A downhole filtration tool to remove sand and other solid particles from production fluid in a subterranean well. The downhole filtration tool includes a perforated mandrel surrounded by at least one filter element made of an open weave polymeric fiberglass material. In addition, the downhole filtration tool may include an additional screen or mesh installed in a separating annulus intermediate of the mandrel and the filter element to provide a filter having improved permeability and resistance to chemical and physical forces.

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a downhole filtration tool for use in oil, gas, and water wells, and more particularly to a downhole filtration tool having a carbon steel mandrel surrounded by a non-metallic element giving the filter improved permeability, resistance to chemical breakdown, and physical strength. 
     2. Description of the Related Art 
     Oil and gas wells and water wells include a wellbore extending into a well to some depth below the surface. Typically, the wellbore is lined with casing to strengthen the walls of the borehole. To further strengthen the walls of the borehole, the annular area formed between the casing and the borehole is typically filled with cement to permanently set the casing in the wellbore. The casing is then perforated to allow production fluids to enter the wellbore and be retrieved at the surface of the well. 
     Various types of downhole equipment, such as pumps and similar devices, are used to move production fluids from within the wellbore to the surface. A typical downhole arrangement would include a string composed of a series of tubes or tubing suspended from the surface. One type of well-known pump is a downhole electrical submersible pump (ESP). The ESP either includes or is connected to a downhole motor which is sealed so that the whole assembly is submerged in the fluid to be pumped. The motor is connected to a power source at the surface and operates beneath the level of the fluid downhole in order to pump the fluid to the surface. A component is connected to the motor which prevents well fluid from entering the motor and equalizes internal motor pressure with the well annulus pressure. 
     A number of factors may be detrimental to the production of the ESP, such as the presence of foreign solid particles, such as sand, sediment, and scale. The amount and size of sand and other solid particles in the fluid may vary widely depending on the well and the conditions encountered. In enhanced recovery operations, for example, fluids may be pumped down the well to stimulate production causing additional movement of sands and solids. The sand and other solid particles act as abrasives and, over time, are damaging to the operation of the pump. 
     Yet another problem typically encountered in wells is an excess amount of gas or gas bubbles entering the intake of the pump causing the pump to decrease in efficiency. ESPs have dramatically lower efficiencies with significant fractions of gas, and at some point, the pump may become “gas locked” and damage to the pump and/or motor may result. 
     Many types of filters have been designed for use with ESPs. Such filters typically include a filter element designed to screen solid particles from the pump intake; however, the filtered particulates often become entrapped in the filter element. The amount of particulate material collected on the filter element is directly proportional to the to the pressure drop that occurs across the filter element. Since an excessive pressure drop across the filter element can significantly reduce fluid flow, the filter element must be periodically changed or cleaned. Often, this is done by removing the ESP from the fluid and removing the filter element. This can be a timely and inconvenient process. Pumps with intricate backwashing systems have been designed, but these are often expensive and cannot be used to retrofit existing systems. As a result, many pumps are generally operated without any filter and therefore experience early pump failure and extensive and costly down time. 
     A problem associated with conventional downhole filtration tools arises in high temperature and/or high pressure applications. High downhole temperatures are generally above 200° F. and up to 450° F., while high downhole pressures are generally above 7,500 psi and up to 15,000 psi. Another problem with downhole filtration tools occurs in both high pH (e.g., more than 8.0) and low pH (e.g., less than 6.0) environments. In these extreme downhole conditions, conventional filters become ineffective and suffer from degradation. 
     It is therefore desirable to provide an improved downhole filtration tool for use in oil, gas, and water wells. 
     It is further desirable to provide a downhole filtration tool that is connected to and suspended from downhole equipment, such as but not limited to, an ESP and operates as an intake to the pump. 
     It is still further desirable to provide a downhole fluid filtration tool capable of separating sand and other solid particles from production fluid while also preventing an undue amount of gas from entering the pump. 
     It is yet further desirable to provide a downhole filtration tool having a carbon steel mandrel surrounded by a non-metallic filter element giving the downhole filtration tool improved permeability, resistance to chemical breakdown, and physical strength. 
     SUMMARY OF THE INVENTION 
     In general, the invention relates to a downhole filtration tool having a metallic mandrel juxtaposed between opposing end fittings. The mandrel has a plurality of diametrical perforations and an interior chamber aligned along an axial flow passage through the downhole filtration tool. The end fittings have opposing generally planar axial or open ends axially aligned and coaxially spaced along the flow passage. The downhole filtration tool also has at least one open weave fiberglass filter element circumferentially surrounding the mandrel. The filter element includes a plurality of angularly biased passages extending upwardly at an angle, such as about 10 degrees, and approximately tangentially in relation to the annulus. The filter element includes vortex flow disrupter sections on opposing terminating ends. Each of the flow disrupter sections may be constructed from a rigid resin forming an internal annular shoulder. In addition, the downhole filtration tool includes a separating annulus between the filter element and the mandrel, with the end fittings closing terminal ends of the annulus. 
     The mandrel can also include a first terminating end with external threads and a second terminating end with external threads. The first terminating end and/or the second terminating end of the mandrel can include a mandrel threadlock, with each of the mandrel threadlocks being respectively axially aligned with a threadlock channel in the end fitting. The mandrel may be fabricated from investment cast precipitation-hardening corrosion-resistant steel, such as carbon steel, with the end fittings also being fabricated from steel. 
     Each of the end fittings can also include a reduced diameter neck with internal threads connected to the external threads of the first terminating end and the second terminating end of the mandrel. Further, each of the end fittings can include a sealing element supported within a circular seal groove for establishing sealing engagement with an external cylindrical sealing surface of the end fitting and an internal cylindrical sealing surface on the vortex flow disrupter section. Additionally, each of the end fittings can include circular sealing elements or seal assemblies located intermediate of an external, circular stop shoulder of the end fitting and the flow disrupter section. The seal assemblies can be carried within a circular seal groove. 
     The filter element of the downhole filtration tool may be fabricated from polyurethane, a phenolic, an epoxy resin or a blended epoxy resin, such as a low viscosity, liquid epoxy resin manufactured from bisphenol A or F and epichlorohydrin. The filter element can also be fabricated from a polymeric composite reinforced by fibers, such as glass, carbon and/or aramid, stacked in layers angled at about 30 degrees to about 70 degrees relative to an axis of the filter element. 
     Moreover, the downhole filtration tool can have a tight meshed screen or other filter media positioned within the separating annulus. The screen may be fabricated from stainless steel, a meta-aramid fiber, or a meta-aramid fiber blended with a para-aramid, antistatic or other synthetic fibers. The screen is supported by a mesh standoff along the perforations of the mandrel, and the filter element, the screen and the mesh standoff concentrically surround the mandrel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional, partial cutaway view of downhole equipment incorporating the downhole filtration tool disclosed herein connected in a production string; 
         FIG. 2  is a diametric cross-sectional view of an example of a downhole filtration tool in accordance with an illustrative embodiment of the invention disclosed herein; 
         FIG. 3  is a cross-sectional view of a lower end fitting of the downhole filtration tool shown in  FIG. 2 ; 
         FIG. 4  is a top plan view of the mounting connector shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of an upper end fitting of the downhole filter tool shown in  FIG. 2 ; 
         FIG. 6  is a bottom plan view of the coupler shown in  FIG. 5 ; 
         FIG. 7  is a cross-sectional view of the mandrel of the downhole filtration tool shown in  FIG. 2 ; 
         FIG. 8  is a cross-sectional view of the vortex flow disrupter section and the filter element of the downhole filtration tool shown in  FIG. 2 ; 
         FIG. 9  is a cross-sectional view along line  9 - 9  of the downhole filtration tool shown in  FIG. 2 ; 
         FIG. 10  is an exploded view of area  10  of the filter element as shown in  FIG. 8 ; 
         FIG. 11  is a diametric cross-sectional view of another example of a downhole filtration tool in accordance with an illustrative embodiment of the invention disclosed herein; 
         FIG. 12  is a cross-sectional view of the mandrel and the filter screen element of the downhole filtration tool shown in  FIG. 11 ; 
         FIG. 13  is an exploded view of area  13  of the mandrel and the filter screen element as shown in  FIG. 12 ; and 
         FIG. 14  is a cross-sectional view along line  14 - 14  of the downhole filtration tool shown in  FIG. 11 . 
     
    
    
     Other advantages and features will be apparent from the following description and from the claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments discussed herein are merely illustrative of specific manners in which to make and use this invention and are not to be interpreted as limiting in scope. 
     While the invention has been described with a certain degree of particularity, it is to be noted that many modifications may be made in the construction and the arrangement of its components without departing from the scope of the invention. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification. 
     The description of the invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. In the description, relative terms such as “front,” “rear,” “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly” etc.) should be construed to refer to the orientation as then described or as shown in the drawings under discussion. These relative terms are for convenience of description and do not require that the machine be constructed or the method to be operated in a particular orientation. Terms, such as “connected,” “connecting,” “attached,” “attaching,” “join” and “joining” are used interchangeably and refer to one structure or surface being secured to another structure or surface or integrally fabricated in one piece. 
     Referring to the figures of the drawings, wherein like numerals of reference designate like elements throughout the several views, and initially to  FIG. 1  depicting a sectional view of a downhole filtration tool  10  and downhole equipment used to raise production fluids to the surface. A subterranean well  12  includes a casing  14  which extends from the surface downhole. The casing  14  includes perforations  16  that allow production fluids to pass through the casing  14 . An electrical submersible pump  18  is lowered into the well  12  beneath the level of fluid. The pump  18  is suspended from a string  20  which may be composed of a series of tubes or tubing suspended from the surface, such as from a rig or derrick (not shown). The pump  18  includes a motor (not shown) that is sealed from the fluids. The motor is powered by electrical energy supplied by an energy source at the surface, such as a generator (not shown). The pump  18  is connected to the downhole filtration tool  10  by way of a seating nipple  22  and/or a tubing sub  24 . The pump  18 , the motor, the seating nipple  22 , the tubing sub  24  and other downhole equipment each has an external diameter less than an interior diameter of the casing  14 . Downhole fluid enters the filtration tool  10  and is forced by the motor upward through an axial flow passage  26  of the downhole filtration tool  10  to the pump  18 , which draws the fluid through the string  20  to the surface where it is collected in a tank (not shown) or otherwise delivered by a pipeline or other known means. 
       FIGS. 2 through 10  illustrate the downhole filtration tool  10  having a first end terminating in an upper end fitting  28 , which connects with an intake end of the pump  18  or may be connected to other downhole equipment, such as the tubing sub  24 . As illustrated, the end fitting  28  has a reduced diameter neck  30  with internal threads  32  that are connected to a first terminating end of a mandrel  34  with external threads  36 . A sealing element  38  may be supported within a circular seal groove  40  of the neck  30 , which establish sealing engagement with an external cylindrical sealing surface  42  of the end fitting  28  and an internal cylindrical sealing surface  44  on a first terminating end of a vortex flow disrupter section  46  of the downhole filtration tool  10 . The end fitting  28  is also provided with circular sealing elements or seal assemblies  48  located intermediate of an external, circular stop shoulder  50  of the end fitting  28  and the flow disrupter section  46 . The seal assemblies  48  may be carried within a circular seal groove  52 . The sealing element  38  and/or the sealing assemblies  48  can be constructed from elastomer and polymer materials capable of accomplishing effective sealing at normal to high operating temperatures and at all pressure ranges. The end fitting  28  also includes an internally threaded section  54  that receives an externally threaded section  56  of the tubing sub  24  and other downhole equipment. Additionally, the end fitting  28  may include a threadlock channel  58  having internal threads  60 . 
     The downhole filtration tool  10  has a second end terminating in a lower end fitting  62 , which connects with the motor or other downhole equipment. The lower end fitting  62  has a first terminating end with a reduced diameter neck  64  having external threads  68  that are connected to the motor or other downhole equipment. The lower end fitting  62  also includes a second terminating end with a reduced diameter neck  70  having internal threads  72  that are connected to a second terminating end of the mandrel  34  with external threads  74 . Similarly to the upper end fitting  28 , the lower end fitting  62  may include a sealing element  76  supported within a circular seal groove  78  of the neck  70 , which establish sealing engagement with an external cylindrical sealing surface  80  of the end fitting  62  and an internal cylindrical sealing surface  82  on a second terminating end of the vortex flow disrupter section  46  of the downhole filtration tool  10 . The end fitting  62  is also provided with circular sealing elements or seal assemblies  84  located intermediate of an external, circular stop shoulder  86  of the end fitting  62  and the flow disrupter section  46 . The seal assemblies  84  may be carried within a circular seal groove  66 . The sealing element  76  and/or the sealing assemblies  84  can be constructed from elastomer and polymer materials capable of accomplishing effective sealing at normal to high operating temperatures and at all pressure ranges. Additionally, the end fitting  62  may include a threadlock channel  88  having internal threads  90 . 
     The mandrel  34  is connected intermediate of and juxtaposed between the upper end fitting  28  and the lower end fitting  62 . An interior chamber  98  within the mandrel  34  is axially aligned along the flow passage  26  through the downhole filtration tool  10 . In addition, a central bore  97  in the upper end fitting  28  and a central bore  99  in the lower end fitting  62  have opposing generally planar axial or open ends that are axially aligned and coaxially spaced along the flow passage  26 . The mandrel  34  includes the first terminating end with external threads  36  and the second terminating end with external threads  74 . In addition, the first terminating end and/or the second terminating end of the mandrel  34  include a mandrel threadlock  92  and  94 , which is axially aligned with the threadlock channel  58  in the upper end fitting  28  and the threadlock channel  88  in the lower end fitting  62 , respectively. The mandrel  34  includes a plurality of diametrical perforations  96  along its length to permit fluids to pass from the well  12  into the interior chamber  98  within the mandrel  34 . The perforations  96  may be round as illustrated or may be slotted or a combination of holes and slots that are punched or drilled through the mandrel  34 . The mandrel  34  may be fabricated from investment cast precipitation-hardening corrosion-resistant steel, such carbon steel accompanied with steel upper and lower end fittings  28  and  62 . 
     A removable filter element  100  concentrically surrounds the mandrel  34 . A separating annulus  102  is formed between the filter element  100  and the mandrel  34 , and the upper end fitting  28  and the lower end fitting  62  close a first terminating end and a second terminating end of the annulus  102 . The filter element  100  includes a plurality of angularly biased passages  104  extending upwardly at an angle  106  of approximately 10 degrees and approximately tangentially  108  in relation to the annulus  102 . If the filter element  100  becomes clogged or damaged, the filter element  100  may be removed and replaced as necessary. In addition, the filter element  100  may be constructed as single standalone elements or as stackable elements. A first end and a second end of the filter element  100  each respectively terminate with the vortex flow disrupter section  46 . The flow disrupter section  46  is constructed of a rigid resin that forms a terminal end collar. The inner periphery of the disrupter section  46  may include an annular shoulder  118  that contacts the neck  30  of the end fitting  28 . 
     The filter element  100  is an open weave fiberglass filter constructed to withstand very high or low pH environments as well as elevated temperatures and high pressure differentials. The filter element is constructed of a polymeric composite that is reinforced by a continuous fiber such as glass, carbon, or aramid, for example, having a porosity of between about 33% to about 43% per linear foot. The individual fibers are typically layered parallel to each other, and wound layer upon layer. However, each individual layer is wound at an angle of about 45 degrees to provide additional strength and stiffness to the composite material in high temperature and pressure downhole conditions. The polymeric composite may be polyurethane, a phenolic, an epoxy resin, such as a low viscosity, liquid epoxy resin manufactured from bisphenol A or F and epichlorohydrin (e.g., EPON™ Resin 862, Momentive Specialty Chemicals, Inc.) or a blended epoxy resin. Prepreg strands and rovings (e.g., Advantax®, Owens Corning Composite Materials, LLC; 346 Type 30® Roving, Owens Corning Composite Materials, LLC) can also be used to form a matrix or the fibers can be wet wound. A post cure process may be performed to achieve greater strength of the material, and heat can be added during the curing process to provide the appropriate reaction energy to drive the cross-linking of the matrix to completion. The composite may also be exposed to ultraviolet light or a high-intensity electron beam to provide the reaction energy to cure the polymeric composite. The foregoing materials are merely examples that may be utilized in constructing the downhole filtration tool  10  and other materials may be employed to suit the particular usage of the downhole filtration tool  10 . 
     Referring now to  FIGS. 11 through 13  illustrating an embodiment of the downhole filtration tool  10  having an additional tight meshed screen or other filter media  110  positioned within the separating annulus  102 . The screen  110  may be constructed from stainless steel, a meta-aramid fiber (e.g., NOMEX®, Du Pont) or a meta-aramid fiber blended with a para-aramid, antistatic or other synthetic fibers. The screen  110  may be supported by a mesh standoff  112  along the perforations  96  of the mandrel  34 . In addition, the terminating ends of the screen  110  may include a double fold  114 . Terminating ends of the screen  110  and the mesh standoff  112  may be respectively secured to the mandrel  34  above the uppermost and below the lowermost perforations  96  by a suitable easily removable tape, band, strap or the like  116 . As illustrated, the filter element  100 , the screen  110  and the mesh standoff  112  concentrically surround the mandrel  34 . 
     During operation, fluid from the well  12  will sequentially flow through the perforations  16  in the casing  14 , through the filter element  100 , through the screen  110 , if present, and/or the mesh standoff  112 , through the perforations  96  in the mandrel  36 , through the interior chamber  98  of the mandrel  36  and through the upper end fitting  28  to an intake nut (not shown) and the pump  18 . The casing perforations  16  will filter out larger solids and the filter element  100  will filter out smaller sand and other solid particles. The screen  110  and the standoff  112 , if present, prevent loss of filter media through the perforations ( 16 ). 
     Whereas, the embodiments have been described in relation to the drawings, it should be understood that other and further modifications, apart from those shown or suggested herein, may be made within the scope of this invention.