Conduit cleaning system and method

A system capable of removing scale deposits from an interior metallic surface of a conduit includes a mixture including a plurality of substantially spherically shaped solid particles and fluid, a mixture delivery tubing insertable into the conduit, and a nozzle attached to the mixture delivery tubing. The nozzle includes a plurality of nozzle jets and is capable of ejecting the mixture to loosen scale deposits from the interior metallic surface of the conduit.

BACKGROUND OF THE INVENTION
 The invention relates generally to the field of apparatus and methods used
 for removing material from inside a conduit. More particularly, the
 present invention relates to a system capable of loosening and removing
 material built-up on the inside surface of, or disposed within, a metal
 conduit.
 Undesirable materials that build-up on the inside walls of conduits, such
 as well tubing, injection lines, pipelines, flowlines, boiler tubes, heat
 exchangers and water lines, or that otherwise collect inside the conduits,
 are known to restrict or interfere with the desired movement of fluids,
 materials and devices, tools, liquids and gases through the conduits. As a
 result, in many cases, the conduit becomes useless, or inoperable for its
 intended purpose. For example, thousands of petroleum wells in this
 country have been shut down or abandoned due to the crippling effect on
 operations of obstructions in the well tubing. Examples of such
 undesirable, or obstructive, materials include barium sulfate, strontium
 sulfate, calcium sulfate, calcium carbonate, iron sulfide, other scale
 precipitates (such as silicates, sulfates, sulfides, fluorides,
 carbonates), cement, corrosion products, deteriorated conduit lining, and
 dehydrated material (such as drilling fluid).
 Existing methods of removing obstructive materials from conduits have
 numerous disadvantages. Various techniques involve the use of a mill or
 bit to remove obstructive material from conduits. In many applications,
 the mills or bits have a short useful life due to damage from contact
 between the mills and bits and commonly occurring hard, dense obstructive
 materials. The mills or bits must therefore be frequently removed from the
 conduit and replaced, consuming time and expense. Further, rotation of the
 mill or bit requires additional component parts, such as a motor, bearings
 and rotary seals, which are complex and costly to manufacture and operate
 and subject to failure. Rotary seals typically limit the use or
 effectiveness of the system due to their vulnerability to wear or damage
 from high temperatures.
 These techniques are also largely ineffective at loosening and removing
 substantially all obstructive material without damaging the conduit. For
 example, the inside walls of conduits cleaned with mills or bits are
 highly subject to damage from contact by the mill or bit. Such contact
 commonly occurs when the obstructions in the conduit are unevenly
 dispersed, causing the mill or bit to jam or rub against, or drill into,
 the side of the conduit. Further, reactive torque due to the rotation of
 the drill or mill can also cause it to contact the inside surface of the
 conduit and cause damage thereto. Such reactive torque also accelerates
 deterioration to the tubing, such as coiled tubing, that carries the mill
 or bit.
 Other conventional cleaning methods utilize jet nozzles that eject only
 liquid or angular-shaped solid particles in a foam or liquid transport
 medium. Typical liquid-only systems insertable in a conduit of significant
 length, such as petroleum tubing and pipelines, operate in low to moderate
 pressure ranges. These systems have proven ineffective at loosening or
 removing commonly encountered hard, tightly bonded obstructive materials,
 such as barium sulfate. The jet systems using angular-shaped solids
 typically damage the inside surface of metal conduits as a result of the
 angular solids cutting, scarring and eroding the metal. These systems lack
 the ability to minimize or control the amount of damage that occurs to the
 metal conduit; therefore, their use is not entirely satisfactory for many
 applications. Further, the angular solids provide an erratic erosion
 pattern, limiting their effectiveness in loosening and removing
 obstructions.
 Thus, there remains a need for a system for loosening and removing
 undesirable materials built-up on the inside surface of metal conduits, or
 that otherwise collect inside the conduits, that does not cause
 substantial or undesirable damage to the conduit. Preferably, the system
 will be simple, and cost effective and easy to manufacture and operate.
 Ideally, the system could utilize existing equipment. Especially well
 received would be a system that can quickly remove all, or substantially
 all, of the undesirable materials. Ideally, the system would not need to
 be rotated and would have static seals unaffected by high temperatures.
 Further, it would be beneficial for the system to be capable of
 recirculating or reusing its cleaning mixture or the constituents of the
 cleaning mixture.
 BRIEF SUMMARY OF THE INVENTION
 In accordance with the present invention, there is provided a system for
 removing obstructive material from inside a conduit that includes a
 mixture including a plurality of substantially spherically shaped solid
 abrasive particles and fluid, a mixture delivery tubing insertable into
 the conduit and a nozzle assembly attached to the mixture delivery tubing.
 The nozzle assembly includes a plurality of nozzle jets capable of
 ejecting the mixture to loosen obstructive material inside the conduit.
 The substantially spherically shaped solid abrasive particles may be
 constructed at least partially of glass, metal, plastic, ceramic, epoxy,
 other suitable material, or a combination thereof, and may have any
 suitable size, such as between about 20 mesh and about 100 mesh. Further,
 the particulate density of the substantially spherically shaped solid
 abrasive particles may be greater or less than the density of the fluid.
 In preferred embodiments, the nozzle assembly is capable of ejecting the
 mixture to loosen obstructive material inside the conduit without
 substantially damaging the conduit, and ejecting the mixture around the
 inner circumference of the conduit without rotating the nozzle assembly.
 The system may include a filter capable of preventing clogging of the
 nozzle jets by particles carried in the mixture. The system may include a
 mixer capable of mixing the substantially spherically shaped solid
 abrasive particles and the fluid to form the mixture, and a pump capable
 of pumping the mixture under pressure into the mixture delivery tubing.
 In another aspect of the invention, there is provided a nozzle assembly for
 ejecting a mixture that includes substantially spherically shaped solid
 abrasive particles and fluid, the nozzle assembly having a central axis
 and being associated with a mixture delivery tubing. The nozzle assembly
 includes a connector member connectable with the mixture delivery tubing,
 a nozzle head member having a plurality of nozzle jets, at least two of
 the nozzle jets disposed at angles of between approximately 80 degrees and
 approximately 100 degrees relative to the central axis of the nozzle
 assembly, and a gauge ring member disposed between the connector member
 and the nozzle head member.
 In alternate embodiments, the nozzle assembly includes a plurality of
 nozzle jet inserts matable with a plurality of recesses in the nozzle head
 member. In alternate embodiments, at least one of the nozzle jets is
 disposed in the nozzle assembly at an angle of approximately 0 degrees
 relative to the central axis of the nozzle assembly. At least one of the
 nozzle jets may be disposed in the nozzle assembly at an angle of between
 approximately 0 degrees and approximately 90 degrees relative to the
 central axis of the nozzle assembly, or at least two of the nozzle jets
 may be disposed in the nozzle assembly at angles of between approximately
 10 degrees and approximately 20 degrees relative to the central axis of
 the nozzle assembly. The nozzle assembly may include a plurality of nozzle
 assembly sections, each nozzle assembly section having a diameter
 different than the diameter of adjacent nozzle assembly sections and
 wherein at least one nozzle jet is disposed in each nozzle assembly
 section.
 The gauge ring may include at least one wide portion and at least one
 external fluid flow passageway, the wide portion(s) and external fluid
 flow passageway(s) disposed between the nozzle jets and the mixture
 delivery tubing. The gauge ring may include a plurality of wide portions,
 each wide portion having an outer bearing surface, the plurality of outer
 bearing surfaces extending around the circumference of the nozzle
 assembly. One or more wide portions may be located proximate to at least
 two of the nozzle jets. The gauge ring may include first and second sets
 of wide portions, the second set of wide portions disposed between the
 first set of wide portions and the plurality of nozzle jets and being at
 least partially offset on the circumference of the nozzle assembly
 relative to the first set of wide portions.
 The nozzle assembly may be disposed in a conduit and include a fishing tool
 connection portion, wherein the fishing tool connection portion is capable
 of being engaged by a fishing tool latch mechanism. Further, the fishing
 tool connection portion may include a recess capable of receiving a
 fishing tool latching mechanism. The nozzle assembly may include a filter
 capable of preventing clogging of the nozzle jets from particles carried
 in the mixture, and the filter may be disposed at least partially in the
 mixture delivery tubing.
 In yet another aspect of the invention, there is provided a system for
 separating substantially spherically shaped solid abrasive particles
 having a known approximate particulate size from a composite effluent that
 includes fluid, obstructive particles from a conduit and the substantially
 spherically shaped abrasive particles, the substantially spherically
 shaped solid abrasive particles having a particulate density that is
 generally less than the density of the obstructive particles. The system
 includes a size-differentiating particle separator capable of removing
 from the composite effluent obstructive particles that are larger in
 particulate size than the substantially spherically shaped solid abrasive
 particles, a first density-differentiating particle separator capable of
 removing from the composite effluent obstructive particles having a
 density greater than the density of the substantially spherically shaped
 solid abrasive particles, and a second density-differentiating particle
 separator capable of separating substantially spherically shaped solid
 abrasive particles from the fluid. This system may also include a gas
 separator; a slurry pump capable of pumping substantially spherically
 shaped solid abrasive particles, an in-line mixer and a fluid pump, the
 fluid and slurry pumps in fluid communication with the in-line mixer; and
 a hopper/jet mixer.
 In another embodiment of the system for separating substantially
 spherically shaped solid abrasive particles, the substantially spherically
 shaped solid abrasive particles have a particulate density that is
 generally greater than the density of the obstructive particles and the
 fluid. This embodiment includes a size-differentiating particle separator
 capable of removing from the composite effluent obstructive particles that
 are larger in particulate size than the substantially spherically shaped
 solid abrasive particles, and a density-differentiating particle separator
 capable of removing substantially spherically shaped solid abrasive
 particles from the composite effluent. This embodiment may also include a
 gas separator and a second density-differentiating particle separator
 capable of separating obstructive particles from the fluid.
 In still another embodiment of the system for separating substantially
 spherically shaped solid abrasive particles, the spherical solids are
 constructed at least partially of ferromagnetic metal, the system
 including a size-differentiating particle separator capable of removing
 from the composite effluent obstructive particles that are larger in
 particulate size than the substantially spherically shaped solid abrasive
 particles, and a magnetic separator capable of removing, from the
 composite effluent, substantially spherically shaped solid abrasive
 particles constructed at least partially of ferromagnetic metal. This
 system may also include a gas separator and a second
 density-differentiating particle separator capable of separating
 obstructive particles from the fluid.
 In another aspect of the invention, there is provided a method of removing
 obstructive material from inside a conduit including forming a mixture
 including fluid and substantially spherically shaped solid abrasive
 particles, supplying the mixture under pressure into a delivery tubing,
 the delivery tubing having a nozzle that includes a plurality of nozzle
 jets, the nozzle adapted to increase the velocity of the mixture upon
 ejection therefrom, inserting the delivery tubing into the conduit,
 positioning the nozzle within the conduit proximate to obstructive
 material in the conduit, and ejecting the mixture through the nozzle
 against the obstructive material to loosen the obstructive material.
 The method of removing obstructions may further include moving the tubing
 through at least a partial length of the conduit to loosen obstructive
 material in the at least partial length of the conduit. The method may
 include removing the delivery tubing from the conduit, replacing the
 nozzle with a second nozzle of a different type or having a different
 configuration than the first nozzle to improve efficiency or effectiveness
 depending upon the particular existing conditions.
 The method may include additional elements, such as: ejecting the mixture
 from the nozzle to loosen the obstructive material inside the conduit
 without substantially damaging the conduit; ejecting the mixture from the
 nozzle to loosen material inside the conduit without rotating the delivery
 tubing and without rotating the nozzle; ejecting the mixture from the
 nozzle at angles of between about 80 degrees and about 100 degrees
 relative to the inside surface of the conduit; connecting a gauge ring to
 the nozzle and moving the delivery tubing through the conduit to detect
 the location of material within the conduit and center the nozzle assembly
 within the conduit.
 In still another aspect of the invention, there is provided a method of
 separating substantially spherically shaped solid abrasive particles
 having a known approximate particulate size from a composite effluent that
 includes fluid, obstructive particles removed from a conduit and the
 substantially spherically shaped abrasive particles, the substantially
 spherically shaped solid abrasive particles having a particulate density
 that is generally less than the density of the obstructive particles,
 including removing from the composite effluent obstructive particles that
 are larger in particulate size than the substantially spherically shaped
 solid abrasive particles, removing from the composite effluent obstructive
 particles having a density greater than the density of the substantially
 spherically shaped solid abrasive particles, and separating substantially
 spherically shaped solid abrasive particles from the fluid. This method
 may also include removing gas from the composite effluent, and may also
 include mixing the substantially spherically shaped solid abrasive
 particles and the fluid to form a mixture, and pumping the mixture into a
 delivery tubing for removing obstructions from inside a conduit.
 In another embodiment of the method of separating substantially spherically
 shaped solid abrasive particles, the substantially spherically shaped
 solid abrasive particles have a particulate density that is generally
 greater than the density of the obstructive particles and the fluid, the
 method including removing from the composite effluent obstructive
 particles that are larger in particulate size than the substantially
 spherically shaped solid abrasive particles, and removing substantially
 spherically shaped solid abrasive particles from the composite effluent.
 This embodiment may also include removing gas from the composite effluent
 and separating obstructive particles from the fluid.
 In another embodiment of the method of separating substantially spherically
 shaped solid abrasive particles, the substantially spherically shaped
 solid abrasive particles are constructed at least partially of
 ferromagnetic metal, and includes removing from the composite effluent
 obstructive particles that are larger in particulate size than the
 substantially spherically shaped solid abrasive particles, and removing,
 from the composite effluent, substantially spherically shaped solid
 abrasive particles constructed at least partially of ferromagnetic metal.
 This embodiment may include removing gas from the composite effluent and
 separating obstructive particles from the fluid.
 Accordingly, the present invention comprises a combination of features and
 advantages which enable it to substantially advance the technology
 associated with removing obstructions from conduits. The conduit cleaning
 system of the present invention includes a mixture having substantially
 spherically shaped solid abrasive particles (as defined herein), a mixture
 delivery tubing and a nozzle assembly capable of efficiently and
 effectively loosening and removing obstructions in the conduit. The system
 of the present invention is capable of loosening and removing the
 obstructions without causing substantial or undesirable damage to the
 conduit. Preferably, the system is simple, cost effective and easy to
 manufacture and operate. Ideally, the system could utilize existing
 equipment. The system does not need to be rotated and can use static seals
 unaffected by high temperatures. Further, the present invention also
 includes a system for recirculating or reusing the spherical solids and
 fluid from the mixture. The characteristics and advantages of the present
 invention described above, as well as additional features and benefits,
 will be readily apparent to those skilled in the art upon reading the
 following detailed description and referring to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Presently-preferred embodiments of the invention are shown in the above
 identified figures and described in detail below. In describing the
 preferred embodiments, like or identical reference numerals are used to
 identify common or similar elements. The figures are not necessarily to
 scale and certain features and certain views of the figures may be shown
 exaggerated in scale or in schematic in the interest of clarity and
 conciseness.
 Referring initially to FIGS. 1 and 2, a conduit cleaning system 10 of the
 present invention capable of loosening and removing obstructive material
 (obstructions) 14 built-up on the interior surface 18 of, or otherwise
 disposed in, a metallic conduit 20 is shown. The obstructions 14 can
 partially, or completely, obstruct the passage of fluids, material or
 equipment through the conduit 20. Many different types of obstructive
 material 14 may be removed with the use of the system 10, including, but
 not limited to, barium sulfate, strontium sulfate, calcium sulfate,
 calcium carbonate, iron sulfide, other scale precipitates (such as
 silicates, sulfates, sulfides, fluorides, carbonates), cement, corrosion
 products, deteriorated conduit lining, and dehydrated material (such as
 drilling fluid). As used herein and in the appended claims, the terms
 "obstructions," "obstructive material" and variations thereof mean all
 types of undesirable materials built-up on the interior surface of, or
 otherwise disposed in, a metallic conduit.
 The metallic conduit 20 illustrated in FIG. 1 is an underground petroleum
 well tubular 21, but the conduit 20 may be any type of tubular element
 containing obstructive material 14 or having obstructive material 14
 disposed on its interior surface 18, such as well tubing, will casing,
 injection lines, pipelines, flowlines, boiler tubes, heat exchangers and
 water lines. Further, it should be understood that the present invention
 is also useful in loosening and removing obstructions in components (not
 shown) associated with or attached to the conduit 20 and having surfaces
 accessible through the conduit 20, such as, but not limited to,
 connectors, safety valves, gas lift valves and nipples.
 Still referring to FIGS. 1 and 2, the system 10 includes an obstruction
 removal mixture 28, a mixture carrier tubing 22 and a nozzle assembly 30.
 An example of tubing 22 is conventional coiled tubing 24, but the tubing
 22 can take any other suitable form. Further, the tubing 22 is preferably
 controllably movable through the conduit 20 and allows delivery of the
 mixture 28 under pressure to the nozzle assembly 30, which ejects the
 mixture 28 against the obstructions 14.
 The obstruction removal mixture 28 includes particles (not shown) that: (1)
 have a spherical or substantially spherical shape; (2) are constructed at
 least partially of solid material (the term "solid" as used herein and in
 the appended claims means not liquid or gaseous); and (3) are abrasive,
 the term "abrasive" as used herein and in the appended claims meaning
 capable of pulverizing, shattering, fracturing or otherwise loosening
 brittle material. These particles are referred to herein and in the
 appended claims as "spherical solids," "spherical solid particles,"
 "substantially spherically shaped solid abrasive particles" and variations
 thereof Other properties of the spherical solids, such as size, density
 and composition, can be selected and varied as desired so long as the
 mixture can be used in accordance with the present invention. For example,
 spherical solids having densities greater or lesser than the density of
 the fluid or of the obstructive materials may be desirable. Examples of
 types of spherical solids include, but are not limited to, particles
 constructed partially or entirely of glass, ceramic, plastic, metal, epoxy
 or combinations thereof; such as glass beads, hollow glass beads, ceramic
 beads and metal shot. Spherical solids having various sizes, such as, for
 example, beads ranging from about 20 mesh to about 100 mesh, may be
 desirable.
 The mixture 28 also includes fluid. As used herein and in the appended
 claims, the term "fluid" means one or more liquids, one or more gasses,
 foam or a combination thereof. In accordance with the present invention,
 the mixture 28, having fluid and spherical solid abrasive particles, is
 useful in the loosening and removal of obstructions 14 built up on the
 conduit surface 18 or otherwise inside the conduit 20. For example, a
 mixture 28 having a concentration of between about 1/8 and about 3/4 lb of
 spherical glass beads, such as beads sized at between about 20 mesh and
 about 100 mesh, per gallon of fluid supplied through the tubing 22 at a
 flow rate of between about 0.50 bbl/min and about 1.50 bbl/min and ejected
 in accordance with the present invention may be used to effectively remove
 various types of obstructions from conduit 20 at rates of between about 1
 ft/min and about 8 ft/min. It should be understood that the present
 invention is not limited to the above example formulation, and any
 suitable formulation of mixture 28 may be used.
 The mixture 28, having spherical solids as described herein, may, if
 desired, be formulated to allow controlled, or minimal, erosion and damage
 to the conduit surface 18. For instance, the composite type, mass,
 particulate size, angle of impact and concentration of the spherical
 solids can be selected to minimize erosion or damage to the conduit
 surface 18. Certain composite types of spherical solids have a greater
 capability of causing generally more or less erosion or damage to the
 conduit surface 18 under similar operating conditions. Spherical solid
 metal or steel shot or beads, for example, generally causes greater
 erosion to a metallic conduit 20 as compared with glass beads under
 similar operating conditions. Further, the smaller the particulate size of
 the individual spherical solid beads or shot, generally the less the
 erosive effect on the conduit surface 18 under similar operating
 conditions in accordance with the present invention. For example,
 effective removal of obstructions 14 with a mixture 28 containing small
 glass beads, such as beads sized at between about 60 mesh and about 100
 mesh, may cause a desirably smooth finish on the conduit surface 18, while
 a mixture 28 with a similar concentration of larger spherical glass beads,
 such as beads sized at between about 20 mesh and about 40 mesh, may cause
 minor dimpling and may create a rougher finish on the interior surface 18.
 The fluid used in the mixture 28 may be any among a variety of fluids
 having characteristics capable of generally uniformly carrying the
 spherical solids through the tubing 22, such as gas, water, other liquids,
 foam or a combination thereof. Various fluids containing chemicals may be
 included in the mixture 28, such as acids or solvents designed to dissolve
 particular types of obstructions. For example, the mixture 28 may be a
 gelled fluid matrix, such as a mixture of about 11/2 quarts of Xanvis
 L.RTM. per barrel of seawater.
 Now referring to FIGS. 2 and 3, the nozzle assembly 30 is preferably
 disposed on the end 26 of the tubing 24, such as with a crimped, or
 rolled, connector 27. The nozzle assembly 30 includes one or more nozzle
 jets 32 capable of allowing ejection of the mixture 28 at a sufficient
 velocity and angle against obstructive material 14 built-up on the surface
 18 to bombard, pulverize, fracture, erode or otherwise loosen the
 obstructions 14 from the surface 18. Any desirable quantity, size,
 orientation and configuration of nozzle jets 32 capable of removing
 obstructions 14 and suitable for the system 10 may be used.
 In one embodiment, such as shown in FIGS. 5 and 5a, the nozzle jets 32 are
 formed integrally into a nozzle head member 33. In another embodiment,
 such as shown in FIGS. 6-6b, the nozzle jets 32 include fabricated or
 commercially available jet inserts 32a matable with threaded recesses 32b
 in nozzle head 33. The jet inserts 32a may be case hardened and may be
 overlaid with strengthening material, such as tungsten carbide, by methods
 known in the art, to prevent washing out. Should a nozzle jet insert 32a
 wash or fall out of an otherwise functionable nozzle head 33, the nozzle
 head 33 may be reused by replacing the nozzle insert 32a. The nozzle head
 33 may be constructed from various types of suitable materials, such as,
 for example, case-hardened commercial heat-treated steel. Material
 hardness of the nozzle head 33 can be increased with conventional
 strengthening treatments that are or become known in the art.
 Referring to FIGS. 2 and 4, the jets 32 may be arranged in the nozzle
 assembly 30 in any configuration suitable for effective use with the
 present invention. In the preferred embodiments, the assembly 30 includes
 numerous jets 32 capable of ejecting mixture 28 at angles of about 80-100
 degrees, preferably about 90 degrees, relative to obstructions 14.
 Depending on various factors, such as the type and velocity of the
 spherical solid particles in the mixture 28 and the hardness of the
 conduit surface 18, this approximate 90 degree jet orientation is capable
 of providing various benefits. For example, damage to the surface 18 of
 the conduit 20 may be minimized due to the shot-peening effect of certain
 types of spherical solid particles in the mixture 28 as they impact the
 surface 18. As obstructions 14 at a particular location on the metal
 surface 18 are pulverized and removed, certain types of spherical solid
 particles (in the mixture 28), such as, for example, glass spheres,
 produce tiny, shallow craters in the surface 18. Subsequently ejected
 spherical solid particles contacting the same location on the surface 18
 will strike the crater peaks, reducing their height and smoothing the
 surface 18, providing a generally cold worked, uniformly compressed, work
 hardened metal layer. As a result, the thickness 20a of the conduit 20 is
 not significantly diminished. Further, in this example, no significant
 erosion is caused to the surface 18, which, after use of the system 10,
 may be more resistant to surface stress cracking than previously. It
 should be understood that this example of a benefit of the approximate 90
 degree jet orientation is not necessary for practice of the present
 invention, and there are other benefits.
 The distance 36 (FIG. 4) from the orifice 35 of a nozzle jet 32 to adjacent
 obstructions 14 is referred to herein as the "standoff" distance. It is
 generally desirable to have a minimal standoff distance 36 for various
 reasons, such as to enable the spherical solids in the mixture 28 to
 contact obstructions 14 at a maximum velocity and, hence, a maximum
 momentum, and to optimize system energy use. In contrast, a longer
 standoff distance 36 of mixture 28 from jets 32 to obstructions 14 will
 result in decreased velocity and momentum at the obstruction 14 and
 require more input energy for effective cleaning because the mixture 28
 decelerates upon being ejected from the nozzle assembly 30. Further, the
 mixture 28 is slowed by the viscous forces of fluid it must pass through
 in the annulus 19 between the nozzle assembly 30 and the conduit 20. In
 addition, the spherical solids in the mixture 28 are subject to velocity
 loss due to eddy formation once ejected from the nozzle assembly 30.
 Effective standoff distances 36 vary depending on numerous factors, such as
 the composition and velocity of the mixture 28 and the diameter and
 quantity of nozzle jets 32. For example, the delivery of a mixture 28
 carrying spherical solid glass beads sized between about 60 mesh and about
 100 mesh with a density of about 160 lb/ft.sup.3 and having an ejection
 velocity of between about 300 ft/sec to about 700 ft/sec at the orifices
 35 of between five and eight jets 32 of nozzle assembly 30 is capable of
 removing obstructions 14 of barium sulfate scale at a standoff distance 36
 of at least about 0.15 inches. It should be understood that the present
 invention is not limited to the examples and values above (or any of the
 various other examples and values described elsewhere herein), all of
 which are provided for illustrative purposes.
 Still referring to FIGS. 2 and 4, the preferred embodiments of the present
 invention include numerous jets 32 that are side nozzle jets 34 disposed
 in the nozzle assembly 30 at angles of between approximately 80 degrees
 and approximately 100 degrees (preferably about 90 degrees) relative to
 the central axis 31 of the nozzle assembly 30. The side jets 34 are
 preferably capable of ejecting mixture 28 generally at angles of about 90
 degrees relative to obstructions 14a located adjacent to the nozzle
 assembly 30 and jets 34. The standoff distance 36 from the jet orifices 35
 of nozzle jets 34 to the adjacent obstructions 14a may thus be minimized.
 Referring to FIGS. 2, 4, 5 and 5a, additional jets 32, such as jets 37 and
 38, may be included in the nozzle assembly 30 to provide the capability of
 at least partially clearing obstructions 14b built-up on the conduit
 surface 18 forward of the nozzle assembly 30, as well as loose or packed
 obstruction material or debris, such as sand, silt and other detritus,
 (not shown) located in the conduit 20 forward of the nozzle assembly 30.
 These jets 37, 38, when included, may assist in clearing a path forward of
 the nozzle assembly 30 to allow movement of the assembly 30 in the conduit
 20 and positioning of the side jets 34 adjacent to the obstructions 14.
 For example, a center jet 37 disposed in the approximate, or exact, center
 of the front of the nozzle assembly 30 is capable of ejecting mixture 28
 generally at an angle of about 0.degree. relative to the central axis 31
 of the nozzle assembly 30. Mixture 28 ejected from jet 37 (FIG. 4) will
 contact obstructions 14b and other material located forward of the nozzle
 assembly 30. One or more angled jets 38 disposed around the center jet 37
 can be oriented to eject mixture 28 at angles between about 0.degree. and
 about 90.degree., such as about 15.degree., relative to the nozzle central
 axis 31, for impacting obstructions 14b located angularly forward of the
 nozzle assembly 30. Thus, one or more jets 32 may be positioned in
 different locations on the nozzle assembly 30 to form one or more "planes
 of obstruction contact" for removal of obstructions 14 and other debris at
 different locations in the conduit 20. In FIGS. 5, 5a, for example, side
 jets 34 form a first (primary) plane of obstruction contact around the
 circumference of the nozzle head 33, center jet 37 provides a second plane
 of contact, and angled jets 38 create a third simultaneous plane of
 contact.
 Referring to FIG. 3, the outer nozzle diameter D.sub.1 of the nozzle
 assembly 30 is dictated by various factors, such as, but not limited to,
 the inner diameter D.sub.2 of the conduit 20, the thickness of the
 obstructions therein (not shown) and the pumping capability of the system
 pumping equipment. It may also be desirable or effective to use several
 nozzle assemblies 30 successively to clean a particular conduit 20. For
 example, a nozzle assembly 30 having a small outer nozzle diameter
 D.sub.1, such as approximately equal to the outer diameter of the carrier
 tubing 24 (FIG. 3), may be used initially to open a "pilot passage"
 through the obstructions 14 in the conduit 20. Thereafter, one or more
 other nozzle assemblies 30, each having a successively larger outer nozzle
 diameter D.sub.1, may be used for removing the obstructions 14 from
 conduit 20.
 Furthermore, a single nozzle assembly 30 may be configured with nozzle jets
 32 located at different nozzle diameters, such as, for example, in the
 embodiment shown in FIGS. 7 and 8. Nozzle head 33 has steps 33a, 33b and
 33c of corresponding diameters d.sub.1, d.sub.2, and d.sub.3 and which
 carry jets 32a, 32b and 32c, respectively. The nozzle head 33 is shown
 also including angled jets 38. This assembly 30 may be useful to clear a
 pilot hole through the obstructions in the conduit (not shown) and also
 removing successive layers of obstructions (not shown). It should be
 understood, however, that the use of numerous nozzle assemblies 30 or a
 nozzle assembly 30 with jets 32 at different nozzle diameters is not
 necessary for the present invention.
 Referring again to FIGS. 3 and 4, any suitable quantity of jets 32 can be
 used. The desired quantity of jets 32 can be determined based on various
 factors, such as but not limited to, the number of planes of obstruction
 contact on the assembly 30, the outer nozzle diameter D.sub.1, the conduit
 inner diameter D.sub.2, the composition of the mixture 28 and the
 thickness and composition of the obstructions 14. Nozzle assemblies 30
 with large outer nozzle diameters D.sub.1 may require additional jets 32
 to effectively remove obstructions 14 from the entire conduit surface 18.
 For example, a nozzle assembly 30 with an outer diameter D.sub.1 of
 between about 1.00 inches and about 1.25 inches and having five to six
 side jets 34 may be capable of sufficiently cleaning a conduit 20 having
 an inner conduit diameter D.sub.2 of between about 2.5 inches and 2.8
 inches, while a nozzle assembly 30 having an outer diameter D.sub.1 of
 between about 2.0 inches and 2.5 inches and ten side jets 34 may be
 necessary for effectively cleaning a conduit 20 having an inner diameter
 D.sub.2 of between about 3.0 inches and about 3.5 inches. Another factor
 that may be desirable for consideration is that the greater the quantity
 of jets 32 contributing to a particular plane of obstruction contact, such
 as jets 34 of FIG. 3, the smaller the size of the removed particles of
 obstruction. For example, the configuration of nozzle 30 in FIG. 9, having
 four side jets 34 spaced evenly around the circumference of the nozzle
 head 33, will create larger sized removed particles of obstruction than
 the configuration of FIG. 10 having ten side jets 34 (for the same
 composition mixture 28 and type of obstruction 14).
 The size and quantity of jets 32 in the nozzle assembly 30 may be selected
 to provide a particular ejection, or contact, velocity or velocity range
 of the mixture 28 at a given supply flow rate into the nozzle assembly 30.
 The velocity (V) of the mixture 28 at each jet orifice 35 equals the total
 flow rate (Q.sub.t) of the mixture 28 through the jets 32 divided by the
 combined cross-sectional areas (A.sub.t) of all jet orifices 35 (V=Q.sub.t
 /A.sub.t). Generally, the greater the quantity of jets 32 ejecting the
 mixture 28, the lower the ejection, or contact, velocity at the same
 supply flow rate into the carrier tubing 22. For example, a flow rate of
 about 0.75 bbl/min. of mixture 28 through a nozzle assembly 30 with seven
 jets 32 each having a diameter of about 0.063 inches may be capable of
 achieving ejection velocities of between about 500 ft/sec.
 Now referring to FIGS. 4 and 11, the nozzle assembly 30 may be equipped
 with a gauge ring, or mandrel, 42 preferably located on the nozzle
 assembly 30 between the jets 32 and the carrier tubing 22. The gauge ring
 42 may have any construction and configuration suitable for use with the
 present invention. Preferably, the gauge ring 42 includes at least one
 wide portion 44 that extends radially from the nozzle assembly 30 and one
 or more external fluid passageways 43 (FIG. 7). The "external" fluid
 passageways 43 are external to the nozzle assembly 30, allowing the flow
 of fluid along the outside of the nozzle assembly 30. The gauge ring 42
 preferably has capabilities which include one or more of the following:
 generally guiding the carrier tubing 22 and nozzle assembly 30 through the
 conduit 20; centering the nozzle assembly 30 within the conduit 20;
 providing outer mandrel bearing surfaces 44a (FIG. 7) for bearing forces
 placed on the nozzle assembly 30 from contact with the conduit surface 18
 (FIG. 2); detecting the presence and location of obstructions on the
 conduit surface 18 (FIG. 2); and allowing a fluid return flow path through
 the annulus 19 (FIG. 2) to the surface (not shown) for the ejected mixture
 28 and removed obstructions.
 The nozzle assembly 20 may be configured with two mandrels (not shown) or a
 mandrel 42 having numerous sets of wide portions 44, such as shown, for
 example, in FIGS. 7 and FIGS. 8, 8a and 8b. In the illustrated embodiment,
 a first set 46 of wide portions 44 is shown offset, such as by 45 degrees,
 relative to a second set 47 of wide portions 44. A space 48 is formed
 between the sets 46, 47 of wide portions 44. The gauge ring 42 is
 "fluted", the flutes 45 forming the fluid passageways 43. Adjacent flutes
 45 of the same set of wide portions 46 or 47 are shown spaced apart 90
 degrees from one another relative to the nozzle assembly central axis 31.
 This type of configuration is capable of providing 360 degrees of combined
 outer mandrel bearing surface 44a around the nozzle assembly 30, while
 allowing a "return flow path" through fluid passageways 43 and space 48.
 The gauge ring 42 may be equipped with a fishing neck 50 capable of being
 connected with or gripped, such as at recess, or groove, 52 (FIGS. 7 and
 8), by a conventional fishing tool (not shown) for recovery of the nozzle
 assembly 30 should the assembly 30 disconnect from the carrier tubing 22
 in the conduit 20.
 A filter 56, such as shown in FIGS. 2 and 3, may be included in the system
 10 for various purposes, such as to regulate the size of the spherical
 solids in the mixture 28 being ejected from the nozzle assembly 30 and to
 prevent plugging of the jets 32. Any suitable filter 56 capable of use
 with the present invention may be used. In the embodiments of FIGS. 2 and
 3, the filter 56 is disposed within the carrier tubing 22 and nozzle
 assembly 30. The illustrated filter 56 includes a perforated mesh 58
 having a plurality of flow holes 59 of predetermined sizes, or diameters.
 To prevent plugging of the nozzle jets 32, the diameter of the flow holes
 59 must be equal to or smaller than the diameter of the nozzle jets 32.
 The mixture 28 flows into the filter 56 from the tubing 22, such that
 spherical solids and any other solid materials in the mixture 28 or tubing
 22 that are larger than the flow holes 59 will enter neither the filter 56
 nor the nozzle assembly 30. Thus, undesirably large spherical solids or
 other material will remain in the tubing 22 outside of the filter 56,
 assisting in preventing both the filter 38 and nozzle assembly 30 from
 becoming clogged thereby. The inclusion of a filter 56, however, is not
 essential for the present invention.
 In another aspect of the invention, a mixture delivery system 60 will now
 be described. Referring to the exemplary embodiment of FIG. 1, the
 delivery system 60 includes a mixing tank 16 for mixing spherical solids
 and fluid, such as a conventionally available tank. In some instances, an
 in-line mixer (not shown) such as, for example, KENICS Static Mixer Model
 1.75-KMA-2, may be used for mixing spherical solids and fluid, although
 not necessary for the present invention. The system 60 also includes a
 pump package 61, such as, for example, the Gardner-Denver Model PAH fluid
 pump, and a tubing insertion mechanism 63 capable of moving the tubing 22
 into, within and from the conduit 20, such as, for example, a conventional
 truck-mounted coiled tubing control unit 64, which is shown including a
 power pack 65, tubing injector 66, hydraulically actuated coiled tubing
 reel 67 and control console 68. It should be understood that the present
 invention is not limited to these specific types of tank 16, pump package
 61 and tubing insertion mechanism 63.
 Referring now to FIGS. 1 and 2, a method for delivering mixture 28 with the
 mixture delivery system 60 to the conduit cleaning system 10 will now be
 described. The spherical solids are mixed and entrained in the desired
 fluid medium by any suitable technique. Some examples of suitable
 techniques include bulk mixing on-the-fly, metering, and batch mixing.
 Mixing on-the-fly may include dumping a metered volume of spherical solids
 into a fluid stream via an in-line mixer (not shown) as described above, a
 jet mixer (not shown), or other conventional device, prior to pumping the
 mixture 28 into the tubing 22 for obstruction removal. Metering involves
 mixing measured amounts of spherical solids into a flow stream of desired
 fluid and recirculating the mixture 28 into tank 16 to measure the exact
 composition of the mixture 28 prior to pumping. In batch mixing, a
 measured volume of fluid is mixed with a measured volume of spherical
 solids in tank 16. The mixture 28 is agitated thoroughly prior to
 commencing pumping and is further agitated during obstruction removal.
 Additional batches of the mixture 28 can be prepared while one batch is
 being pumped.
 A suitable pump package 61, such as fluid pump 62, is used to pump the
 mixture 28 through the tubing 22 at a sufficient flow rate for effective
 obstruction removal. Generally, if the flow rate of the mixture 28 through
 the tubing 22 is within a range that does not exceed the pressure rating
 of the tubing 22, the flow of spherical solids through the tubing will not
 significantly erode or damage the tubing 22, such as commercially
 available coiled tubing 24.
 A method for loosening and removing obstructions from inside a conduit 20
 with the use of the conduit cleaning system 10 will now be described. The
 tubing 22 is inserted into the conduit 20 to position the nozzle assembly
 30 at a desired location in the conduit 20 for obstruction removal.
 Preferably, the tubing 22 is controllably movable within the conduit 20 or
 within a desired portion or portions of the conduit 20 to allow the
 controlled removal of obstructions 14 therefrom. Any suitable conventional
 mechanism or technique may be used for moving the tubing 22 into, within
 and from the conduit 20. In the embodiment shown in FIG. 1, for example,
 an operator (not shown) controls the rate of injection and movement of the
 tubing 22 in the conduit 20 with the conventional truck-mounted coiled
 tubing control unit 64.
 S The mixture 28 pumped into the tubing 22 is ejected from the nozzle
 assembly 30 through the jets 32 at a velocity such that the force of the
 mixture upon the obstructions 14 will pulverize, fracture, erode or
 otherwise loosen the obstructions 14 from the conduit 20 preferably with
 minimal erosion or damage to the conduit surface 18. A gauge ring, or
 mandrel, 42, when included on the nozzle assembly 30, such as shown in
 FIG. 2, may be used to assist in locating obstructions 14, positioning the
 nozzle assembly 30 for obstruction removal, guiding the nozzle assembly 30
 through the conduit 20, determining when obstructions 14 have been
 removed, and other possible functions as described above. Further, wide
 portions 44 of the mandrel 42 may be positioned on the nozzle assembly 30
 substantially adjacent to certain jets 32, such as side jets 34, allowing
 timely positioning of such jets 32 adjacent to obstructions 14 encountered
 by the wide portions 44 for obstruction removal.
 The obstruction removal rate may be affected by a multitude of factors,
 including, but not limited to, the composite type, mass, size and
 concentration of the spherical solids in the mixture 28, the nozzle jet 32
 configuration, and the frequency and intensity of impact by the spherical
 solids in the mixture 28 upon the obstructions 14. It should be
 understood, however, that the present invention is not limited to any
 particular combination, or combinations, of any such variables, but
 encompasses all combinations suitable for use with the present invention.
 For example, the obstruction removal rate generally increases as the mass
 of the spherical solids in the mixture 28 increases, under otherwise
 constant conditions. The mass of the spherical solids in the mixture 28
 may be selectively increased, such as by increasing the concentration of
 the spherical solids in the mixture 28, or by increasing the particle size
 of the spherical solids, or a combination of both. Removed obstruction
 particle size may be important for various reasons, such as when targeting
 particular types of obstructions 14 for chemical reactivity where it may
 be desirable to have small sized removed particles, or to improve
 transport capabilities of removed obstruction particles.
 Still referring to FIGS. 1 and 2, as the obstructions 14 are removed from
 the conduit surface 18, the ejected mixture 28 and removed obstruction
 particles, referred to collectively herein as the "composite effluent 100"
 are preferably circulated, as shown with flow arrows 70 in FIG. 2, out of
 the conduit 20 through the annulus 19 formed between the tubing 22 and the
 conduit surface 18. The ejected mixture 28 alone, or with a suitable
 additional fluid, may serve as the return fluid for carrying, or forcing,
 the removed obstruction particles up the conduit 20 to the surface 12. It
 should be noted that the size of removed obstruction particles may affect
 their rate of evacuation. For example, large removed particles generally
 require a greater velocity and/or viscosity of the return fluid in the
 annulus 19 for moving the removed obstruction particles to the surface 12.
 The composite effluent 100 may be collected and disposed of in any suitable
 manner. In the embodiment of FIG. 1, for example, the composite effluent
 100 exits the conduit 20 through an outlet 72. A stripper assembly 76
 seals around the tubing 22 and directs the composite effluent 100 to a
 collection tank 78 via line 80, which is connected to the outlet 72.
 The spherical solids and fluid in the composite effluent 100 may be
 separated and reused in the obstruction removal process with the use of
 any suitable separation/return system 74. An example of a
 separation/return system 74 is illustrated in FIG. 12. This system 74
 includes a size-differentiating particle separator 104 being capable of
 separating out large obstruction particles from the composite effluent
 100, such as, for example, a conventional shale shaker 104a having a
 screen, or mesh. The system 74 also includes a small particle separator
 106 capable of separating out either small obstruction particles or
 spherical solids from the composite effluent 100. Examples of separators
 106 include, but are not limited to, a set of conventional hydrocyclones
 106a, or a conventional centrifuge (not shown), or a conventional magnetic
 separator (not shown). To separate out the fluid from the effluent 100 for
 reuse, the system also includes a fluid/particle separator 108 capable of
 separating out small sized particles from fluid of the composite effluent
 100, such as, but not limited to, a set of conventional hydrocyclones 108a
 or a conventional centrifuge (not shown). The system also includes
 composite effluent pumps 110, 112 capable of pumping the composite
 effluent 100 within the system 74, such as, but not limited to,
 conventional centrifugal pumps.
 Also included in the system 74 may be a gas separator 102 capable of
 separating out and venting gas from the composite effluent 100, such as a
 mud-gas separator or "poorboy" degasser of conventional oil field design;
 a conventional in-line mixer 114 capable of mixing spherical solid
 particles with fluid to form mixture 28, such as Kenics Static Mixer Model
 1.75-KMA-2; a fluid pump 116 capable of pumping fluid to the mixer 114,
 such as a triplex well servicing pump; and a slurry pump 118 capable of
 pumping spherical solid particles into a fluid stream, such as an SQ
 Special unit having a Binks 41-14900 hydraulic motor and Graco King.RTM.
 56:1 fluid section.
 An exemplary method of separating used spherical solid particles from a
 composite effluent 100 in accordance with the present invention will now
 be described. Referring to FIG. 1, the composite effluent 100 may be
 passed through a choke manifold (not shown) for one or more purposes, such
 as, for example, to reduce pressure on the composite effluent stream
 directed into the separation/return system 74. Another purpose may be to
 maintain "backpressure" on the well during use of the present invention to
 prevent excessive gas or oil influx into the well casing 21 from the
 formation 101. The backpressure can be adjusted by opening or closing the
 choke manifold (not shown) to ensure that the conduit cleaning system 10
 and the separation/return system 74 are maintained in a steady-state
 condition, neither gaining fluids from nor losing them to the formation
 101. It should be understood that passing the composite effluent 100
 through a choke manifold is not necessary for practice of the present
 invention.
 Now referring to FIG. 12, the composite effluent 100 may be passed, such as
 through hard piping (not shown), to a gas separator 102 where any gas in
 the composite effluent 100 is removed from the effluent 100. The gas may
 be vented to the atmosphere, flared or recovered for compression and sale
 or otherwise collected for disposal. Hazardous quantities of any toxic gas
 constituents, such as hydrogen sulfide and carbon dioxide, may be removed
 from the normal breathing zone for workers. Installation of a mist
 extractor (not shown) in this gas separator 102, though not necessary for
 the present invention, can be included to prevent harmful mists and
 aerosols from entering the atmosphere.
 The composite effluent 100 is passed through a size-differentiating
 particle separator 104 that separates large particles of obstruction 14
 and any other large debris in the composite effluent 100 that are larger
 than the particulate size of the spherical solids in the effluent 100.
 Particles separated by separator 104 may include large particles of
 removed obstruction 14, rust from the conduit 20 or from various
 equipment, formation particles and agglomerations of smaller particles. In
 the preferred embodiment, the effluent is piped to a shale shaker 104a
 having a screen, or mesh, (not shown) with passage holes sized to allow
 the passage therethrough of fluid, the spherical solids and other
 particles equal in size or smaller than the spherical solids. The fluid,
 spherical solids and other such small particles pass through the separator
 104 and are collected, such as in a holding tank (not shown). The holding
 tank, if used, can be equipped with an agitator (not shown) to keep
 particles in suspension pending their subsequent removal from the fluid.
 Particles having a particulate size greater than the screen or mesh holes
 are collected, such as in a particle, or cuttings, bin 126 for subsequent
 disposal.
 The spherical solids are thereafter separated from the remaining particles
 of removed obstruction 14 and any other debris in the effluent 100 with
 the use of a small particle separator 106. This can be achieved in various
 ways. For example, a centrifuge (not shown) or set of hydrocyclones 106a
 could be used to separate the particles based on particle density. The
 configuration of FIG. 12 having hydrocyclones 106a is useful when the
 spherical solids possess a density that is generally smaller than the
 density of the particles of obstruction 14 and fluid in the effluent 100,
 such as, for example effluent 100 having glass bead spherical solids and
 obstruction particles of common barium sulfate. In the embodiment of FIG.
 12, the effluent 100 is passed through a set of hydrocyclones 106a
 designed to provide density separation. The heavier (more dense)
 obstruction, or waste, particles are removed from the lighter spherical
 solids/fluid mixture. These obstruction particles may be collected in a
 particle bin 126, passed through a fluid/particle separator (not shown),
 such as a shale shaker similar to shale shaker 104a for remaining fluid
 removal, or otherwise disposed of. The remaining effluent 100 (primarily
 or exclusively fluid and spherical solids) is piped to a fluid/particle
 separator 108 capable of separating the spherical solids from the fluid.
 In the example of FIG. 12, a set of small diameter, high efficiency
 hydrocyclones 108a is used to separate all remaining particles from the
 fluid.
 If, however, the spherical solids are more dense than the removed particles
 of obstruction 14, the small particle separator 106 can also be a
 density-differentiating particle separator, such as hydrocyclones 106a
 described above. In this instance, the more dense spherical solids are
 separated from the lighter obstruction particles/fluid mixture and may be
 collected for reuse, such as in a slurry tank similar to tank 128 shown in
 FIG. 12. The remaining effluent 100, including fluid and obstruction, or
 waste, particles, can be collected and disposed of, or piped to a
 fluid/particle separator 108, or hydrocyclones 108a, for separating all
 remaining particles from the fluid.
 Operating conditions can be adjusted to optimize small solids separation
 with the use of hydrocyclones 106a, a centrifuge (not shown) or a similar
 small particle separator 106. Numerous variables, such as hydrocyclone
 106a diameter, the number of hydrocyclones 106a, pump rate and pressure
 into the hydrocyclone(s) 106a, or centrifuge speed, can be adjusted to
 achieve the desired separation. For example, energy to operate
 hydrocyclones 106a can be provided with a conventional pump (not shown).
 Pump pressure can be adjusted with the use of a valve (not shown) at the
 inlet of the separator 106a. Variable speed motors can be used to change
 hydrocyclone pump rate or centrifuge speed.
 The spherical solids may instead be separated from the small removed
 obstruction particles and other debris in the composite effluent 100 based
 on other particle properties, such as ferromagnetic attraction,
 electrostatic activity or particle chemistry. For example, spherical
 solids constructed at least partially of ferromagnetic metal, such as
 steel shot, can be separated using a small particle separator 106 that is
 a conventional rotating magnetic separator (not shown). Similarly as the
 method described above, the more dense spherical solids are separated from
 the lighter obstruction particles/fluid mixture and may be collected for
 reuse, such as in a slurry tank similar to tank 128 shown in FIG. 12. The
 remaining effluent 100, including fluid and obstruction, or waste,
 particles, can be collected and disposed of, or piped to a fluid/particle
 separator 108, or hydrocyclones 108a, for separating all remaining
 particles from the fluid.
 In all cases, the separated spherical solid particles may be collected in a
 slurry tank 128 for reconditioning, reuse or disposal. Additional
 spherical solids can be added to the slurry tank 128. If the fluid is also
 separated from the composite effluent 100 as described above (the fluid
 may include chemicals that are more expensive than the spherical solids),
 the fluid may be collected in a fluid tank 130 for reconditioning, reuse
 or disposal. The tank 130 may be an agitated tank where rheology can be
 adjusted to ensure optimum properties.
 Still referring to FIG. 12, an exemplary method for reuse of used,
 recovered spherical solids in accordance with the present invention will
 now be described. Fluid for forming mixture 28 is pumped from the fluid
 tank 130 or another fluid source (not shown) to in-line mixer 114 through
 the fluid pump 116. The recovered spherical solids are pumped from slurry
 tank 128 through the slurry pump 118 into the fluid stream entering the
 mixer 114. The fluids and spherical solids are mixed in the in-line mixer
 114 to form the mixture 28. The mixture 28 is then pumped into the carrier
 tubing 22. Additional spherical solids may be added to the mixture 28,
 such as when the recovered spherical solids are worn or when a greater
 concentration of spherical solids is desired in the mixture 28. For
 example, prior to pumping the recovered spherical solids in the fluid
 stream entering the mixer 114, the spherical solid slurry may be pumped,
 such as with the use of a pump 134 similar to the composite effluent pumps
 110, 112 described above, from the slurry tank 128 through a conventional
 hopper/jet mixer 136, where additional spherical solids may be added to
 the spherical solid slurry.
 While preferred embodiments of this invention have been shown and
 described, modifications thereof can be made by one of ordinary skill in
 the art without departing from the spirit or teachings of this invention.
 The embodiments described and illustrated herein are exemplary only and
 are not limiting. Many variations and modifications of the systems and
 methods of the present invention are possible and are within the scope of
 the invention. Further, the systems and methods of the present invention
 offer advantages over the prior art that have not been addressed herein
 but are, or will become, apparent from the description herein, such as,
 but not limited to: the present invention is easy to manufacture and
 operate and does not have complex component parts; the conduit cleaning
 system 10 is not affected by high temperature and has no requirement for
 rotating components; and the result of the system 10 causing little or no
 damage to the conduit 20 from the mixture 28 impacting the conduit 20,
 from reactive torque or from contact between the system 10 and the
 conduit. Accordingly, the scope of the invention is not limited to the
 embodiments described herein.