US2933137A - Plastic well screen and wells utilizing the screens and method of operation - Google Patents

Description

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3 Sheets-Sheet l MI] Bllll lllll] [lllll llllllfl CROSS REFERENQE A. A. D'AUDIFFRET ETAL PLASTIC WELL SCREEN AND WELLS UTILIZING THE .SQREENS AND METHOD OF OPERATION Original Filed April 10, .1957

April 19., 1960 INVENTOR. ADOLPH A d'AUDIFFRET WILLIAM c. LAVELY RQEERT E.RE|MUND BY /WKT ATTORNEYS P" 1960 A. A. D'AUDIFFRET ET 2,933,137

PLASTIC WELL SCREEN AND WELLS UTILIZING THE SCREENS AND METHOD OF OPERATION Original Filed April 10, 1957 3 Sheets-Sheet 2 INVENTOR- ADOLPH AG'AUDIFFRET WILLIAM C. LAVELY w mf T m m7 m ATTORNEYS April 19, 1960 A. A. D'AUDIFFRET ETAL 2,933,137 7 PLASTIC WELL SCREEN AND WELLS UTILIZING THE SCREENS AND METHOD OF OPERATION Original Filed April 10, 1957 3 Sheets-Sheet 55 FIG '13 INV ADOLPH A. dAiS'EIE'i-RET WILUAM c. LAVELY ROBERT E. REIMUND ATTORNEYS PLASTIC WELL SCREEN AND WELLS UTILIZING THE SCREENS AND METHOD OF OPERATION Adolphe A. dAudiifret, Robert E. Reimund, and William C. 'Lavely, Columbus, Ohio, assignors to Ranney ilnited States atent Method Water Supplies, Inc, Columbus, Ohio, a corporation of West Virginia Original application April 10, 1957, Serial No. 651,990.

Divided and this application March 5, 1958, Serial No. 719,296

3 Claims. (Cl. 16642) This invention relates to well apparatus, particularly for water wells and is particularly concerned with a vertical type well apparatus and to a method of installation thereof and a method of maintainingthe apparatus in efiicient operation, and to an improved screen structure for such well apparatus. r I

Vertical wells include a well casing which is driven vertically downwardly into the earth until it'transverses may be up to eight or ten inches or more diameter, .but

also calls for the development of an aquifer bed surrounding at least the screen portion of the casing so that there "will be a relativelyfree supply'of' water into the casing to be pumped therefrom.

Due to the nature of'such a well, however, it naturally occurs that the rate of fluid flow offthe" water into the casing increases as the water'approaches the casing and this leads to turbulence and to loss of head, the gradient of which increases as the well screen is approached. The effect of the turbulence and loss in head of the water is deposition of solids from the water, particularly insoluble carbonates which precipitate due to the release of carbon dioxide from the water by the turbulence set up therein.

The insoluble carbonates tend to form deposits, particularly in the immediate vicinity of the well screen and on the screen itself where the water passes into the casing through small passages and flows" about relatively sharp corners. 1 This sedimentation then tends to become cemented together by colloidal iron, alumina, and silicates in the water and this cementing together of the carbonates fixes them in place and forms a hard encrustation that gives-rise to serious decrease in eificiency of the well.

When the etficiency of a. well of this nature drops a predetermined amount, the encrustation is treated by acidifying the well through theaddition thereto of an acid, usually about 15% muriatic acid, which dissolves or loosens a considerable amount of the encrustation. The amount of such encrustation, however, that can be released or removed in this manner is extremely limited because only a relatively weak acid concentration can be employed without damaging the-well screen. For this reason, no conventional Well having a metal screenlis ever restored to complete operating efficiency and some times acid treatment of a wellbecomes ineffective after the second or third application. Such a well might have to be abandoned due to inefficiency.

In severe cases, it might be necessary to treat a well with acid as often as once a year and it will beevident, therefore, that the problem of encrust-atio'n of a well 2,933,137 Patented Apr. 19, 1960 It is another object of this invention to provide a method of installing a well screen and for maintaining the well screen and the aquifer surrounding the screen clean and free of sedimentation and encrustation, but without in any way impairing the mechanical strength of the screen as occurs when acids are used on metal screens.

A still further object of the present invention is the provision of an improved method of manufacturing a well screen to impart extremely high mechanical strength thereto while making the screen substantiallyv pervious to corrosive influences encountered when the screen is in place in the ground or when the screen is cleaned to restore its operating efliciency.

. A still further object of this invention is the provision of a novel type well screen that overcomes or permits overcoming the principal drawbacks occurring in connection with conventional type vertical wells.

These and other objects and advantages of this invention will become more apparent upon reference to the following specification taken in connection with the accompanying drawings, wherein:

V Figure l is a vertical cross section through a well according to the present invention showing, rather diagrammatically, a finished installation;

Figure 2 is a view of the well showing the casing driven to its most advancedposition' and a well screen according to the present invention inserted therein;

Figure 3 is a view like Figure 2, but shows the ar casing being retracted upwardly to exposethe screen;

Figure 4 is a'view like Figure 3, but shows the well casing, i-n-its fully retracted position and with a seal in place between the lower end of the casing and the upper end of a blank pipe positioned at the top of the upper section of the screen pipe;

Figure 5v is a view showing the manner in, which a well according to the present invention is treated to remove built-up deposits or encrustations therefrom;

Figure 6 is a view drawn at somewhat larger scale than Figure 5 showing the construction that might be employed for the packer forming a part of thestructur utilized in treating the well; 7

Figure 7 is a fragmentary view showing the use of a plastic-covered surge block to force the' acidified solution in the Well throughout the aquifer bed surrounding the screen pipe;

Figure 8 is a fragmentary view showing a manner in which the lowermost end of the lowermost screen pipe could be sealed if so desired, thereby facilitating the forcing of the acid through the screen pipeduring the aforementioned treatment;

Figure 9 is a perspective view showing one of the screen Referring to the drawings somewhat more in detail,

s as the well installation disclosed in Figure 1 comprises a conventional metal well casing extending downwardly into the earth through a water-bearing stratum. According to. the present invention the lower end. of casing 10.

carries a screen section 12 which may c'onsistof one or more screen pipe sections fitted together in end to end relation and rigidly connected. I Between the upper end of the screen. section and the lower end of casing 10 is a blank pipe 14 also joined to the'screen pipe and sealed within the well casing by sealing means indicated at 16.

Extending downwardly into the well casing is a pipe 18 and this pipe may carry at its lower end a pump 20 of a conventional type.

According to the present'invention the screen sections of the screen pipeand the blank pipe 14 are made of a reinforced acid resistant plastic material. In particular, reinforced polyester resins are known to be satisfactory because of the great strength of reinforced polyester resin and its great resistance to corrosion, including resistance to strong acids with which the wells are to be treated. Furthermore, polyester resin isof a non-electrolytic nature and thus discourages the deposition. of insolublecarbonates. ,This probably comes about because of the lack of the screen than on the outside as indicated at 32 in Figure 11. The thickness of the wall of such'a screen may be as little as A and sufiicient strength will be had for the purposes of the present invention.

The manufacture of the screen may be carried out by forming tubular sections and thereafter cutting the holes therein. Such sections might be formed by windingj fabric on a mandrel while simultaneously spraying the plastic material thereon, thus to build up the required thickness of reinforced wall. Also, as mentioned above,

. a flock filled plastic might be sprayed on the mandrel or 42 therein pressed outwardly by springs 44. This mandrel is arranged for being driven in rotation by a motor 46 and as the mandrel rotates a spray head 48 supplies the resinous material while a heat lamp 50 at least initiates of static electricity generated by the passage of water into the polyester screens, as opposed to what occurs when water passes through a metallic screen.

,For the reinforcement, a material, such as fiber glass, nylon or Orlon, in the form of either a woven fabric, or a felted fabric, or flock, can be employed with satisfactoryresults. These materials all have high strength and can be made extremely resistant to any chemical that might be encountered in the wells either during normal use orduring treatment thereof. It ,will be understood, however, that substantially any material could be employed as a reinforcing means merely by making certain that all exposed surfaces of the screen elements were completely covered with polyester resin.

In installing a well apparatus according to the present invention a casing 10 is first driven downwardly to the desired depth and preferably with a detachable driving head 22 associated therewith. When the casing has reached the proper depth, the screen pipe section with the attached blank pipe section is then lowered into the well. At this time the installation appears as it does in Figure 2.

Thereafter, the well casing is retracted upwardly and the well screen and the drivingpoint or driving head 22 remain in position. 7 7

After the well casing hasbeen retracted to the proper point, the seal 16 is put in place. This can be done by pouring polyester resin into the space between the lower end of the well casing and the upper end of blank pipe 14. This will form a fluid-tight seal of great strength between the casing and the blank pipe.

Thereafter, the aquifer bed can be developed according to well-known practice by removing the fines therefrom and thecasing can then be capped and a pump placed provide for the maximum strength and also to insure a smooth and continuous surface.

The strength is important because according to the present invention relatively larger screen holes are em- Wall, of the said sections. This is important in order to ployed whereby considerable material is either removed by 3 /2" long and are dbOUIKs" wider on the inside the curing thereof whereby the pipe section built up on the mandrel can be removed therefrom for being cured under the proper temperature conditions. The retractable pins 42 permit the pipe section easily to be stripped from the mandrel, particularly where the mandrel is provided with a slight draft.

It will be evident that sheet fabric material could be employed with the Figures 12 and 13 fabricating arrangement merely by having the fabric punched so that the pins 42 would extend through the holes in the fabric as the material was wound up thereon.

Returning now to Figures 5, 6 and 7, upon a well in stallation accordingtothe present invention becoming inefficientdue to encrustation of the screen pipe and the surrounding aquifer, the pump 20 is withdrawn from the well and there is inserted into the well a packer 60 adapted for engaging the inside of the blank pipe 14 in sealing relation thereto. The packer may be of the expansible type illustrated or may be of a type utilizing resilient annular rings orcups. In any case, the packer forms a seal within plastic pipe 14 which prevents any communication between the water in the Well and the metalwell causing 10. I

The packer 60 has plastic pipes 62 and 64 extending therethrough and pipe 62 has a check valve 65 therein and is adapted for receiving a supply of acid from a source 66. Due to the acid-resistant nature of the packer and the pipes at the lower'end of the well, a full strength acid can be employed and will also permit the use of acids other than muriatic. For example,.hydrofluo1ic acid may be'used and this will permit elimination of a silicate encrustations which are not effected by muriatic or hydrochloric acid of any concentration.

The pipe 64 preferably leads away from the well to'a' remote location or through a discharge pump and will convey away any. foam or gases vgenerated in the well by the acid supplied thereto. 7

After the acid has been supplied to the well, it may be caused to surge through the gravel pack surrounding the screen pipe by the introduction of compressed air through one or the other of pipes 62, 64 if so desired. This would facilitate'in distributing the acid through the gravel pack so that more acid could be added inorder to-bring the concentration of acid in the body of water about the lower endof the well to the desiredlevel.

Q It may also be desirable after the concentration referred tohas been reached, to remove the packer, and insert a plastic-covered surge block 68 as illustrated in Figure 7, which could be employed for working the concentrated acid throughout the entire gravel pack area by reciprocating the block vertically, and thus promote extremely eflicient removal of encrustation from the entire region effected thereby.

After the treatment with the surge block, the block is drawn and the packer is then preferably replaced in the well and the acid is drawn from the well through the packer so that when the pump 20 is again restored to the well pure water will be supplied thereto.

It will be apparent that the blank pipe 14 which has been referred to could in certain circumstances be eliminated or it might be provided by making the uppermost section of the screen pipe with'a blank portion thereon.

It will also be evident that the several plastic pipe sections could be connected together simply by cementing or they could be providedwith sleeve-like couplings in addition to the cementing, if desired.

It will also be evident that the lower end of the screen pipe section could be enclosed by a sealing plug 70 poured therein if found necessary thereby to close the screen pipe in such a manner that the acids supplied thereto would be forced to flow throughthe screen open ings and remove the encrustation referred to.

It has been mentioned that the screen pipe could be formed by cutting the slots in blank pipes but when this is done the edges of the slots should be sprayed or otherwise treated to provide them with a layer of polyester resin whereby the screen pipe is charcterized, as mentioned before, by having a continuous and unbroken surface of polyester resin.

From the foregoing it will be apparent that what is provided by the present invention is a greatly improved vertical well, particularly characterized-in that the well can be restored at any time to its original operating efficiency and this restoration can be accomplished many times, rather than only two or three times, as in the case of a Well having a metal screen.

efiicient operating conditiong'installing a well casing in the ground, providing the well casing with a screen pipe portion at the lower end consisting of reinforced poly,- ester resin, said screen pipe section being sealed to the casing and having a blank portion at the casing end for receiving a packer, inserting an acid resistant packer into the said blank portion and sealing it thereto, and introducing strong acid through the packer into the screen pipe for dissolving and releasing encrustations formed thereon, the said method including the step of removing the packer following the introduction of acid into the screen pipe therethrough, mechanically surging the acid through the screen pipe and gravel pack, then reinserting the packer, and removing the acids from the well.

2. A method of installing and maintaining a well which comprises; installing a metal well casing in the ground, fixing to the lower end of the casing in sealed relation thereto a screen pipe of reinforced acid-resistant resinous material and of only slightly smaller diameter than the While the present invention is particularly concerned with vertical wells, it does not, of course, precluded the use of the plastic well screens in connection with horizontal wells. All of the same reasons for using screens would not be present in horizontal wells because wells of this nature have little or no tendency to become encrusted and thus do not require acid treatment. Theadvantage would obtain, however, of great strength and lightness, resistance to electrolysis and a reduced initial cost.

It will be evident that many modifications could be made in the structure and procedures'illustrated and described. In particular, the manner of manufacturing the plastic well screen would be subject to considerable modification while still adhering to known practices. One

such modification would consist of forming the mandrel on which the well screen is made up in three or more parts having tapered wedge members thereon for forming the screen slots. Such a mandrel would be constructed so as to be collapsible whereby it could be collapsed and the screen. removed therefrom.

casing, inserting an acid resistant packer into the well casing and sealingly engaging the upper end of the screen pipe therewith, and introducing acids stronger than could be used'on a metal screen pipe through the packer into the screen pipe and therethrough into the filter bed around the screen pipe, and also withdrawing the acids from the pipe'through the packer whereby to remove encrustations formed on the screen pipe and in the gravel pack surrounding the screen pipe and to treat the well with acid while preventing any contact between the acid and The material referred to in the specification for the g screen is polyester, a commercial product of this nature being sold under the trade name of Mylar, but many other plastics have the quality of being acid resistant and could, in many cases, the utilized as a substitute for the polyester resin. Among such other materials are the vinyl or vinylidene plastics, such as Tygon or Saran, the epoxies, such as Araldite, and long chain polyethylene polymers or halogen substitution products thereof, particularly the fluoro or chloro derivatives.

It will be understood that this invention is susceptible any metallic part of the well.

3. A method of maintaining a well which comprises; installing a metal casing in the ground, sealingly attaching to the lower end of the casing a pipe section which is of an acid-resistant resinous material, connecting pumping means with the casing and pumping the well until encrustations form on and about the screen pipe section that reduce the well efficiency to a predetermined amount,

detaching the pumping means from the well, introduca ing strong acid into the screen pipe section while preventing the acid from coming in contact with the metal well casing whereby to dissolve the encrustations, removing the acid and dissolved encrustations from the well while preventing any contact thereof with the metal well I casing, and again connecting the pumping-means with the well casing and resuming pumping of the well.

References Cited in the, file of this patent UNITED STATES PATENTS Battle Oct. 15, 1957

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