Apparatus and method for filtering a fluid

Apparatus and method for filtering contaminated fluids at various locations using at least a first and second filter unit mounted on a mobile base. Each filter unit has a plurality of filter vessels with each of the filter vessels having a plurality of filter elements and dual plate mounting. In each filter unit, the contaminated fluid is first coarse filtered and then fine filtered. Means are provided to by-pass either the first or second filter unit so that the filter elements can be changed or for by-passing both the first and second unit when desired.

BACKGROUND OF THE INVENTION 
This invention relates to the filtering of contaminated fluids so as to 
remove the contaminants therefrom and more particularly in relationship to 
dual filtering units wherein one filtering unit may be by-passed for 
cleaning of the other filtering unit or both of the filtering unit may be 
by-passed when the contamination level of the fluid is below that which 
requires filtering and in particular to the on-site use of such filtering 
units in the drilling, operating or closing of a well hole. 
BACKGROUND OF THE INVENTION 
During many operations of the drilling, operating or closing of a well 
hole, it is necessary to use completion fluids. Such well activities 
include pay zone drilling and/or underreaming, perforating, gravel 
packing, chemical treatments, hydraulic fracturing, cleanout, well 
killing, zone selective operations, and tubing and hardware replacement. 
The different kinds of operations require different kinds of completion 
fluids to be used but in all instances it is necessary that the completion 
fluids must be solids free, i.e., the completion fluids should contain 
less than 2 parts per million of solids, all smaller than two microns 
nominal size. To obtain this degree of cleanness, an on-site solids 
removal system, such as that illustrated in the article, "Completion 
Fluids for Maximizing Productivity--State of the Art" published in the 
Journal of Petroleum Technology, January 1983 pages 47-55, is used. In 
this type of installation, it is necessary to install the solids removal 
system and leave it in place during all the operating time of the well 
hole even though it is not necessary to use completion fluids during all 
the time that the well hole is in operation. 
Dual filtering units wherein one filtering unit may be by-passed for 
cleaning or replacing the filtering elements therein are disclosed in Carr 
(U.S. Pat. No. 3,397,784); Brown (U.S. Pat. No. 3,618,781); Bradel et al. 
(U.S. Pat. No. 3,757,956); and Parquet et al. (U.S. Pat. No. 4,033,870). 
Dickerson (U.S. Pat. No. 4,049,548) discloses a mobile unit for 
demineralizing water to satisfy nuclear grade requirements comprising 
banks of cylinders wherein each cylinder may be separated from the system 
for replacement. The foregoing patents do not disclose a mobile filtering 
system for on-site use in a well hole operation comprising dual filter 
units each having a plurality of filter vessels having filter elements of 
different pore sizes. In all of the foregoing patents, it is necessary 
that the fluid be sent through at least part of the filtering units at all 
times during the operation thereof. 
BRIEF SUMMARY OF THE INVENTION 
This invention provides a dual system of filtering units wherein the 
contaminated fluid may be passed through a first and second filter unit at 
the same time or wherein one of the filter units may be by-passed so that 
the filter elements therein may be removed and replaced with new filter 
elements. The filtering system is also provided with means so that both 
the first and second filter units may be by-passed when the fluid involved 
has a contamination level that does not require the removal of solids 
therefrom. 
In the preferred embodiment of the invention, the filtering system 
comprises a first and a second filter unit. Each filter unit comprises a 
first and a second filter vessel, each vessel having a plurality of filter 
elements therein. The filter elements in the first filter vessel are a 
relatively coarse micron filter element and the filter elements in the 
second filter vessel are a relatively fine micron filter element. Means 
are provided for connecting the inlet side of each filter unit to a supply 
of the fluid to be treated and means are provided to connect the outlet 
side of each filter unit to a discharge conduit which conduit is 
preferably connected to the suction side of a rig pump. Means are also 
provided to connect the discharge conduit directly to the supply of fluid. 
Valve means are provided to open and close all of the connecting means so 
that both filter units may operate at the same time; one of the filter 
units may be by-passed for the replacement of filter elements therein; or 
both of the filter elements may be by-passed. 
In the preferred embodiment of the invention, the filter vessels are 
designed so that they may be mounted on a mobile base, such as a trailer, 
and moved to an on-site location and after being connected to the source 
of fluid and the suction side of the drill rig be ready for operation. 
Therefore, the filtering system may be readily moved from one well site to 
another well site for use when needed. 
It is an object of this invention to provide a dual filter system with 
means for by-passing the filtering system. 
It is another object of this invention to provide a dual filter system with 
means for by-passing the filtering system for use with completion fluids 
at well hole operations which can be readily transported from one well 
hole to another well hole. 
It is another object of this invention to provide a dual filtering system 
having a first and second filter unit, each having filter elements of 
different pore sizes. 
Other features and advantages of the invention will be apparent from the 
following more particular description of preferred embodiments as 
illustrated in the accompanying drawing in which like reference characters 
refer to the same parts throughout the various views. The drawing is not 
necessarily to scale, emphasis instead being placed upon illustrating the 
principles of the invention.

DETAILED DESCRIPTION OF THE INVENTION 
In the preferred embodiment of the invention, as illustrated in FIGS. 1 and 
2, there is provided a filtering system 2 which is mounted on the bed 4 of 
a trailer which is provided with wheels 6 so that it may be readily 
transported to a desired location. The filtering system 2 is primarily for 
use with completion fluids used in well hole operations so that it must be 
able to be moved over rough terrain. In some instances, it may be 
desirable to replace the wheels 6 with skids (not shown). 
The filtering system 2 comprises a first filter unit 8 comprising a first 
filter vessel 10 and a second filter vessel 12 and a second filter unit 14 
comprising a first filter vessel 16 and a second filter vessel 18. Piping 
means 20, including an on-off valve 22, extend from the inlet 24 of the 
first vessel 10 to piping means 26 terminating at an end 28 which is 
connected to a supply of fluid by conventional pipe joint means (not 
shown). An on-off valve 29 is located between the piping means 26 and the 
end 28. Piping means 30, including an on-off valve 32, extend from the 
inlet 34 of the first vessel 16 to the piping means 26. An on-off valve 33 
cooperates with the on-off valves 29, 22 and 32 to control the flow of the 
supply fluid through filter vessels 10 and 12 or 16 and 18 or to by-pass 
the filter vessels 10, 12, 16 and 18 completely. The first vessels 10 and 
16 are provided with removable lids 36 and 38 which are held in position 
thereon by means 40 and 42. Drain means 44 and 46 are provided for the 
first vessels 10 and 16. 
The filtered fluid exits from adjacent the bottom of the first vessels 10 
and 16 through piping means 48 and 50 and enters into second vessels 12 
and 18 through inlets 52 and 54 adjacent to the tops thereof. Piping means 
56 and 58, including on-off valves 60 and 62, extend from the outlets 64 
and 66 of the second vessels 12 and 18 to a discharge conduit 68 which 
discharge conduit 68 is connected by conventional means (not shown) to the 
suction side of a rig pump (not shown). The second vessels 12 and 18 are 
provided with removable lids 70 and 72 which are held in position thereon 
by means 74 and 76. Drain means 78 are provided for the second vessel 18. 
Similar drain means (not shown) are provided for the second vessel 12. A 
boom 80 with crank means 82 is provided for cooperation with the handles 
84 on the removable lids 36, 38, 70 and 72 for a purpose described below. 
In each of the filter vessels 10, 12, 16 and 18, there is mounted a plate 
86 which is secured to the inner surface 88 of each vessel by suitable 
means, such as a continuous weld 90, so as to form a continuous seal 
between the inner surface 88 and the plate 86 and also to hold the plate 
86 in the desired location. The plate 86 is provided with a plurality of 
openings 92, which in the preferred embodiment are circular but can be of 
any desired geometrical configuration. A plurality of bolts 94 having 
external threads are permanently secured to the plate 86 by suitable 
means, such as by welding. In the preferred embodiment illustrated in FIG. 
3, there are five openings 92 and five bolts 94, spaced equidistantly 
apart and one central opening 92. 
A filter basket 96 is illustrated in FIG. 4 and comprises an annular ring 
98 having a recessed portion 100 opening inwardly so as to form a 
supporting surface 102. A generally cylindrical band 104 is secured to the 
bottom surface 106 of the annular ring 98 by suitable means, such as by 
welding. A generally cylindrical member 108 formed from flattened expanded 
metal is secured to the inner surface of the band 104 by suitable means, 
such as by welding. A bottom 110, also formed from flattened expanded 
metal, is provided with an upstanding side wall 112 which side wall 112 is 
secured to the outer surface of the cylindrical member 108 by suitable 
means, such as by welding. 
In FIG. 5, there is illustrated a filter bag 114 adapted to be used in the 
filter basket 96. The filter bag 114 may be formed from any appropriate 
material such as rayon, nylon, polyester, polypropylene or other similar 
materials and can be supplied in 100, 50, 25, 10, 5 and 1 micron sizes. 
The open end of the filter bag 114 is secured to a ring 116 formed from 
steel or other suitable material and having a diameter slightly greater 
than the depth in an axial direction of the recess 100 in the annular ring 
98 for a purpose described below. The filter bag 114 is secured to the 
ring 116 by wrapping a portion of the filter bag around the ring 116 and 
sewing it in place. 
An assembled filter element 118 is illustrated in FIG. 6. In making the 
assembly illustrated in FIG. 6, the plate 86 has been welded to the inner 
surface 88 of the vessel. A sealing gasket 120 having a plurality of 
openings 122 corresponding in number to the number of openings 92 is 
placed over the upper surface 124 of the plate 86 so that the openings 122 
are aligned over the openings 92. The sealing gasket 120 has an outer 
diameter slightly less than the inner diameter of the vessel 10, 12, 16 or 
18. A filter basket 96 is then inserted through each opening 92 until the 
bottom surface 106 is in contact with the portion of the sealing gasket 
120 surrounding each opening 92. A filter bag 114 is then inserted into 
the filter basket 96 until the ring 116 is in contact with and supported 
by the surface 102 of the annular ring 98. If desired, the filter bag 114 
may be positioned in the filter basket 96 before the filter basket 96 is 
assembled. A sealing gasket 126 having a plurality of openings 128 
corresponding in number to the number of openings 92 is positioned within 
the vessel so that a portion of the sealing gasket 126 surrounds each of 
the openings 128 and is in contact with the upper surface 130 of each 
annular ring 98. The sealing gasket 126 has an outer diameter slightly 
less than the inner diameter of the vessel 10, 12, 16 or 18. The diameter 
of the openings 128 is substantially smaller than the diameter of the 
openings 92 to ensure the contact between the portions of the gasket 126 
and the upper surface 130 of each annular ring 98. The sealing gasket 126 
has a plurality of openings 132 corresponding in number and location to 
the bolts 94 so that when the sealing gasket 126 is positioned in each 
vessel 10, 12, 16 or 18 the threaded portion of the bolts 94 extend 
through the openings 132. A plate 134 having a plurality of openings 136 
spaced equidistantly apart and corresponding in number to the number of 
bolts 94 and of a size to allow passage of the bolts 94 therethrough is 
positioned in each vessel 10, 12, 16 or 18 so that the bolts 94 extend 
through the openings 136. The plate 134 is also provided with a plurality 
of openings 138 corresponding in number to the number of openings 128 and 
when in assembled relationship, the openings 138 are aligned with the 
openings 128. The outer diameter of the plate 134 is slightly less than 
the inner diameter of each vessel 10, 12, 16 or 18 to allow for relative 
movement in a longitudinal direction between each plate 134 and each 
vessel 10, 12, 16 or 18. A nut 140 is threaded onto each bolt 94 and 
tightened so as to move plate 134 toward plate 86. The nuts 140 are 
tightened in an amount sufficient to move plate 134 toward plate 86 so 
that the gasket 126 forms an effective seal between the plate 134 and each 
upper surface 130 of each annular ring 98 and the gasket 124 forms an 
effective seal between the plate 86 and the bottom surface 106 of each 
annular ring 98. Also, the sealing gasket 126 acts on the ring 116 so that 
the ring 116 is firmly seated on the surface 102. 
In one embodiment of the invention, each vessel 10, 12, 16 and 18 has a 
diameter of about 30 inches, a height of about 38 inches and a wall 
thickness of about 3/8 inch and a bottom thickness of about 1/2 inch. The 
plate 86 is 3/8 inch in thickness, has a diameter of about 29 1/4 inches 
and is welded by a continuous weld to the inner surface 88 of each vessel. 
The diameter of each opening 92 is about 7 1/2 inches. The annular ring 98 
has an outer diameter of about 85/8 inches., an inner diameter of about 6 
13/16 inches, the diameter of the recess 100 is about 7 1/4 inches and the 
axial depth of the recess 100 is about 3/16 inch. The band 104 is formed 
from 10 gauge steel having a width of about 1/2 inch and formed into a 
band having an outer diameter of about 7 1/8 inches. The generally 
cylindrical member 108 is formed from 1/2-13 flattened expanded metal, 
such as carbon steel, and has an inner diameter of about 6 13/16 inches. 
The bottom 110 is formed from a similar material and the outside diameter 
of the wall 112 is about 7 inches. Each gasket is formed from nitrile or 
other similar material generally used in forming gaskets. The plate 134 
has a thickness of about 1/4 inch and a diameter of about 29 1/8 inches. 
The bolts 94 are 1.times.2 1/2 inch bolts with mating nuts 140. The 
vessels 10, 12, 16 and 18 are mounted on the bed 4 by any conventional 
means and the various conduits and valves are joined together in a 
conventional manner. 
In operation, the trailer with all of the various components mounted 
thereon is pulled to an on-site location. The end 28 is connected to a 
supply of fluid and the discharge conduit is connected to the suction side 
of a rig pump. If the fluid does not have to be filtered, the valves 29, 
22, 32, 60 and 62 are in a closed position and the valve 33 is in an open 
position. If the supply fluid is to be filtered, the valve 33 is moved to 
a closed position and the valves 29, 22 and 60 are moved to an open 
position so that the supply fluid moves through filter vessels 10 and 12 
and the filtered fluid exits through discharge conduit 68. Suitable gauges 
142 are provided to indicate when the filter bags 114 in the baskets 96 of 
the filter vessels 10 and 12 have to be changed. When this is necessary, 
the valves 22 and 60 are moved to a closed position and the valves 32 and 
62 are moved to an open position so that the supply fluid moves through 
filter vessels 16 and 18 and the filtered fluid exits through discharge 
conduit 68. The lid 40 is loosened and lifted and moved by the boom 80 and 
crank 82 to an out of the way location and the filter bags 114 in the 
filter vessel 10 are removed and new filter bags are installed. The cover 
40 is then repositioned and secured. The operation is then repeated on the 
filter vessel 12. In most operations, the filter bags 114 will be in the 
sizes described above with the filter bags 114 in the filter vessels 10 
and 16 being of a relatively coarse micron cut and the filter bags 114 in 
the vessels 12 and 18 being of a relatively fine micron cut. 
While the preferred embodiments of the invention have been illustrated and 
described herein, it may be otherwise embodied and practiced within the 
scope of the following claims.