Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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GAS IMPULSE DEVICE AND METHOD OF USE THEREOF
FIELD OF THE INVENTION
The present invention relates generally to the rehabilitation, stimulation,
development
and maintenance of oil and water wells, pipes, reservoirs, channels and the
like, and in
particular to the use of air or gas apparatus for achieving same.
BACKGROUND OF THE INVENTION
Among the variety of methods known in the art of oil and water well
rehabilitation and
maintenance, are methods which involve the use of chemical or explosive
materials for
the removal of hard deposits and other encrustations. Alternative methods
known in the
art employ high pressure jetting techniques in the well-cleaning process.
Variations of
these methods are also utilized for the cleaning and maintenance of other
liquid or dry
storage and transport facilities such as reservoirs, crucibles, tanks,
pipelines and
channels.
A consideration of cleaning processes which employ explosives for the removal
of hard
deposits and encrustations, raises a number of important concerns. Such
concerns
include safety issues surrounding the manufacture, transport, usage and
storage of
explosive material, as well as concerns regarding the risk of structural
damage to a water
or oil well, or other storage or transport facility undergoing treatment.
Turning now to cleaning methods involving the use of high pressure jetting -
which by
way of example, are employed to remove hard scale deposits from wells and
pipelines -
these methods involve the application of a high pressure jet, such as a water
jet, to an
area of deposits, so as to first penetrate and then "strip off' the deposits
by driving a fluid
wedge between them and the surface to which they are attached. Disadvantages
surrounding this method include limited effectiveness owing to dissipation of
hydraulic
power which may result from line losses, activation of the jet in a liquid
environment, and
difficulties in controlling movement of the jet.
In addition to the above-described rehabilitation, cleaning and maintenance
techniques,
there are also known in the art, treatment methods which involve the use of
air or gas
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blasting apparatus. US Patent No. 5,579,845 to Janson et al for example,
entitled
"Method for Improved Water Well Production", teaches generally, a method by
which
pressure waveforms and mass displacement within a well bore volume are used
for
stimulating, refurbishing or otherwise increasing production from water wells.
Referring now to US Patent No. 4,966,326, entitled "Air-Blasting Cartridge",
there is
described an example of air blasting apparatus which may be used for
performing such
treatment methods. This patent describes an air-blasting cartridge comprising
a housing
subdivided into an inlet chamber and a discharge chamber by virtue of a piston
arranged
lengthwise along a longitudinal axis of the housing. The inlet chamber
communicates
with a source of compressed air through an air admission tube which runs the
length of
the cartridge through an axial port of the piston. The discharge chamber
communicates
with the inlet chamber through an annular gap between the air admission tube
and the
piston, and is adapted to communicate with the surrounding atmosphere at the
instant of
its discharge, by means of at least one open-ended passage made in the housing
close
to the inlet chamber, wherein a pressure relief valve is provided at the
outlet end of the
passage.
While the above apparatus is intended for use in cleaning industrial pipelines
including
sewer pipelines, its efficiency - especially with respect to well
rehabilitation and
maintenance - is limited by the very construction of the cartridge. In
particular, the
provision for the cartridge to communicate with the surrounding environment
through the
above-described pressure relief valve, creates a significant limitation upon
the piston's
opening speed which increases in accordance with the hydrostatic pressure.
Further, the
cartridge's pressure relief valves are likely to become clogged rather
quickly, especially
when the apparatus is used in a liquid environment containing an appreciable
quantity of
suspended particles.
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SUMMARY OF THE INVENTION
The present invention seeks to provide improved apparatus, and an effective
and
environmentally friendly method, for water and oil well rehabilitation,
stimulation,
development and maintenance, which overcome the disadvantages of known art.
The
present invention also seeks to provide improved apparatus and method for the
cleaning
and maintenance of other liquid and dry storage and transport facilities.
There is thus provided, in accordance with a preferred embodiment of the
invention, a self-firing and self-propelling gas impulse device which
includes:
a housing having a longitudinal axis, a gas inlet port, and one or more gas
discharge ports;
an inlet chamber, arranged for gas communication with a source of compressed
gas via the inlet port and operative to receive compressed gas therefrom;
a pressurization chamber arranged for gas communication with the inlet chamber
thereby to facilitate a build-up of pressurized gas therein, and arranged for
selectable
gas communication with the one or more discharge ports; and
a piston unit arranged along the longitudinal axis of the housing between the
inlet
chamber and the pressurization chamber, and selectably movable between a first
operative position and a second operative position, whereat in the first
operative position
the piston unit prevents gas communication between the pressurization chamber
and the
one or more discharge ports, and whereat in the second operative position the
piston
unit is retracted so as to facilitate gas communication between the
pressurization
chamber and the one or more discharge ports, and the piston unit is operative
to move
between the first and the second operative positions in response to a force
differential
across the piston unit in a direction parallel to the longitudinal axis, such
that when the
piston unit is in the first operative position and the gas pressure in the
pressurization
chamber is of at least a predetermined magnitude, the piston unit is operative
to move
towards the second operative position in response to the gas pressure and at
least a
predetermined minimum force differential thereby to facilitate a rapid high
pressure
exhaustion of gas in the pressurization chamber to the exterior of the housing
via the
one or more discharge ports.
Additionally, in accordance with a preferred embodiment of the present
invention,
at least a portion of the piston unit is operative to move within a sealing
arrangement
such that when the piston unit is in the first operative position, the sealing
arrangement
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and the piston unit cooperate so as to prevent gas communication between the
pressurization chamber and the one or more discharge ports.
Further, in accordance with a preferred embodiment of the present invention,
the
inlet port is formed at an upstream end of the gas impulse device, and the
pressurization
chamber is formed at a downstream end of the gas impulse device.
Additionally, in accordance with a preferred embodiment of the present
invention,
the piston unit includes an upstream-facing end portion having an upstream-
facing end
surface and a downstream-facing end portion having a downstream-facing end
surface.
Further, in accordance with a preferred embodiment of the present invention,
when the piston unit is in the first operative position, the inlet chamber is
operative to
contain a gas having a pressure of up to a first magnitude and the
pressurization
chamber is operative to contain a gas having a pressure of up to a second
magnitude,
and when the upstream-facing end surface is exposed to the gas pressure of the
first
magnitude a first force is developed thereat, and when the downstream-facing
end
surface is exposed to the gas pressure of the second magnitude a second force
is
developed thereat, and the predetermined minimum force differential
corresponds to the
difference in the respective magnitudes between the first and second forces.
Additionally, in accordance with a preferred embodiment of the present
invention,
the predetermined minimum force differential is related to the ratio between
the first and
second gas pressure magnitudes and the ratio between the areas of the end
surfaces.
Further, in accordance with a preferred embodiment of the present invention,
the
first operative position includes a first extreme position and the second
operative position
includes a second extreme position and the movement of the piston unit towards
the
second operative position in response to the gas pressure and the
predetermined
minimum force differential, includes a movement of the piston unit towards the
second
extreme position.
Additionally, in accordance with a preferred embodiment of the present
invention,
the piston unit includes an upstream-facing end portion having an upstream-
facing end
surface and a downstream-facing end portion having a downstream-facing end
surface,
and the movement of the piston unit towards the second operative position in
response
to the gas pressure and the predetermined minimum force differential is a
first movement
of the piston unit out of the sealing arrangement, and the piston unit has a
further
downstream-facing surtace such that upon the piston unit moving out of the
sealing
arrangement, the further downstream-facing surface suddenly becomes exposed to
the
pressurized gas within the pressurization chamber, thereby to cause the piston
unit to
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rapidly move towards the second extreme position in a second movement and so
as to
cause the rapid high pressure exhaustion of gas.
Further, in accordance with a preferred embodiment of the present invention,
the
device includes a variable-sized discharge chamber arranged between the
pressurization
chamber and the one or more discharge ports such that when the piston unit is
in the
first operative position, the sealing arrangement and the piston unit
cooperate so as to
prevent gas communication between the pressurization chamber and the discharge
chamber, and the discharge chamber increases in size as the piston unit moves
from the
first extreme position towards the second extreme position, and the rapid high
pressure
exhaustion of gas from the pressurization chamber to the exterior of the
housing is also
via the discharge chamber.
Additionally, in accordance with a preferred embodiment of the present
invention,
the portion of the piston unit is a first portion of the piston unit and the
sealing
arrangement is a first sealing arrangement, and the gas impulse device also
includes a
second sealing arrangement.
Further, in accordance with a preferred embodiment of the present invention,
the
device also includes a variable-sized damper chamber arranged between a second
portion of the piston unit and the second sealing arrangement such that when
the piston
unit moves from the first extreme position towards the second extreme
position, the
damper chamber decreases in size thereby to increase the pressure therein so
as to
apply a damping force to the piston unit.
Additionally, in accordance with a preferred embodiment of the present
invention,
the pressurization chamber communicates with the inlet chamber via a generally
cylindrical passage which extends through the piston unit.
Alternatively, in accordance with another embodiment of the present invention,
the inlet chamber communicates with the inlet port via an air admission
conduit which
extends through the piston unit.
Additionally, in accordance with the other embodiment of the present
invention,
the pressurization chamber communicates with the inlet chamber via an annular
gap
arranged between a generally cylindrical inner surface of the piston unit and
a generally
cylindrical outer surface of the air admission conduit.
Further, in accordance with a preferred embodiment of the present invention,
the
device includes apparatus for controlling the supply of gas to the inlet
chamber.
Additionally, in accordance with a preferred embodiment of the present
invention,
the inlet chamber is configured for gas communication with the inlet chamber
of another
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gas impulse device thereby to enable the controlled supply of gas to a
plurality of
interconnected gas impulse devices.
Further, in accordance with a preferred embodiment of the present invention,
the
one or more discharge ports broadens as they extend towards the exterior of
the
housing.
Additionally, in accordance with one embodiment of the present invention, the
one or more discharge ports are arranged transverse to the longitudinal axis
of the
housing.
Alternatively, in accordance with another embodiment of the present invention,
the one or more discharge ports are arranged at an angle less than ninety
degrees with
respect to the longitudinal axis of the housing.
There is also provided in accordance with another preferred embodiment of the
invention, a method of rehabilitating a container, having therein a liquid and
having a wall
construction the wall construction having thereon undesired substances sought
to be
removed, wherein the method includes:
positioning within the liquid a gas impulse device in an orientation generally
parallel to a portion of the wall construction to be rehabilitated; and
operating the gas impulse device so as to repeatedly discharge cleaning jets
of a
predetermined gas towards the portion of the wall construction, thereby to
separate the
undesired substances therefrom, and thereby also to propel the gas impulse
device
along a travel path generally parallel to the portion of the wall construction
thus to deliver
successive cleaning jets to successive portions of the wall construction.
Additionally, in accordance with the other preferred embodiment of the present
invention, the step of operating the gas impulse device includes the step of
selectably
supplying compressed gas to the gas impulse device, including selectably
releasing
compressed gas from the gas impulse device.
Further, in accordance with the other preferred embodiment of the present
invention, the step of operating the gas impulse device includes supplying to
the gas
impulse device a compressed gas whose main component is selected from the
group
consisting of:
(i) air,
and (ii) nitrogen.
Alternatively, in accordance with the other preferred embodiment of the
present
invention, the step of operating the gas impulse device includes supplying to
the gas
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impulse device a compressed gas whose main component is carbon dioxide, so as
to
give rise to the formation of carbonic acid upon operation of the device.
Optionally, in accordance with the other preferred embodiment of the present
invention, the method includes the step of introducing a chemical compound
into the
liquid prior to the step of operating the gas impulse device, so as to give
rise to a
chemical reaction of the chemical compound with the undesired substances.
In accordance with the yet another preferred embodiment of the present
invention, the container is a well and the step of operating the gas impulse
device
causes an increase in pressure in the well, and the method also includes the
step of
packing at least a region of the well prior to the step of operating the gas
impulse device,
so as to limit liquid displacement in the packed region and to substantially
maintain the
pressure increase therein during the step of operating the gas impulse device.
Optionally, in accordance with the other preferred embodiment of the present
invention, the method includes the step of releasing excess pressure from the
packed
region of the well so as to prevent an increase of pressure within the well of
greater than
a predetermined magnitude.
Additionally, in accordance with one embodiment of the present invention where
the wall construction includes a rock formation containing a liquid flow, the
method may
include the step of causing a continued increase in pressure within the packed
region of
the well, such that the step of operating the gas impulse device is operative
to cause
fracturing of a portion of the rock formation, thereby to improve a liquid
flow therefrom
into the well.
Further, in accordance with another embodiment of the present invention, the
method includes the step of introducing a proppant into the well prior to the
step of
operating the gas impulse device, thereby to support fractures within the
outer rock
formation upon operation of the gas impulse device.
There is also provided in accordance with yet another embodiment of the
invention, a method of rehabilitating a container, having therein a liquid and
having a wall
construction the wall construction having thereon undesired substances sought
to be
removed, wherein the method includes:
positioning in the container a gas impulse device in an orientation generally
parallel to a portion of the wall construction to be rehabilitated; and
supplying a predetermined gas to the gas impulse device so as to provide a
blast
of gas in the form of a jet directed towards the wall construction, so as to
separate the
undesired substances therefrom.
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Additionally, in accordance with the other embodiment of the present
invention,
the method includes repeating the step of supplying a predetermined gas to the
gas
impulse device so as to provide further blasts of gas in the form of jets
directed towards
the wall construction.
There is also provided in accordance with yet a further embodiment of the
invention, a method of rehabilitating a well, having therein a liquid and
having a well
screen the well screen having thereon undesired substances sought to be
removed,
wherein the method includes:
positioning within the liquid a gas impulse device in an orientation generally
parallel to a portion of the well screen to be rehabilitated; and
operating the gas impulse device so as to repeatedly discharge cleaning jets
of a
predetermined gas towards the portion of the well screen, thereby to separate
the
undesired substances therefrom, and thereby also to propel the gas impulse
device
along ~ a travel path generally parallel to the portion of the well screen
thus to deliver
successive cleaning jets to successive portions of the well screen.
There is also provided in accordance with yet another embodiment of the
invention, a method of rehabilitating a well, having therein a liquid and
having a well
screen the well screen having thereon undesired substances sought to be
removed,
wherein the method includes:
positioning in the well a gas impulse device in an orientation generally
parallel to
a portion of the well screen to be rehabilitated; and
supplying a predetermined gas to the gas impulse device so as to provide a
blast
of gas in the form of a jet directed towards the well screen, so as to
separate the
undesired substances therefrom.
Additionally, in accordance with the other embodiment of the present
invention,
the method includes repeating the step of supplying a predetermined gas to the
gas
impulse device so as to provide further blasts of gas in the form of jets
directed towards
the well screen.
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BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood and appreciated from the
following detailed description, taken in conjunction with the drawings, in
which:
FIG. 1 is a schematic illustration of a gas impulse device constructed in
accordance with a preferred embodiment of the present invention, connected to
an
external pressurized gas source by means of a high pressure supply conduit,
and
inserted for use in a water well;
FIG. 2 is an axial sectional view of a gas impulse device constructed in
accordance with a preferred embodiment of the present invention, illustrating
the
device's piston unit in a first extreme position prior to firing of the
device, whereat the
piston unit is operative to seal the pressurization chamber from the device's
discharge
ports;
FIG. 2A is a cross-sectional view taken along the line X-X of FIG. 2 depicting
the
gas impulse device's cylindrical housing and piston guide only;
FIGS. 2B and 2C are respective side and plan views of the gas impulse device's
first ring element;
FIG. 3 is a view similar to that of FIG. 2, illustrating an upstream traversal
of the
device's piston unit, thereby allowing for gas communication between the
device's
pressurization chamber and discharge ports so as to create a gas blast;
FIG. 4 is a view similar to that of FIGS. 2 and 3, illustrating the device's
piston unit
in a second extreme position subsequent to firing of the device;
FIGS. 5A and 5B are axial sectional views of a gas impulse device constructed
in
accordance with an alternative embodiment of the present invention, and
respectively
illustrating first and second extreme positions of the device's piston unit,
corresponding
to extreme positions of the piston unit prior to and subsequent to firing of
the device;
FIG. 6 is an axial sectional view of a gas impulse device constructed in
accordance with a further alternative embodiment of the present invention,
wherein a
controlling valve unit is connected to the device's inlet chamber;
FIG. 7 is a schematic illustration of the gas impulse device of FIGS. 1-4
inserted
for use in a pipeline;
FIG. 8 is a schematic illustration of the gas impulse device of FIGS. 1-4
inserted
for use in a sewer pipeline;
FIG. 9 is a schematic illustration of the gas impulse device of FIGS. 1-4
inserted
for use in a reservoir;
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FIGS. 10-12 are schematic illustrations of various pressure phases resulting
from
a gas blast generated by the gas impulse device of FIGS. 1-4;
FIG. 13 is a schematic illustration of the gas impulse device of FIGS. 1-4
inserted
for use in a well and operated in conjunction with a packer unit;
FIG. 14 is a schematic illustration similar to FIG. 13, depicting the gas
impulse
device of FIGS. 1-4 inserted for use in a well and operated in conjunction
with two packer
units arranged in a straddle arrangement; and
FIG. 15 is a schematic illustration of the gas impulse device of FIGS. 1-4
permanently or semi-permanently installed for use in a well, and operable in
conjunction
with a guiding and centralizing mechanical pulley system.
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DETAILED DESCRIPTION OF THE INVENTION
The description set out hereinbelow relates to apparatus and method used in
the
rehabilitation, stimulation, development and maintenance of water and oil
wells. It will be
appreciated however, that while the description refers generally to water and
oil wells,
the described apparatus and method may be easily modified for application to
the
cleaning and maintenance of pipelines, channels, reservoirs, bins, crucibles
and other
similar liquid or dry storage and transport facilities, some of which are
described herein in
conjunction with FIGS. 7-9.
Referring generally to FIGS. 1-4 and 7-15, there is seen a rapid self-firing,
self-propelling
gas impulse device, referenced 10, constructed and arranged in accordance with
a
preferred embodiment of the invention. When operated in accordance with a
related
method of the invention as described hereinbelow, device 10 produces impulses
or
"blasts" of gas which are operative to apply forces to a surrounding area of
the well,
storage or transport facility within which the device is being operated, so as
to effectively
dislodge deposits therefrom. Additionally, in accordance with the present
embodiment,
the impulse forces produced by the gas impulse apparatus, are further
operative to
propel device 10 along a predetermined course so as to enable repeated firing
within
contiguous portions of the facility undergoing treatment.
In use, device 10 is typically operable under pressures of up to 400
atmospheres in the
case of oil wells, and up to 200 atmospheres in the case of water wells.
Further, device
10 is constructed to operate effectively in any of a multiplicity of
orientations such that it
may be used for cleaning vertical, horizontal and inclined wells and pipelines
as
described hereinbelow in conjunction with FIG. 1 and FIGS. 7-9.
Referring more particularly to FIGS. 2-4, gas impulse device 10 preferably has
a
cylindrical housing 12 which houses a gas receiving unit 14 at one end, and an
inlet
chamber 16 formed within an end cap 18 at the other end. During operation of
the
device, inlet chamber 16 receives pressurized gas - such as compressed air,
nitrogen or
carbon dioxide - from an external pressurized gas source 100 (FIG. 1), through
an inlet
port 18a formed in end cap 18, whereafter the gas transfers to gas receiving
unit 14 so
as to ultimately cause the device's piston unit, referenced 30, to be
activated as
described hereinbelow. Upon activation of piston unit 30, pressurized gas is
released
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through discharge ports 20, and creates a gas blast illustrated by arrows 17
of FIG. 1. As
noted above, the gas blast created by device 10 is operative to dislodge
deposits from
selected portions of the well, as well as to provide a jet force for
propelling the apparatus
along a predetermined course.
It is noted that the configuration and orientation of discharge ports 20 play
a significant
role in determining the efficacy of the gas blast provided by gas impulse
device 10. In a
preferred embodiment of the invention as illustrated in FIGS. 2-4, discharge
ports 20
broaden laterally as they extend towards perimeter, 70, of cylindrical housing
12 (FIG.
2A) so as to form Laval-type nozzles. Discharge ports 20 are preferably also
angled
between 45° to 90° with respect to a longitudinal axis, 75, of
cylindrical housing 12. This
combination of broadening and angled discharge ports 20, enhances both the
velocity of
the gas released during a gas blast, and provides for an effective jet force
in the
propulsion of device 10. It is noted however, that the invention is not
intended to be
limited by the configurations of discharge ports 20 as described, and
alternative
embodiments may well include, for example, discharge ports arranged laterally
with
respect to axis 75, such as in cases where it is desirable not to provide a
jet force during
operation of the apparatus.
Prior to commencing a detailed consideration of the various components of gas
impulse
device 10, it is noted that for purposes of convenience, gas receiving unit 14
is
considered in the description below as being located downstream with respect
to inlet
chamber 16 and end cap 18. Furthermore, references to "firing" of the
apparatus, relate
to the creation of a gas blast by means of releasing pressurized gas through
discharge
ports 20 as described hereinbelow.
Considering now gas receiving unit 14 in more detail, there is seen provided
therein, a
conical, longitudinally extending, gas receiving or pressurization chamber,
referenced 19,
which is operative to hold a charge of high pressured gas. Located upstream of
a
narrowing upstream portion 19a (FIG. 2) of chamber 19, is a first damper ring
22 which is
preferably formed of a durable, elastic material such as a high density
polyethylene
material, and which serves as both an energy damping element and a sealing
element.
In a preferred embodiment of the invention, first damper ring 22 is coupled
with a first
ring element 24 such as a steel ring, which has formed on an upstream-facing
surface
thereof, lugs 26 which act as spacers (also seen in FIGS. 2B and 2C). First
ring element
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24 is operative to protect first damper ring 22 from damage during operation
of
device 10. There are also provided O-ring seals 25, mounted inside grooves 27
(FIG. 2)
formed within gas receiving unit 14 and first damper ring 22. O-ring seals 25
function to
seal the area of contact between cylindrical housing 12 and gas receiving unit
14, as well
as the area of contact between cylindrical housing 12 and first damper ring
22.
Referring still to FIGS. 2-4, piston unit 30 is seen to be arranged within
cylindrical
housing 12, so as to lie in coaxial alignment with axis 75 of the cylindrical
housing.
During operation of device 10, piston unit 30 moves between a first extreme
position
(FIG. 2) and a second extreme position (FIG. 4), thereby closing and opening
discharge
ports 20 to the release of pressurized gas.
Piston unit 30 is typically formed of toughened stainless steel and has three
integrally
formed sub-units - namely: a longitudinally arranged piston body 32, a piston
head 33,
and a piston nose 34. As illustrated in FIGS. 2-4, piston body 32 is movably
positioned
inside a second damper ring 36 and adjacently positioned second ring element
37, whilst
piston nose 34 is configured for entry into first damper ring 22 and first
ring element 24
when the piston unit assumes its first extreme position prior to firing of the
impulse
device (FIG. 2). In a preferred embodiment of the invention, second damper
ring 36 is
formed generally similar to but somewhat longer than first damper ring 22,
whilst second
ring element 37 is formed generally similar to first ring element 24 but does
not possess
lugs.
In addition to serving as an energy damping element and a sealing element,
second
damper ring 36 also functions as a guide element for piston body 32.
Additionally, O-ring
seals referenced 35, are mounted within grooves 18b of end cap 18, and 36a of
second
damper ring 36, so as to seal the areas of contact between end cap 18 and
cylindrical
housing 12, and second damper ring 36 and cylindrical housing 12,
respectively.
There is also provided a sleeve-shaped piston guide 38, which is
concentrically arranged
around piston head 33, and which is operative to guide the piston head as
piston unit 30
moves between its extreme first and second positions. Piston guide 38 is
typically formed
from a durable, corrosion-resistant material such as a polyamide or bronze
based
material. First openings within the piston guide, referenced 38a, are arranged
adjacent to
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discharge ports 20, so as to enable the exit of pressurized gas upon the
firing of device
10.
Referring still to piston unit 30, there is seen in FIGS. 2-4, a longitudinal
passage 40,
which axially extends through an inner hollow of the piston unit. Passage 40
is arranged
such that it is contiguous with inlet chamber 16, and provides for gas
communication
between the inlet chamber and pressurization chamber 19. There is also
provided, an
orifice element 42, which is threadedly attached to an inner portion 34a (FIG.
2) of piston
nose 34, and which is prevented from exiting a downstream end 40a of passage
40 by
means of a stopper ring 44.
In addition to inlet chamber 16 and pressurization chamber 19, gas impulse
device 10
includes two further chambers, referenced herein as discharge chamber 50 and
damper
chamber 60. As illustrated in FIGS. 2-4, the configurations of discharge
chamber 50 and
damper chamber 60 vary in accordance with the position of piston unit 30 at a
given
point in time during operation of the apparatus. As seen particularly in FIG.
3, discharge
chamber 50 provides for the throughflow of pressurized gas from pressurization
chamber
19 to discharge ports 20, following the withdrawal of piston nose 34 from
first damper
ring 22 and first ring element 24 in the course of piston unit 30 moving
upstream towards
its second extreme position (FIG. 4). Also seen in FIG. 3, is a cylindrical
shaped cavity,
referenced 62, formed within cylindrical housing 12, and arranged for gas
communication
with damper chamber 60 via second openings 38b of piston guide 38. Further,
there is
also formed within piston head 33, at least one preferably narrow bore which
allows for
further gas communication between discharge chamber 50 and damper chamber 60
during the operation of device 10. FIGS. 2-4 illustrate two such bores,
referenced 39.
Referring still to FIGS. 2-4, operation of gas impulse device 10 in performing
a method of
the invention, is now described.
Initially, compressed gas is fed from a high pressure external gas source 100
(FIG. 1) to
inlet chamber 16 via a suitable high pressure supply conduit 102 (FIG. 1)
which is
attached to end cap 18. The compressed gas entering inlet chamber 16 via inlet
port
18a, flows downstream in a direction indicated by arrow 80 (FIG. 2), such that
it enters
passage 40 of piston unit 30. Once the pressure within inlet chamber 16
reaches a
predetermined magnitude, the continued supply of compressed gas causes the gas
to
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flow into pressurization chamber 19 via orifice element 42, which because of
its narrow
internal diameter, d, (FIG.2) has a limiting effect upon the rate at which the
compressed
gas passes through to the pressurization chamber. At the same time, the
pressure
within inlet chamber 16 results in the application of a force of compressed
gas to an
upstream annular end surface 32a of piston body 32, as indicated by arrow 82
(FIG. 2).
In cases where the operation of device 10 commences while piston unit 30 is
positioned
upstream of its first extreme position (FIG. 2), the above-described force
causes a
downstream movement of piston unit 30 relative to pressurization chamber 19,
after
which piston nose 34 is seen to be fully engaged with first ring element 24
and first
damper ring 22 as illustrated in FIG. 2. In this position, a generally
annular,
downstream-facing first shoulder 33a of piston head 33 is seen to abut lugs 26
of first
ring element 24 such that discharge chamber 50 assumes a small, generally
annular
volume between the adjacent surfaces of piston head 33, piston nose 34, and
first ring
element 24.
Referring still to FIG. 2, it is seen that the above-described downstream
traversal of
piston head 33 causes discharge ports 20 to become blocked off from the
compressed
gas contained within the various chambers of impulse device 10. Furthermore,
the entry
of piston nose 34 into first damper ring 22, creates a seal between
pressurization
chamber 19 and discharge chamber 50. In this position, bores 39 provide for
gas
communication between discharge chamber 50 and damper chamber 60 thereby
maintaining equal pressure within those chambers. Since, in a preferred
embodiment of
the invention, there is only a very small difference between the surface areas
of first
piston head shoulder 33a and an upstream-facing second piston head shoulder
33b, the
respective forces applied to these shoulder surfaces are effectively balanced.
Following the full entry of piston nose 34 into first damper ring 22 as
described, the
additional feeding of compressed gas into device 10 creates an increase in
pressure
within pressurization chamber 19. This increase in pressure, causes an
increasing force
to be applied to an end surface 34b of piston nose 34 as indicated by arrow 84
of FIG. 2.
Once the force applied to end surface 34b exceeds the sum of the force applied
to end
surtace 32a and the frictional forces arising between damper rings 22, 36,
piston guide
38, and adjacent surfaces of piston unit 30, the piston unit will begin to
move towards
inlet chamber 16. It is noted that in a preferred embodiment of the invention -
wherein the
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area of end surtace 34b is greater than the area of end surtace 32a - the
pressure in
pressurization chamber 19 required to initiate an upstream traversal of piston
30 towards
inlet chamber 16, may be less than the magnitude of pressure within the inlet
chamber.
As piston unit 30 commences its traversal towards inlet chamber 16, the
resulting
withdrawal of piston nose 34 from first damper ring 22 and first ring element
24, exposes
shoulder 33a of piston head 33 to the gas pressure within pressurization
chamber 19,
such that an additional force is suddenly applied to shoulder 33a as indicated
by arrows
86 of FIG. 3. Thus, the initial upstream movement of piston unit 30, leads to
a sudden
increase in the force applied to the downstream-facing surfaces of the piston
unit,
thereby causing a sudden, rapid movement of the piston unit towards inlet
chamber 16.
Referring now to FIGS. 3 and 4 together, it can be seen that the rapid
upstream traversal
of piston unit 30 as described, causes an instantaneous opening of discharge
ports 20,
which in turn provides for a rapid discharge of pressurized gas from
pressurization
chamber 19 into the surrounding environment. It is this rapid discharge of
pressurized
gas which produces the gas blast depicted by arrows 17 in FIGS. 1 and 7-9.
It may also be seen from FIGS. 3 and 4, that as piston unit 30 continues its
upstream
movement towards inlet chamber 16, the inner dimensions of discharge chamber
50
increase in size thereby providing an enlarged passage for pressurized gas to
flow from
chamber 19 to ports 20. At the same time, damper chamber 60 decreases in size
until it
becomes a small annular volume, formed between piston unit 30 and second ring
element 37 (FIG. 4).
FIGS. 3 and 4 further illustrate that as piston head 33 moves rapidly upstream
so as to
open discharge ports 20, side facing surfaces 33c and 33d of the piston head
abruptly
disconnect cavity 62 from the contracting damper chamber 60. While some of the
gas
contained within damper chamber 60 transfers to chamber 50 via bores 39, the
sudden
blocking-off of cylindrical cavity 62 sharply increases the pressure in damper
chamber 60
thereby creating a compressed gas layer (not seen) between upstream-facing
shoulder
33b of piston head 33 and second ring element 37. This compressed gas layer
functions
to provide a damping effect for the rapidly traversing piston unit 30.
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Furthermore, owing to the decrease in pressure within chamber 19 upon the
release of
pressurized gas via discharge ports 20, and the increased pressure in both
damper
chamber 60 and inlet chamber 16, the respective forces applied to shoulder 33b
of
piston head 33 and end surface 32a of piston body 32, cause piston unit 30 to
move
rapidly back to its initial "pre-firing" position (FIG. 2).
It will be appreciated that in practice, the entire firing cycle described
above is rapidly
repeated by continuing the supply of compressed gas to inlet chamber 16.
Typically, gas
impulse device 10 is capable of firing at an approximate rate of up to 3.0 gas
blasts per
second. Once a desired number of firing cycles has been achieved, operation of
the
apparatus may be terminated by ceasing the supply of compressed gas to inlet
chamber
16. Device 10 may then be removed from the subject well, pipe, or reservoir
for
subsequent use.
Turning now to FIGS. 5A and 5B, there is seen a gas impulse device, referenced
110,
which is constructed and arranged in accordance with an alternative embodiment
of the
invention. Like the previously described embodiment, gas impulse device 110 is
a
self-firing, self-propelling device, and incorporates all the basic features
of gas impulse
device 10 described above. By way of contrast to device 10, however, inlet
chamber 116
is arranged distally to end cap 118, while gas receiving unit 114 is arranged
adjacent to
end cap 118 such that a downstream portion 119b of pressurization chamber 119
is
housed within the end cap. For purposes of clarity, various components of
device 10
which are incorporated into device 110, are depicted in Figs. 5A and 5B with
similar
reference numerals to those of FIGS. 2-4, but with the addition of a prefix
"1".
As illustrated in FIGS. 5A and 5B, inlet chamber 116 is configured to receive
compressed
gas (not shown) from external source 100 and supply conduit 102 (FIG. 1) via
an air
admission tube 190 connected to inlet port 118a. Tube 190 is typically
arranged such
that it axially extends through the device's piston unit, referenced 130. A
cylindrical
sleeve 131, which is preferably formed of a flexible elastic material such as
high density
polyethylene, typically defines the inner surface of piston unit 130.
During operation of the invention, compressed gas received from gas source 100
(FIG.
1) enters inlet chamber 116 via an outlet port 192 of tube 190. Thereafter,
the incoming
gas flows to pressurization chamber 119 in a direction indicated by arrow 180,
via a
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cylindrical gap 194 formed between an outer surface 190a of tube 190, and an
inner
surtace 131 a of piston sleeve 131.
Aside from the above-mentioned constructional and operational differences
between
devices 10 and 110, gas impulse device 110 is operative to produce a gas blast
in a
generally similar manner to gas impulse device 10; i.e. via the successive
rapid
movement of piston unit 130 between a first "pre-firing" position (FIG. 5A)
and a second
"post-firing" position (FIG. 5B). This rapid movement of piston unit 130
successively
closes and opens discharge ports 120 to the release of pressurized gas from
pressurization chamber 119, in generally the same manner as is described
hereinabove
in relation to the corresponding components of gas impulse device 10.
Turning now to FIG. 6, there is seen a gas impulse device, referenced 210,
which is
constructed and arranged in accordance with a further alternative embodiment
of the
invention. In this figure, components similar to those of device 10, are
depicted with
similar reference nwmerals to those of FIGS. 2-4, but with the addition of a
prefix "2".
In contrast to devices 10 and 110 - which as noted above are self-firing
devices - gas
impulse device 210 is constructed and arranged such that the timing of its
firing may be
easily controlled; either by an operator for example, or by a suitable
controlling system
such as a computerized control system. Thus, whilst being configured generally
similar to
device 10, gas impulse device 210 incorporates a controlling valve unit 295
which is
arranged between inlet port 218a and conduit 102 (FIG. 1), and serves to
control the
supply of gas to inlet chamber 216. Furthermore, piston unit 230 has a piston
body end
surface 232a which is larger than piston nose end surface 234b, so that firing
of the
piston unit will not automatically occur upon compressed gas entering
pressurization
chamber 219.
In operating device 210, valve unit 295 is set in a first operative position,
preferably by
means of a solenoid mechanism, so that compressed gas is fed from high
pressure
external gas source 100 (FIG. 1) to inlet chamber 216 via conduit 102 (FIG.
1), thereby
causing a downstream flow of gas as indicated by arrow 280 (FIG. 2). The
continued
supply of gas to inlet chamber 216 is operative to move piston unit 230
downstream into
its "pre-firing" first extreme position as illustrated in FIG. 6, as well as
to cause a flow of
compressed gas into pressurization chamber 219 via passage 240 and orifice
element
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242. These processes are substantially the same as those described above in
relation to
device 10, and thus are not repeated herein.
Upon command of an externally generated electrical signal, valve unit 295 is
moved into
a second operative position, whereby gas communication between conduit 102 and
inlet
chamber 216 is closed off, and gas is released from the inlet chamber into the
environment via one or more holes in the valve unit (not shown). As a result
of the sharp
decrease in pressure within inlet chamber 216, the force applied to piston
nose end
surface 234b, as denoted by arrow 284, will be sufficient to cause an initial
upstream
movement of piston unit 230.
As previously described in relation to device 10, the withdrawal of piston
nose 234 from
damper ring 222 and ring element 224, exposes shoulder 233a of piston head 233
to the
gas pressure within pressurization chamber 219, thereby causing a sudden,
rapid
movement of piston unit 230 towards inlet chamber 216. This rapid upstream
movement
of piston unit 230 towards its second extreme position (i.e. corresponding to
the position
of piston unit 30 in FIG.4), allows for gas communication between
pressurization
chamber 219 and discharge ports 220, so as to generate a gas blast in a manner
substantially similar to that described above in relation to device 10.
Furthermore,
discharge ports 220 are preferably inclined like discharge ports 20 of device
10, so that a
blast produced by device 210 will be operative to cause jet propulsion of the
gas impulse
apparatus.
As noted above, it is a particular feature of the current embodiment, that the
firing of
device 210 may be controlled by an operator or suitable computerized
controlling
program. Thus, where additional firing of the apparatus is desired, further
electrical
signals are sent to valve unit 295 at appropriate time intervals, so as to
repeat the
process described above.
It is also noted that a further feature of gas impulse device 210 is that the
provision of
valve unit 295, allows for a series or "string" of such devices to be
connected together. In
such case, a first device 210 is directly connected to gas source 100 (FIG. 1)
via conduit
102, and additional devices 210 are connected in series, preferably via their
inlet
chambers 216 so as to enable the transfer of gas along the series of devices
210 when
valve units 295 are set in their first operative positions.
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Returning now to a further consideration of the preferred embodiment of the
invention,
FIGS. 1 and 7-9 illustrate and exemplify use of gas impulse device 10 in a
plurality of
environments. Generally speaking, the apparatus of the invention may be
employed in
the rehabilitation and maintenance of water or oil wells, including vertical,
horizontal and
inclined wells, as well as for the cleaning and maintenance of pipelines of
any type.
Similarly, the apparatus of the invention may be used for the cleaning and
maintenance
of tanks, bins, crucibles, channels, reservoirs, and other similar liquid or
dry storage and
transport facilities as previously indicated. Furthermore, the gas impulse
apparatus of the
invention may be used in combination with chemical treatment techniques,
generally
similar to those discussed in further detail in conjunction with FIGS. 13-15.
By way of non-limiting example, FIGS. 1 and 7-9 illustrate device 10 inserted
for use in
the following environments: a water or oil well, referenced 500 (FIG. 1), an
inclined
pipeline, referenced 700 (FIG. 7) such as may be used in industrial production
facilities, a
horizontal sewer pipeline, referenced 800 (FIG. 8), and a reservoir,
referenced 900 (FIG.
9). These drawings also illustrate operation of gas impulse device 10 in a
plurality of
orientations ranging from vertical positioning (FIG. 1 ), inclined positioning
(FIG. 7), and
horizontal positioning (FIGS. 8 and 9).
Referring now to FIGS. 10-12, operation of gas impulse device 10 is described,
in the
context of performing well rehabilitation and maintenance.
As illustrated in FIG. 10-12, device 10 - which is connected to an external
gas supply 100
(FIG. 1) via supply conduit 102 - is lowered into a well, referenced 500. In
the example at
hand, well 500 is a water well encompassed by a porous well screen 505. A
water-permeable gravel pack 510 separates well screen 505 from a surrounding
aquifer,
referenced 515, within which the well 500 is located. Upon the release of
pressurized
gas from gas impulse device 10 in the manner described hereinabove, a high
pressure
gas bubble (not seen) is created. This high pressure gas bubble gives rise to
a powerful
shock wave, which is illustrated as a pressure wave, referenced 520, in FIGS.
10-12. In
the description set forth hereinbelow, the effect of pressure wave 520 is
described in
association with three pressure phases which result from the gas blast
generated by
impulse device 10.
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Referring more specifically to FIG. 10, the first resulting pressure phase of
a gas blast
generated by device 10 is depicted by a portion 520a of wave 520 having a
sharp
positive gradient as seen. Wave portion 520a denotes a sharp increase in
pressure in
the region of well 500 and aquifer 515 surrounding the device's discharge
ports 20. This
increase in pressure has the desirable effect of dislodging deposits from
adjacent
portions of well screen 505, as well as fracturing the deposits due to a
sudden increase
in pressure within the deposit pores. It is noted that the magnitude of
impulse pressure
required to dislodge deposits from the well screen, will be less than the
magnitude of
static pressure necessary to achieve an equivalent result.
As is also indicated in FIG. 10, the above-described high pressure gas bubble
and
associated shock wave generates a strong outward flow of water through screen
505
and gravel pack 510 into aquifer 515, as depicted by arrows 530. In cases
where these
outward flows are generated by impulses emanating from inclined discharge
ports 20 -
such as are included in impulse device 10 (FIGS. 2,3 and 4) - a region of low
pressure,
referenced 532, forms beneath each strong outflow of water, which in turn
gives rise to
an inflow of water from aquifer 515 into well 500 as illustrated by arrows
534. These
outflows of water into aquifer 515, and inflows of water into well 500, are
operative to
further dislodge and wash away deposits and encrustations from screen 505 and
gravel
pack 510 as they travel therethrough.
Referring now to FIG. 11, the second phase resulting from a blast of gas
impulse device
10 is indicated by a portion 520b of wave 520 having a sharp negative gradient
as seen.
During this phase, the high pressure gas bubble created by the firing of
device 10,
enlarges and loses pressure as it travels through the water medium of well
500. Upon
coming into contact with screen 505, the enlarged gas bubble is divided into a
plurality of
pulsating smaller gas bubbles (not shown). Thus the pressure in the treated
zone
decreases such that water from well 500 and aquifer 515 - previously pushed
outwards
by the former high pressured gas bubble - begins to flow back into the well,
thereby
generating a strong backflow of water into well 500. Arrows 536 of FIG. 11
depict a pair
of water streams flowing back into well 500 at these locations.
Referring now to FIG. 12, portions 520c of wave 520 depict the third pressure
phase of a
gas blast produced by gas impulse device 10. In effect, this phase is a
combination of
an alternating series of the first two pressure phases described above, on a
diminishing
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scale, wherein derivative pressure waves resulting from the original shock
waves,
generate further rises and falls in pressure which diminish in magnitude over
time.
These derivative pressure waves also lead to outward and inward flows of water
between well 500 and aquifer 515, as depicted by arrows 540 and 542 of FIG.
12, which
similarly decrease in strength over time.
Considering now the combined pulsating effect of the three pressure phases
described
above in conjunction with FIGS. 10-12, it is seen that the apparatus and
method of the
invention provide an effective means for performing well rehabilitation and
maintenance.
Among the factors contributing to the effective dislodging, and in some cases
destruction, of deposits and encrustations in the processes described above,
are the
effects produced by:
(a) the repeated powerful shock waves generated by gas impulses;
(b) the resulting vibrations of surfaces upon which the deposits or
encrustations
are lodged;
(c) the strong liquid flows through surfaces upon which the deposits or
encrustations are lodged (e.g. liquid flows from well 500 to surrounding
aquifer
515 and back, which pass through screen 505 and gravel pack 510); and
(d) the sudden increase in pressure within the pores of deposits or
encrustations,
thereby resulting in the fracture of those deposits or encrustations.
Furthermore, in apparatus where inclined discharge ports are employed to
produce jet
forces, any buoyant forces emanating from the aforesaid shock waves and liquid
flows,
will be counter-balanced by the jet force generated with each gas blast. In
this way,
undesired jerking of the gas impulse apparatus being used may be eliminated,
thereby
enabling the continuous and accurate treatment of various zones of well 500 as
the
apparatus moves in a downward direction.
Referring now to FIG. 13, operation of gas impulse device 10 for performing
well
rehabilitation is described in accordance with an alternative method of the
invention. As
seen in FIG. 13, impulse device 10 is operated in conjunction with a
cylindrical packer
unit, referenced 370, which is inserted into well 500 above the gas impulse
device. When
operating device 10 as described in conjunction with FIGS. 2-4, packer unit
370 functions
to enhance the propagation of wave energy throughout the area of the well
being
treated, by reducing the upward displacement of water. The inclusion of a
packer unit
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also aids in a more effective dispersion of chemical reagent where chemical
treatment is
combined with gas blasting.
Considering now FIG. 13 in more detail, packer unit 370 is seen to be fitted
between a
supporting pipe 372 and well screen 505. Pipe 372 is in tum supported and
centralized
by means of a stabilizing element, referenced 374, and is covered by a cap,
referenced
376. In order for packer unit 370 to fit tightly between pipe 372 and well
screen 505, the
packer unit preferably has an inner diameter, D,, roughly equal to the outer
diameter, DZ,
of supporting pipe 372, and an outer diameter, D3, roughly equal to the inner
diameter,
D4, of well screen 505.
In accordance with the alternative method of the invention, compressed gas is
fed from
external gas source 100 (FIG. 1) to inlet chamber 16 of device 10, via conduit
102 in
generally the same manner as described above in conjunction with FIGS. 2-4. As
seen in
FIG. 13, conduit 102 extends through cap 376, and for reasons which will be
understood
from the following description, preferably has a smooth outer surface 102a. A
suitable
sealing element 378 is also provided to seal the area of contact between
conduit 102
and cap 376.
As device 10 is fired by the continued supply of gas to inlet chamber 16, the
jet force
created by each firing of the device, will be operative to overcome the
frictional force
which exists between sealing element 378 and outer surface 102a of supply
conduit 102,
thereby causing a downward displacement of device 10 so as to enable the
continuous
treatment of various zones within the well 500. Typically, a manometer
referenced 380 is
used to measure pressure at the top of well 500, and a discharger 382 is
provided for
dissipating excess pressure as required.
In another method of the invention - wherein device 10 and packer unit 370 are
used in
combination with chemical agents employed to enhance the well rehabilitation
process -
a further measurement device, referenced 384, may optionally be provided. By
way of
example, device 384 may take the form of a pH measuring device, where acid is
used in
conjunction with gas impulse device 10 and packer unit 370.
The use of chemical agents in well rehabilitation and similar processes is
well known in
the art, and hence not described herein in great detail. For purposes of
completeness
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however, the present method may be exemplified by the addition of chlorine
directly into
the well, prior to commencing operation of gas impulse device 10, so as to
form a weak
acid. Similarly, the supply of compressed carbon dioxide (C02) from gas source
100
(FIG. 1 ) to inlet chamber 16, will be operative to produce carbonic acid
(HZC03) upon
release of the compressed gas into the well under high pressure during
operation of
device 10.
In yet a further alternative method of the invention, more than one packer 370
may be
used in conjunction with the gas impulse apparatus of the invention. Thus, for
example,
a device 10 may be used in conjunction with two packer units, arranged in a
straddle
arrangement such as is seen in FIG. 14, whereby device 10 is lowered into a
well or
other facility between two packers 370a and 370b, so as to isolate the impulse
pressures
produced upon operation of device 10 to a region of the well defined by the
region
located between the two packer units. In accordance with known methods, packer
units
370a and 370b may be inflatable packers - wherein packer unit 370a is
supported
between pipe 372 and screen 505 as previously seen in conjunction with FIG.
13, and
packer 370b is supported between well screen 505 and an extension pipe 371
which
may be threaded onto an end of device 10 for example. Fig 14 also depicts
inflating
pipes 373a and 373b by means of which packer units 370a and 370b are inflated.
Turning now to FIG. 15, operation of a gas impulse device for performing well
rehabilitation and maintenance is described in accordance with yet a further
embodiment
of the invention wherein the impulse apparatus is permanently or semi-
permanently
installed within a well. Such installation may be useful where it is expedient
to deploy gas
impulse apparatus within a well on a long term basis, thereby obviating the
need for
costly and time-consuming hoisting, pump connection and pump disconnection
procedures.
In accordance with the present embodiment, a self-firing gas impulse device -
or
alternatively, a valve-operated gas impulse device - is installed inside a
water or oil well,
and is typically supported by a pulley system which is operative to guide and
centralize
the gas impulse apparatus. By way of example, FIG. 15 illustrates a self-
firing gas
impulse device 10, installed within a water well 500 below a turbine 1000, and
suspended from a mechanical pulley system, referenced 1010. Connected to
pulley
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system 1010, is a preferably steel operating string, referenced 1015, which
enables
lowering and raising of device 10 as required.
In use, compressed gas is supplied from source 100 (FIG. 1) to inlet chamber
16 of
device 10, via conduit 102, as previously described. After each firing of
impulse device
10, the gas apparatus is lowered either by means of a jet force achieved
through the
provision of inclined discharge ports 20 (FIGS. 2-4), or alternatively, with
the aid of string
1015 such as may be controlled by an operator. After a desired section of well
500 has
been treated, the gas impulse apparatus may be raised by means of steel string
1015
and pulley system 1010, and stored in an appropriate section of the well. A
directional
valve, referenced 103, is typically provided within conduit 102 to prevent a
backflow of
gas towards source 100, in order that a pressure equilibrium is able to be
maintained
between the pressure inside device 10 and the hydrostatic pressure within well
500. This
equilibrium of pressure, together with the final positioning of piston unit 30
in its first
extreme position (FIG. 2) upon conclusion of the firing process, ensures that
water will
not enter device 10 through discharge ports 20 during storage of the device.
It is noted that in accordance with the present embodiment of the invention,
well
treatment by means of a permanently or semi-permanently installed gas impulse
device,
may also be used in conjunction with chemical treatment techniques as
described above,
so as to provide a highly effective treatment process.
Considering now the wider application of the gas impulse apparatus of the
invention, it is
noted that the gas impulse devices described hereinabove may also be used, or
modified for use, in a formation-fracturing process, which in accordance with
a method of
the invention, provides significant advantages over known hydrofracturing
techniques.
In brief, existing hydrofracturing techniques involve the injection of high
pressure water
into rock formations surrounding a water well, so as to increase the size of
existing
cracks and crevices formed therein, and in some cases to create new fractures.
These
techniques are commonly utilized in an effort to improve formation
permeability and well
yield. Generally one or two inflatable packers are used, and in some cases,
propping
agents or "proppants" - such as sand, plastic beads or glass - are used to
keep open the
fractures. It is an important aspect of the hydrofracturing process that only
clean,
disinfected water is injected into the formation crevices, since the use of
contaminated
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water can result in contamination of the well being treated. Thus, it is not
uncommon for
a water well to become contaminated where the high pressure water used in a
hydrofracturing procedure is taken from the surface water of the well.
As an alternative to the hydrofracturing technique described above, the gas
impulse
apparatus of the present invention may be utilized to achieve results similar
to, and
generally better than, common hydrofracturing techniques. In accordance with a
method
of the present invention, a gas impulse device such as device 10, is inserted
into a well
together with one or two packer units 370, and is operated in generally the
same manner
as previously described above in conjunction with FIGS. 13 and 14. The gas
impulses
thereby produced are operative to increase the size of existing fractures
within a
formation surrounding the well, as well as to create new fractures therein. As
with regular
hydrofracturing techniques, proppants for supporting open fractures may be
introduced
into the well prior to operation of the apparatus.
One difference however, between the present method and the methods described
in
conjunction with FIGS. 13 and 14, is that in the present case, pressure is not
dissipated
via discharger 382 during the continued operation of device 10. Thus, the
present
method provides for a continuing increase in pressure within a well, thereby
assisting in
the fracturing process achieved by gas impulse device 10.
Comparing the operation of gas impulse device 10 to that of known
hydrofracturing
apparatus, the present invention provides a number of advantages over common
hydrofracturing techniques. These advantages include: a minimal risk of well
contamination through the use of a gas injection process rather than a water
injection
process; a higher effectiveness of sudden gas impulses produced in accordance
with the
invention, as compared to the slower increasing liquid pressures employed in
hydrofracturing techniques; and, an elimination of the need for separate well-
cleaning
apparatus and hydrofracturing equipment.
It will be appreciated by persons skilled in the art, that the full scope of
the invention and
its applications, extends well beyond the various embodiments of the invention
described
hereinabove. As exemplified above, the gas impulse apparatus of the invention
may be
easily used, or modified for use, in conjunction with a number of well-
cleaning,
rehabilitation and maintenance techniques already existing and known in the
art.
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Similarly the described apparatus may be used to clean and maintain other
liquid or dry
storage and transport facilities in conjunction with related known methods.
For the
purposes of completeness, it is noted that such methods are contemplated as
falling
within the scope of the invention, even though they may not be explicitly
refer-ed to
herein.
It will thus be appreciated by persons skilled in the art, that the present
invention is not
limited by what has been shown and described hereinabove merely by way of
illustrative
example. Rather, the scope of the present invention is limited solely by the
claims which
follow:
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