Well screen for non-vertical well systems

Abstract

Systems and methods for supplying water to a desalination plant from a subsurface feedwater supply using one or more slant or horizontally directionally drilled (“HDD”) wells. In particular embodiments, an angled well screen pipe is 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. The filter pack can be placed using a system of tremie pipes or can be pre-packed prior to insertion inside temporary casings.

What is claimed is: 
     
         1 . A system for supplying water from or sending water to an aquifer, the system comprising:
 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;   wherein the well screen comprises an outer portion for admitting water from or injecting water into the aquifer;   wherein 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; and   wherein 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. 
   
     
     
         2 . The system of  claim 1 , further comprising 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. 
     
     
         3 . The system of  claim 1 , further comprising a containment material surrounding the filter pack and securing the filter pack to the outer portion of the well screen. 
     
     
         4 . A method of constructing a system for supplying water from or sending water to an aquifer, the method comprising the steps of:
 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;   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;   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   withdrawing the casing from the aquifer while leaving the well screen and filter pack in the aquifer.   
     
     
         5 . The method of  claim 4 , wherein the step of placing the filter pack comprises the steps of:
 removably positioning one or more tremie pipes in the space formed between the well screen and the outer casing portion; and   pumping loose filter pack material through the one or more tremie pipes into the space formed between the well screen and the outer casing portion.   
     
     
         6 . The method of  claim 4 , further comprising 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.   
     
     
         7 . A system for supplying water from or sending water to an aquifer, the system comprising:
 a well screen extending substantially non-vertically within an aquifer; and   a filter pack substantially surrounding and adjacent to the well screen;   wherein the well screen comprises an outer portion for admitting water from or injecting water into the aquifer;   wherein the outer portion of the well screen defines an inner conduit for channeling water admitted from or to be injected into the aquifer; and   wherein 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. 
   
     
     
         8 . The system of  claim 7 , further comprising 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. 
     
     
         9 . The system of  claim 7 , further comprising a containment material surrounding the filter pack and securing the filter pack to the outer portion of the well screen. 
     
     
         10 . A method of constructing a system for supplying water from or sending water to an aquifer, the method comprising the steps of:
 extending a casing substantially non-vertically into an aquifer, the casing comprising an outer casing portion that defines an inner casing conduit;   extending a well screen substantially non-vertically within the inner casing conduit 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;   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   withdrawing the casing from the aquifer while leaving the well screen and filter pack in the aquifer.   
     
     
         11 . The method of  claim 10 , wherein the step of placing the filter pack comprises the steps of:
 removably positioning one or more tremie pipes in the space formed between the well screen and the outer casing portion; and   pumping loose filter pack material through the one or more tremie pipes into the space formed between the well screen and the outer casing portion.   
     
     
         12 . The method of  claim 10 , further comprising 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.