having its inlet end connected to the discharge opening of said hopper, said tube being inclined upwardly and having a discharge opening at its upper end; a spiral conveyor rotatably mounted in said tube in a direction to convey material upwardly therein,the charging end of said conveyor being disposed in the lower portion of said hopper and the conveyor blades having a relatively close clearance with the inner wall of said tube to eiect positive displacement of the material therein, and the upward inclination ofthe tube being so correlated to the pitch of the blades that intimate admixture of the material is eiected during its passage through the conveyor tube; a wet mixing chamber having its inlet disposed beneath the discharge opening in said conveyor tube; a mixing element rotatably mounted in said chamber; a conduit for supplying Water to said chamber; means interposed in 5 said conduit for controllably varying said water supply; common driving means for said mixing element and said spiral conveyor; a variable speed transmission in the driving connection from said common driving means to said conveyor whereby the delivery capacity of said conveyor can be varied independently of the actuation of. said mixing element; and a discharge connection from said mixing chamber to the point of use.

2. Apparatus as defined in claim 1, in which said last-named discharge connection includes a vertically adjustable discharge conduit whereby the rate of discharge from said mixing chamber may be controllably varied.

3. Cement mixing apparatus comprising: a vertically disposed mixing chamber, a funnel detachably secured to the upper end of said chamber, a conveyor having its discharge end detachably secured to said funnel whereby cement discharged from the conveyor passes through the funnel and into the chamber, driving means for said conveyor including a shaft journalled in a bearing supported on said funnel, a separable driving connection between said shaft and said conveyor, and driving means for said shaft.

4. Cement mixing apparatus as dened in f claim 3, in which said last-named driving means' includes a driving element rotatably mounted on said mixing chamber, and a separable driving connection between said driving element and said shaft.

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