US2266000A - Well strainer - Google Patents

Description

Patented D ec. .16, 1941 UNITED STATE WELL s'mAmEa Robert s. charles, New York, N. Lassimor to A Layne & Bowler, Incorporated, Memphis, Tenn.,

a corporation of Delaware Application ootober v, 194o,`sorio.1 No. 360,043

(c1. iss-) 5 Claims'.

This invention relates to certain new and useful improvements in means and methods for surrounding well screens with aggregate such as gravel to accomplish an efiicient strainer permity ting large liquid ow yet holding back the sands from which the liquid is drawn, and particularly to means and methods for so placing thel aggregate that it will be graduated progressively in size' from the strainer outward to the surrounding liquid bearing sands to eilect this accomplishment.

Much difficulty has been encountered in well building in that ordinarily the strata, from which the liquid desired is to be drawn, is a very ne sand, which will flow freely with the liquid through the openings of the usual screen unless such.openings are so restricted as to seriously aiect the well capacity. In combating this difdculty Well builders have made extensive use of gravel as a supplementary screening me-- dium around a coarse strainer or screen in the well toassist in retarding the passage of the ne sand or similar materials with the liquid into the pump suction pipe. The gravel or other aggregate of such medium should be largest adjacent the screen and should decreasein size progressively outward towardthe sands, but great difculty has been encountered in even approximating the desired structure, and even where it has been accomplished in part there is greatly undesired variation along the length oi the strainer and at the best much uncertainty during construction as to what is being accomplished and thereafter as to what has been accomplished.

In usual gravel well practice a typical well is bored from the surface with a desired diameter, as say forty-two inches, and ordinarily cased to the level of the sand. When this bore reaches the liquid bearing sand a chamber is reamed out in the sand to anenlarged diameter, as say sixty inches. It is the walls of this liquid bearing sand chamber which present the dimculties in the art, as this sand mustbe held back away from the screen. After the chamber has been reamed, it is customary to` lower into the bore an inner casing having a diameter of say eighteen inches, this casing having one or more secJ-f tions of screen of the same diameter depending therefrom. The sections are ordinarily twenty feet long and are connected by short pipe sections or collars which are screwed or welded to rigidly connect the sections.

bottom of the screenl is lowered therearound, and

coarsegravel is fed from the surface through a pipe into' the space between the sleeve and the screen until this space'is substantially filled and packed. A second sleeve, of, say, thirty-eight inches in diameter and. of length equal to that of the `irst sleeve, is then lowered around the first sleeve and a somewhat liner gravel is similarly fed into the space between the sleeves.`

that used in the preceding sleeve. The remaining space in the bearing sand chamber outside the last sleeve is-then iilled preferably with a y the effectiveness of the gravel protection and im- I pedethe eiliciency of the construction. .Among these are the fact that a substantial void is created between the strata of gravel upon removal of the sleeves causing slumping of the gravel strata which is often so uneven as to de- Vfeat the systematic graduation of gravel size A sleeve, say twenty-eight inches in diameter K outwardly through the successive strata jand to large extent reduces the eiilciency of the structure. The lowering of successive sleeves around the screen is a slow and laborious process and obviously requires a` multiplicity of operations which can only be effected after the primary well bore has been completed. Ordinarily accurate centering of the sleeves around the strainer is to say the least dimcult, resulting lin irregularities and variations of thickness in the gravel strata. If to avoid this result lspacing means.

are employed, the packing yand weight of the gravel in the space between sleeves or between screen and sleeve makes the removal of the sleeve more diilicult, creates additional void spaces, and usually disrupts the desired stratication of the sized materials. A a

-This invention, therefore, has for vits principal object the solution of these problems inthe method of` enclosing a well screen in gravel or other aggregate to accomplish a wellfstrainer.

A further object isto provide a method of enclosing a well screen in aggregate, which enclosurewill `be completed. upon the surface and prior to lowering the screen into the well.

A further object is to provide a method of vand of sufficient length to extend from top to accurately determining and xing the aggregate strata to protect and supplement a well screen.

A further object is 'to provide a method of creating of such aggregate strata and well screen a unitary strainer assembly, adapted for placing in position in a -well; and

A further object is to provide a method of producing an aggregate protection for a well screen in which the aggregate is in strata of accurately determined size and content, around the well screen, when the strainer unit is completed'in the well. x

The means by which the-foregoing and other objects of the invention are accomplished includes using a soluble bonding agent with which the aggregate is fixed around the screen, and also includes the casting around the screen of one or more annular shells, consisting of the aggregate and the soluble'bonding agent, before positioning of such screen for use.

The manner of the accomplishment of the objects of the invention will be readily understood upon consideration of the accompanying drawing, in which:

` Fig. 1 is a sectional elevation of the liquid bearing strata of a well, with a well screen, and unitary structure of protecting yand graduated aggregate therearound in use-position in the Well.

Fig. 2 is -an enlarged sectional elevation of a fragmentary portion of a well screen with unitary aggregate protection shells of graduated aggregate concrete bonded in place, the outer metal form used in construction being shown prior to removal.

Fig. 3 is a sectional plan view taken as on the line III- III of Fig. 2; and

Fig. 4 is a section of a fragment of a strainer screen, having a protective coating surface.

Referring now to the drawing in which the parts are indicated by numerals:

II is a well bore of desired diameter lined with an outer casing I2, extending to the liquid bearing sands, in which a chamber I3, of diameter greater than that of the well bore II, has been reamed out. been lowered into the well.

Depending from the inner casing I5, is a well screen I1 which is secured thereto by a collar 2|, adapted to fit around the lower portion of the casing and a sleeve extension I8 of the upper end of the screen I1, to each of which it is rigidly secured by suitable means, such as welding.

In preferred form well screen I1 is formedfrom a sheet of metal, in which a plurality of cuts are'made. The metal is uniformly pushed outwardly adjacent and above the cuts to form shutter-like flanges 26, with liquid receiving openings 21 therebetween. The sheet is then integrally covered with a substantially uniform protective coating 28 of rubber, japan or other suitable material, ladapted to resist corrosion of bscreen I1 by the passage therethrough of corrosive solvents, the use of which is hereinafter described. The screen I1 is then rolled-into desired shape. It will be understood that while the openings 21 are :described as being between flanges 26, they may be formed by perforation or in other manner as desired. In any event the screen I1 should be coated against corrosive elements, although this coating is also optional.

Additional screen sections may be depended beloW this rst section as needed or desired, the

upper portion of an additional screen 23 being shown similarly secured to the lower end of screen i1 as by collar 25.'

I5 is an inner casing which has Y.

In Figs. 2 and 3 a substantially completed gravel wall strainer structure is shown in which 3|, 33 and 35 are annular shells of gravel concrete cast concentrically around the screen I7. The gravel used in shell 33 is somewhat finer than that employed in shell 3|, and that in shell 35 still smaller than that in shell 33, the gravel in each shell being bonded together by a soluble cement or other bonding agent.

In the stage shown the form 31 for the outer shell 35 is shown in position around that shell. This form 31 is shown halved for easy removal after hardening of the shell cast therein, and is adapted to be clamped in shaping position as by ears 38 carried by form 31 and adapted to receive bolts 40. Spacing pins 45, which are adapted to maintain form 31 concentric with strata 33, and to maintain the desired uniformity throughout of shell 33 may be used.

In producing the unitary gravel wall strainer illustrated, a halved form similar to form 31, but of smaller diameter is secured in forming position around screen I1, and preferably maintained in. concentric position as by spacing pins similar to pins 45. The annular space is then lled with concrete consisting of a coarse gravel or other suitable aggregate and a soluble bonding agent, which may be a cement of known type containing an excess of calcium carbonate and which is readily attacked as by hydrochloric acid. 'I'he concrete is allowed to set up or harden and forms a shell of uniform thickness around screen I1. The form is then removed, a larger form,

similar to that previously used and'described is centered around and spaced away from shell 3|, and in vsimilar manner an annular space of uniform thickness iscreated and maintained, which space is lled with similar concrete differing from that of shell 3| in that the aggregate used is ner. This shell is allowed to set up and the form removed. y

Successive shells are outwardly added through similar steps, the size ofl the aggregate in each being successively decreased, until strainer structure of the size desired for use is built up. Preferably the successive shells are beveled'at their lowe'r ends, as at 50, but it will be understood that the structure may be formed otherwise. It will be understood that the bonding material need not;v

Well bore I| is formed from the surface'into A the liquid-bearing sands, and casing I2 is posi.-

tioned in well bore in usual manner, and chamber I3 is under-reamed in these bearing sands to desired diameter. In such condition the well is ready for the llowering of the strainer structure therein. A section of screen is lowered until a minor portion only extends above the surface where it is supported While a second section is placed thereover and secured thereto in manner described. The lowering is resumed and additional structures vare added in similar'manner as required, and lowering into the well completed.

After the strainer structure and inner casing is lowered into the well, aggregate, preferably nner than that used in the outer shell of the strain-- ers, is introduced to ll the remaining space in chamber I3. In this step the bevel 50 permits.

this nal gravel to more readily fill the space or void existing around collar 25.

Variations, in desired graduation outward from,l

the strainer.

In ordinary practice gravel is found to be the best aggregate, but any suitable aggregate may be used provided that it not be attacked by the leaching agent. In the specification and claims the term grave is intended to be synonymous with the term aggregate I claim:

1. llrhe method of enclosing a Well` screen in' aggregate which includes the steps, prior to low-v ering said screen into a Well, of positioning a form around and spaced away from the surface of said screen, casting in said form, in uninterrupted association with said screen surface, a rst shell of substantially imperforate concrete comprising said aggregate bonded together by a soluble bonding agent, said first shell upon setting being bonded to said screen surface by said association and said agent, removing said form after setting to free the outer surface of said first shell, and repeating said steps to cast about said screen a plurality of shells each of successively smaller aggregate, each said shell having uninterrupted association with a. contiguous shell surface and being bonded thereto to form of said screen and said shells 'a unitary assembly; subsequently lowering said assembly into a well and destroying said bonding by passing a solvent outward through said screen to form independent aggregate strata of predetermined content surrounding and successively decreasing outwardfrom said screen.

2. The method of enclosinga well screen in aggregate which includes the steps, prior to lowering said sreen into a well, of positioning a form around and spaced away from the surface of 'said screen, casting in said form, in uninterruptedassociation with said screen surface, a first shell of substantially imperforate concrete comprising said aggregate bonded together by a soluble' bonding agent, said first shell upon setting being.

bonded to said screen surface by said association and said agent, removing said form after setting to free the outer surface of said'flrst shell, and

repeating said steps to cast about said screen a` plurality of shells each of successively smaller aggregate, eachsaid shell having uninterrupted association with a contiguous shell surface and being bonded thereto to form of rsaid screen and said shells a unitary assembly; subsequently lowering said assembly into a well, introducing loose aggregate around said assembly to fl1l` spaces between said assembly and said well, and destroyying said bonding by passing a solvent outward through said screen, to formaggregate strata of predetermined content surrounding said screen said strata being supported by said loose aggregate. Y

3. A preformed unitary assembly adapted to be lowered into a. well, comprising a foraminated Awell screen and a shell around said screen, said shell consisting of aggregate and a bonding agent, said shell comprising a plurality of annular sec' tions in integrated association, the sizes of the ag'- gregate 'in said sections progressively decreasing outward from said screen, said shell being bonded by said agent to said screen, and said bonding agent being soluble to permit freeing of said aggregate. l

4. A preformed unitary assembly adapted to be lowered into a well, comprising a foraminated Well screen and agsubstantially imperforate shell of concrete aroundsaid screen, said concrete consisting of graded aggregate and a bonding agent, said shell comprising a plurality of annular sections in uninterruptedly integratedv association, the sizes ofthe aggregate in said`sections being graded and progressively decreasing outward from said screen, said shell being bonded by said agent to said screen in, uninterrupted Icontact,

' said bonding agent beingxsoluble to free said aggregate.` s

5. A preformed assembly for use ina well,

comprising a foraminated well screen and a plurality of substantially imperforate shells secured around said screen, said shells each consisting of aggregate and a bonding agent, the size of the aggregate in said shells progressively decreasing`- outward from said screens, each said shell lying in uninterrupted 'association with a contiguous shell surface and being homogeneously integrated therewith, the first said shell being bonded by said agent to said screenv in uninterrupted con-,

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