U.S. patent application number 09/052876 was filed with the patent office on 2001-06-14 for integral well filter and screen and method for making and using same.
Invention is credited to DOESBURG, JAMES M.., LUBRECHT, MICHAEL D..
Application Number | 20010003313 09/052876 |
Document ID | / |
Family ID | 21980486 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003313 |
Kind Code |
A1 |
DOESBURG, JAMES M.. ; et
al. |
June 14, 2001 |
INTEGRAL WELL FILTER AND SCREEN AND METHOD FOR MAKING AND USING
SAME
Abstract
An integral well filter and screen and a method for making and
using it are described. A first embodiment includes a perforated
cylindrical well screen with a filter assembly in its interior. The
filter assembly includes a pliable filter material bonded to a
filter support. The filter support is a plastic lattice rigid
enough to hold the shape of the filter assembly and keep the filter
material in contact with the inner surface of the well screen, yet
deformable enough that the filter assembly can be formed into a
shape consistent with the interior of the well screen. A second
embodiment includes a well screen with a filter made of a rigid,
porous material placed inside the well screen. Because the filter
is rigid, it needs no filter support. Methods of manufacturing each
of the embodiments are presented. For the first embodiment, the
method includes bonding the filter support to the filter material;
forming the filter assembly into a cylindrical shape complementary
to the inner surface of the well screen; securing abutting edges of
the filter assembly to maintain its shape and rigidity, and ensure
complete filtration, and inserting the filter assembly into the
well screen. The manufacture of the filter in the second embodiment
is similar, but does not include the bonding of a filter support to
the rigid, porous material. Finally, a method of installing the
filter and screen in a horizontal well is presented.
Inventors: |
DOESBURG, JAMES M..; (DES
MOINES, WA) ; LUBRECHT, MICHAEL D.; (CARNATION,
WA) |
Correspondence
Address: |
PERKINS COIE LLP
1201 3RD AVENUE , SUITE 4800
SEATTLE
WA
98101-3099
US
|
Family ID: |
21980486 |
Appl. No.: |
09/052876 |
Filed: |
March 31, 1998 |
Current U.S.
Class: |
166/227 ;
175/61 |
Current CPC
Class: |
E03B 3/20 20130101; E21B
43/08 20130101 |
Class at
Publication: |
166/227 ;
175/61 |
International
Class: |
E03B 003/18 |
Claims
1. An integral well filter and screen, comprising: a well screen
having inner and outer surfaces, first and second ends, an internal
volume bounded by the inner surface and both ends, and a plurality
of perforations positioned between the first and second ends and
extending between the inner and outer surfaces; and a filter
positioned in the internal volume of the well screen wherein the
filter is comprised of a layer of a pliable filtration material,
has inner and outer surfaces and first and second ends, and wherein
the filter is inserted in the internal volume of the well screen so
that the outer surface of the filter is in contact with the inner
surface of the well screen.
2. The integral well filter and screen of claim 1, further
comprising a substantially rigid filter support having inner and
outer sides, the outer side of the filter support being engageable
with the inner surface of the filter and attached thereto such that
the outer surface of the filter is kept in contact with the inner
surface of the well screen.
3. The integral well filter and screen of claim 2, further
comprising a second layer of the pliable filtration material
attached to the inner side of the filter support.
4. An integral well filter and screen, comprising: a well screen
having inner and outer surfaces, first and second ends, and an
internal volume bounded by the inner surface and both ends, and a
plurality of perforations positioned between the first and second
ends and extending between the inner and outer surfaces; and a
filter positioned in the internal volume of the well screen wherein
the filter has inner and outer surfaces and first and second ends,
and wherein the filter is inserted in the internal volume of the
well screen such that the outer surface of the filter is in contact
with the inner surface of the well screen and the inner surface of
the filter is an innermost surface of the integral well filter and
screen.
5. The integral well filter and screen of claim 4 wherein the
filter is comprised of a substantially rigid porous material.
6. The integral well filter and screen of claim 4 wherein the
filter is comprised of a layer of a pliable filtration
material.
7. The integral well filter and screen of claim 6, further
comprising a substantially rigid filter support having inner and
outer sides, the outer side being engageable with the inner surface
of the filter.
8. The integral well filter and screen of claim 7 wherein the outer
side of the filter support is attached to the inner surface of the
filter.
9. The integral well filter and screen of claim 8, further
comprising a second layer of the pliable filtration material
attached to the inner side of the filter support.
10. A method of making an integral well filter and screen,
comprising the steps of: selecting a length of a cylindrical stock
to make the well screen, the well screen then extending between a
first end and a second end, having inner and outer surfaces, and
having an internal volume bounded by the inner surface and both
ends; perforating the well screen around a circumference thereof at
a plurality of positions between the first and second ends of the
well screen, the perforations extending between the inner and outer
surfaces thereof; and inserting a filter in the internal volume of
the well screen, the filter having inner and outer surfaces and the
outer surface of the filter being in contact with the inner surface
of the well screen.
11. The method of claim 10 wherein the filter comprises a layer of
a pliable filtration material and further comprising the steps of
attaching a filter support to one side of the filter and forming
the filter and support into a shape complementary to and engageable
with the inner surface of the well screen.
12. The method of claim 11, further comprising the step of
attaching a second layer of the pliable filtration material to the
filter support such that the filter support is sandwiched between
two layers of pliable filtration material.
13. The method of claim 10 wherein the filter comprises a
substantially rigid porous material and further comprising the
steps of forming the filter into a shape complementary to and
engageable with the inner surface of the well screen.
14. A well, comprising: a well bore; and an integral well filter
and screen placed inside the well bore wherein the integral well
filter and screen comprises a well screen having inner and outer
surfaces, first and second ends, an internal volume bounded by the
inner surface and both ends, and a plurality of perforations
positioned between the first and second ends and extending between
the inner and outer surfaces, and a filter positioned in the
internal volume of the well screen.
15. The well of claim 14 wherein the well bore comprises at least
one downwardly directed portion, at least one substantially
horizontal portion, and at least one upwardly directed portion.
16. The well of claim 14 wherein the well bore comprises at least
one downwardly directed portion and at least one substantially
horizontal portion.
17. The well of claim 14 wherein the filter has inner and outer
surfaces, and wherein the filter is inserted in the internal volume
of the well screen such that the outer surface of the filter is in
contact with the inner surface of the well screen.
18. The well of claim 17 wherein the filter comprises a layer of a
pliable filtration material and further comprising a substantially
rigid filter support having inner and outer sides, the outer side
of the filter support being engageable with the inner surface of
the filter and attached thereto such that the outer surface of the
filter is kept in contact with the inner surface of the well
screen.
19. The well of claim 18, further comprising a second layer of the
pliable filtration material attached to the inner side of the
filter support.
20. The well of claim 17 wherein the filter comprises a
substantially rigid porous material and wherein the inner surface
of the filter is an innermost surface of the integral well filter
and screen.
21. A method of drilling a horizontal well, comprising the steps
of: selecting a length of a cylindrical stock to make the well
screen, the well screen then extending between a first end and a
second end, having inner and outer surfaces, and having an internal
volume bounded by the inner surface and both ends; perforating the
well screen around a circumference thereof at a plurality of
positions between the first and second ends of the well screen, the
perforations extending between the inner and outer surfaces
thereof; inserting a filter in the internal volume of the well
screen, the filter having inner and outer surfaces and the outer
surface of the filter being in contact with the inner surface of
the well screen; drilling a well bore; and inserting the well
screen with the filter therein into the well bore.
22. The method of claim 21 wherein the step of drilling the well
bore comprises drilling at least one downwardly directed portion,
at least one substantially horizontal portion, and at least one
upwardly directed portion.
23. The method of claim 21 wherein the step of drilling the well
bore comprises drilling at least one downwardly directed portion
and at least one substantially horizontal portion.
24. The method of claim 21 wherein the filter comprises a pliable
material and further comprising the steps of attaching a filter
support to one side of the filter, forming the filter and support
into a shape complementary to and engageable with the inner surface
of the well screen, and inserting the filter in the internal volume
of the well screen.
25. The method of claim 24, further comprising the step of
attaching a second layer of the pliable filtration material to the
filter support such that the filter support is sandwiched between
two layers of pliable filtration material.
26. The method of claim 21 wherein the filter comprises a
substantially rigid porous material and further comprising the
steps of forming the filter into a shape complementary to and
engageable with the inner surface of the well screen.
27. A method of drilling a horizontal well, comprising the steps
of: drilling a well bore; and inserting an integral well filter and
screen into the well bore wherein the integral well filter and
screen comprises a well screen having inner and outer surfaces,
first and second ends, and an internal volume bounded by the inner
surface and both ends, and a plurality of perforations positioned
between the first and second ends and extending between the inner
and outer surfaces, and a filter positioned in the internal volume
of the well screen.
28. The method of claim 27 wherein the step of drilling the well
bore comprises drilling at least one downwardly directed portion,
at least one substantially horizontal portion, and at least one
upwardly directed portion.
29. The method of claim 27 wherein the step of drilling the well
bore comprises drilling at least one downwardly directed portion
and at least one substantially horizontal portion.
30. The method of claim 27 wherein the filter comprises a pliable
material and further comprising the steps of attaching a filter
support to one side of the pliable material, forming the filter and
support into a shape complementary to and engageable with the inner
surface of the well screen, and inserting the filter in the
internal volume of the well screen.
31. The method of claim 27, further comprising the step of
attaching a second layer of the pliable filtration material to the
filter support such that the filter support is sandwiched between
two layers of pliable filtration material.
32. The method of claim 27 wherein the filter comprises a
substantially rigid porous material and further comprising the
steps of forming the filter into a shape complementary to and
engageable with the inner surface of the well screen, and inserting
the filter in the internal volume of the well screen.
Description
TECHNICAL FIELD
[0001] The present invention pertains to well casings used in well
drilling applications, and in particular to an integral well filter
and screen used as a casing in horizontal wells, and methods for
making and using same.
BACKGROUND OF THE INVENTION
[0002] Wells generally are either vertical or horizontal. Vertical
wells are more commonly known, but in certain applications
horizontal wells have several advantages. Environmental site
remediation, i.e., the removal of subsurface contamination or
in-place treatment of zones of soil or groundwater contamination,
is one area where horizontal wells are superior to vertical ones.
Reasons for the superiority of horizontal wells include increased
linear footage of the well in contact with the contaminated zone,
and the ability to drill beneath surface obstructions or existing
sites without the disturbing ongoing operations at the site. A
horizontal well may be either single-ended or double-ended. In a
single-ended well, one end of the well is at the ground surface and
the other is below ground; this is also known as a "blind hole." In
a double-ended completion, both ends of the well are at the ground
surface.
[0003] Completing a horizontal well usually involves two phases:
drilling a well bore and installing a casing. Drilling begins with
digging a launch pit at the point where the drill head will be
inserted into the ground and, if it is a double-ended well, digging
an exit pit where the drill head will emerge from the ground. The
drill head has a transmitter therein which broadcasts a signal that
enables the operator to determine its exact location, and is
controlled and steered either remotely through radio signals from a
control unit or directly through input provided through wires
inside the drill rods. The drill head is inserted into the ground
at the launch pit and drilling begins. The operator guides the
drill head downward to the desired depth, horizontally for the
desired length of the well, and, if it is a double-ended well,
upward to the exit pit. Different and more complex well structures,
for example with several horizontal portions at different depths
and orientations, are also possible.
[0004] Installing the casing is the second part of the well
completion. The casing is a generally tubular member whose
functions include keeping the well bore from caving in and
transporting contaminants to the surface once the well is
operating. The casing usually consists of a perforated well screen
through which liquids and gases can enter and leave the well
screen, and may include a means of filtration coupled thereto. The
installation method will depend on whether the well is single-ended
or double-ended. In a double-ended well, the drill head pulls
behind it a drill string while it is guided from the launch pit to
the exit pit; when the drill head emerges at the exit pit, the
drill string emerges with it. A well casing is attached to drill
string and the drill string is pulled from the exit pit back toward
the launch pit, pulling the casing with it back through the well
bore. In a single-ended well, the drill head is removed from the
well bore when the drilling is complete and the casing is then
pushed into the well bore through the launch pit. In either case,
movement of the casing through the well bore may be facilitated
using a lubricant such as drilling mud or guar-gum fluid. If a well
screen is fragile, it can be installed using a carrier casing.
After the well bore is drilled, it is reamed out and a solid casing
with an inner diameter larger than the outside diameter of the well
screen is installed. The well screen is placed within and pulled
through the carrier casing. The carrier casing is then removed,
leaving the well screen in place. Carrier casings make the
installation expensive.
[0005] Despite their advantages, horizontal wells present special
installation and operation problems that vertical wells do not.
Horizontal well casings are subject to higher stresses and have a
higher potential for damage during installation than vertical wells
of similar dimensions. Stresses in a vertical casing tend to be low
and only become a problem if the wells are very deep, so that
gravitational forces acting on the casing are large. By contrast,
horizontal casings are subjected to higher tensile forces because
of frictional forces between the casing and the well bore and
because of stress concentration in the casing as it bends to
conform to turns in the well bore. Frictional forces on the casing
are more pronounced in horizontal wells because the weight of the
casing pulls it into contact with the lower part of the well bore.
Stress concentrations are higher in horizontal casings because more
force must be applied to overcome the friction and because of
bending stresses induced in the casing when it is forced to conform
to turns in the well bore that are characteristic of horizontal
wells. Furthermore, horizontal well casings may be required to
resist crushing forces that result if the well bore collapses onto
the casing. In addition to experiencing higher stresses, horizontal
casings are also more likely to receive abrasion damage from the
sides of the well bore as the casings are pushed or pulled through
the well bore.
[0006] Aside from installation problems, the most pronounced
operational difference between vertical and horizontal wells is the
increased tendency of soil, sand, and other fine particulate matter
to enter the well casing through perforations in the well screen.
Over long periods of time, particulate matter in the casing can
lead to clogging of the well, damage to pumping equipment connected
to the casing at the surface, and a variety of other problems. The
usual way of dealing with this problem in vertical wells is to
apply a filter pack to the casing. The orientation of the well
casing in a horizontal well makes application of a filter pack more
difficult.
[0007] In a vertical well, the well casing is held at or near the
center of the well bore using a type of spacer known as a
centralizer. Loose sand is distributed around the well casing to
form a natural filter pack, with the sand gradation and slot size
of the screen being chosen to provide the appropriate filtering.
Natural filter packs have been unsuccessful in horizontal wells
because it is difficult to create a sand pack completely
surrounding the casing, numerous centralizers must be used to
support the weight of the horizontal casing; the centralizers cause
drag and high forces on the casing during installation.
[0008] Three main types of filter packs have been tried on
horizontal wells with varying degrees of success. The simplest is
the "natural pack," which essentially is a well screen with no
filter at all. The natural pack can work quite well, depending on
the use of the well and the grain size of the soil. If, however,
the application is one that is prone to sedimentation, such as a
groundwater extraction well, the natural pack does not work as
well. Or, if it is used in an injection well, it can become silted
or sanded if the operation of the well is cycled or temporarily
suspended.
[0009] The next type of filter pack used on horizontal wells is the
field constructed filter, also known as a "field wrap." The usual
way of doing this is to wrap some form of non-woven filter material
around the outside of the well screen. This method provides extra
filtration, but can be expensive and time consuming, especially in
the field. The filter material is robust, but it tends to increase
the frictional drag between the well bore and the casing during
installation. If a snag occurs during installation, the casing may
break or the filtration material may become dislodged, leaving gaps
through which soil can enter the screen.
[0010] The third type of filter pack is the integrated filter pack,
and these come in two varieties. The first uses a synthetic well
screen with wide slots and is covered with an external, tubular
composite of filtration materials. The composite consists of a
layer of fine, medical-grade synthetic mesh sandwiched between two
layers of heavier mesh, and is installed on the well screen with
heat shrink tubing bonded to the ends. Installation of this type of
filter pack in a horizontal well bore is difficult due to the poor
bonding of the filter to the base pipe, and therefore usually
requires a carrier casing for installation. The second variety of
integrated filter pack consists of a porous filter screen made of
sintered polyethylene resin beads. The porous construction of the
filter screen, however, limits its tensile strength and makes a
carrier casing a requirement for installation.
SUMMARY OF THE INVENTION
[0011] The present invention is a well casing comprising an
integral well filter and screen for use in well installations and a
method for making and using the casing. One embodiment includes a
well screen with a filter placed in an internal volume of the
screen. The well screen is typically made of high-density
polyethylene and has therein a plurality of perforations to allow
fluid communication between the inside of the well screen and the
outside. The well screen can be manufactured to any length. The
filter includes a pliable filter material to which is bonded a
substantially rigid but deformable filter support that keeps the
filter material in contact with an inner surface of the well
screen. The first embodiment is manufactured by bonding the filter
support to the filter material, forming the filter assembly into a
shape that fits into the internal volume and keeps the filter
material in engagement with an inner surface of the well screen,
inserting the filter assembly into the internal volume, and
securing the assembly therein.
[0012] A second embodiment also has a well screen with an internal
filter, but in this embodiment the filter is made of a
substantially rigid material so that it needs no filter support.
Instead, the filter material is simply formed into a cylindrical
shape corresponding to the interior dimension of the well screen,
joined at the abutting edges, and inserted inside the well screen
as is the first embodiment.
[0013] The embodiments of the invention solve several of the
problems of the prior art. Because the filter is inside the well
screen, filter damage during insertion of the screen into the well
bore is eliminated or substantially reduced. Putting the filter
inside the screen and using a pliable filter material with a filter
support bonded thereto result in a thinner cross section that
allows the screen to bend easily when it goes around corners in
well bores. The configuration also allows better tailoring of the
stiffness of the combination to the application, has excellent
hydraulic performance, is more durable, and costs half as much as
present screen/filter casings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1a is an isometric view of a first embodiment of an
integral well filter and screen.
[0015] FIG. 1b is a cross section of the first embodiment taken
substantially through the line 1B-1B in FIG. 1a and showing the
filter and screen installed in a well bore.
[0016] FIGS. 2a-2d illustrate the structure of a filter in the
first embodiment and, in sequence, illustrate a method of
manufacturing the first embodiment.
[0017] FIG. 3a is an isometric view of a second embodiment of an
integral well filter and screen.
[0018] FIG. 3b is a cross section of the second embodiment taken
substantially through line 3B-3B in FIG. 3a and showing the filter
and screen installed in a well bore.
[0019] FIGS. 4a-4c illustrate the structure of the filter in the
second embodiment and, in sequence, illustrate a method of
manufacturing the second embodiment.
[0020] FIGS. 5a-5b are cross sections through a typical
double-ended horizontal well illustrating the method of drilling a
well and installing a casing.
DETAILED DESCRIPTION OF THE INVENTION
[0021] An integral well filter and screen for use as a well casing
in a horizontal well is described herein in reference to specific
embodiments. In the following description, numerous specific
details are set forth to provide a thorough understanding of the
present invention. One skilled in the relevant art, however, will
readily recognize that the present invention can be practiced
without one or more of the specific details reflected in the
embodiments described herein.
[0022] FIG. 1a shows a first embodiment of an integral well filter
and screen 20 having as its main components a well screen 22 and a
filter assembly 24 positioned within the well screen. The well
screen 22 is made from a length of pipe and has therein a series of
perforations 26. The pipe typically has a diameter between 2 and 8
inches and comes in 10 or 20 foot sections, but the well screen 22
can be made to any length by fusing together several sections of
pipe, by cutting the desired length of pipe from a single section,
or both. High-density polyethylene (HDPE) pipe sold under trade
names such as Phillips Petroleum Driscopipe or Chevron Plexco is
most often used, but the pipe can be made of any material suitable
for the application; other possible pipe materials include
polyvinyl chloride, fiberglass reinforced epoxy, carbon steel, and
stainless steel.
[0023] The perforations 26 are shown as longitudinal slots in the
well screen 22 but may be of any shape suitable for the
application, including longitudinal slots, longitudinal slits,
transverse slots or slits, circles, squares, or any combination of
these or others. The perforations 26 extend from the exterior
surface 28 of the well screen 22 through to the interior surface 30
of the well screen 22, allowing fluid communication between an
internal volume 29 of the well screen 22 and its exterior. The
perforations 26 are sized based on the required tensile strength of
the well screen and the open area required to treat the soil
contamination. Typical diameters for round perforations are between
{fraction (1/16)}and 1/2inches. Longitudinal slots are typically
1-1/2inches long with a width between 1/8and 3/8inches. Transverse
slits typically remove 60% of the cross-sectional area of the well
screen at the longitudinal position where they arc located.
[0024] The filter assembly 24 resides in an internal volume 29 of
the well screen 22 and is sized and shaped so as to conform to the
shape of the interior surface 30 and remain in engagement
therewith. The filter assembly 24 includes a pliable filtration
material 32 and a filter support 34 bonded to one side of the
filtration material 32.
[0025] FIG. 1b shows a cross-section of the first embodiment of the
integral filter and screen 20 installed inside a well bore 36 and
illustrates its operation. Once installed, the integral well filter
and screen 20 is used for removal of liquids and gases from the
surrounding soil 38 or insertion of liquids and gases into the
surrounding soil 38. In a typical application, air is pumped out of
the casing by a pump (not shown) attached to the casing at the
ground surface, thus pulling liquids or gases from the surrounding
soil 38 through the perforations 26 and into the interior volume 29
of the well filter and screen, as shown schematically by the wavy
arrows in FIG. 1b. The filter assembly 24 allows the entry of
liquids and gases into the internal volume 29 while keeping soil,
sand, and other fine particulate matter from entering.
[0026] FIGS. 2a-2d illustrate the structure of the first embodiment
of the integral well filter and screen 20 and, taken in sequence,
illustrate its method of manufacture. FIG. 2a illustrates the
construction of the filter assembly 24, which includes the
filtration material 32 bonded to the filter support 34. The
filtration material is typically a non-woven material such as
DuPont.RTM. Trevira, but may be any material capable of filtration.
The filtration material is chosen based on the required apparent
opening size, which depends directly on the thickness of the
material; typical thicknesses range between {fraction (1/16)}and
1/4of an inch. The filter support used in this embodiment is a
high-density polyethylene lattice that is rigid enough to hold the
shape of the filter assembly once it is inserted in the internal
volume 29 of the well screen 22, yet flexible enough that the
filter assembly 24 can be formed into a shape that conforms to the
interior surface 30 of the well screen 22. The filter support is
typically purchased from the manufacturer of the filtration
material and comes pre-bonded to the material. For example,
DuPont.RTM. Trevira comes from the factory with the HDPE lattice
already bonded thereto. Although typically made of HDPE, the filter
support can also be made in a variety of configurations and
materials. For example, it could be a PVC lattice or a stainless
steel mesh or lattice.
[0027] FIG. 2b shows the filter assembly 24, the filter support 34
having been fused or thermally bonded to the filtration material
32. In FIG. 2c, the filter assembly 24 is formed into a cylindrical
shape such that two edges 40 are abutting each other. A strip 42 of
filtration material (FIG. 2d) about 2 inches wide is placed over
the abutting edges 40 to hold the cylindrical shape of the filter
assembly 24, increase its strength and rigidity, and ensure
complete filtration around the circumference of the filter. FIG. 2d
shows the filter assembly 24, once in the proper shape, being
inserted into the internal volume 29 of the well screen 22. The
size of the filter assembly 24 is such that, once it is placed in
the internal volume 29, the filtration material 32 will be in
engagement with the interior surface 30 of the well screen 22.
[0028] FIG. 3a shows a second embodiment of the well filter and
screen 120 that includes the well screen 122 having perforations
126 as before, although in this embodiment they are transverse
slits rather than longitudinal slots. In this embodiment, the
filter 144 is made of a rigid, porous material rather than a
pliable filtration material bonded to a filter support. As with the
first embodiment, the filter 144 fits within the internal volume
129 of the well screen 122 and engages the interior surface 130 of
the well screen 122.
[0029] FIG. 3b illustrates the operation of the second embodiment,
which is much like the operation of the first embodiment described
above. Once the well bore 36 is drilled, the integral well filter
and screen 120 is inserted therein. In a typical application, air
is pumped out of the interior volume 129 of the well screen 122 by
a pump (not shown) located on the surface of the ground. As shown
schematically by the wavy arrows in FIG. 3b, the porous filter 144
allows liquids and gases from the surrounding soil 38 to move into
the internal volume 129 and be pumped out to the ground surface,
while preventing the entry of sand, soil, and other fine
particulate matter into the internal volume 129. Over the long
term, this filtration prevents accumulation of particulate
materials in the well screen, prevents damage to the pumps at the
surface of the ground, and avoids various other problems.
[0030] FIGS. 4a-4c illustrate the structure of the second
embodiment and a method of manufacture. FIG. 4a illustrates the
substantially rigid, porous material 144 in an initial state.
Typically, the rigid, porous material is between {fraction
(1/16)}and 1/4inch thick and is made of sintered polyethylene
beads. Its porosity is controlled by varying the heat and pressure
applied during sintering. The most commonly used rigid porous
materials are any of the porous plastics made by Porex.RTM.
Corporation. The rigid porous material 144 is formed into a
cylindrical shape as shown in FIG. 4b until the abutting edges 146
are nearly in contact with each other. As with the first
embodiment, the filter is sized and shaped to fit in the internal
volume 129 of the well screen 122, with the filter 144 engaging the
interior surface 130 of the well screen 122. FIG. 4c illustrates
the insertion of the filter 144 into the internal volume 129 of the
well screen 122. The filter 144 is aligned in the internal volume
129 such that the abutting edges 146 are not aligned with any
perforations, thus ensuring complete filtration. In a second method
of manufacture (not shown), the filter 144 is initially formed into
its final cylindrical shape and then simply inserted in the
interior volume 129 of the well screen 122.
[0031] FIGS. 5a and 5b illustrate a method of drilling a
double-ended horizontal well and installing the integral well
screen and filter 20 or 120. FIG. 5a shows the drilling process. An
entrance pit 48 and an exit pit 50 are dug at the desired entry and
exit positions, respectively, of the drilling head; these are
usually located on either side of the remediation zone. Using a
directional drilling unit 52, a drill head 54 is inserted into the
entrance pit 48 and begins drilling the well bore. The path of the
drill generally includes at least three portions: a downwardly
directed portion 47, a substantially horizontal portion 49, and an
upwardly directed portion 51. Different and more complex
configurations are possible, such as wells having multiple
horizontal portions at different depths below the surface and
multiple upwardly and downwardly directed portions. The drill head
is controlled by an operating using either a remote control that
sends signals to the drill head, or using signals sent to the drill
head through wires attached thereto. As the drill head drills the
well bore, it pulls behind it a drill string 56. When the drill
head 54 arrives at the exit pit 50 it is pulled out of the ground
along with the drill string 56.
[0032] FIG. 5b shows the casing installation. Once the drill head
54 has arrived at the exit pit 50, it is removed from the well
bore. If necessary, the well bore can be reamed to increase its
size. The drill string is connected to the well filter and screen
20 or 120. A lubricant such as guar-gum fluid is pumped into the
well bore and the directional drilling unit 52 pulls the drill
string 56 and the filter and screen 20 back through the well bore
36 until the filter and screen extend between the exit pit 50 and
the entrance pit 48. Any desired hardware, such as pumps (not
shown), can then be attached to the ends of the filter and screen
at the ground surface.
[0033] The process illustrated in FIGS. 5a and 5b is for a
double-ended well. In a single-ended well (not shown), the end of
the well bore is underground rather than at an exit pit 50. To get
a single-ended well, an entrance pit 48 is dug at the desired
location. The directional drilling unit inserts the drill head 54
into the entrance pit, drills the well bore 36 to the desired
location, and pulls the drill head 54 back out through the well
bore. At that point, a lubricant is pumped into the well bore and a
well filter and screen 20 or 120 with its blind end capped is
pushed through the entrance pit into the completed well bore until
it extends between the entrance pit and the end of the well
bore.
[0034] Although specific embodiments of, and examples for, the
present invention are described herein for illustrative purposes,
various equivalent modifications are possible within the scope of
the invention, as will be recognized by those skilled in the
relevant art. The teachings provided herein of the present
invention can be applied to other integral well filters and screens
and method for making and using the same, not necessarily the
exemplary well filter and screen described above. In general, in
the following claims, the terms used should not be construed to
limit the invention to the specific embodiments disclosed in the
specification and the claims, but should be construed to include
all integral well filters and screens that operate under the claims
and provide a method for making and using the integral well filter
and screen. Accordingly, the invention is not limited by the
disclosure, but instead its scope is to be determined entirely by
the following claims.
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