Cross-Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Application No. 62/158,382 filed May 7, 2015 and which is hereby incorporated herein by reference in its entirety.

Technical Field

[0002] The disclosed technology relates generally to well systems and, more particularly, to non-vertical well systems employing a single slant well, an array of slant wells, or multiple arrays of slant wells for supplying feedwater from a near-shore or sub- sea aquifer to a desalination plant.

Description of the Related Art

[0003] Water developers in California and other coastal communities throughout the world are increasingly considering seawater desalination as a potential source of water for municipal and industrial supplies. Limited groundwater supplies in coastal areas, poor inland groundwater quality, and the decreasing reliability of imported water have made seawater desalination a viable consideration. Seawater desalination has been made even more viable through more cost-effective and efficient subsurface intake systems and water treatment technologies.

[0004] Subsurface slant well feedwater systems produce water from near-shore and offshore subsurface aquifer systems. One of the primary requirements for a successful slant well beneath the ocean is the ability to prevent fine-grained materials from entering the well. Where native subsea aquifer materials are too fine to provide a natural filter pack (e.g., consisting of coarse-grained unconsolidated sands and gravels), it is necessary to place an artificial filter pack around the screened portions of the well.

[0005] Slant well drilling is included in the practice of drilling non-vertical wells. Non-vertical wells are typically used in the petroleum industry and are also known as horizontally directionally drilled wells (HDD wells) when a portion of the well may be substantially horizontal. Slant wells are also used in other applications, such as drilling beneath roadways or rivers in order to provide conduits for facilities.

[0006] Slant well desalination subsurface intake systems present significant advantages over traditional open-water desalination plant intakes. These advantages include avoidance of entrainment and impingement impacts to marine life, reduction or elimination of costly reverse osmosis pretreatment (e.g., not subject to ocean water impurities such as algae blooms), and reduction or elimination of permanent visual impacts. Slant well systems are buried systems (i.e., there are little or no visual impacts on the land surface), as the wells and connecting pipelines are typically completed below the land surface. [0007] In the past, slant well technology had not been successfully applied to subsea construction of desalination feedwater supplies, as fine-grained subsea materials entering the well during pumping would clog the well screen slot openings, reducing performance of the well. Once the well screen slot openings are clogged, it becomes very difficult or near impossible to continue to pump water. As described in U.S. Pat. Nos. 8,056,629 and 8,479,815, placement of an engineered artificial filter pack around the screened portions of the slant well helps stabilize the subsea aquifer materials and prevent migration of fine sand and silt materials (from subsea aquifers) into the well, inhibiting the screen portions from becoming clogged and improving the water quality of the desalination feedwater. It has been found, however, that, in slant wells, settlement of the filter pack may lead to fine-grained materials entering the slant well over time, eventually clogging the well screen slots.

[0008] Accordingly, there is a need for a reliable slant well system that is better able to supply water from near-shore or subsea aquifers to a desalination plant without becoming clogged with fine-grained materials (e.g., fine sands and silts) over time. The present invention satisfies these needs and provides further related advantages.

Brief Summary of Embodiments

[0009] The present invention may be embodied in certain systems and methods for providing a subsurface feedwater supply to a desalination plant through a single slant well or through a well field of slant wells. According to various embodiments of the disclosed technology, the process involves constructing a system of angled wells (slant wells) that obtain a desalination feedwater supply from permeable aquifer systems near or beneath a saline water source (e.g., ocean, sea, or salty inland lake). The slant wells induce recharge through the floor of the ocean, sea, or inland lake due to the hydraulic head difference between the slant well pumping level and the level of the ocean, sea, or lake. The slant wells also receive recharge from horizontal flow in subsea and near-shore aquifers. As the supply source is relatively constant, the water supply to the slant well system generally provides a long-term, sustainable water source.

[0010] In one embodiment, the slant wells are typically constructed from a few degrees below horizontal to a few tens of degrees below horizontal. In other embodiments, the slant well angles may vary from zero to ninety degrees below horizontal.

[0011] According to various embodiments of the disclosed technology, each slant well is drilled at an angle beneath the subsea or near-shore aquifer, and a cylindrical well screen is placed within the borehole. The well screen is perforated to permit saltwater to enter the well screen and eventually be pumped through a pipe to a desalination plant. Filter material surrounding the slant well screen is either natural or artificially placed. In an artificially placed filter pack, an engineered filter pack material is placed in the annular space between the well screen and the borehole wall to inhibit migration of fine-grained aquifer materials into the well during pumping. Unlike vertical wells where gravel feed pipes are typically placed in the annular space between the well screen and the borehole wall to permit periodic "topping up" of the filter pack and further inhibit migration of fine-grained aquifer materials into the well during pumping, slant well construction makes topping up not feasible.

[0012] According to various embodiments of the disclosed technology, the angled well screen is perforated around only a portion of its circumference and, in particular, a lower portion of its circumference. This configuration permits some of the filter pack material to remain above the perforations in the annular space between the non-perforated portion of the well screen circumference and the borehole wall. The filter pack material in this space can then act as a reservoir for the filter material. In this configuration, the partial perforation pattern permits some vertical settlement of the filter pack over time while still preventing the perforations in the well screen from directly contacting fine-grained materials in the aquifer. By placing some of the filter pack materials adjacent a non-perforated portion of the well screen circumference, this configuration provides a built-in filter pack reservoir along the length of the well screen, permitting the filter pack to undergo some settlement without compromising the well's ability to stabilize the aquifer.

[0013] An angled well screen configuration permits a filter pack reservoir to be maintained above the top of the well screen to inhibit migration of fine-grained aquifer materials from entering the well screen pipe if settlement of the pack falls below the top of the pipe. Perforation of a lowermost portion of the angled well screen pipe permits the filter pack reservoir to occur above the top of the well screen perforations and extending to the borehole wall (or the uppermost level of the artificial pack). This design permits vertical settlement of the artificial filter pack over time without compromising the ability of the well to stabilize fine-sand aquifer materials. If a well filter pack comprises a pre-pack assembly and materials, a higher percentage of the well's circumference may comprise perforations, as settlement of the pack may be less in the case of pre-packed screens.

[0014] According to an embodiment, the disclosed technology provides a system for supplying water from or sending water to an aquifer. The system comprises a well screen extending within an aquifer along an axis angled less than ninety degrees below horizontal and a filter pack substantially surrounding and adjacent to the well screen. The well screen comprises an outer portion for admitting water from or injecting water into the aquifer. The outer portion of the well screen extends along the axis and defines an inner conduit for channeling water admitted from or to be injected into the aquifer. The outer portion of the well screen comprises an upper perimeter section that is substantially free of perforations and a lower perimeter section comprising a plurality of perforations.

[0015] In one embodiment, the system further comprises one or more tremie pipes removably positioned adjacent to the outer portion of the well screen for channeling loose filter pack material to an area surrounding the outer portion of the well screen. In another embodiment, the system further comprises a containment material surrounding the filter pack and securing the filter pack to the outer portion of the well screen.

[0016] According to another embodiment, the disclosed technology provides a method of constructing a system for supplying water from or sending water to an aquifer. The method comprising the steps of (1) extending a casing into an aquifer along an axis angled less than ninety degrees below horizontal, the casing comprising an outer casing portion that extends along the axis and that defines an inner casing conduit; (2) extending a well screen within the inner casing conduit along the axis so that a space is formed between the well screen and the outer casing portion, the well screen comprising an upper perimeter section that is substantially free of perforations and a lower perimeter section comprising a plurality of perforations; (3) placing a filter pack in the space formed between the well screen and the outer casing portion so that the filter pack is adjacent to and substantially surrounds the well screen; and (4) withdrawing the casing from the aquifer while leaving the well screen and filter pack in the aquifer.

[0017] In one embodiment, the step of placing the filter pack comprises the steps of removably positioning a tremie pipe in the space formed between the well screen and the outer casing portion, and pumping loose filter pack material through the tremie pipe into the space formed between the well screen and the outer casing portion. In another embodiment, the method further comprises the steps of placing the filter pack in a containment material, and securing the filter pack and containment material to the well screen before extending the well screen within the inner casing conduit.

[0018] Other features and aspects of the disclosed technology will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the disclosed technology. The summary is not intended to limit the scope of any inventions described herein, which are defined solely by the claims attached hereto.

Brief Description of the Drawings

[0019] The technology disclosed herein, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the disclosed technology. These drawings are provided to facilitate the reader's understanding of the disclosed technology and should not be considered limiting of the breadth, scope, or applicability thereof. It should be noted that, for clarity and ease of illustration, these drawings are not necessarily made to scale.

[0020] FIG. 1 is a side elevational view of an angled well placed beneath an ocean floor for producing water from aquifers near or beneath the ocean floor and for delivering feedwater to a seawater reverse osmosis (SWRO) desalination plant, in accordance with one embodiment of the technology described herein.

[0021] FIG. 2A is a side elevational view of a portion of an angled well screen for use in the angled well of FIG 1, in accordance with one embodiment of the technology described herein, the well screen having perforations in a lower portion of its circumference and substantially surrounded by a filter pack, which is shown partially in cross-section and partially in outline. [0022] FIG. 2B is a cross sectional view, taken along the line 2B-2B in FIG. 2A, of the angled well screen of FIG. 2A, showing the perforations in the lower portion of the circumference.

[0023] FIG. 3 is a perspective view of a pre-packed well screen surrounded by an artificial filter pack contained within a mesh, in accordance with one embodiment of the technology described herein, the well screen, filter pack, and mesh positioned to be inserted inside a temporary casing.

[0024] FIG. 4 is a perspective view of a portion of a pre-packed well screen joint surrounded by an artificial filter pack contained within a mesh, in accordance with one embodiment of the technology described herein, with an end support structure welded onto the well screen joint to further hold the artificial filter pack in place.

[0025] FIG. 5 is a perspective view of a portion of a well screen joint surrounded by an artificial filter pack placed by tremie pipes, in accordance with one embodiment of the technology described herein.

[0026] FIG. 6A is a side elevational view of a portion of a fully horizontal well screen surrounded by a filter pack, in accordance with one embodiment of the technology described herein, with the filter pack shown in cross-section.

[0027] FIG. 6B is a cross-sectional view, taken along the line 6B-6B in FIG. 6A, of the well screen and filter pack of FIG. 6A.

[0028] FIG. 7 is a side elevational view of an HDD well placed beneath an ocean floor for producing water from aquifers near or beneath the ocean floor and for delivering feedwater to a seawater reverse osmosis desalination plant, in accordance with one embodiment of the technology described herein.

[0029] FIG. 8 is a flowchart showing a method of constructing a system for supplying water from or sending water to an aquifer.

[0030] The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the disclosed technology is limited only by the claims and the equivalents thereof.

Detailed Description of the Embodiments

[0031] Embodiments of the technology disclosed herein are generally directed toward slant or HDD wells. More particularly, the various embodiments of the technology disclosed herein relate to slant or HDD wells that produce water from permeable deposits near or beneath saline water bodies (e.g., oceans, seas, and inland lakes) or inject concentrate return into deposits beneath saline water bodies. In various embodiments, the invention can provide a long-term, sustainable feedwater supply for a desalination plant with virtually unlimited recharge potential.

[0032] With reference now to the figures, and particularly to FIG. 1 thereof, there is shown a slant well 1 drawing feed water from a subsurface aquifer 2. Water 3 from permeable aquifer materials comprising the subsea aquifer 2 enters the slant well screen 4 recharged from the overlying ocean 5 as well as horizontal flow 6. The slant well 1, receiving recharge from sources 3 and 6, pumps water to a desalination plant in the direction of arrow 7 through an appropriate pipeline (not shown).

[0033] Similar slant well systems are described in U.S. Pat. Nos. 8,056,629 and 8,479,815, which are incorporated by reference as if fully set forth herein. Although the slant well systems disclosed in U.S. Pat. Nos. 8,056,629 and 8,479,815 are a vast improvement over previous slant well systems, certain limitations exist, particularly respecting the settlement of filter packs leading to problems of fine-grained sediment entering the slant well.

[0034] During the lifetime of an artificially filter-packed vertical well, the filter material placed in the annular space between the borehole wall and the well screen tends to lose volume due to compaction and settlement over time. To refill the filter pack, gravel feed pipes are placed in the annular space between the well screen and borehole wall. This allows for periodic topping up of the filter pack preventing migration of fine-grained aquifer materials into the well during pumping. In vertical wells, the gravitational forces acting downward are parallel to the vertical axis of the well, and the filter pack completely surrounds the well screen.

[0035] In angled wells, such as those discussed here, which typically vary from a few degrees to a few tens of degrees below horizontal, gravitational forces also act vertically but do so throughout the entire well screen length. Due to the angled wells' method of construction, there is no filter pack reservoir other than the volume of filter material resting above the top of the well screen pipe. It has been found that, over time, consolidation of this overlying filter material may result in the pack settling to the point that the top of the well screen is exposed directly to fine-grained aquifer materials. If the angled well screen is perforated throughout the entire circumference of the well screen pipe, settlement of the pack will expose well perforations directly to aquifer materials, which could result in fine-grained aquifer materials entering the well screen pipe and, potentially, catastrophic well failure.

[0036] To inhibit this from happening, the slant well 1, in one embodiment of the present invention, has an angled well screen pipe perforated only in a lower portion of its perimeter, allowing some filter pack material to remain above the perforations (in the annular space between the top of the perforations and the borehole wall) and act as a reservoir. This partial perforation or "half-moon" pattern allows for some vertical settlement of the filter pack over time but still provides a reservoir to avoid the situation of the well screen directly contacting the aquifer. In this way, the partial perforation design effectively creates a built-in filter pack reservoir for every lineal foot of well screen length, which allows for filter pack settlement without compromising the well's ability to stabilize the aquifer.

[0037] Although sometimes referred to herein as a "half-moon" pattern, the partial perforation pattern is not limited to a design in which the perforated and unperforated sections of the well screen each constitute half of the perimeter of the well screen. In some embodiments, the perforated section of the well screen constitutes more than half of the perimeter of the well screen, while the unperforated section of the well screen constitutes less than half of the perimeter of the well screen. In other embodiments, the perforated section of the well screen constitutes less than half of the perimeter of the well screen, while the unperforated section of the well screen constitutes more than half of the perimeter of the well screen.

[0038] Referring to FIGS. 2A and 2B, there is shown is a side elevational view and a cross sectional view of a portion of a slant well screen 9 with a half-moon pattern of perforations 8, in accordance with an embodiment of the present disclosure. In this example, an 18-inch diameter pipe is perforated in the lower 57 percent of the pipe's circumference. This is a percentage of the circumference being perforated relative to 100 percent of the circumference being perforated, not a percentage of the well screen open area.

[0039] As shown in FIG. 2B, the lower perimeter section of the well screen 9 comprises eight spaced, slot-like perforations 8 going around the circumference of the well screen. For comparison, a 100-percent perforation pattern would consist of 14 perforations going around the circumference of the well screen. On other

embodiments, the number of perforations varies with pipe diameter as well as perforation length.

[0040] Table 1 below shows perforation percentages for exemplary 14-inch and 18-inch well screen pipes. The percentages shown in Table 1 are relative to a full circumference perforated screen. To arrive at these figures, it was assumed that the outer diameter of a 14-inch inner-diameter well screen is 14 inches + 2 x ¼ inch wall + 2 x ¼ inch collars + 1/8 inch weld bead, which is approximately 15 1/8 inches. The circumference is then equal to 47.4925 inches. Each perforation is 3 inches long with 1.75-inch spaces between louvers. Thus, for a 14-inch inner-diameter well screen, the sum of 10 x 3 inch louvers + 10 x 1.75 inch spaces = 47.5 inches, which corresponds to a 100 percent perforation percentage of the outer circumference of the well screen. Similarly, it was assumed that the outer diameter of an 18-inch inner-diameter well screen is approximately 21 inches, which corresponds to an outer circumference of about 66 inches. If each perforation is 3 inches long with a 1.75-inch space between louvers, then 14 perforations x 3 inches/louver + 14 x 1.75 inch spaces = 66.5 inches, or 100 percent perforation coverage on the outer circumference of the well screen.

Table 1. Percentage of pipe circumference perforated versus number of perforations for 14-inch and 18-inch well screens.

[0041] In FIG. 2A, the filter pack reservoir is shown as well as the settlement of the filter pack. The perforated pipe forming the angled well screen 9 is placed within an angled borehole 10 having a diameter greater than the diameter of the well screen. In the example of FIG. 2A, the artificial filter pack 11, which had been placed in the annular space between the angled well borehole 10 and the perforated pipe 9, and which had initially filled that annular space, has now settled to the level 12, permitting fine-grained materials 14 to move into the space vacated by the filter pack. A filter pack reservoir 13, however, exists above the top of the perforations 8, providing a filter pack reservoir for inhibiting the migration of fine-grained aquifer materials 14 inside the angled well 9.

[0042] In this example, the total initial available filter pack reservoir 15 has decreased to the reduced filter pack reservoir 13. As can be seen, however, even with the settlement of the filter pack 11 below the top of the well screen pipe 9, there is sufficient filter pack material above the well screen perforations 8 to avoid migration of the fine-grained materials 14 into the well.

[0043] This can be further seen in FIG. 2B. As shown in FIG. 2B, the well screen 9 comprises a substantially cylindrical outer portion 20 for admitting water from or injecting water into the aquifer. The outer portion 20 of the well screen 9 defines an inner conduit 21 having a substantially circular cross-section for channeling water admitted from or to be injected into the aquifer. The outer portion 20 of the well screen 9 comprises an upper perimeter section 22 that is free or substantially free of perforations and a lower perimeter section 23 comprising eight spaced slot-like perforations 8 going around the circumference of the well screen 9. Because the upper perimeter section 22 is free or substantially free of perforations, a filter pack may settle below the top of the well screen 9 without exposing the perforations 8 in the lower perimeter section 23 to fine-grained aquifer materials.

[0044] Referring back FIG. 2A, the angled well screen 9 extends within the aquifer along an axis 24 having an angle 25 with respect to the horizontal 26 that is less than ninety degrees. The artificial filter pack 11 substantially surrounds and is adjacent to the angled well screen. Through the spaced perforations 8 in the outer portion 20, water may be admitted from or injected into the aquifer. Although the perforations 8 are shown extending circumferentially around the outer portion 20 of the well screen 9 in a slot-like fashion, in other embodiments, the perforations 8 may extend axially along the outer portion 20. Also, as discussed above, the number of perforations 8 may vary with well-screen diameter as well as perforation length.

[0045] Referring to FIG. 3, there is shown a portion of a slant well screen having a partial perforation pattern 16, in accordance with an embodiment of the present disclosure. Surrounding the well screen is an artificial filter pack contained between the well screen and a containing mesh or other porous containment material 17. Loose artificial filter pack material 18 is placed in the annular space between the well screen and the mesh or other containment material 17 prior to insertion of the well screen, filter pack, and containment material inside the temporary casing 19. The mesh or other containment material 17 thus secures the artificial filter pack material 18 to the outside of the well screen, reducing or eliminating the need for positioning a tremie pipe in the borehole for channeling lose filter pack material to the area surrounding the well screen.

[0046] After the borehole 10 is created in the aquifer 2, the temporary casing 19 is extended through the borehole into the aquifer along the axis of the borehole. In one embodiment, the temporary casing 19 comprises an outer casing portion 27 that extends along the axis and that defines an inner casing conduit 28. The well screen 9 is then extended within the inner casing conduit 28 along the axis so that a space is formed between the well screen 9 and the outer casing portion 27. As described above, the well screen 9 comprises an upper perimeter section 22 that is substantially free of perforations and a lower perimeter section 23 comprising a plurality of perforations 8.

[0047] In the embodiment of FIG. 3, the artificial filter pack material 18 is placed in the temporary casing 19 at the same time as the well screen 9. After the well screen 9 has been extended into the temporary casing 19, the artificial filter pack material 18 fills the annular space formed between the well screen 9 and the outer casing portion 27. The temporary casing 19 is then withdrawn from the aquifer 2 while leaving the well screen 9 and artificial filter pack material 18 in the aquifer.

[0048] Referring to FIG. 4, there is shown a portion of a slant well screen joint 29 having a partial perforation pattern 16, in accordance with an embodiment of the present disclosure. As described above, the number and coverage of the perforations may vary from that shown. Surrounding the well screen joint 29 is a pre-packed artificial filter pack 30 contained between the well screen joint and a containing mesh or other porous containment material 17. Loose artificial filter pack material 18 is placed in the annular space between the well screen joint 29 and the mesh or other

containment material 17 prior to insertion of the well screen, filter pack, and

containment material inside the temporary casing 19 (see FIG. 3). The mesh or other containment material 17 may contain centering guides (not shown) to hold the annular space open while the filter pack material 18 is being added. The mesh or other containment material 17 thus secures the artificial filter pack material 18 to the outside of the well screen joint 29, reducing or eliminating the need for positioning a tremie pipe in the borehole for channeling lose filter pack material to the area surrounding the well screen joint.

[0049] Once the artificial filter pack 30 is placed, end support structures 31 are welded onto the well screen joint 29 at both ends to further hold the artificial filter pack in place. Each end support structure 31 is a flat, annular-shaped piece positioned at an end of the well screen joint 29 and extending radially outward from the outer portion 20 to the mesh or other containment material 17.

[0050] The pre-packed well screen joint 29 may be welded with together with another pre-packed well screen joint 29 in the field using a casing collar 32. The casing collar 32 is a substantially cylindrical piece welded on its inner surface to the well screen joint 29 using a weld bead 33.

[0051] Referring to FIG. 5, there is shown a portion of a slant well screen joint 29 having a partial perforation pattern 16, in accordance with another embodiment of the present disclosure. As described above, the number and coverage of the perforations may vary from that shown. Surrounding the well screen joint 29 is an artificial filter pack 34 placed by a pair of tremie pipes 35. Using the tremie pipes 35, loose artificial filter pack material 18 is placed adjacent the well screen joint 29 as the temporary casing and tremie pipes are withdrawn from the borehole. The well screen joint 29 may have centering guides (not shown) to center the well screen joint within the temporary casing before the temporary casing is removed from the borehole. In one embodiment, centralizers or other support structure may be placed or formed on the casing collars 32 to hold the tremie pipes 35 in position.

[0052] The tremie pipes 35 thus channel lose filter pack material 18 to the area surrounding the well screen joint 29. In one embodiment, the tremie pipes 35 place the filter pack material 18 as a slurry of filter material and water under pressure. The tremie pipes may be placed above the top of the well screen joints 29 so that the filer pack material 18 fills the annular space between the well screen joints 29 and the borehole wall with the assistance of gravity.

[0053] Referring to FIGS. 6A and 6B, there is shown a portion of a full horizontal well screen 9 surrounded by an artificial filter pack 11 after placement in a borehole 10. These figures show the total initial available filter pack reservoir 15 before any settlement of the artificial filter pack 11.

[0054] Referring to FIG. 7, there is shown a telescoping HDD well 36 drawing feed water 37 from a subsurface saltwater aquifer 38. Feed water 37 from permeable aquifer materials 39 comprising the saltwater aquifer 38 enters the HDD well screen 40 recharged from the overlying ocean 41. The telescoping HDD well 36 pumps saline water to a desalination plant (not shown) through a buried collector pipeline 42.

[0055] The telescoping HDD well 36 comprises a submersible pump 43 that pumps water from the well to the buried collector pipeline 42. The well is recharged from induced infiltration from beneath the ocean floor 44. The freshwater-saltwater interface is shown by the number 45. Because the telescoping HDD well 36 is completed below the ocean floor 44, it avoids entrainment and impingement impacts to marine life. In addition, the filtration process of the subsurface aquifer materials 39 reduces or eliminates costly reverse osmosis pretreatment. Furthermore, the telescoping HDD well system 36 may be completed below the land surface 46 to eliminate aesthetic impacts.

[0056] Referring to FIG. 8, there is shown a method 100 of constructing a system for supplying water from or sending water to the aquifer 2. In step 110, the temporary casing 19 is extended into the aquifer 2 along an axis angled less than ninety degrees below horizontal. As shown in FIG. 3, the temporary casing 19 comprises an outer casing portion 27 that extends along the axis and that defines an inner casing conduit 28.

[0057] In step 120, loose artificial filter pack material 18 is placed in the containment material 17 to form an artificial filter pack 11. The filter pack and containment material are secured to the well screen 9 so that they may be extended within the temporary casing 19 at the same time as the well screen.

[0058] In step 130, the well screen 9 is extended within the inner casing conduit 28 along the axis so that a space is formed between the well screen 9 and the outer casing portion 27. As shown in FIGS. 2A and 2B, the well screen 9 comprises an upper perimeter section 22 that is substantially free of perforations and a lower perimeter section 23 comprising a plurality of perforations 8.

[0059] In step 140, the artificial filter pack 11 is placed in the space formed between the well screen 9 and the outer casing portion 27 so that the artificial filter pack 11 is adjacent to and substantially surrounds the well screen. If step 120 is performed, then this step 140 occurs at the same time as step 130.

[0060] In step 150, the temporary casing 19 is withdrawn from the aquifer 2 while leaving the well screen 9 and artificial filter pack 11 in the aquifer.

[0061] In one embodiment, step 120 is omitted. In its place, step 140 of placing the artificial filter pack 11 comprises removably positioning a tremie pipe in the space formed between the well screen 9 and the outer casing portion 27, and pumping loose filter pack material through the tremie pipe into that space.

[0062] Although the disclosed technology is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the disclosed technology, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the technology disclosed herein should not be limited by any of the above-described exemplary embodiments.