Abstract:
A system for a water supply well that incorporates a vertical well with one or more horizontally drilled collectors extending therefrom. All of the horizontally drilled collectors may be constructed using horizontal directional drilling techniques with the main drilling equipment positioned on the ground surface and thereby defining a surface port for accessing the horizontal collector. The horizontal collector may be cleaned and maintained through the surface port without requiring access through the vertical well.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. provisional patent application Ser. No. 61/832,143 filed on Jun. 6, 2013, the disclosure of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The subject matter disclosed herein relates to wells and systems for optimizing their production efficiency. 
     BACKGROUND 
     U.S. Pat. No. 2,280,851 to Leo Ranney, the disclosure of which is hereby incorporated by reference, discloses a system for collecting ground water that uses a vertically oriented caisson, combined with one or more well points that extend horizontally out from the bottom of the caisson in a radial pattern. This system is commonly known as a Ranney Collector System, and it has been used in water supply systems for municipalities and other large-volume water consumers. The design is primarily used adjacent to large bodies of surface water to collect water therefrom. 
     Despite the benefits of Ranney Collector Systems, they have several drawbacks. For example, the system requires a vertical caisson that is large enough in diameter to operate a horizontal drilling system at its base that allows drilling outwards radially through the sides of the caisson. Accordingly, there are limitations on the construction of smaller systems for use where water supply demands are less. 
     The system requires that a crew perform work at the bottom of a caisson, which is a confined space posing stringent health and safety threats to workers, and the system has limitations on the length of radial collectors that can practically be installed. The maximum horizontal collector length is approximately 250 feet. Also, the radial collectors are unguided and are not steered into position, meaning that they cannot be directed to follow high production zones, and the radial collector points extending from the caisson are not easily accessible for cleaning and maintenance. 
     SUMMARY 
     The present subject matter overcomes these issues with the Ranney Collector System. In a disclosed embodiment, the system is a form of liquid supply well that incorporates a vertical caisson with one or more horizontally drilled collectors extending therefrom. The horizontal collectors of the well may be constructed with equipment positioned on the ground surface rather than in the caisson. Radial collectors may be installed using horizontal directional drilling techniques, combined with methods for connecting the radial collectors to the vertical casing. A major innovation of this technique is the ease of maintenance because the ends of the radial collector “arms” are accessible from the surface after construction, thereby facilitating routine cleaning and maintenance of the collector arms. 
     In disclosed embodiments, improved seals for operably connecting the radial collectors to a vertical well are also disclosed. For example, the seals can be formed by selectively removing sealing material that secured the radial collector to the vertical well to define a chamber in which fluid from the radial collector flows. Alternatively, expandable connectors can operably engage the radial collector at the vertical well. 
     The foregoing and other objectives, features, and advantages will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a system for improving collection of fluid from a well in accordance with an embodiment of the subject matter disclosed herein. 
         FIG. 2  is a side schematic view of a system for improving collection of fluid from a well in accordance with an alternative embodiment of the subject matter disclosed herein. 
         FIG. 3  is a side schematic view of a system for improving collection of fluid from a well in accordance with a second alternative embodiment of the subject matter disclosed herein. 
         FIG. 4  is a side schematic view of a possible radial collector for use in the system for improving collection of fluid from a well in accordance with the embodiments shown in  FIGS. 1-3 . 
         FIG. 5  is a side schematic view of an alternative possible radial collector for use in the system for improving collection of a fluid from a well in accordance with the embodiments shown in  FIGS. 1-3 . 
     
    
    
     DETAILED DESCRIPTION 
     A system for improving the fluid collection from a well and a method of construction of the system are disclosed in  FIGS. 1-5  and described herein. 
     The present subject matter is a fluid collection system  10  that uses horizontal directional drilling technology combined with improved methods of installation to install a system of substantially horizontal, radial collectors  12  for a fluid supply  14 . The fluid is preferably water. Horizontal directional drilling makes use of various methods to locate and steer a drill bit and downhole assembly along a predetermined underground path accurately in three dimensions. 
     Referring to  FIGS. 1 &amp; 2 , a smaller diameter caisson  20  than needed for a Ranney Collector System is advanced below the ground surface  22  to a defined depth. This caisson  20  may be significantly smaller in diameter, and does not need to be watertight since neither tools nor workers need be in the bottom of the well during construction and installation of the substantially horizontal radial collectors  12 . As one example, the caisson  20  may be constructed of reinforced concrete rings, with easily breached knock-out locations for receiving the distal ends of the substantially horizontal radial collectors  12  with horizontal drilling tools  24 . The caisson  20  may also be a solid pipe or suitable material. 
     Following placement of the caisson  20 , one or more horizontal radial collectors  12  are directionally drilled, preferably from the ground surface  22  using horizontal directional drilling techniques, to intersect the caisson  20  at the specified depth for each collector  12 . The bore used to form the collector defines a surface port  30  through which the horizontal collector  12  can be cleaned and maintained without requiring access through the caisson  20 . The final step is to place a vertical riser casing  40  in the caisson  20 , optionally backfill the caisson  20  with drain rock  42 , and then install the pump (not shown) in the vertical riser casing  40 . 
     In addition to the cost savings associated with the horizontal radial collectors  12 , there is a significant cost savings in the construction of the caisson  20 , since the diameter can be reduced significantly from the typical 13 feet. The diameter can be reduced because no construction activities actually occur inside the caisson  20 . The caisson  20  simply provides a wet-well capability to collect fluid from the horizontal radial collectors  12 . There is no requirement for a finished floor or watertight walls in the caisson  20 . 
     Referring to  FIG. 3 , in relatively arid regions of shallow unconfined aquifers with relatively low horizontal transmissivity, one method for water resource development that has proven effective is the installation of horizontal collectors  12  that conduct water to a central location. From this location, the water can be pumped to the surface for consumption without creating a localized cone of depression that quickly exhausts the aquifer in the immediate area of the pump. 
     A vertical riser casing  40 , installed within the wet well  62 , to contain a submersible pump (not shown) or the subsurface components of a surface-mounted turbine pump, sufficient to meet the pumping requirements for the well. 
     Sand and gravel  66  is optionally backfilled within the interior of the wet well  62 . Additionally, such sand and gravel  66  may also be provided to support the vertical riser casing  40  and provide a graded sand pack around the vertical riser casing  20 . 
     One or more radial collectors  12 , with horizontal perforated sections  70  that penetrate the vertical wet well  62  at the desired depth are provided. These radial collectors  12  may be 1000 feet long, or more and emplaced using surface-based directional drilling methods previously described. Outside the wet well  62 , the casing  20  can be slotted to meet design requirements for the in situ material and desired well performance. The radial collectors  12  are installed slightly inclined, preferably 1-2% downward gradient toward the vertical wet well to facilitate gravity drainage of water to the wet well  62 . 
     The section of the radial collector  12  that penetrates into the wet well  62  may be perforated with numerous slots or holes to enhance hydraulic connectivity with the sand/gravel filter within the well, or may be cut and removed after installation to maximize the open area for flow into the wet well  62 . 
     In the case of multiple radial collectors  12 , converging on a centrally-located wet well  62 , the vertical depth of each radial collector  12  is adjusted where it penetrates the wet well  62  to prevent interference between the casings during installation. 
     Bentonite/cement grout  74  surrounding the upper portion of the wet well  62  to prevent surface water infiltration is provided. 
     An exemplar method of construction is disclosed below: 
     Excavate for the wet well caisson  20 , place gravel bedding  80 , and set the well caisson  20 . Depending on the required depth, this may be with a bucket auger, other large diameter boring method, extended reach excavator, or clamshell type bucket. 
     Drill one or more radial collectors  12  to the desired depth. The radial collectors intersect the wet well  62  at the base of the entry curve, and continue outward beneath the surface water body or fluid supply  14 . A precision intercept is drilled directly though the wet well  62  casing wall and out the other side. Borings could be single or double-ended, either exiting on the far side of the surface water body, or terminating beneath it. The well casing and screen would then be placed. 
     An alternative drilling method is to drill from the opposite side of the surface water body, to intersect the wet well at depth. In a single-ended installation using this method knock off technology may be used, which enables installation of up to a 4 inch well casing through the drill rods, assures installation even in caving alluvial materials. The bore profile preferably maintains a slight gradient (1-2%) towards the wet well, to facilitate gravity drainage towards it. 
     After the radial collectors  12  (which are also referred to as “horizontal laterals” herein) are complete, drilling mud is pumped out and the boreholes and wet well are flushed to remove the residual mud. 
     The vertical casing is placed in the wet well, preferably in a central location that avoids direct contact with all horizontal laterals. 
     Develop the radial collectors  12  by jetting and pumping from the wet well. 
     If the radial collectors  12  wells will be cut flush (or nearly so) with the caisson walls, complete this step and cap the well end with a screened cover to exclude sand or gravel. 
     Backfill the wet well interior with sand and gravel. 
     Grout the exterior annulus between the excavation and the wet well. 
     For some applications, the configuration may be simplified. Drilling precision intercepts to vertical wells—piercing the vertical casing at a designated location with a radial collector can be accomplished using conventional horizontal drilling technology. This can be adapted to provide multiple radial collectors directly into a vertical well casing, without the need to construct the wet well. Another potential solution is to simply place the horizontal collector in proximity to the vertical well, without a physical connection, but establishing a close hydrologic connection and preferential pathway between the horizontal collector and vertical well. 
     Description of a Horizontal Directional Drilled Well with Radial Penetration Grout Seal. 
     Referring to  FIG. 4 , an alternative possible embodiment of the horizontal directional drilled (“HDD”) radial collector well  10  is disclosed. A vertical bore  80  is excavated using suitable means. A vertical casing or caisson  20  is then lowered into the vertical bore  80 . This casing or caisson  20  may have constructed in it weakened circular areas or “knock outs” that are designed to give way easily when impacted by horizontal drilling tools approaching from the exterior of the casing. These knock outs are situated at a known depth and orientation beneath the ground surface. 
     One or more directional radials are then advanced toward the vertical bore from a selected distance. The directional radial borings are guided to penetrate the vertical bore and casing at the designed location and orientation, encountering the knockouts and pushing them aside. 
     Perforated or slotted well casing  82  of the desired design is either pushed into the directional boring. This may be done in either a double ended configuration, with solid casing extending through two penetrations and crossing the vertical casing, or in single ended configurations, with the casing end exposed in the vertical casing annulus. 
     To complete the well, cement grout or concrete  84  is pumped into the bore annulus  86  and inside the vertical casing  20  to a depth that adequately covers the vertical casing penetrations. Once the cement sets, a pump chamber  86  is then drilled into the center of the cemented zone within the vertical casing, exposing the open ends of the radial collector casings. A vertical pump casing (not shown) is then lowered into the pump chamber and secured using any of a number of standard well construction methods. The bore annulus is backfilled with granular material  90 , grout  92  and optionally cement bore backfill  103  to meet health agency requirements for potable water wells. 
     Description of HDD Well with Expansive Seal 
     Referring to  FIG. 5 , another embodiment of the HDD radial collector well  10  is disclosed. A vertical bore  80  is excavated using suitable means. A vertical casing or caisson  20  is lowered into the vertical bore  80 . This casing or caisson  20  may have constructed in it weakened circular areas or “knock outs” that are designed to give way easily when impacted by horizontal drilling tools approaching from the exterior of the casing. These knock outs are situated at a known depth and orientation beneath the ground surface. 
     One or more directional radials are then advanced toward the vertical bore from a selected distance. The directional radial borings are guided to penetrate the vertical bore and casing at the designed location and orientation, encountering the knockouts and pushing them aside. 
     Perforated or slotted well casing  82  of the desired design is either pushed into the directional boring. This may be done in either a double ended configuration, with solid casing extending through two penetrations and crossing the vertical casing, or in single ended configurations, with the casing end exposed in the vertical casing annulus. 
     To complete the well, the radial well casing  96  is sealed to the caisson  20 . There are several options that may be completed in this embodiment of the well completion. In one option, the casing is pulled through an expandable rubber or plastic torus  100  that encircles the outer circumference of the casing. This seal is pushed up tight against the vertical casing wall. The seal may be located on either the interior or exterior wall of the vertical casing, depending on the preferred construction method, borehole stability, or other factors. Once in place, the expandable seal  100  is inflated with air, grout, expansive catalyzed foam, or other material to form a tight seal between the vertical riser casing  40  and the caisson  20 . 
     Once the seals are in place, a vertical pump casing (not shown) is then lowered into the pump chamber and secured using any of a number of standard well construction methods. The bore annulus is backfilled with granular material  90  and grout  92  to meet health agency requirements for potable water wells. A pump and discharge line (not shown) are then installed in the pump casing (not shown). 
     The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the subject matter is defined and limited only by the claims which follow.