Abstract:
In order to simplify the cleaning and disinfection of water wells, perforated casings are installed outside and adjacent to a water well casing and screen. This installation provides cleaning and disinfection capability of the well without removing the well&#39;s pump. The number of adjacent perforated casings can range from one for a small diameter well to three or more for lager diameter wells. The perforated casings define alternating blank sections and perforated sections.

Description:
The present invention generally relates to earthen wells, and, more particularly to the cleaning and refurbishing of water wells. This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The Government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     All earthen wells, over time, whether oil or water wells, become degraded, usually in a manner that severely decreases a well&#39;s production rate. This degradation typically results from clogging of the well&#39;s perforated casing and gravel (filter) pack. This clogging is the result of naturally occurring chemical precipitates, such as calcium carbonate or silica, and gelatinous masses produced by iron-secreting bacteria, or other toxic and non-toxic anaerobic bacteria that are in the groundwater. These clogging deposits restrict the oil or water from entering the perforated casing, significantly reducing well performance, and increasing corrosion and encrustation of the casing and screens. 
     Previous attempts to solve these clogging problems have been difficult and expensive. In most cases, removal of the well&#39;s pump is required to allow complete access into the well. After the removal of the pump, the well can be treated using appropriate chemical and mechanical techniques. However, even these measures do not assure success, and often it is necessary to drill a completely new well. In any event, these measures are costly and difficult, and the use of chemicals and mechanical cleaning devices can easily result in damage to well casing and screen sections. The cost of pump removal alone can easily run into tens of thousands dollars. 
     Surprisingly little effort has been devoted to investigating the benefits of well maintenance programs. The use of appropriate well maintenance programs would improve well performance and extend well life. This neglect is probably due to additional program costs, and the fact that changes in this industry are not easily effected. 
     In the past, some water wells had small-diameter metal pipes welded to the outside of the casing. These small diameter pipes normally extended only to the top of the well screen and to below the location of the well pump. Pressure transducers or measuring tapes could be inserted into these pipes to monitor changes in water levels without interfering with the pump. However, these pipes provided no means for cleaning the well. 
     The present invention solves many repair problems associated with clogged water wells. The invention allows easy and complete access to the exterior of the well casing, screen, and gravel pack where clogging originates. Over time, regular scheduled use of the invention can significantly improve well performance and reduce pumping costs. Current repair efforts are inefficient because they require first that the well pump be removed, and second that the interior of the well screen be cleaned. Both of these functions are laborious and time consuming. 
     It is therefore an object of the present invention to provide apparatus and method for the clearing of clogs from water wells. 
     It is another object of the present invention to provide apparatus and method capable of cleaning and disinfecting wells. 
     It is another object of the present invention to provide apparatus allowing direct access to the exterior surfaces of the gravel pack, well screen, and casing of a water well so that they can be efficiently cleaned and disinfected. 
     It is a feature of the present invention that well pumps and other surface equipment do not need to be removed from the well in order for cleaning and disinfecting of the well to be accomplished. 
     Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     SUMMARY OF THE INVENTION 
     To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the apparatus of this invention comprises least one perforated casing situated adjacent to an outside surface of a water well casing having a top and a bottom, the at least one perforated casing extending from a first position at the top of the water well casing to a second position at the bottom of the water well casing.  3 . In another aspect of the present invention, and in accordance with its purposes, a method of cleaning a water well comprises the steps of installing at least one perforated casing adjacent to an outer surface of a water well casing having a top and a bottom, the at least one perforated casing extending from the top of the water well casing to the bottom of the water well casing, and forcing appropriate chemicals and surfactants through the at least one perforated casing to clean the water well. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is cross-sectional view of a typical water well. 
     FIG. 2 is a cross-sectional and top view of a typical water well with the cleaning device according to the present invention in place. 
     FIG. 3 contains pictorial views of various configurations for perforated sections according to the present invention. 
     FIG. 4 contains an illustration of one arrangement of blank sections and perforated sections according to the present invention as well as some methods of connecting adjoining sections. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides an apparatus and method for the cleaning and disinfecting, where appropriate, of water wells. The invention can be understood most easily through reference to the drawings. 
     Referring to FIG. 1, there can be seen a typical water well  11  in which casing  12  has been inserted, shown as both a side view and top view. Casing  12  includes blank section  12   a , perforated section  12   b  along an appropriate length of the middle portion of its length, and blank casing  15  and bottom plug  12   c . Casing  12  is surrounded by gravel pack  13 , and is situated in borehole  14 . Cement seal  16  and concrete pad  17  surround the upper portion of casing  12  in the area of casing  12  where the well&#39;s pump and associated housing (not shown) are located. A protective conductor casing  18  is often located in the upper portions of the casing  12  to prevent hydraulic communication between shallow and deep geological units through the wellbore annulus. 
     In operation, ground water flows through gravel pack  13 , and through perforated section  12   b  in casing  12 , and collects in casing  12 . A pump located in the upper portion of casing  12  (not shown) then pumps the collected water to the surface. 
     Over time, gravel pack  13  and outside portions of perforated section  12   b  become clogged with naturally occurring chemical precipitates, such as calcium carbonate or silica, and residue from iron-secreting bacteria, or other toxic and nontoxic anaerobic bacteria that are introduced while drilling the well, or may be naturally occurring. These clogging deposits restrict ground water from entering casing  12 , significantly reducing well production and increasing corrosion on the inside portions of perforated sections  12   b.    
     As seen in FIG. 2, elements of the present invention can be seen in a typical water well installation, shown in both side and top views. The water well disinfecting and refurbishing apparatus of the present invention includes a small casing  21 , whose diameter can range between approximately 1.0 to 4.0 inches. The device can easily fit into borehole  14  at any desired location around the outside circumference of the well casing  12 . A normal configuration would include between one (1) and three (3) small casings  21 , although more could be employed based on a particular well diameter. As shown in FIG. 2, small casing  21  alternates between blank sections  21   a  and perforated sections  21   b . Small casing  21  extends from the surface to lower end of perforated section  12   b.    
     FIG. 3 illustrates the construction of typical perforated sections  21   b , depicting various possible perforations. As seen, perforated section  21   b  is cylindrical with a diameter of approximately 1.0 to 4.0 inches. It has openings, several configurations of which are illustrated, that allow liquids, but not gravel, to pass through. The openings in perforated section  21   b  allow cleansing and disinfecting solutions to be pumped through the top blank section  21   a  of small casing  21  (FIG.  2 ). The cleansing and disinfecting solutions include such substances as commercially available disinfectants, acids, surfactants, or any other appropriate chemicals. 
     It may become necessary in certain situations to concentrate the flow of cleansing agents or disinfectants through a particular arrangement of one or more perforated sections  21   b . To accomplish this with the present invention, it only is necessary to insert a length of blank casing, having an outside diameter just slightly smaller than the inside diameter of small casing  21 , into small casing  21  to cover the perforations desired. This will increase the flow through uncovered perforations of selected perforated sections  21   b.    
     In FIG. 4, a typical configuration of small casing  21  is illustrated with several means of connection between blank sections  21   a  and perforated sections  21   b . As shown, the blank section  21   a  at the surface could be threaded or have any other appropriate connection for connecting to cleaning solutions. As sections of small casing  21  are supplied in 10 to 40 foot lengths, an appropriate number of blank sections  21   a  could be used before reaching perforated section  12   b  of casing  12  (FIG.  2 ), depending on the depth of the water well. 
     Individual sections can be connected in various ways according to the material from which small casing  21  is made. If small casing  21  is metallic, sections could be connected using beveled ends and welding, collared ends and welding, or threaded ends. If made of plastic, sections could have threaded ends or be coupled with connectors and adhesive. Blanks sections  21   a  and perforated sections  21   b  can be arranged in any appropriate manner down the length of small casing  21 . Small casing  21  is sealed with end plug  21   c . Alternative materials that may be used for sections of small casing  21  include mild carbon and stainless steels, reinforced fiberglass epoxy, plastics, or other materials commonly used in oil and water wells. 
     Small casing  21  can be any appropriate casing having the characteristics delineated herein. One such casing that can be used with the present invention is manufactured by UOP® under the mark of JOHNSON® SCREENS. UOP® is located at P.O. Box 43118, St. Paul, Minn. 55164-3118. 
     Referring back to FIG. 2, appropriate cleansing and disinfecting solutions easily can be introduced directly into the gravel pack  13  of water well  11  by pumping the solutions into small casing  21 . These fluids flow down small casing  21 , and exit through perforated sections  21   b  into gravel pack  13 . This route must be followed because of small casing  21  being sealed by end plug  21   c  (FIG. 4 a ). Once in gravel pack  13 , the solutions will act to clean and disinfect water well  11 . There is no need to remove either surface or downhole equipment to clean the well. In large diameter wells, multiple small casings  21  are installed to insure that the water well  11  will be thoroughly cleaned. The introduction and circulation of chemical cleaners into the small casing  21  and then into the water well  11  can also be improved by using a standard well swab designed to fit the small diameter casing  21 . 
     Small casing  21  is most easily installed at the time of well drilling since it can be put into place during installation of the well casing. However, the present invention can also be used with existing wells. In this event, the pump assembly must be removed to allow placing small casings  21  inside the well casing  11 , and then reinstalling the well pump. 
     The present invention allows many functions to be performed on water well  11  that have previously been either impossible or very difficult and expensive. Some wells have had small-diameter metal pipes welded to the sides of casing that extend downward to the top of the well screen. These pipes provide transducer access to the top of the screen for water level monitoring. However, these pipes do not allow for well cleaning because they do not extend the full extent of the screen and gravel pack. 
     Well maintenance without the need to remove the well pump is allowed by the present invention. This means that time, labor, and money are saved. Hence, routine well cleaning and maintenance are more likely to be completed. Thus, higher production levels can be maintained for much longer periods of time compared to wells with no maintenance. 
     The fact that wells build up clogging layers of material is alleviated by the present invention, since all of the clogging substances are treatable by chemicals and surfactants. Should the need arise to restore lost production capacity to a water well, one need only attach appropriate tubing to small casing  21 , and pump chemicals and surfactants into well  11 . Well  11  is then surged by alternately turning the pump on and off until the chemicals and surfactants are thoroughly mixed in gravel pack  13  and well screen  12   b . This procedure is repeated until well&#39;s production capacity has been restored. Then the offending substances and chemicals are pumped from well  11 , and all wastes are properly disposed of prior to well  11  being returned to normal use. 
     The ability of the present invention to provide this access to the interior of a water well and gravel pack allows a well operator unprecedented abilities to maintain the well. This maintenance can be performed efficiently and inexpensively through use of the present invention. 
     Examples of appropriate chemicals and surfactants that are used to clean water wells equipped with the present invention include acids, detergents, chlorine, other antibacterial compounds, and fungicidal compounds. Of course the actual chemicals to be employed will depend on the situation at a particular water well. The benefits of the present invention can be appreciated most easily when one considers the benefits of accomplishing cleaning of a well without having to remove the well&#39;s pump. 
     As the present invention allows efficient access to the entire length of a well&#39;s screen and gravel pack, it permits the inexpensive and effective cleaning of water wells. This means that a well&#39;s initial performance can be maintained for a longer period of time. It also means that the well will have lower energy costs associated with pumping, and that the well&#39;s operational life can be extended. 
     The present invention will find application in water wells throughout the world. In the United States alone there are approximately 800,000 water wells drilled annually. With the present invention installed in a significant percentage of these new wells, the savings to municipalities and individuals could be great. The present invention can accomplish the effective cleaning of water wells through relatively simple components, assuring meaningful benefits to well operators and owners. 
     The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.