[0001] The present invention relates to the field of well maintenance, in particular water
well maintenance but is applicable to any type of extraction well, when it is necessary
to intervene in a borehole so as to ensure a minimum production volume or an increment
of production.
[0002] Document
US7360596B2 describes an apparatus and method to regenerate permeability of a well by use of
pressure pulses. However, this method generates particulate matters which pollute
the surrounding liquid, so that pumping/cleaning/filtering operations are necessary
in any case and especially when used in a water well, and all these steps lead to
increase costs and time of such maintenance. In addition, the pulse generator is not
protected against rocks or debris which could fall onto the pulse generator during
use.
[0003] Document
US9057232B2 describes an apparatus and method to regenerate permeability of a well by use of
pressure pulses, with the use of packers to isolate specific portions of the well
screen to regenerate. However, this document does not propose any efficient solution
to treat the pollution nor to protect the pulse generator from being damaged/blocked
into the well.
[0004] The present invention aims to address the above-mentioned drawbacks of the prior
art, and to propose first a well regenerating apparatus and method which provide efficient
regeneration of a well, and which also provide protection to the pulse generator from
being damaged/blocked into the well.
[0005] In this aim, a first aspect of the invention relates to a well regenerating apparatus
comprising:
a treatment device, arranged to regenerate a well screen in a treatment zone of the
well screen,
at least an upper packer and a lower packer arranged to isolate the treatment zone
between the upper packer and the lower packer,
characterized in that the well regenerating apparatus comprises a sliding sleeve,
moveable between:
- a lifting position in which the sliding sleeve is connected to both the upper packer
and the lower packer,
- a treatment position, in which the sliding sleeve is disconnected at least from one
of the upper packer and the lower packer, so as to allow the treatment device to face
directly the well screen.
[0006] The well regenerating apparatus according to the above embodiment comprises two packers
which are expandable to isolate or confine a specific treatment zone of the well.
Typically, the packers are introduced and lifted towards the treatment zone in a retracted
state, and are expanded when located at the desired depth, to form a transverse partition
so as to close the well cross section. In addition, the well regenerating apparatus
comprises a sliding sleeve (typically a tubular part or hollow part) which is attached
to the two packers during the lifting of the packers through the borehole up or down.
In the present disclosure, the lower packer is the one intended to be located at the
deepest position (the closest to the bottom of the well) and the upper packer is the
one intended to be located at the highest position (the closest to the surface of
the well). At this stage, the sliding sleeve is in the lifting position, and provides
mechanical linking between the two packers. Once the packers are deployed to isolate
the treatment zone, the sliding sleeve is at least partially removed from the treatment
zone. In other words, the sliding sleeve is detached from at least one of the packers
and moved at least partially away out of the treatment zone (typically via a sliding
or translation movement). Consequently, the treatment device can directly access or
face the well screen to perform an efficient treatment / regeneration of the well
screen, while being protected in the treatment zone by the two packers from foreign
debris or material coming from the rest of the well. In particular, in the treatment
position, sliding sleeve is disconnected from lower packer, so that the treatment
device may face directly the well screen.
[0007] Typically, when the sliding sleeve is in the treatment position, the two packers
are still secured or linked by wires.
[0008] In other words:
- in the lifting position, the sliding sleeve is fully crossing the treatment zone so
that efficient and robust link is provided between the two packers, but meanwhile
the sliding sleeve constitutes in a given extent a "screen" or "shield" between the
treatment device and at least a part of the well screen to treat,
- in the treatment position, the packers are attached or in close fitment with the well
screen, so that the sliding sleeve in lifting position providing mechanical link is
not necessary anymore and the sliding sleeve can be at least partially removed to
be placed in the treatment position, thereby removing the above mentioned "screen"
or "shield" between the treatment device and at least a part of the well screen to
treat: the treatment device can directly face all the well screen to treat, so that
the treatment will be fully effective. In the treatment position, there is no central
tubing or central element linking the upper and lower packers. Solely cables or wires
are present to link and secure the two packers together.
[0009] According to an embodiment, the well regenerating apparatus comprises at least one
connector arranged to be reversibly set in:
- a connecting state in which the connector provides an attachment between the sliding
sleeve and at least the upper packer,
- a disconnecting state in which the connector releases the attachment between the sliding
sleeve and the upper packer.
Such connector provides the capacity to repeatedly attach / detach the sliding sleeve
and at least the upper packer as many times required to treat several treatment zones
in the well.
[0010] According to an embodiment:
- in the connecting state, the connector blocks at least five degrees of freedom and
preferably six degrees of freedom between the sliding sleeve and at least the upper
packer,
- in the disconnecting state, the connector releases at least one degree of freedom
between the sliding sleeve and at least the upper packer, so that the upper packer
can provide a sliding joint to the sliding sleeve, and preferably a sliding pivot
joint.
In other words, in the connecting state, there is no free relative rotation between
sliding sleeve and at least the upper packer so that a movement of the sliding sleeve
is fully transmitted to the upper packer, and in the disconnecting state, relative
movement such as translation / rotation is authorized between sliding sleeve and upper
packer.
[0011] According to an embodiment, the lower packer is engaged via a secondary connector
with the sliding sleeve when the sliding sleeve is in the lifting position, and the
lower packer is fully disengaged / separated from the sliding sleeve when the sliding
sleeve is in the treatment position.
[0012] According to an embodiment, said connector comprises:
- at least one cam track provided on one of the upper packer or the sliding sleeve,
- at least one protrusion provided on the other of the upper packer or the sliding sleeve
and arranged to travel along the cam track,
and wherein the cam track comprises:
- a locking portion for receiving the protrusion, so as to attach the sliding sleeve
to the upper packer,
- an open end portion for releasing the protrusion, so as to detach the sliding sleeve
from the upper packer.
[0013] Such cam track provides a secured engagement, as it typically requires to the protrusion
an axial movement to leave the locking portion, a rotational movement to reach the
open end portion, and an axial movement to leave the open end portion. As an example,
to get the connector into disconnecting state, lowering 50 mm sliding sleeve, plus
70 degrees to the right of rotation, plus 120 mm of vertical lift must be applied
to allow fully rotation movement and vertical movement inside of treatment window.
[0014] According to an embodiment, the well regenerating apparatus comprises a tubing string
arranged for linking the upper packer to a hoisting or lifting equipment located at
surface, wherein the sliding sleeve is attached to the tubing string or is part of
the tubing string so as to form a distal part of the tubing string. In other words,
the sliding sleeve is the terminal part or deepest part of the tubing string, which
facilitates to impart the movement of the sliding sleeve between the lifting position
and the treatment position and vice versa: an equipment located at the surface of
the well can easily be used to move the sliding sleeve by an action onto the tubing
string. In the present disclosure, surface means the ground level, from where typically
operators organize and control the maintenance, which is often an open air site.
[0015] According to an embodiment, the well regenerating apparatus comprises at least one
air supply connector:
- connected to the sliding sleeve and/or to the tubing string,
- located above the upper packer so as to generate an air lift in the sliding sleeve
and in the tubing string, at least when the sliding sleeve is in the treatment position.
The use of the tubing string terminated by the sliding sleeve to drain the liquid
in the treatment zone with air lift avoids any additional piping between the surface
and the treatment zone. The tubing string, communicating with the sliding sleeve advantageously
provides a direct channel to pump the liquid in the treatment zone, so that the limited
amount of contaminated liquid can be easily and safely pumped up to the surface. This
avoids to fully drain of filter the well. Preferably, the air supply connector is
located on the tubing string, few meters above the sliding sleeve.
[0016] According to an embodiment, the well regenerating apparatus comprises at least one
permanent link such as a metallic cable, attached to both the upper packer and the
lower packer. Such metallic cable or wire provides a safety link which allows to remove
the two packers, even if the sliding sleeve in the treatment position or tubing string
is solely attached or linked to the upper packer.
[0017] According to an embodiment, the well regenerating apparatus comprises an inspection
device, arranged to inspect the well screen in the treatment zone.
[0018] According to an embodiment, the well regenerating apparatus comprises a main lifting
unit, arranged to move downwardly and/or upwardly and/or in rotation the sliding sleeve.
[0019] According to an embodiment, the well regenerating apparatus comprises a secondary
lifting unit, arranged to move downwardly or upwardly the treatment device in the
sliding sleeve. The channel provided by the sliding sleeve and tubing string allows
to lift up or down the treatment device safely through the interior side of the tubing
string / sliding sleeve: there is no risk of impact / blockage even if foreign material
(rocks, damaged parts of the well casing or screen...) fall from above the treatment
zone, as the treatment device is supplied through the internal channel of the sliding
sleeve and tubing string.
[0020] According to an embodiment, the secondary lifting unit is arranged to move downwardly
or upwardly the inspection device in the sliding sleeve. There is no need to remove
the full well regenerating apparatus: as the sliding sleeve is in the treatment position,
the inspection device can easily inspect the well screen before/after treatment and
via the internal space of tubing string and as clear water has (immediately) replaced
the contaminated liquid.
[0021] According to an embodiment, the treatment device is arranged to generate any physical
or chemical treatment to develop/treat the well.
[0022] According to a particular embodiment, the treatment device is arranged to generate
impulse waves or shock waves or pressure waves in the treatment zone.
[0023] According to a particular embodiment, the treatment device is arranged to inject
a treatment fluid into the treatment zone.
[0024] According to an embodiment, the upper packer and/or the lower packer are expandable
or inflatable so as to be reversibly set in:
- a retracted state in which the upper packer and/or the lower packer are freely insertable
into the well,
- an expanded state in which the upper packer and/or the lower packer are in contact
with a well wall, such as the well screen.
[0025] According to an embodiment, the upper packer and/or the lower packer in the retracted
state present an external dimension or diameter within ±30% and preferably ±20% of
the external dimension or diameter of the tubing string.
[0026] According to an embodiment, the upper packer and/or the lower packer comprise a moving
adaptor or sleeve arranged to compensate longitudinal shortening of rubber envelope
during lateral expansion.
[0027] According to an embodiment, the well regenerating apparatus comprises a pressure
control unit, arranged to control and adjust an inflating pressure of an inflation
fluid fed to the upper packer and/or the lower packer, so as to set a maximum allowed
difference of pressure between the treatment zone and the rest of the well, when the
upper packer and/or the lower packer are in the expanded state. The packers are inflated
at a given pressure to ensure isolation of the treatment zone, but when air lift is
generated in the tubing string, it might be necessary to allow liquid income into
the treatment zone to avoid collapsing of the well screen or casing. In this aim,
the pressure in the packers is set so that above a given difference of pressure between
the treatment zone and rest of the well, the packers will become leaky and will allow
liquid to enter the treatment zone.
[0028] According to an additional or alternative embodiment, the well regenerating apparatus
comprises a pressure control unit, arranged to control and adjust a contact pressure
between the well wall and the upper packer and/or the lower packer, so as to set a
maximum allowed difference of pressure between the treatment zone and the rest of
the well, when the upper packer and/or the lower packer are in the expanded state.
[0029] According to an embodiment, the pressure control unit is arranged to be located at
the surface, and a feed hose is provided between the pressure control unit and at
least the upper packer.
[0030] According to an embodiment, the sliding sleeve is made of unitary pieces of tube,
so as to provide a capacity of adjusting a height or length of the treatment zone.
In other words, the unitary pieces of tube are provided with a given length (such
as 1 m) and can be connected/disconnected before lifting in the well so as to define
an adequate treatment zone, in relation to a preliminary inspection for example. In
practice, the length of the window treatment is adjusted taking into account well
characteristics and clogging situation. It can be defined from 1 m to whatever the
distance is considered to proceed with the process.
[0031] Another aspect of the invention relates to a method for regenerating a well, comprising
the steps of:
- introducing in the well at least an upper packer and a lower packer,
- isolating a treatment zone of a well screen between the upper packer and the lower
packer,
- introducing in the well a treatment device arranged to regenerate a well screen in
a treatment zone,
- moving a sliding sleeve between:
- a lifting position in which the sliding sleeve is connected to both the upper packer
and the lower packer,
- a treatment position, in which the sliding sleeve is disconnected at least from one
of the upper packer and the lower packer, so as to allow the treatment device to face
directly the well screen,
wherein the step of introducing and locating the treatment device in the treatment
zone and the step of moving the sliding sleeve can be performed in any order. The
packers are introduced into the well until they reach the treatment zone while the
sliding sleeve is in the lifting position, providing robust and reliable mechanical
link between the two packers. Once the packers are isolating the treatment zone, typically
after expansion, the sliding sleeve can be partially removed out of the treatment
zone to go in the treatment zone, so that the treatment device can be efficiently
used in the treatment zone, free of the sliding sleeve. In particular, in the treatment
position, sliding sleeve is disconnected from lower packer, so that the treatment
device may face directly the well screen.
[0032] According to an embodiment, the treatment device is introduced and located in the
treatment zone by a step of passing the treatment device through the sliding sleeve.
This step of supplying the treatment device through the sliding sleeve provides full
protection against collisions or blockages due to fallen rocks, debris around the
sliding sleeve / tubing string.
[0033] According to an embodiment, the method for regenerating a well comprises, before
the step of moving the sliding sleeve, a step of expanding the upper packer and/or
the lower packer until contact of at least a portion of said upper packer and/or lower
packer with a well wall, such as the well screen.
[0034] According to an embodiment, the method for regenerating a well comprises a step of
regenerating the well screen, by generating with the treatment device impulse waves
or shock waves or pressure waves in the treatment zone, and/or any physical or chemical
process to treat the well screen.
[0035] According to an embodiment, the method for regenerating a well comprises a step of
inspecting the well screen in the treatment zone, by a step of passing an inspection
device through the sliding sleeve.
[0036] According to an embodiment, the method for regenerating a well comprises a step of
pumping liquid in the treatment zone, with a step of generating a pumping flow with
an air lift created in a tubing string connected to the sliding sleeve, so that the
pumping flow passes through the sliding sleeve.
[0037] According to an embodiment, the method for regenerating a well comprises a step to
inject or pump additives and/or chemicals pumped from surface through air supply connector
(and air-lift pipe) and sliding sleeve to increase the regeneration capacity of the
process. So the flow through air supply connector (and air-lift pipe) may be from
the well to the surface or to the treatment zone (aquifer formation) through the air-lift
pipe and screen area. Flow may work in two ways in order to get maximum efficiency
[0038] According to an embodiment, the method for regenerating a well comprises a step of
allowing a leaking flow to pass into the treatment zone from the rest of the well,
by a step of adjusting a contact pressure between the well wall and the upper packer
and/or the lower packer so as to set a maximum allowed difference of pressure between
the treatment zone and the rest of the well.
[0039] According to an embodiment, the method for regenerating a well comprises a step of
injecting chemical and/or additive substance into the treatment zone through the sliding
sleeve. The additional chemical or additive can enhance the treatment process and
is easily provided from the surface through the tubing string and sliding sleeve.
[0040] Other features and advantages of the present invention will appear more clearly from
the following detailed description of particular non-limitative examples of the invention,
illustrated by the appended drawings where:
- figure 1 represents a simplified sketch of a well partially filled of liquid, and
comprising a well screen needing maintenance to be regenerated ;
- figure 2 represents the well of figure 1, to show the installation of a well regenerating
apparatus comprising two packers in a deflated state and being lifted down into the
well ;
- figure 3 represents the well of figure 2, with the well regenerating apparatus with
the packers located in a treatment zone, and being in an inflated state, a sliding
sleeve being coupled to the two packers, in a lifting position ;
- figure 4 represents the well of figure 3, with the well regenerating apparatus having
the sliding sleeve in a treatment position, lifted up compared to figure 3 ;
- figure 5 represents the well of figure 4, with a treatment device of the well regenerating
apparatus positioned in the treatment zone between the two packers ;
- figure 6 represents the well of figure 5, during a step of treatment and/or pumping
liquid from the treatment zone ;
- figure 7 represents a connector arranged to provide a removable or reversible attachment
between the sliding sleeve and at least a packer, in particular an upper packer.
[0041] Figure 1 represents a well drilled in ground 10. Ground 10 is composed of layers
11 and 12, the layer 11 in this example being saturated with liquid L. Liquid L is
typically water but the disclosure is not limited to water. The well comprises a well
screen WS which is porous to allow liquid L to pass from the saturated zones 11 to
the wellbore, for collection and pumping via a pumping tube PT and a pump P. Of course,
figure 1 is very simplified, and the well might comprise cemented area, or gravel
pack...
[0042] During production, sand, fine particles, mud or corrosion might generate clogged
areas CA of the well screen WS and reduce its porosity (capacity to let the liquid
pass through the well screen WS), so that production volumes are affected.
[0043] For this reason it might be required to regenerate the well screen (to remove and
clean the foreign material accumulated in the well screen WS), and the present disclosure
proposes an advantageous method and apparatus for regenerating the well screen WS
of the well.
[0044] Typical methods to remove the foreign material which plugs or blocks the well screen
WS are either mechanical treatments (with generation of pressure waves or shock wave
or pulse waves or any other physical process) or chemical treatments (with injection
in vicinity of the clogged area of a chemical substance (such as acid) arranged to
remove or transform or dissolve the foreign material.
[0045] Figure 2 represents the well of figure 1 where the regular production equipment's
(pump P and pumping tube PT) have been removed to facilitate the regeneration maintenance.
[0046] In this aim, a well regenerating apparatus is introduced in the well with a crane
CA comprising a main lifting unit 61 and attached to a truck, and comprises notably:
- a tubing string 50 made of unitary tubing string tubes 51,
- an upper packer 31,
- a sliding sleeve 20 made of unitary sliding sleeve tubes 22,
- a lower packer 32.
[0047] The equipment is lifted down in the well by assembling progressively the unitary
tubing string tubes 51 from the top portion of the tubing string 50 located at the
surface, so as to position the upper packer 31, sliding sleeve 20 and lower packer
32 at the level of the deepest clogged area CA, as shown figure 2.
[0048] The unitary tubing string tubes 51 can be screwed together, via threaded ends, to
form the tubing string 50, and the unitary sliding sleeve tubes 22 can be screwed
together as well, via threaded ends, to form the sliding sleeve 20, also screwed to
the tubing string 50. Other assembly techniques are possible, such as fast interlock
joints, spring locking joints...
[0049] Preliminary inspection (with a camera) can be made to determine the height of this
deepest clogged area CA, so as to adjust, before introduction of the well regenerating
apparatus into the well, the quantity of unitary sliding sleeve tubes 22, to make
sure that the upper packer 31 is located a bit above the deepest clogged area CA and
the lower packer 32 is located a bit below the deepest clogged area CA.
[0050] The upper packer 31 and lower packer 32 are expandable so as to be set in a deflated
state as shown figure 2, and might be set in an inflated state as will be shown figure
3, 4, 5 and 6. Pneumatic or hydraulic packers, comprising rubber vessels can be typically
used, but one can consider to use any other solution to expand / retract the upper
packer 31 and lower packer 32.
[0051] While the tubing string 50 is lifted down in the wellbore, a packer hose 33 and an
air lift hose 52 are deployed in the well, outside of the tubing string 50 and unitary
tubing string tubes 51.
[0052] The upper packer 31 and lower packer 32 are attached together via metallic cables
37 for securing the packers together, as shown figure 7, and a secondary hose 34 is
joining the upper packer 31 and lower packer 32 for distributing inflating pressure
/ fluid to the lower packer 32. Secondary hose 34 might be directly connected to the
packer hose 33, or via a pressure regulator to set specific pressure in lower packer
32.
[0053] As an example, if the well casing ranges from approx. 205 mm to 305 mm (approx. from
8" to 12"), the internal diameter of the tubing string and/or the sliding sleeve might
be approx. 80 mm (approx. 3").
[0054] As an example, if the well casing ranges from approx. 305 mm to 405 mm (approx. from
12" to 16"), the internal diameter of the tubing string and/or the sliding sleeve
might be approx. 100 mm (approx. 4").
[0055] As an example, if the well casing ranges from approx. 405 mm to 505 mm (approx. from
16" to 20"), the internal diameter of the tubing string and/or the sliding sleeve
might be approx. 120 mm (approx. 5").
[0056] The upper packer 31 and lower packer 32 can also be attached/detached to/from the
sliding sleeve 20, and figure 7 shows an example of reversible connection between
the parts.
[0057] The upper packer 31 is attached to the sliding sleeve via a connector 35 comprising:
- one cam track 35a provided on one of the upper packer 31 or the sliding sleeve 20,
- one protrusion 35b provided on the other of the upper packer 31 or the sliding sleeve
20 and arranged to travel along the cam track 35a,
and wherein the cam track 35a comprises:
- a locking portion where the protrusion 35b is shown on figure 7, so as to attach the
sliding sleeve 20 to the upper packer 31 (for vertical travel / lifting in the wellbore
when the packers are in the retracted or deflated state)
- an open end portion (located on the left side on figure 7) for releasing the protrusion
35b, so as to detach the sliding sleeve 20 from the upper packer 31, typically in
the inflated state.
[0058] In a preferred embodiment, only the upper packer 31 is attached to the sliding sleeve
20 by a connector 35, no connector being provided at the lower packer 32 level.
[0059] However, the lower packer 32 might be attached to the sliding sleeve 20 via another
connector 36 comprising:
- one secondary cam track 36a provided on one of the lower packer 32 or the sliding
sleeve 20,
- one secondary protrusion 36b provided on the other of the lower packer 32 or the sliding
sleeve 20 and arranged to travel in the secondary cam track 36a,
and wherein the secondary cam track 36a comprises an open end portion (located on
the left side on figure 7) for releasing the secondary protrusion 36b, so as to detach
the sliding sleeve 20 from the lower packer 32.
[0060] One should notice that in this configuration on figure 7, as the packers are attached
to the sliding sleeve 20, the length of metallic cables 37 and secondary hose 34 is
longer than the distance between the packers.
[0061] When tubing string 50 is fully deployed and lifted in the wellbore as shown figure
2, the packers might be expanded, as shown figure 3. At this stage, pressure is supplied
to the upper packer 31 and lower packer 32 via the packer hose 33 to the upper packer
31 and secondary hose 34 to the lower packer 32.
[0062] As a consequence of pressure supply, the upper packer 31 and lower packer 32 expand
(their outer diameter increases), until their outer surface contacts the well screen
WS, as shown figure 3. At the end of the expansion step, the deepest clogged area
CA is confined or isolated from the rest of the well. That is to say that liquid L
located between the upper packer 31 and lower packer 32 cannot (or very little) flow
above the upper packer 31 or below the lower packer 32.
[0063] As will be further explained in relation to figure 6, the upper packer 31 and lower
packer 32 are inflated with a given pressure, which is determined in relation to the
depth of the clogged area CA to treat (the height of the liquid column is a parameter
to consider to determine the pressure of inflation of the packers, as will be explained
in relation to figure 6).
[0064] In summary, in the situation of figure 3, the well regenerating apparatus (the upper
packer 31, lower packer 32, sliding sleeve 20) is positioned in the wellbore in regards
to the clogged area CA to treat, and the upper packer 31, lower packer 32 isolate
the liquid in this treatment zone and are mechanically linked together by the sliding
sleeve 20.
[0065] Then, as the upper packer 31 and lower packer 32 are in the expanded or inflated
state, in firm contact with the well screen WS, it is possible and proposed to remove
at least partially the sliding sleeve 20 from the treatment zone.
[0066] This requires to disconnect the sliding sleeve 20 from the packers, and as shown
by the arrows drafted at the level of the truck in figure 3:
- at a step A, the tubing string 50 and sliding sleeve 20 are lifted down or vertically
translated for a small distance downward (so that protrusion 35b (embarked on sliding
sleeve 20) of figure 7 travels to the horizontal and lower portion of cam track 35a),
- at a step B, the tubing string 50 and sliding sleeve 20 are rotated versus the packers
(so that protrusion 35b and secondary protrusion 36b of figure 7 travel to be aligned
respectively with the open end portion of cam track 35a and open end portion of secondary
cam track 36a) so as to unlock the sliding sleeve 20 from the packers.
[0067] Figure 4 shows a step C of removal or upward movement of the sliding sleeve 20, with
a upward arrow drafted at the level of the truck. Indeed, after step B of rotation,
the protrusion 35b and secondary protrusion 36b are aligned with the open end portion
of the cam tracks 35a, 36a, so that vertical translation or lift is possible so as
to remove, as shown, the sliding sleeve 20 from the treatment zone defined between
the packers. In other words the sliding sleeve has been moved from a lifting position
(in which sliding sleeve 20 is located between the upper packer 31 and lower packer
32, see figure 2 and 3) to a treatment position (in which sliding sleeve 20 is partially
of fully removed from the zone between the upper packer 31 and lower packer 32, see
figure 4, 5 and 6).
[0068] Therefore, when the sliding sleeve 20 has been moved away from the lifting position
to the treatment position, one can say that a window has been opened in the treatment
zone.
[0069] As also shown figure 4, a treatment device 41 can be inserted inside the tubing string
50, and lifted down via a treatment line 42 and secondary lifting unit 62 attached
to the crane CA. this operation can be realized before, in parallel or after the disconnection/movement
of the sliding sleeve 20.
[0070] In summary, in the configuration of figure 4, the well regenerating apparatus, after
steps A, B and C of figures 3 and 4, has been set in a configuration where the treatment
zone is free of any central tube, as the sliding sleeve 20 is not anymore located
between the upper packer 31 and lower packer 32. There is not anymore any central
link or tube joining the two packers, which remain in position because of the pressure
applied to the external membrane contacting the well screen WS.
[0071] Figure 5 shows the well regenerating apparatus operated to treat the well screen
WS. Indeed, the secondary lifting unit 62 has lifted the treatment device 41 down
to the treatment zone, i.e. between the upper packer 31 and lower packer 32, via treatment
line 42, and the treatment device 41 can be controlled to treat the clogged area CA.
The treatment will be efficient, as the treatment device 41 directly faces the well
screen WS (there is no wall / no sliding sleeve 20 between the treatment device 41
and the well screen WS)
[0072] One should note that the treatment device 41 is travelling inside the tubing string
50 and sliding sleeve 20, so that it is fully protected during all travel in the wellbore.
Even if debris or rocks or foreign material fall from the well wall, such obstacles
will remain outside the internal channel (tubing string 50) and the treatment device
41 can be safely and reliably positioned in the treatment zone.
[0073] In detail in this example, the treatment device 41 is a pulse generator supplied
in energy via the treatment line 42 to generate pressure or shock or pulse waves in
the liquid L, so that the particles, corrosion, fines, mud will be detached from the
well screen WS. However, other treatment methods can be used, such as chemical treatments
for example. One should note on figure 5 that the deepest clogged area has disappeared,
and that liquid L in the treatment zone is now mixed with particles / foreign material.
[0074] After or during this step of treatment, another advantage provided by the well regenerating
apparatus is that only the liquid located in the treatment zone is polluted by the
material removed from the well screen. Also, it is proposed to pump only this polluted
liquid so as to minimize the operating time and liquid to waste.
[0075] In this aim, as the treatment zone is in direct communication with internal channel
of the tubing string 50 and sliding sleeve 20, an air lift can be advantageously generated
in the tubing string 50 and sliding sleeve 20 with air supply provided by the air
lift hose 52. As shown figure 6 an upward movement / pumping of liquid L located in
the treatment zone is generated in the tubing string 50 and sliding sleeve 20.
[0076] Liquid L is easily supplied from the saturated layer 11, as the well screen WS is
now regenerated. However, if flow from the saturated layer 11 is not sufficient to
compensate the air lift flow, liquid L can be supplied from the rest of the well.
In this aim, it is proposed to accurately set the pressure in the upper packer 31
and/or in the lower packer 32 so as to allow leaks into the treatment zone. Indeed
if the flow from the saturated layer 11 is not sufficient to compensate the air lift
flow, pressure in liquid located in the treatment zone will be lower than the hydrostatic
pressure in liquid located just above the upper packer 31 and/or than the hydrostatic
pressure in liquid located just below the lower packer 32.
[0077] It is proposed to inflate the upper packer 31 and/or the lower packer 32 with a pressure
not exceeding a maximum pressure being calculated to be a bit greater than the hydrostatic
pressure of liquid located just above the upper packer 31 and/or of the liquid located
just below the lower packer 32. In any case, the maximum pressure packer may be inflated
is a function of rubber element manufacturer or type of packer used.
[0078] Maximum depression or maximum differential pressure between the treatment zone located
between the packers in relation with the rest of the well might be a function of the
following well characteristics:
Type of casing (pvc, steel, stainless steel, etc) ;
Type of screen area (louver, wired, bridge, drilled, slotted, etc);
Screen situation. Corrosion, aged, deformed, damaged, etc. ;
Grade of screen clogging ;
Flow of the well ;
[0079] And the differential pressure might be a function of the packer characteristics (rubber
thickness, kind...).
[0080] As a non limitative example, it is proposed to have :

with
- Pup is the inflating pressure supplied to the upper packer 31,
- Ph1 is the hydrostatic pressure of liquid located just above the upper packer 31 (might
be measured, or calculated as a function of the liquid column height and liquid density
or weight),
- k1 is the maximum allowable pressure difference, with for example:
2 bars ≤ k1 ≤ 8 bars with for example a preferred value of 5 bars for a well casing of 205 mm,
in PVC, when all pressures are in bars ;
5 bars ≤ k1 ≤ 15 bars with for example a preferred value of 10 bars for a well casing of 305
mm, in steel, when all pressures are in bars.
[0081] As a non limitative example, it can be also proposed to have :

with
- Plp is the inflating pressure supplied to the lower packer 32,
- Ph2 is the hydrostatic pressure of liquid located just below the lower packer 32 (might
be measured, or calculated as a function of the liquid column height and liquid density
or weight),
- k2 is the maximum allowable pressure difference, with for example:
2 bars ≤ k2 ≤ 8 bars with for example a preferred value of 5 bars for a well casing of 205 mm,
in PVC, when all pressures are in bars ;
5 bars ≤ k2 ≤ 15 bars with for example a preferred value of 10 bars for a well casing of 305
mm, in steel, when all pressures are in bars.
[0082] As an alternative, it might be proposed to set the same inflating pressure in the
two packers (and actual pressure inside packers will be slightly different, the difference
being caused by the altitude difference and liquid column height).
[0083] This embodiment allows liquid L from the rest of the well to enter the treatment
zone in case the saturated layer 11 cannot supply enough liquid to compensate the
air lift pumping. In addition, this protects the well screen or well casing to be
damaged/collapsed by a too high difference of pressure between outer part of casing
and treatment zone.
[0084] The inflating pressure in the packers might be adjusted from the surface during the
maintenance, with for example a pressure control unit operated by a user. Inflating
pressure in packer is regulated from surface in a continuous mode and it may be modified
according to obtained results.
[0085] As shown figure 6, the polluted liquid PL from the treatment zone is pumped to the
surface via the tubing string 50 to be collected in a reservoir 71, and a pumping
device 72 can be used to assist this operation. This operation might be simultaneous
to the treatment operated by the treatment device.
[0086] The treatment device 41 is still located in the treatment zone at this stage, but
it might be independently lifted up if necessary. It is also possible to take advantage
of the secondary lifting unit 62 to lift an inspection device (such as a camera) to
check if the well screen WS in the treatment zone is in the expected state / shape,
when the liquid L has be renewed and is clear enough for visual / camera inspection.
[0087] Once the deepest clogged area is treated, the well screen WS is regenerated and the
well regenerating apparatus can be removed to treat another clogged area. In summary:
- the air lift is stopped, reservoir 71 is disconnected from the tubing string 50,
- the treatment device 41 and/or inspection device are removed from the tubing string
50,
- the sliding sleeve 20 is moved from the treatment position of figures 4, 5, 6 into
the lifting position of figure 2, 3 (via the tubing string 50 and steps C, B, A),
- the packers are deflated so as to be set back in the deflated / retracted state,
- the tubing string and well regenerating apparatus are lifted up to the second clogged
area CA, via the main lifting unit 61 (and by removing unitary tubing string tubes
51).
[0088] One should note the following:
- in case the coupling between the lower packer 32 and sliding sleeve 20 is difficult
/ impossible, the metallic wires 37 allow to still lift up the system,
- in case the coupling between the upper packer 31 and sliding sleeve 20 is difficult
/ impossible, or if the sliding sleeve is in the treatment position, one can implement
a stopper (a stop collar or shoulder on the sliding sleeve for example) in the bottom
part of the sliding sleeve to abut the upper packer 31 and still lift up the system,
- the quantity of unitary sliding sleeve tubes 22 can be adjusted between two treatments,
- a production test can be implemented via the air lift (or regular pumping equipment)
to check the capacity of production volume of a given part of the well screen, after
treatment and before moving back the sliding sleeve 20 in the lifting position.
[0089] In summary, the well regenerating apparatus provides the below advantages:
- the height of the treatment zone is easily tunable before lifting all the system down
into the well, with the unitary sliding sleeve tubes 22,
- the treatment device 41 faces directly the well screen WS to treat when the sliding
sleeve 20 has been moved into the treatment position (out of the treatment zone),
- the treatment device 41 is safely and independently travelled from surface to the
treatment zone via the internal channel of the tubing string 50 / sliding sleeve 20,
and vice versa,
- the liquid L of the treatment zone contaminated during / after treatment is not spread
into the rest of the well but is safely contained in the treatment zone thanks to
the upper packer 31 and lower packer 32 inflated and in contact with the well screen,
- the liquid L of the treatment zone contaminated during / after treatment is safely
and easily pumped to the surface via the air lift generated into tubing string 50
/ sliding sleeve 20,
- the well screen is protected from pressure damage even if the saturated layer 11 cannot
supply liquid to compensate the air lift, thanks to the pressure management of the
packers,
- the secondary lifting unit can easily lift the treatment device and/or an inspection
device to fully treat the treatment zone.
[0090] It is of course understood that obvious improvements and/or modifications for one
skilled in the art may be implemented, still being under the scope of the invention.
1. A well regenerating apparatus comprising:
a treatment device (41), arranged to regenerate a well screen (WS) in a treatment
zone of the well screen (WS),
at least an upper packer (31) and a lower packer (32) arranged to isolate the treatment
zone between the upper packer (31) and the lower packer (32),
characterized in that the well regenerating apparatus comprises a sliding sleeve (20), moveable between:
- a lifting position in which the sliding sleeve (20) is connected to both the upper
packer (31) and the lower packer (32),
- a treatment position, in which the sliding sleeve (20) is disconnected at least
from one of the upper packer (31) and the lower packer (32), so as to allow the treatment
device (41) to face directly the well screen (WS).
2. The well regenerating apparatus according to the preceding claim, comprising at least
one connector (35) arranged to be reversibly set in:
- a connecting state in which the connector (35) provides an attachment between the
sliding sleeve (20) and at least the upper packer (31),
- a disconnecting state in which the connector (35) releases the attachment between
the sliding sleeve (20) and the upper packer (31).
3. The well regenerating apparatus according to the preceding claim, wherein said connector
(35) comprises:
- at least one cam track (35a) provided on one of the upper packer (31) or the sliding
sleeve (20),
- at least one protrusion (35b) provided on the other of the upper packer (31) or
the sliding sleeve (20) and arranged to travel along the cam track (35a), and wherein
the cam track (35a) comprises:
- a locking portion for receiving the protrusion (35b), so as to attach the sliding
sleeve (20) to the upper packer (31),
- an open end portion for releasing the protrusion (35b), so as to detach the sliding
sleeve (20) from the upper packer (31)
4. The well regenerating apparatus according to any one of the preceding claims, comprising
a tubing string (50) arranged for linking the upper packer (31) to a hoisting or lifting
equipment located at surface, wherein the sliding sleeve (20) is attached to the tubing
string (50) or is part of the tubing string (50) so as to form a distal part of the
tubing string (50).
5. The well regenerating apparatus according to the preceding claim, comprising at least
one air supply connector:
- connected to the sliding sleeve (20) and/or to the tubing string (50),
- located above the upper packer (31) so as to generate an air lift in the sliding
sleeve (20) and/or in the tubing string (50), at least when the sliding sleeve (20)
is in the treatment position.
6. The well regenerating apparatus according to any one of the preceding claims, comprising
at least one permanent link, such as a metallic cable (37), attached to both the upper
packer (31) and the lower packer (32).
7. The well regenerating apparatus according to any one of the preceding claims, comprising
a main lifting unit (61), arranged to move downwardly and/or upwardly and/or in rotation
the sliding sleeve (20).
8. The well regenerating apparatus according to any one of the preceding claims, comprising
a secondary lifting unit (62), arranged to move downwardly or upwardly the treatment
device (41) in the sliding sleeve (20).
9. The well regenerating apparatus according to any one of the preceding claims, wherein
the treatment device (41) is arranged to generate a physical or chemical process such
as impulse waves or shock waves or pressure waves in the treatment zone.
10. The well regenerating apparatus according to any one of the preceding claims, wherein
the upper packer (31) and/or the lower packer (32) are expandable or inflatable so
as to be reversibly set in:
- a retracted state in which the upper packer (31) and/or the lower packer (32) are
freely insertable into the well,
- an expanded state in which the upper packer (31) and/or the lower packer (32) are
in contact with a well wall, such as the well screen (WS).
11. The well regenerating apparatus according to the preceding claim, comprising a pressure
control unit, arranged to control and adjust an inflating pressure of an inflation
fluid fed to the upper packer (31) and/or the lower packer (32), so as to set a maximum
allowed difference of pressure between the treatment zone and the rest of the well,
when the upper packer (31) and/or the lower packer (32) are in the expanded state.
12. The well regenerating apparatus according to any one of the preceding claims, wherein
the sliding sleeve (20) is made of unitary pieces of tube (22), so as to provide a
capacity of adjusting a height or length of the treatment zone.
13. Method for regenerating a well, comprising the steps of:
- introducing into the well at least an upper packer (31) and a lower packer (32),
- isolating a treatment zone of a well screen (WS) between the upper packer (31) and
the lower packer (32),
- introducing into the well a treatment device (41) arranged to regenerate a well
screen (WS) in a treatment zone,
- moving a sliding sleeve (20) between:
- a lifting position in which the sliding sleeve (20) is connected to both the upper
packer (31) and the lower packer (32),
- a treatment position, in which the sliding sleeve (20) is disconnected at least
from one of the upper packer (31) and the lower packer (32), so as to allow the treatment
device (41) to face directly the well screen (WS),
wherein the step of introducing and locating the treatment device (41) in the treatment
zone and the step of moving the sliding sleeve (20) can be performed in any order.
14. Method for regenerating a well according to claim 13, comprising, before the step
of moving the sliding sleeve (20), a step of expanding the upper packer (31) and/or
the lower packer (32) until contact of at least a portion of said upper packer (31)
and/or lower packer (32) with a well wall, such as the well screen (WS).
15. Method for regenerating a well according to any one of claim 13 to 14, comprising
a step of regenerating the well screen (WS), by generating with the treatment device
(41) a physical or chemical process such as impulse waves or shock waves or pressure
waves in the treatment zone.
16. Method for regenerating a well according to any one of claim 13 to 15, comprising
a step of inspecting the well screen (WS) in the treatment zone, by a step of passing
an inspection device through the sliding sleeve (20).
17. Method for regenerating a well according to any one of claim 13 to 16, comprising
a step of pumping liquid in the treatment zone, with a step of generating a pumping
flow with an air lift created in a tubing string (50) connected to the sliding sleeve
(20) so that the pumping flow passes through the sliding sleeve (20).
18. Method for regenerating a well according to the preceding claim, comprising a step
of allowing a leaking flow to pass into the treatment zone from the rest of the well,
by a step of adjusting a contact pressure between the well wall and the upper packer
(31) and/or the lower packer (32) so as to set a maximum allowed difference of pressure
between the treatment zone and the rest of the well.
19. Method for regenerating a well according to any one of claim 13 to 18, comprising
a step of injecting chemical and/or additive substance into the treatment zone through
the sliding sleeve.