Patent Publication Number: US-2015064034-A1

Title: Modular intake filter system, apparatus and method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/870,635 to Davis, filed Aug. 27, 2013 and entitled “MODULAR INTAKE FILTER SYSTEM, APPARATUS AND METHOD,” which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention described herein pertain to the field of artificial lift pumping systems. More particularly, but not by way of limitation, one or more embodiments of the invention enable a modular intake filter apparatus, system and method for artificial lift pump systems. 
     2. Description of the Related Art 
     Artificial lift pumping systems are found in virtually all production wells today. Artificial lift systems are used for pumping fluid from a well bore. Typically, the produced fluid is oil, water, natural gas or a mixture of those fluids. One type of artificial lift pump system for downhole applications is an electric submersible pump (ESP) assembly. A typical ESP assembly is illustrated in  FIG. 27  and includes a conventional motor  1 , a conventional seal section  2  downstream of the motor, a conventional intake section  3  downstream of the seal section  2 , and a centrifugal pump  4  downstream of the conventional intake  3 . The pump assembly components each have shafts running longitudinally through their centers. The motor operates through a power cable connected to the surface and causes the shafts to rotate. Well fluid enters the centrifugal pump through the conventional intake section  3  and is lifted by the stages of centrifugal pump  4 . 
     Other artificial lift pumping systems include rod pumps (beam lift), progressive cavity pumps, hydraulic pumps and jet pumps. Rod pumps, for example, are long slender cylinders inserted inside the tubing of a well. Rod pumps gather fluid from beneath the pump and lift them to the surface. Typically, rod pumps include a barrel, valves, piston and fittings. As the beam pumping system rocks back and forth, this operates the rod string, sucker rod and sucker rod pump, which work similarly to pistons inside a cylinder. The sucker rod pump lifts the oil, water and/or natural gas from the reservoir through the well to the surface. 
     Recently, a method of natural gas extraction known as hydraulic fracturing (“Facing”) has become economically important. Fracing makes use of artificial lift pumping systems. One challenge to economic and efficient artificial lift operation is pumping fluid containing sand, dirt, rock and other solid contaminants (“media”). Wells, which can be up to 12,000 feet deep in the ground, are commonly contaminated with media. Artificial lift pumping systems have tight clearances and/or high rotational speeds, and are therefore greatly impacted by media in the fluid—the pumps are susceptible to abrasive and erosive wear, and are also subject to problems such as pump starvation (insufficient flow), and cavitation, which is damage to pump components from bubbles created by vortexes in the well fluid. In recent years, some effort has been made to utilize flexible screens to filter large solids out of the well fluid in artificial lift pumping applications, but these screens suffer from drawbacks that fail to protect pumps from mechanical damage, abrasive and erosive wear from media, pump starvation and cavitation. Further, traditional screen designs are not easily customizable for an array of well environments having a variety of types and sizes of media in the well fluid. 
     Currently, many artificial lift designs combat media by using intake screens that contain large slots or perforations that block media from passing through the screen. In some instances, media is trapped and retained in the screen. These intake screens are limited in surface area, and over time, trapped contaminants may eventually clog the slots or perforations in the screen, thereby reducing inflow performance or starving the pump for fluid. Starving the pump can potentially cause pump failure due to the loss of mechanical lubrication in the pump by the absence of well fluid. In addition, if an ESP pump is starved for fluid, the loss of cooling well fluid passing by the motor can cause pump failure due to excessive heat produced by the electrical motor. Alternatively, the slots or perforations in the intake screen may be too large to contain much of the abrasives. For example, the slot or perforation may be a quarter of an inch in diameter, but the media may be only a micrometer in diameter and easily pass through the slots or perforations in the screen. If abrasives are not caught in the screen, they enter the pump and cause damage. 
     With respect to ESP pumps, there are typically two classes of traditional intake sections currently in use: bolted-on intakes and integral intakes. Bolted-on intake sections are usually bolted to an upper tandem or middle tandem pump, connecting the seal section to the pump, and contain a flexible screen with holes or slots. Typical intake screen perforations or slots may be between about ¼inch and 5/16 of an inch in diameter.  FIG. 1A  illustrates an example of a traditional bolted-on intake with a slotted screen of the prior art.  FIG. 1B  illustrates an example of a traditional bolted-on intake with a perforated screen of the prior art. These types of intake screens are prone to clogging, and are not typically effective at filtering smaller media. 
     Integral intakes, on the other hand, are usually used on lower tandem pumps and on lower tandem gas separators. The term “integral” denotes that the intake is part of the component assembly or finished product. In integral intakes, the intake functions as both the pump or gas separator base and pump intake. Integral intake sections are typically made from a single piece of metal for the body.  FIG. 2A  illustrates an example of an integral intake section on a pump base of the prior art.  FIG. 2B  illustrates an example of an integral intake section of the prior art on a gas separator. Intake ports of integral intakes, such as those shown in  FIG. 2A  and  FIG. 2B , are not well suited to filter media from well fluid because they have large intake ports without any mechanism to filter out abrasive particles. 
     Thus, solids ingested into artificial lift pumping systems create a large amount of potential problems. It would be an advantage for pump intake sections, such as ESP intakes and rod pump intakes, to prevent a greater percentage of foreign solids from being ingested into the pump during operation, over a longer period of time than typical screens, without starving the pump or degrading inflow performance. It would also be an advantage to easily configure a pump with a media filter of sufficient surface area to better protect the pump from contaminants and plugging. Therefore, there is a need for a modular intake filter system, apparatus and method for artificial lift pumping applications. 
     BRIEF SUMMARY OF THE INVENTION 
     A modular intake filter system, apparatus and method for artificial lift pumping applications is described. An illustrative embodiment of an electric submersible pumping system comprising a modular intake filter for screening media from well fluid comprises an electric submersible pump (“ESP”) assembly comprising an intake shaft that transfers horsepower from a seal section to a centrifugal pump of the ESP assembly, and an intake section secured between the seal section and the centrifugal pump by a head on a downstream side and a base on an upstream side, the intake section comprising at least two modular intake filters comprising a perforated housing, each modular intake filter threadedly engaged to an adjacent modular intake filter by a guide, and a porous media cartridge sealed to an exterior of the perforated housing, wherein a porosity of the porous media cartridge is selected to prevent media of a chosen size from entering the centrifugal pump. In some embodiments, a number of the at least two modular intake filters is determined by calculating an area of filtration material required by dividing a selected flow rate of pumped fluid by a permeability of the porous media cartridge, and calculating the number of the at least two modular intake filters by dividing the area of filtration material required by a surface area of a single modular intake filter. In some embodiments, the system comprises a radial support bearing comprising a rotatable sleeve keyed to the intake shaft and a stationary bushing pressed into the guide. In certain embodiments, the system further comprising at least three radial support bearings, wherein one of the at least three radial support bearings is located in each of the head, guide and base. In some embodiments, the system further comprises a screen surrounding the exterior of the porous media cartridge. In certain embodiments the porous media cartridge comprises a media grade of between 0.1 and 100. In further embodiments, there are between two and forty modular intake filters. 
     An illustrative embodiment of a modular intake filter apparatus for an artificial lift pumping system comprises at least one modular intake filter comprising a perforated housing supportively engaged to a production pump of an artificial lift assembly, and a porous media cartridge sealed to an exterior of the perforated housing, wherein a porosity of the porous media cartridge is selected to prevent media of a chosen size from entering the production pump, and wherein a number of the at least one modular intake filter in the apparatus is determined by calculating an area of filtration material required by dividing a selected flow rate of pumped fluid by a permeability of the porous media cartridge, and calculating the number of the at least one modular intake filters by dividing the area of filtration material required by a surface area of a single modular intake filter. In some embodiments, the threaded perforated housing is threaded to the production pump by a head, wherein the head further comprises a spider bearing pressed into the head and a stationary bushing of a hydraulic bearing set pressedly coupled to the spider bearing. In certain embodiments the production pump is a multistage centrifugal pump. In other embodiments, the production pump is a rod pump. In certain embodiments, the viscosity of the pumped fluid is about 1.0 centipoise and the selected flow rate is about 116.6 gallons per minute. 
     An illustrative embodiment of a method of filtering media from a fluid entering an artificial lift pump system, the method comprises selecting a porosity for a media cartridge to use in a modular intake filter for an artificial lift pumping application, installing a media cartridge of the selected porosity on a perforated housing to form the modular intake filter, and a step for computing a number of modular intake filters required to maintain a selected flow rate, the computation comprising at least the factors of a surface area of one of the modular intake filter, the selected flow rate of pumped fluid, and a permeability of the media cartridge of the selected porosity. In some embodiments the method further comprises joining in series the required number of modular intake filters as computed. In certain embodiments, the required number of modular intake filters are joined by threading in series with a guide. In some embodiments, the step for computing the number of modular intake filters comprises rounding based on the magnitude of modules. In some embodiments, the step for computing the number of modular intake filters needed is comprises rounding based on proximity to a nearest whole number of modules. 
     In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of the invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
         FIG. 1A  illustrates an example of a traditional bolted-on intake with a slotted screen of the prior art. 
         FIG. 1B  illustrates an example of a traditional bolted-on intake with a perforated screen of the prior art. 
         FIG. 2A  illustrates an example of an integral intake of the prior art on a pump base. 
         FIG. 2B  illustrates an example of an integral intake of the prior art on a gas separator. 
         FIG. 3  is an elevation view of an ESP pump assembly making use of a modular intake filter of an illustrative embodiment. 
         FIG. 4  is a perspective view of a single modular intake filter of an illustrative embodiment with an outer layer broken away. 
         FIG. 5  is a cross sectional view taken across line  5 - 5  of  FIG. 4  of an illustrative embodiment of a modular intake filter. 
         FIG. 6  is an enlarged view of one embodiment of a modular intake filter. 
         FIG. 7  is a perspective view of a modular intake section of an illustrative embodiment for an ESP assembly. 
         FIG. 8  is an elevation view of a modular intake section of an illustrative embodiment. 
         FIG. 9  is a cross sectional view taken along line  9 - 9  of  FIG. 8  of a modular intake section of an illustrative embodiment. 
         FIG. 10  is a cross sectional view taken along line  10 - 10  of  FIG. 8  of a guide of an illustrative embodiment. 
         FIG. 11  is a cross sectional view taken along line  11 - 11  of  FIG. 8  of a modular intake filter of an illustrative embodiment. 
         FIG. 12  is a perspective view of an illustrative embodiment of a modular intake section having three modules. 
         FIG. 13  is a perspective view of an illustrative embodiment of a modular intake section having four modules. 
         FIG. 14  is a perspective view of an illustrative embodiment of a modular intake filter with outer layers broken away. 
         FIG. 15  is a cross sectional view taken across line  15 - 15  of  FIG. 14  of an illustrative embodiment of a modular intake filter. 
         FIG. 16  is an enlarged view of a modular intake filter. 
         FIG. 17  is a perspective view of a base of an illustrative embodiment 
         FIG. 18  is a perspective view of a head of an illustrative embodiment. 
         FIG. 19  is a perspective view of a guide of an illustrative embodiment. 
         FIG. 20  is a perspective view of a modular intake section of an illustrative embodiment for a rod pump assembly. 
         FIG. 21  is a top view of a modular intake section of an illustrative embodiment for a rod pump assembly. 
         FIG. 22  is a cross sectional view taken across line  22 - 22  of an illustrative embodiment of a rod pump modular intake section. 
         FIG. 23  is an enlarged macroscopic view of a porous media cartridge of an illustrative embodiment. 
         FIG. 24  is an enlarged microscopic view of a porous media cartridge of an illustrative embodiment. 
         FIG. 25  is a flow chart of an illustrative embodiment of a method of installing a modular intake filter into an ESP assembly. 
         FIG. 26  is an elevation view of a rod pump assembly having a modular intake section of an illustrative embodiment. 
         FIG. 27  is a conventional ESP assembly of the prior art. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     A modular intake filter system, apparatus and method will now be described. In the following exemplary description, numerous specific details are set forth in order to provide a more thorough understanding of embodiments of the invention. It will be apparent, however, to an artisan of ordinary skill that the present invention may be practiced without incorporating all aspects of the specific details described herein. In other instances, specific features, quantities, or measurements well known to those of ordinary skill in the art have not been described in detail so as not to obscure the invention. Readers should note that although examples of the invention are set forth herein, the claims, and the full scope of any equivalents, are what define the metes and bounds of the invention. 
     As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a modular intake filter may also refer to multiple modular intake filters. 
     As used in this specification and the appended claims, the terms “media”, “solids”, “laden well fluid,” “foreign solids” and “contaminants” refer to sand, rocks, rock particles, soils, slurries, and any other non-liquid, non-gaseous matter found in the fluid being pumped by an artificial lift pumping system. 
     As used in this specification and the appended claims, the term “perforated housing” refers to a perforated or slotted supportive, skeleton-like structure for an intake section that, together with the head, guide(s) and/or base, holds and aligns the intake section in the pump assembly. 
     As used in this specification and the appended claims, the terms “modular” and “module” refer to largely identical components of similar size, construction and porosity that may be connected to one another by engagement in a series, such as threaded and/or bolted engagement. In an electric submersible pump (ESP) assembly, one or more modules may be placed between the centrifugal pump and/or gas separator on one hand, and the seal and/or motor on the other hand. In a rod pump assembly, one or more modules may be placed between the gas separator and rod pump. 
     As used in this specification and the appended claims, the term “guide” describes a coupling between two intake modules that allows one module to be threadedly engaged with another module. In some embodiments, a “guide” may be similar to guides conventionally employed in seal sections of ESP assemblies. 
     As used in this specification and the appended claims, the term “permeability” with respect to a porous media cartridge is a measure of the ability of a fluid to flow through the porous media cartridge, expressed as a rate per area. A porous media cartridge&#39;s permeability is a measured characteristic of the material that depends upon the viscosity and state of matter of the fluid flowing through the porous media cartridge, the pressure drop of the fluid flowing through the material and the thickness of the porous media cartridge. 
     Illustrative embodiments may improve a pump assembly&#39;s handling of solids in well fluid. A porous media cartridge may be placed circumferentially about a supportive, perforated housing of a pump assembly&#39;s intake section. The porosity of the porous media cartridge may be selected based upon well conditions, such as the size, type and/or quantity of media mixing with well fluid, and assist in controlling a maximum size of media allowed to pass into the pump. The intake section may be modularized to maintain a desired flow rate regardless of the chosen porosity of the porous media cartridge. The presence of multiple filter modules may increase the run life of the pump by increasing the time to plugging of the intake, as a result of the substantially increased surface area of the intake of illustrative embodiments. Multiple modules may be threadedly engaged to one another using guides. In some embodiments, a slotted or perforated screen may be wrapped about the outside of the porous media. 
     Illustrative embodiments may prevent a majority of solids larger than a selected size from entering a pump, such as a centrifugal pump or a rod pump, during operation. The modular intake filter system of illustrative embodiments improves over traditional intake sections and traditional intake screens by operating over a longer period of time without starving (shutting off) the inflow performance of the pump. The invention may extend the run life of the artificial lift pump system by preventing smaller media from entering the pump system than would otherwise be possible with traditional intake filters, since the porous media cartridge may filter much smaller particles than conventional screens. Further, the invention may provide for an intake section that is customizable to individual well environments and resistant to clogging due to an increased surface area. 
     Illustrative embodiments may lower the cost of the pumping equipment (such as ESP pumping equipment) while increasing production by extending pump run life. Pumps utilizing the invention may not require internal coating of the equipment (such as tungsten carbide coating to harden surfaces of pump components), the use of extensive abrasive resistant technology, or other abrasive combative equipment, such as a “sand seal.” Illustrative embodiments may keep solids and other media from entering or accumulating on the top of the seal section of ESP assemblies by preventing media from being taken into the pump in the first place. 
     While adding numerous modular intake filters of illustrative embodiments to artificial lift assemblies may increase the initial cost of the pump, the modular intake filter reduces overall costs from a long term perspective by better protecting the pump from solids and other media and hence increasing the run life. Further, the increased surface area of the filter provided by illustrative embodiments may increase flow and reduce the potential for plugging and the time between plugging. In addition, the modularity of the intake filters of illustrative embodiments, allows an intake section to be easily customized for a particular well environment, such as based on the composition of the well fluid, and the size of abrasive media present therein. 
     One or more embodiments of the invention provide a modular intake filter system, apparatus and method, for use in artificial lift pumping applications, such as ESP applications and rod pump applications. While for ease of illustration, illustrative embodiments are primarily described in terms of an ESP application for pumping oil, water and/or gas, nothing herein is intended to limit the invention to those embodiments. Illustrative embodiment may be similarly employed in rod pump assemblies, progressive cavity pumps, hydraulic pumps, and jet pump assemblies. 
     Pump Assembly 
     The modular intake filter of illustrative embodiments may be placed in an artificial lift pump assembly in place of, or in addition to, the conventional intake section. An illustrative embodiment of ESP pump assembly making use of a modular intake section of an illustrative embodiment is shown in  FIG. 3 . As shown in  FIG. 3 , ESP assembly  30  is located beneath the ground inside casing  32 . Perforations  34  in casing  32  allow well fluid to enter casing  32  and be lifted by ESP assembly  30 . Motor  36  may be an electric motor such as a three-phase, two-pole squirrel cage induction motor, permanent magnet motor or a wound type motor. Motor  36  may obtain power through a power cable (not shown) connected to a power source at the surface of the well. Motor  36  turns a motor shaft, which extends longitudinally through the center of motor  36 . In order to function properly, electrical motor  36  must be protected from well fluid ingress, and seal section  38  provides a fluid barrier between the well fluid and motor oil. Motor oil resides within seal section  38 , which is kept separated from the well fluid. In addition, seal section  38  supplies oil to electrical motor  36 , provides pressure equalization to counteract expansion of motor oil in the well bore and carries the thrust of centrifugal pump  42 . The seal section has a shaft that is connected to the motor shaft, for example by splining, such that the seal section shaft rotates with the motor&#39;s shaft. 
     As shown in  FIG. 3 , seal section  38  is bolted to intake section  315 , intake section  315  being downstream of seal section  38 . Intake section  315  may be bolted and/or threaded to seal section  38  with base  360 . Intake section  315  includes an intake shaft  330  (shown in  FIG. 5 ) extending longitudinally through its center. The intake shaft  330  is coupled, for example splined, to the seal section shaft on one side and the centrifugal pump shaft on the other side, such that all the shafts rotate together during operation of electric motor  36 . As illustrated in  FIG. 3 , three modular intake filters  305  are included in intake section  315 . One or more modular intake filters  305  may be used in illustrative embodiments. The three modular intake filters  305  shown in  FIG. 3  are threaded to one another by two guides  340 . Head  300  secures intake section  315  to centrifugal pump  42 . Well fluid enters centrifugal pump  42  through intake section  315 . Centrifugal pump  42  may be a multistage centrifugal pump and lift fluid through production tubing (not shown) to the surface of the well. 
     Modular Intake Filter Components 
     An intake section of an artificial lift assembly of illustrative embodiments includes one or more modular intake filters.  FIGS. 4-6  illustrate a modular intake filter  305  of an illustrative embodiment. Various embodiments of modular intake filter  305  may include perforated housing  310  and porous media cartridge  320 . Perforated housing  310  may be stainless steel, 9-chrome, or another strong, corrosion resistant material. Unlike a traditional screen, perforated housing  310  may be a tubularly shaped, solid piece of metal that acts as a supportive skeleton for porous media cartridge  320 . The perforated housing includes holes, slots, ports or perforations (perforations) that allow for entrance of fluid into the pump, and with respect to multistage pumps, direct the fluid into the first stage of the pump. The perforations in the perforated housing may not substantially contribute to the filtration of solids in well fluid. Instead, porous media cartridge  320 , which wraps around the perforated housing like skin, may carry the primary filtration function. 
     Modular intake filter  305  may vary in porosity depending on the size of the pores (porosity or media grade) selected for porous media cartridge  320 . Illustrative embodiments of porous media cartridge  320  are shown in  FIGS. 23 and 24 .  FIG. 23  illustrates a macroscopic view of a porous media cartridge having a media grade of 40.  FIG. 24  illustrates a microscopic view of a porous media cartridge  320  having a media grade of 40. In some embodiments, the slots or perforations of perforated housing  310  and/or screen  1400  (shown in  FIG. 14 ) may not affect the porosity of modular intake filter  305  since porous media cartridge  320  may prevent passage of significantly smaller media than perforated housing  310 . For example, porous media cartridge  320  may prevent passage of media on the order of microns in diameter (for example, 40 microns or larger in the case of a media grade of 40), rather than on the order of inches in diameter as would a traditional screen. In certain embodiments, the combination of the size of the openings of perforated housing  310  and the porosity of porous media cartridge  320  may determine the porosity of modular intake filter  305 . In other embodiments, the combination of the size of openings of perforated housing  310 , the porosity of porous media cartridge  320  and the slots or perforations in an outer screen  1400  may determine the porosity of modular intake filter  305 . 
     Porous media cartridge  320  may be a sintered, porous metal, isometric and tubular in shape, which surrounds the outer surface of perforated housing  310 . In other embodiments, porous media cartridge  320  may be a fiberglass weave or any corrosion resistant, porous material consistent with a selected media grade. Porous media cartridge  320  may be located outside perforated housing  310 , for example porous media cartridge  320  may circumferentially surround perforated housing  310  so as to provide a filtration layer with a desired porosity. Porous media cartridge  320  may entirely enclose perforated housing  310  in a tubular fashion, and may be sealed, such that fluid passing into the pump must first pass through porous media cartridge  320  prior to entering a pump of an artificial lift assembly. Porous media cartridge  320  and/or a screen  1400  (shown in  FIG. 15 ) may be installed on intake section  315  such that the outer diameter of the pump assembly remains uniform. 
     Different porosity, and hence control over the maximum allowable particle size that can be admitted inside the pump, may be achieved by using different materials or different media grades for porous media cartridge  320 . In some embodiments, porous media filter  320  may be “316 Stainless Porous metal,” which is available in various porosity sizes (various media grades). Mott Corporation of Farmington, Conn. supplies suitable porous metal. Using this metal for the media filter has several advantages. The 316 stainless steel is less prone to corrosion, it is strong and it may not collapse under high differential pressure (plugging). Exemplary media grades are 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 40 and 100. In general, the media grade may be the mean micron rating of the porous metal or other porous material. For example, a media grade of “10” or “10.0” may prevent 90% of particles in a liquid stream having a 10.0 micrometer outer diameter or larger from passing through the cartridge. The percentage of media of a given size that may be prevented from passing through porous media cartridge  320  having a selected porosity may depend upon the porous material employed and/or the composition of the well fluid. For example, 90% of media having an outer diameter of 10.0 micrometers or greater may be prevented from passing through porous media cartridge  320  of media grade 10 in a liquid stream, but 99.9% of that sized media may be prevented from passing through porous media cartridge  320  of media grade 10 in a gas stream. In some embodiments, a material for use as porous media cartridge  320  may include a stainless steel metal cylinder having a selected porosity size. In some embodiments, the porosity of porous media cartridge  320  may be selected based on the type, quantity and/or size of media found in the well environment and/or fluid to be pumped. 
     In some embodiments, a traditional perforated or slotted flexible screen may be used around the outside of porous media cartridge  320 .  FIGS. 14-16  illustrate an embodiment of a modular intake filter  305  including perforated housing  310 , porous media cartridge  320  and screen  1400 . In such instances, the porous media cartridge  320  may be sandwiched and/or sealed between perforated housing  310  and the screen  1400 . In instances where screen  1400  is employed, screen  1400  may be rolled, wrapped around the assembled module and welded along seam  1405 . It may not be necessary to seal screen  1400  on the top and bottom sides, since screen  1400  includes large slots or perforations (on the order of inches) in any event. 
     Shaft  330  shown in  FIGS. 5 and 15 , provides the transfer of horsepower from seal section  38  to centrifugal pump  42  on an ESP assembly, for example. Shaft  330  may be splined on the ends. In such embodiments, the splines engage into couplings in the seal section shaft and pump shaft, which transfers shaft  330  movement and power from seal to pump. 
     Perforated housing  310  may include threading on the top and bottom sides of the tube in order to be threaded to a head  300 , base  360  and/or guides  340 . Modular intake filter  305  may be bolted and/or threadedly connected to a pump, seal section, motor and/or one or more other modular intake filter  305  of illustrative embodiments in one or more of four combinations—head  300  to base  360 , head  300  to guide  340 , guide  340  to guide  340 , or guide  340  to base  360 . Head  300  may be located at the downstream most side of intake section  315  and base  360  may be located at upstream most side of intake section  315 . 
     An illustrative embodiment of head  300  is shown in  FIG. 18 . An illustrative embodiment of base  360  is shown in  FIG. 17 . Head  300  and base  360  may each include two sides: one intake side  1700  to be secured to the adjacent perforated housing  310  of a filter module  305 , and one component side  1705  to be secured to the adjacent artificial lift assembly component, for example a pump, gas separator or seal section. Head  300  and base  360  may be drilled and tapped to include threaded bolt holes on a neck and flange  1710 . In this way, in an ESP embodiment for example, head  300  may be secured to the pump of the ESP assembly and base  360  may be secured to the seal section of the ESP assembly. In embodiments where intake section  315  is placed in a different location in an artificial lift assembly (somewhere other than between the pump and the seal section), then head  300  and base  360  provide for secure fastening to the pump components located immediately downstream and upstream of the pump intake  315  respectively. The intake side  1700  of head  300  and base  360  facing perforated housing  310  may include threads  1715  for threaded engagement to perforated housing  310  and/or modular intake filter  305 . Guide  340  may comprise threads  1715  on both sides for threaded engagement to perforated housing  310  and/or modular intake filter  305 .  FIG. 19  is an illustrative embodiment of guide  340 . In some embodiments, guide  340  may be similar to a guide located in a convention ESP seal section. 
     Radial Support Components 
     Head  300 , base  360  and/or guide  340  of modular intake filter  305  may include a bearing set for radial support. Radial support becomes increasingly important as the length of intake section  315  increases. An intake section  315  that includes multiple modules may be significantly longer than traditional intake sections. For example, an intake section of an illustrative embodiment including 10 modules may be in excess of 13 feet long, as opposed to traditional intakes that are only one or two feet in length.  FIG. 10  shows an illustrative embodiment of a supportive bearing set included in a guide  340 . Bearing set  450  including bushing  420  and sleeve  410  may provide for radial support on shaft  330 . Sleeve  410  may be keyed or otherwise attached to rotatable shaft  330  such that it rotates with shaft  330  inside stationary bushing  420 . The rotation of sleeve  410  inside bushing  420  creates a radial support bearing during operation of the artificial lift assembly. As the length of intake section  315  is increased through the addition of modules, additional sleeve  410  and bushing  420  sets  450  may be added in head  300 , base  360  and/or guide  340  for radial support. 
     Sleeve  410  may be keyed to shaft  330  and rotate at the same speed as shaft  330 . Bushing  420  may be pressed into spider bearing  400  and/or the wall of head  300 , base  360  and/or guide  340  and remain stationary during operation of the pump assembly. Spider bearing  400  may be pressed into head  300 , base  360  and/or guide  340  where a bushing  420  is placed and may assist in securing bushing  420  such that it remains stationary during pump operation. During operation of the pump, a thin film of fluid may form in between rotating sleeve  410  and stationary bushing  420 , providing hydrodynamic and/or hydraulic support. 
     Bushing  420  and/or sleeve  410  may be made of tungsten carbide or other suitable material at least as hard as the abrasive solids found in the laden well fluids, for example media smaller than the selected size to be filtered. For example, the bearing surface may be tungsten carbide, silicon carbide, titanium carbide, or other materials having similar properties. Ceramic as well as other manmade compounds, or steel alloys having special surface coatings to increase surface hardness may also be used. Examples of suitable coatings may include nickel boride, plasma type coatings or surface plating like chrome or nickel. Diffusion alloy type coatings may also be suitable. In some embodiments, a sufficient amount of media is filtered from the well fluid by modular intake filter  305  such that a hard material or coating is not necessary for bearing set  450 . As additional modules  305  are added to intake section  315  and the length of section  315  increases, additional bearing sets of bushing  420  and sleeve  410  may be included in the head  300 , base  360  and guides  340  of the section  315  in order to provide support and reduce the risk of buckling. 
     Intake Section Modules 
     Intake section  315  may comprise one or more modules. One or more modular intake filter  305  may be joined together to create intake section  315 . A first modular intake filter  305  may be threadedly joined to an adjacent modular intake filter  305  with guide  340 . For example, an intake section including two modular intake filters  305  is shown in  FIGS. 7-9 . An intake section including three modular intake filters  305  is shown in  FIG. 12 , and an intake section  315  including four modular intake filters  305  is shown in  FIG. 13 . Embodiments including more than four modular intake filters  305 , or only a single modular intake filter  305 , are also contemplated, as described in detail herein. In some embodiments, intake section  315  having two modules, as shown in  FIGS. 7-9 , may comprise three bearing sets  450  for radial support: one in head  300 , one in guide  340  and one in base  360 . Similarly, embodiments of an intake section  315  having three modules  305 , such as that shown in  FIG. 12 , may comprise four bearing sets  450 : one set  450  in each of the head  300 , base  360  and two guides  340 . In yet further embodiments, an intake section  315  comprising a single module as for example shown in  FIG. 5 , may include two bearing sets, one in head  300  and one in base  360 . 
     A desired porosity of porous media cartridge  320 , and hence intake section  315 , may be selected. For example, the selection may be based on the size, composition and/or quantity of media in the pumped fluid. Once a desired porosity of porous media cartridge  320  and/or intake section  315  is chosen, one would determine the number of modular intake filter  305  to install in intake section  315  based on the area of filtration material needed to maintain a desired flow rate and/or acceptable pressure drop. One could, for example, install a single modular intake filter  305 , or one could install 20 modular intake filters. If one were to select a media size of, for example 20 microns as the maximum allowable particle size that may be admitted inside the pump, the required filter surface area would be much larger than a filter for solids of 100 microns as the maximum allowable particle size, if the desired flow rate is to be maintained. In particular, one may determine the number of modular intake filter  305  to be included in intake section  315  by considering desired flow rate, permeability of the porous media cartridge  320  of the chosen porosity (media grade), and the fixed surface area of a single modular intake filter  305 . 
     Table 1 provides examples of how to compute the number of modular filters  305  required to maintain a flow rate, with a selected porosity of a porous media cartridge having a given permeability with respect to a fluid of known viscosity, where a single module has a surface area of 1.6057 ft 2  (e.g., a cylinder/tube having a height of 16 inches and a circumference of 4.6 inches). An exemplary calculation may proceed as follows: 
     First, select a media grade for porous media cartridge  320 . The media grade may be selected based upon the maximum sized media that will be allowed to enter into pump intake  315 . For example, if a porosity of “5” is selected, 90% of media in the well fluid having an outer diameter of 5.0 micrometers or larger may be prevented from passing through porous media cartridge  320 . The porous media cartridge  320  having the selected media grade (porosity), employed in a fluid of a known viscosity, at a particular pressure drop, will have an associated permeability as a feature of the porous media cartridge  320 . In this example, porous media cartridge  320  with a porosity of 5 has a liquid permeability of 6.8 gpm/ft 2  at a 1.0 psi pressure drop and a fluid viscosity of 1.0 centipoise. This information may be determined, for example, by flow curves of porous media cartridge  320 . 
     Second, select the desired flow rate of the pump. The desired flow rate may depend upon the particulars of the pumping application such as the type of fluid being pumped, the composition of the fluid be pumped and/or the type of pump employed—for example an ESP pump or a rod pump. In this example, the desired flow rate is 116.6 gallons per minute (gpm). 
     Third, divide the desired flow rate by the permeability of the porous media cartridge  320  having the selected porosity, to determine the area of filtration material required at the selected porosity. This formula may be expressed as 
     
       
         
           
             
               A 
               = 
               
                 
                   FR 
                   Desired 
                 
                 P 
               
             
             ; 
           
         
       
     
     where A is the area of filtration material needed at the selected porosity, FR Desired  is the desired flow rate, and P is the permeability of porous media cartridge  320  at the selected porosity. Continuing with the example, if a porosity of 5 is selected and a desired flow rate of 116.6 gpm is chosen, then P is 6.8 gpm/ft 2  if the fluid is liquid, and A=17.147 ft 2 . 
     Fourth, divide the area of filtration material needed by the surface area of a single modular intake filter  305  and/or the surface area of porous media cartridge  320  contained on a single filter module  305 . The surface area of a single modular intake filter  305  and/or the surface area of filtration material sealed onto a single modular intake filter  305  may be fixed based upon the particular type of pump employed. In the example, a single module  305  has a surface area of 1.6057 ft 2 . Thus, the number of modules needed may be calculated using the formula 
     
       
         
           
             
               M 
               = 
               
                 A 
                 S 
               
             
             ; 
           
         
       
     
     where M is the number of modules needed, A is the area of filtration material needed, and S is the surface area of a single module  305 . Continuing with the example, if a surface area (A) of 17.147 ft 2  of filtration material is needed, and the surface area of a single module  305  is 1.6057 ft 2 , then 10.596 modules are needed in this example. 
     Fifth, round the number of modules to a whole number based on the selected rounding method. For example, it may be desired to round to the nearest whole number. In this case, 10.596 modules may be rounded up to eleven modular intake filters  305 . 
     In the illustrative example, eleven modular intake filters may then be joined in series as described herein, for example threaded and/or bolted, to form intake section  315 , and incorporated into an artificial lift pump assembly. Additional exemplary calculations to determine the number of modular intake filters  305  which may be employed in an intake section  315  are illustrated in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Modular Filter Quantity Calculations 
               
               
                 Using 1.0 centipoise (cP) as the viscosity of the  
               
               
                 well fluid and 116.6 gallons per minute (gpm) as the desired flow rate: 
               
            
           
           
               
               
               
               
            
               
                 Media Grade 
                   
                   
                   
               
               
                 (porosity) 
                 10 
                 5 
                 1 
               
               
                   
               
               
                 Permeability for 
                 12 gpm/ft 2  @  
                 6.8 gpm/ft 2  @ 
                 1.8 gpm/ft 2  @ 
               
               
                 a liquid fluid 
                 1 PSI drop 
                 1 PSI drop 
                 1 PSI drop 
               
               
                   
               
               
                 Area of filtration  material required = 
                 
                   
                     
                       
                         
                           116.6 
                            
                           
                               
                           
                            
                           gpm 
                         
                         
                           12 
                            
                           
                               
                           
                            
                           gpm 
                            
                           
                             / 
                           
                            
                           
                             ft 
                             2 
                           
                         
                       
                     
                   
                 
                 
                   
                     
                       
                         
                           116.6 
                            
                           
                               
                           
                            
                           gpm 
                         
                         
                           6.8 
                            
                           
                               
                           
                            
                           gpm 
                            
                           
                             / 
                           
                            
                           
                             ft 
                             2 
                           
                         
                       
                     
                   
                 
                 
                   
                     
                       
                         
                           116.6 
                            
                           
                               
                           
                            
                           gpm 
                         
                         
                           1.8 
                            
                           
                               
                           
                            
                           gpm 
                            
                           
                             / 
                           
                            
                           
                             ft 
                             2 
                           
                         
                       
                     
                   
                 
               
               
                   
               
               
                 Square feet of 
                 9.71667 
                 17.147 
                 64.7 
               
               
                 filtration 
                   
                   
                   
               
               
                 material needed 
                   
                   
                   
               
               
                 at this media 
                   
                   
                   
               
               
                 grade 
                   
                   
                   
               
               
                 Modules needed 
                 6 modules 
                 11 modules 
                 40 modules 
               
               
                 to maintain 
                   
                   
                   
               
               
                 desired flow rate 
               
               
                   
               
            
           
         
       
     
     As illustrated by the above calculations, the formula for determining the minimum number of modules required to maintain a desired flow rate may be also be expressed as 
     
       
         
           
             
               M 
               = 
               
                 
                   FR 
                   Desired 
                 
                 
                   P 
                   * 
                   S 
                 
               
             
             ; 
           
         
       
     
     where M is the number of modules required, FR Desired  is the desired flow rate, P is the permeability of the filtration material and S is the surface area of a single module  305 . 
     The ability of the invention to allow the installation of porous media cartridge  320  of varying porosity is important to the application because doing so allows control of the maximum allowable particle size that may be admitted inside the pump. The modularity of intake section  315  allows one to maintain flow rates despite the porosity selected, which porosity may be selected from a wide range of possibilities as described herein, for example media grades ranging from 0.1 to 100. Over the run life of a pump system, all filters may eventually plug off, which may starve the pump for fluid and create a pressure differential in the pump. In the modular intake filter of the invention this problem may be combated by the presence of multiple filter modules. 
     The above exemplary calculations use 1.0 cP as the viscosity of the fluid to be pumped. The viscosity of the pumped fluid will depend on the composition and temperature of the fluid, with higher temperatures lowering the viscosity of the fluid. Water at 160° F. has a viscosity of approximately 0.4 cP. Oil mixed in with the water will increase the viscosity. In some embodiments, the viscosity of pumped fluid will between 1.0 cP and 10.0 cP, with most applications being on the lower end of that range. 
     The above exemplary calculations use 116.6 gpm as the desired flow rate. The desired flow rate may vary based upon the application and may be between 500 barrels of fluid per day (BPD) to 4,000 BPD, which would be between 14.583 gpm and 116.66 gpm. 
     The above exemplary calculations also use 1.6057 ft 2  as the fixed surface area of a single module  305 . The surface area of a single module  305  may be fixed based upon the particular pump series design, for example a type “513 intake” or a type “400 intake”. The surface area of a single module  305  may also be fixed based upon the type of artificial lift system employed, such as an ESP assembly or a rod pump assembly. 
     Because the surface area of a single module is fixed, a fraction of a module may not be employed, thus fractions of a module so calculated may be rounded up or down to a whole number of modules as illustrated by Table 1. Rounding may be based on proximity to the closest whole number of modules, may be based upon the magnitude of modules, or may be based on another similar consideration. An example of rounding based on proximity to a closest whole number may be by rounding up if the calculation produces a fraction of 0.5 or greater, and rounding down if the fraction is less than 0.5. An example of rounding based on magnitude of modules may be rounding up if 20 or fewer modules will be included, and rounding down if greater than 20 modules will be included in intake section  315 . Rounding based on the magnitude of modules may be employed to minimize cost and/or length of intake section  315 . 
     Installing Modular Intake Section in Pump Assembly 
       FIG. 25  is an illustrative embodiment of a method of installing a modular intake filter  305 , for example, into an ESP assembly. At step  500 , perforated housing  310  may be installed onto base  360 . At step  510 , slide O-ring  350  (shown in  FIG. 9 ), over perforated housing  310  and press against the shoulder of base  360 . O-ring  350  may be an o-ring set and/or made of synthetic rubber, a rubber composition and/or a fluoropolymer elastomer such as Viton (a registered trademark of E. I. Du Pont De Nemours &amp; Company), or other material suitable for the environment. Next, slide porous media cartridge  320  over perforated housing  310  at step  520 , followed by a second O-ring  350 , which may be an O-ring set, braced on the shoulder of base  360  at step  530 . In some embodiments, sealant may be used instead of, or in addition to, the O-rings  350 . If another module  305  is needed in intake section  315  at step  540 , for example as calculated above, guide  340  may be installed at step  550 , perforated housing  310  may be installed on guide  340  at step  560 , and steps  510  through  530  may be repeated bracing the O-rings  350  against guide  340  rather than against base  360 . Steps  550 ,  560  and then steps  510  through  530  may be repeated until it is determined at step  540  that another module  305  is not needed. 
     If another module  305  is not needed, head  300  may be installed to complete the intake body at step  570 . Sleeves  410  and retaining rings  435  may be installed onto shaft  330  at step  580 . Shaft  330  may be installed into the intake body to complete intake section  315  at step  590 . At step  595 , the completed modular intake section  315  may be threaded and/or bolted to the components above and below intake section  315  in the pump assembly. In some embodiments, modules  305  of intake section  315  may be threaded to one another, and the modular intake section  315  may be bolted at head  300  to a pump, and bolted at base  360  to the seal section of the pump assembly. In such embodiments, a seal may be created in head  300  of the modular intake section  315  when the pump is installed, the pump holding the O-rings  350  on the pump, which seals against the inner diameter of the modular intake head  300 . 
     O-rings  350  and/or sealant may be placed against the shoulder of perforated housing  310  in order to form a seal between the body of perforated housing  310  and porous media cartridge  320 . If this seal is not made, solids may bypass porous media cartridge  320  at the shoulder. The first O-ring  350  may create a seal between porous media cartridge  320  and perforated housing  310  to prevent foreign solids from being ingested into the pump during operation. Second O-ring  350  attaches porous media cartridge  320  to perforated housing  310  in a replaceable and yet well-sealed fashion. In some embodiments, sealant may be used in place of, or in addition to, O-rings  350 . 
     Modular Intake in Motion 
     When modular intake filter  305  is in motion, shaft  330  is turned from a base spline via the coupling to seal section  38  of the pump assembly. Sleeve  410  may be keyed to rotating shaft  330 , thus rotating with shaft  330 . Sleeve  410  rotates inside of stationary bushing  420 , creating a radial support bearing during operation. Sleeve  410  and/or bushing  420  may be made of tungsten carbide or any other suitable material as detailed elsewhere herein or known to those of skill in the art. The radial support bearings may be affixed in the head  300 , base  360  and/or guide  340  of intake section  315  and/or modular intake filter  305 . 
     Radial support bearing set  450  may be held in place with retaining rings  435  (shown in  FIG. 5 ) on shaft  330  above and below sleeve  410 . Retaining rings  435  may be held in shaft  330  by a retaining ring groove. Shaft stop  440  (shown in  FIG. 5 ) may be located at the ends of shaft  330 , the shaft stop  440  contained within retaining rings  435  in addition to the outer sleeves  410 . In some embodiments, only two shaft stops  440  may be used regardless of the number of modules  305  in an intake section  315 , since they are installed near the ends (top and bottom sides) of shaft  330 . Shaft stop  440  may prevent shaft  330  from sliding out of the assembly. For each head  300 , base  360  and guide  340  there may be one radial support bearing set  450  having a bushing  420  and sleeve  410 . In some embodiments, a single module will have two radial support bearings, one in head  300  and one in base  360 . In some embodiments, a triple module with a head  300 , two guides  340 , and a base  360  would have four radial support bearings. Shaft  330  transmits rotation from the seal section  38  of the pump assembly to the pump  42  via a spline and coupling at the head  300 . 
       FIG. 10  illustrates a cross section of a guide of one or more embodiments of the invention. Guide  340  may be threaded on both ends to allow connecting two perforated housings  310  to each other (top to bottom) using threads  1715  on perforated housing  310 . Guide  340  may also enable the addition of spider bearing  400 . Spider bearing  400  may house radial support bushing  420  and may remain stationary, while shaft  330  and sleeve  410  rotate. Multiple flow passages  430  around spider bearing  400  allow fluid flow to pass from module  305  to module  305  and eventually into the lower pump above head  300 . 
       FIG. 11  illustrates a cross section of the modular intake filter apparatus of one or more embodiments of the invention midway down a modular intake filter  305 . This figure illustrates that porous media cartridge  320  is circumferentially disposed about perforated housing  310 . Between perforated housing  310  and shaft  330  is cylindrical opening  1100  allowing well fluid to flow to the pump. 
     Rod Pump Assembly 
     For ease of illustration and so as not to obscure the invention, the aforementioned description has been with respect to an ESP assembly embodiment. However, illustrative embodiments may be employed in other types of artificial lift assemblies, for example rod pump assemblies (also termed beam lift), hydraulic pumps, progressive cavity pumps or jet pumps. In such embodiments, modifications to intake section  315  may be required, particularly with head and base connections to adjacent pump assembly components. A rod pump assembly embodiment will now be described so as to illustrate the types of modifications which may be employed in order to implement illustrative embodiments in various types of artificial lift assemblies other than ESP assemblies. 
       FIG. 26  is an illustrative embodiment of a beam lift assembly making use of a modular intake filter of an illustrative embodiment. As shown in  FIG. 26 , beam lift assembly  2600  is located downhole in rod pump casing  2605 . Well fluid enters casing  2605  through perforations  2610  which may be beneath beam lift assembly  2600 . Bull plug  2615  may be at bottom end of gas separator  2620 . Gas separator  2620  may assist in separating gas from pumped fluid prior to entry into rod pump  2630 . Intake section  315 , which includes one or more modular intake filters  305 , may be secured between gas separator  2620  and rod pump  2630 . Intake head box  2645  may be bolted onto modular intake filter  305  and connected to rod pump  2630  by head pin  2675 , which may be a 2⅞ external upset end (EUE) pin and/or nipple. Intake base box  2655  may be bolted onto modular intake filter  305 . Base box  2655  may be fitted with nipple  2670 , which nipple  2670  may connect to base receiving box  2650 , securing intake section  315  to gas separator  2620 . This may allow intake section  315  to be placed below rod pump  2630  and above gas separator  2620 . In some embodiments head box  2645 , base box  2655  and/or base receiving box  2650  may be 2⅞ inch female EUE box connections, and head pin  2675  and/or base nipple  2670  may be EUE pin 2 2/78 male connections. Part measurements may vary based upon the size and type of pump assembly employed. 
     Concentric to the beam lift assembly  2600  may be a dip tube  2625  that extends longitudinally through rod pump  2630 , intake section  315  and gas separator  2620 . The assembly would allow for intake section  315  to serve as an intake while still allowing gas separator  2620  to provide gas free liquid to rod pump  2630 . 
       FIGS. 20-22  illustrate an intake section  315  for a rod pump assembly such as beam lift assembly  2600 . As shown in  FIGS. 20 and 22 , modular intake filter  305  and guide  340  for a rod pump embodiment is as described above with respect to an ESP assembly embodiment. Rod intake head  2635  with head box  2645  may be configured to attach to rod pump  2630  with pin  2675 . Rod intake base  2640  with base box  2655  are designed for attachment to gas separator  2620  with nipple  2670 . Bolt-on discharge base box  2655  and/or head box  2645  may be a threaded and flanged sealed connecting device, converting tubing (pipe) threads to a bolted and sealed flange, thus allowing the modular intake  315  to integrate onto rod pump  2630  and/or gas separator  2620 .  FIG. 21  is a top view of an illustrative embodiment of an intake section  315  for a rod pump embodiment. Bolts  2100  are shown in  FIGS. 21 and 22 , which secure base box  2655  to base  2640  and head  2635  to head box  2645 . 
     With respect to a rod pump embodiment, the determination of the number of modules needed in intake section  315  is similar to that of an ESP embodiment, taking into consideration differences such as the fixed surface area of a module, which may be different from that of an ESP embodiment, depending upon the dimensions of the pump for example, or any differences in what may be an acceptable flow rate or pressure drop based on the particular rod pump application. 
     Thus, the invention described here provides one or more embodiments of a modular intake filter system, apparatus and method. While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims. The foregoing description is therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.