U.S. patent application number 12/298934 was filed with the patent office on 2009-08-20 for method and tool for unblocking a control line.
This patent application is currently assigned to WEATHERFORD FRANCE SAS. Invention is credited to Jean-Luc Jacob.
Application Number | 20090205831 12/298934 |
Document ID | / |
Family ID | 37603794 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090205831 |
Kind Code |
A1 |
Jacob; Jean-Luc |
August 20, 2009 |
METHOD AND TOOL FOR UNBLOCKING A CONTROL LINE
Abstract
A method to release a control line for a safety valve removably
disposed in a nipple (9) of a wellbore production tubing, comprises
the steps of: --removing the safety valve from the nipple;
--setting into the nipple a sealing tool (41) which sealingly
connects the control line (10) and a mini tubing (42) running down
into the production tubing; --increasing the pressure of a fluid
into the mini tubing to cause fluid to flow into the control line
through the sealing tool.
Inventors: |
Jacob; Jean-Luc; (Poey de
Lescar, FR) |
Correspondence
Address: |
WONG, CABELLO, LUTSCH, RUTHERFORD & BRUCCULERI,;L.L.P.
20333 SH 249 6th Floor
HOUSTON
TX
77070
US
|
Assignee: |
WEATHERFORD FRANCE SAS
Belloq
FR
|
Family ID: |
37603794 |
Appl. No.: |
12/298934 |
Filed: |
April 13, 2007 |
PCT Filed: |
April 13, 2007 |
PCT NO: |
PCT/IB2007/051339 |
371 Date: |
February 10, 2009 |
Current U.S.
Class: |
166/311 ;
166/192; 166/67 |
Current CPC
Class: |
E21B 34/105 20130101;
E21B 34/10 20130101 |
Class at
Publication: |
166/311 ;
166/192; 166/67 |
International
Class: |
E21B 37/00 20060101
E21B037/00; E21B 33/12 20060101 E21B033/12; E21B 23/04 20060101
E21B023/04; E21B 41/00 20060101 E21B041/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 5, 2006 |
FR |
0651641 |
Claims
1. A method to release a control line (10) for a safety valve (8)
removably disposed in a nipple (9) of a wellbore production tubing
(3), comprising the steps of: removing the safety valve from the
nipple; setting into the nipple a sealing tool (41) which sealingly
connects the control line (10) and a mini tubing (42) running down
into the production tubing; increasing the pressure of a fluid into
the mini tubing to cause fluid to flow into the control line
through the sealing tool.
2. The method according to claim 1, further comprising the step of
increasing the pressure of a fluid alternatively into the mini
tubing and into the control line.
3. The method according to claim 1, further comprising the step of
increasing the pressure of a fluid intermittently into the mini
tubing.
4. The method according to claim 1, further comprising the step of
increasing the pressure of a fluid intermittently into the control
line.
5. The method according to any of claims 1 to 4, comprising the
step of moving a piston (48) into the sealing tool to provide a
multiplicator effect on the pressure increasing.
6. The method according any of claims 1 to 5, wherein the fluid is
a solvent liquid.
7. The method according any of claims 1 to 5, wherein the fluid is
an incompressible liquid.
8. The method according to claim 6, wherein the fluid is diesel
oil.
9. A wellbore installation (1) comprising a production tubing (3)
with a nipple (9) for receiving a working device (40),
characterized in that the working device comprises a sealing tool
(41) having a sealed chamber (45,56,52,54,51) defined with an
inside cylindrical wall of the nipple (9) and two seals (46) spaced
apart from each other according to an axial direction (A) of the
production tubing; and a mini tubing (42) running down said
production tubing (3) and connected to said sealed chamber for
flowing a fluid against the inside cylindrical wall of the nipple
(9).
10. The wellbore installation of claim 9, wherein said nipple is
fitted for receiving a safety valve (8) actuated by a control line
(10) issuing into said sealed chamber.
11. The wellbore installation of claim 9, wherein the inside
cylindrical wall of the nipple against which flows the fluid
comprises a weak area.
12. The wellbore installation according to any of claims 9 to 11,
wherein the sealing tool further comprises a pressure intensifier
means.
13. The wellbore installation according to any of claims 9 to 11,
wherein the sealing tool comprises a movable piston (48).
14. The wellbore installation according to claim 13, wherein the
piston comprises two end sides (49,50) having different surface
areas.
15. The wellbore installation according to claim 14, wherein the
piston is bored with a check valve (55) disposed in a bore
(54).
16. The wellbore installation according to claim 15, wherein the
bore (54) in the piston (48) is obstructed with a ball (57) dropped
into the mini tubing (42).
17. The wellbore installation according to claim 16, wherein a dart
(60) running down into the mini tubing holds the ball out of the
bore.
18. The wellbore installation according to any of claims 9 to 17,
wherein the two seals (46) are O-ring packings arranged in the
sealing tool (41) and bearing against the inside cylindrical wall
of the nipple (9).
19. The wellbore installation according to any of claims 9 to 18,
wherein the mini tubing is connected to a pressure-supplying pump.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method to release, or
unblock, a control line of a safety valve, more particularly of a
subsurface safety valve configured to control fluid flow through a
production tubing string as well as a well bore installation
comprising a working device and arranged to implement such a
method.
[0003] 2. Description of the Related Art
[0004] Surface-controlled, subsurface safety valves (SCSSVs) are
commonly used to shut in oil and gas wells. Such SCSSVs are
typically fitted into a production tubing in a hydrocarbon
producing well, and operates to block the flow of formation fluid
upwardly through the production tubing should a failure or
hazardous condition occurs at the well surface.
[0005] Typically SCSSVs are configured as rigidly connected to the
production tubing (tubing retrievable), or may be installed and
retrieved by wireline, without disturbing the production tubing
(wireline retrievable). During normal production, the subsurface
safety valve may be maintained in an open position by the
application of hydraulic fluid pressure transmitted to an actuating
mechanism. The hydraulic pressure is commonly provided by clean oil
supplied from a surface fluid reservoir to the SCSSV through a
control line. A pump at the surface, controlled by a control panel,
delivers regulated hydraulic fluid under pressure. The control line
resides within the annular region between the production tubing and
a surrounding well casing. The SCSSV provides automatic shutoff of
production flow in response to one or more well safety conditions
that can be sensed and/or indicated at the surface. Examples of
such conditions include a fire on the platform, damage to the well
head, for example resulting from a truck or a boat colliding with
the well head, a high/low flow line pressure condition, a high/low
flow line temperature condition, and operator override. These and
other conditions produce a loss of hydraulic pressure in the
control line, thereby causing a flapper to close so as to block the
flow of production fluids up the tubing. In other words, where a
failure or hazardous condition occurs at the well surface, fluid
communication between the surface reservoir and the control line is
broken. This, in turn, interrupts the application of hydraulic
pressure against the actuating mechanism. The actuating mechanism
recedes within the valve, allowing the flapper to close against an
annular seat.
[0006] Most surface controlled subsurface safety valves are
"normally closed" valves, i.e., the valve is in its closed position
when the hydraulic pressure is not present. The hydraulic pressure
typically works against a powerful spring and/or gas charge acting
through a piston. In many commercially available valve systems, the
spring power is overcome by hydraulic pressure acting against the
piston, producing longitudinal movement of the piston. The piston,
in turn, acts against an elongated "flow tube". In this manner, the
actuating mechanism is a hydraulically actuated and longitudinally
movable piston that acts against the flow tube to move it within
the tubing and across the flapper.
[0007] During well production, the flapper is maintained in the
open position by force of the piston acting against the flow tube
downhole. Hydraulic fluid is pumped into a variable volume pressure
chamber (or cylinder) and acts against a seal area on the piston.
The piston, in turn, acts against the flow tube to selectively open
the flapper member in the valve. Any loss of hydraulic pressure in
the control line causes the piston and actuated flow tube to
retract. This in turn causes the flapper to rotate about a hinge
pin to its valve closed position, for example by means of a torsion
spring, and in response to upwardly flowing formation fluid. In
this manner, the SCSSV is able to provide a shutoff of production
flow within the tubing as the hydraulic pressure in the control
line is released.
[0008] During work into the well or well maintenance, for example
to clean the production tubing or to take measurements, the SCSSV,
which is generally removable, is removed from the production tubing
by wireline in order to clear the way. The control line, which
usually runs along the outside of the production tubing, has an
open aperture in the production tubing. Dust, grease or sand can
inopportunely enter and block the control line, i.e. creating a
plug or increasing significantly the resistance to movement of the
fluid in the control line. Consequently, once the SCSSV is
reinstalled, the regulated pressure delivered at the surface by the
pump is not transmitted to the actuating mechanism and the flapper
of the valve remains in the closed position.
[0009] A procedure consisting in installing an isolation sleeve
facing the control line aperture before working into the well when
the safety valve is removed prevents the contamination and the
obstruction of the control line, but such procedure is rarely used
since it is time consuming.
[0010] To prevent the control line from getting blocked, filtering
systems are used to limit the contamination of the control line but
do not show satisfactory results.
[0011] The only known method to clear the blocked fluid from the
control line consists in creating an overpressure in the control
line with the pump at the surface to expel the blockage. The
efficiency of such a method is very limited and numerous control
lines remain blocked.
[0012] The control line cannot be replaced because it is typically
cemented into the annulus between the production tubing and the
surrounding casing.
[0013] The use of a safety valve is compulsory in oil and gas
wells. Therefore wells with blocked control line are: [0014]
closed, i.e. the production is stopped and an other well must be
dug resulting in huge expenses; [0015] operated without a safety
valve, which is very unsafe; [0016] in flowing using a velocity
valve as a safety valve, such velocity valves having the drawbacks
of being very long and difficult to adjust, and of choking the well
of about 60% its diameter.
[0017] Therefore, a need exists for an improved method and a device
to release a control line of a SCSSV.
SUMMARY OF THE INVENTION
[0018] The present invention is directed to a method to release a
control line for a safety valve removably disposed in a nipple of a
wellbore production tubing, comprising the steps of: [0019]
removing the safety valve from the nipple; [0020] setting into the
nipple a sealing tool which sealingly connects the control line and
a mini tubing running down into the production tubing; [0021]
increasing the pressure of a fluid into the mini tubing to cause
fluid to flow into the control line through the sealing tool.
[0022] Such a method permits pushing the blockage upwardly through
the control line, i.e. reversing the fluid pressure applied to the
control line that would usually maintain the valve in its open
position, and then releasing the pressure applied to the control
line to move, disintegrate, and eject the blockage from the control
line.
[0023] In other embodiments, the method also includes the steps of:
[0024] increasing the pressure of a fluid alternatively into the
mini tubing and into the control line, thereby creating an
oscillation effect on the blockage to ease its removal; [0025]
increasing the pressure of a fluid intermittently into the mini
tubing and/or into the control line; [0026] moving a piston into
the sealing tool to provide a multiplicator effect on the pressure
increasing, so as to exert on the blockage a pressure higher than
the pressure that can be held in a mini tubing.
[0027] The fluid used to push the blockage is more particularly a
incompressible solvent liquid, such as diesel oil, in order to
cause an additional cleaning and disaggregating effect on the
blockage.
[0028] According to the invention, a wellbore installation
comprising a production tubing with a nipple for receiving a
working device is also provided. The working device comprises:
[0029] a sealing tool having a sealed chamber defined with an
inside cylindrical wall of the nipple and at least two seals spaced
apart from each other according to an axial direction of the
production tubing; and [0030] a mini tubing running down said
production tubing and connected to said sealed chamber for flowing
a fluid against the inside cylindrical wall of the nipple.
[0031] Said nipple is preferably fitted for receiving a safety
valve actuated by a control line issuing into said sealed chamber
so that the fluid flowing against the inside cylindrical wall of
the nipple penetrates the control line and permits a releasing
operation of the control line. But such an installation can also be
used to cause perforations in the cylindrical wall of the nipple if
the inside cylindrical wall of the nipple against which flows the
fluid comprises for instance a weak area.
[0032] Additionally the sealing tool may further comprise a
pressure intensifier with a movable piston having two end sides of
different surface areas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] So that the manner in which the above recited features of
the present invention are attained and can be understood in detail,
a more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0034] FIG. 1 is a cross-sectional view of a wellbore illustrating
a production tubing having a subsurface safety valve controlled
through a control line.
[0035] FIG. 2 is a cross-sectional view of a subsurface safety
valve in its open position.
[0036] FIG. 3 is a cross-sectional view of the subsurface safety
valve of FIG. 2 in its closed position.
[0037] FIGS. 4, 5, 6, 7, and 8 are cross-sectional views of a same
device to release a control line according to the invention at
various moments during the carrying out of the method in accordance
with the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] A detailed description will now be provided. Various terms
as used herein are defined below. To the extent a term used in a
claim is not defined below, it should be given the broadest
definition persons in the pertinent art have given that term, as
reflected in printed publications and issued patents. In the
description that follows, like parts are marked throughout the
specification and drawings with the same reference numerals. The
drawings may be, but are not necessarily, to scale and the
proportions of certain parts have been exaggerated to better
illustrate details and features of the invention. One of normal
skill in the art of subsurface safety valves will appreciate that
the various embodiments of the invention can and may be used in all
types of subsurface safety valves, including but not limited to
tubing retrievable, wireline retrievable, injection valves, or
subsurface controlled valves.
[0039] For ease of explanation, the invention will be described
generally in relation to a cased vertical wellbore. It is to be
understood, however, that the invention may be employed in an open
wellbore, a horizontal wellbore, or a lateral wellbore without
departing from principles of the present invention. Furthermore, a
land well is shown for the purpose of illustration; however, it is
understood that the invention may also be employed in offshore
wells or extended reach wells that are drilled on land but
completed below an ocean or lake shelf.
[0040] FIG. 1 presents a cross-sectional view of an illustrative
land wellbore installation 1. The wellbore installation 1 comprises
a casing string 2 completed with a string of production tubing 3
therein. The production tubing 3 defines an elongated bore through
which fluids may be pumped upward as indicated by the arrow 4.
[0041] FIG. 1 further illustrates a wellhead 5, a master valve 6, a
flow line 7, a subsurface safety valve assembly 8 mounted in a
nipple 9 and connected to a control line 10, a plug seat 11 and a
perforated screen 12. In operation, opening the master valve 6
allows pressurized hydrocarbons residing in a producing formation
13 to flow through the perforated screen 12 and into the production
tubing 3. Cement seals an annulus between the casing and the
production tubing in order to direct the flow of hydrocarbons.
Hydrocarbons (illustrated by arrow 4) flow into the production
tubing 3 through the open subsurface safety valve assembly 8,
through the wellhead 5, and out into the flow line 7. The
subsurface safety valve assembly 8, also noted safety valve 8
hereinafter, is also used for selectively controlling the flow in
the production tubing 3. The safety valve 8 may be moved between an
open position and closed position by providing or not hydraulic
pressure, as indicated by the double arrow 14. A pump 15 actuated
by a control panel 16 supply the hydraulic pressure to the safety
valve through the control line 10. Hydraulic pressure holds a
flapper closure mechanism within the safety valve, described in
greater detail below in connection with FIGS. 2 and 3, in the open
position.
[0042] During the production operation, the valve remains in the
open position. However, the flow of hydrocarbons may be stopped at
any time during the production operation by switching the safety
valve from the open position to the closed position. This may be
accomplished either intentionally by having the operator remove the
hydraulic pressure applied through the control line, or through a
catastrophic event at the surface such as an act of terrorism.
[0043] FIG. 2 presents a cross sectional view illustrating the
safety valve 8 in an open position. A bore 20 in the valve 8 allows
fluids such as hydrocarbons to flow up through the valve 8 during a
normal operation. The valve includes a top and bottom sub (not
shown), which ones are threadedly connected inside the nipple 9
mounted in series with the production tubing 3. The safety valve 8
is consequently removable. The valve includes a chamber 21 in fluid
communication with the hydraulic control line 10. The hydraulic
control line carries fluid such as clean oil from a surface control
reservoir down to the chamber 21.
[0044] In the arrangement of FIG. 2, the chamber 21 is configured
to receive a piston 22, the piston 22 typically defines a small
diameter piston which is movable within the chamber 21 between an
upper and a lower position. Movement of the piston 22 responds to
hydraulic pressure from the surface, i.e. from the control line 10.
Alternatively, the piston may be a large concentric piston, which
is pressure actuated.
[0045] As illustrated in FIG. 2, the valve may also include a
biasing member 23. Preferably, the biasing member defines a spring
23. The spring resides in the tubular body below the piston. A
lower end of the spring 23 abuts a spacer bearing 24 and an upper
end of the spring abuts a lower end 25 of the piston. The spring
operates in compression to bias the piston upward. Movement of the
piston from the upper position to the lower position, provided by
supplying hydraulic pressure into the chamber, compresses the
spring against the spacer bearing.
[0046] Disposed below the spacer bearing 24 is a flapper 26. The
flapper 26 is rotationally attached by a pin 27 to a flapper mount.
The flapper pivots between an open position and a closed position
in response to movement of a flow tube 28. A shoulder 29 is
provided for a connection between the piston 22 and the flow tube
28. In the open position, a fluid pathway is created through the
bore 20, thereby allowing the flow of hydrocarbons through the
valve 8. Conversely, in the closed position, the flapper blocks the
fluid pathway through the bore, thereby preventing the flow of
hydrocarbons through the valve, as showed in FIG. 3.
[0047] Further illustrated in FIG. 2, a lower portion of the flow
tube 28 is disposed adjacent the flapper 26. The flow tube 28 is
movable longitudinally along the bore 20 of the valve 8 in response
to axial movement of the piston 22. Axial movement of the flow
tube, in turn causes the flapper to pivot between its open and
closed positions.
[0048] In the open position, as illustrated in FIG. 2, the flow
tube blocks the movement of the flapper, thereby causing the
flapper to be maintained in the open position. In the closed
position, as illustrated in FIG. 3, the flow tube frees the flapper
thereby allowing the flapper to rotate on the pin and to move to
the closed position, i.e. the flapper seals off the bore.
[0049] Typically, the flow tube remains in the open position
throughout the completion operation and later production. However,
if the flapper is closed during the production operation, it may be
reopened by moving the flow tube back to the open position.
Generally, the flow tube moves to the open position as the piston
moves to the lower position and compresses the biasing member
against the spacer bearing. Typically, fluid from the control line
enters the chamber, thereby creating a hydraulic pressure on the
piston. As more fluid enters the chamber, the hydraulic pressure
continues to increase until the hydraulic pressure on the upper end
of the piston becomes greater than the biasing force on the lower
end of the piston. At that point, the hydraulic pressure in the
chamber causes the piston to move to the lower position. Since the
flow tube is operatively attached to the piston, the movement of
the piston causes longitudinal movement of the flow tube in front
of the flapper.
[0050] During closure of the valve, no hydraulic pressure is
supplied through the control line and fluid in the chamber exits
into the control line, thereby decreasing the hydraulic pressure on
the piston. As more fluid exits the chamber, the hydraulic pressure
continues to decrease until the hydraulic pressure on the upper end
of the piston becomes less than the opposite force on the lower end
of the piston. At that point, the force created by the spring
causes the piston to move to the upper position. Since the flow
tube is operatively attached to the piston, the movement of the
piston causes the movement of flow tube that liberates the flapper.
The flapper is then forced into closed position by a spring 30 and
by the overpressure generated by hydrocarbon.
[0051] Consequently, the opening and the closure of the subsurface
safety valve is controlled via the control line 10. The control
line is more particularly a conduit that can be filled with fluid,
more especially with clean oil, this fluid acting as a means to
transmit hydraulic pressure generated and regulated at the surface
up to the chamber 21 of the safety valve 8. The control line 10
extends from the hydraulic pressure supplying pump 15 controlled by
a control panel 16 up to the nipple 9 in which is arranged the
safety valve 8, through the area between the well casing 2 and the
production tubing 3. The control line comprises a surface end with
a surface aperture connected to the pump 15 and a subsurface end
with a subsurface aperture 31. The subsurface aperture 31 of the
control line 10 issues in the nipple 9 proximate the inside
cylindrical wall of the nipple. When the safety valve 8, described
with reference to FIGS. 2 and 3, is secured inside the nipple 10,
the subsurface aperture 31 of the control line faces the aperture
of the chamber.
[0052] If the flow of oil into the control line is interrupted,
because a plug or a blockage occurs in the control line, no
hydraulic pressure can be supplied to the piston and the safety
valve remains closed. If this happens, the blockage can be removed
from the control line using the method in accordance with the
invention.
[0053] The idea on which the invention is based consists in
releasing the jamming blockage by acting on it, through the
subsurface aperture.
[0054] For that, the safety valve is removed from the production
tubing and the production tubing is closed with a plug set in the
plug seat 11 disposed below the nipple 9 where the blocked control
line 10 issues. A control line releasing device is then introduced
into the production tubing 3 and secured into the nipple 9 in which
the safety valve is to be set and therefore in which the control
line issues.
[0055] FIGS. 4 to 8 illustrate the releasing device 40 in
accordance with the invention secured inside the nipple 9.
[0056] The releasing device 40 comprises a sealing tool 41 and a
mini tubing 42 sealingly arranged on top of the sealing tool 41.
The sealing tool is particularly run down the production tubing by
snubbing or coil tubing. Snubbing consists in assembling the mini
tubing with mini tubing parts, of about 10 meters length, as the
sealing tool is run down the production tubing, with the use of a
snubbing machine. The mini tubing parts are sealingly connected to
form the mini tubing. Coil tubing consists in unrolling and shaping
the mini tubing so as to run down in straight line the mini tubing
in the production tubing. In both cases the mini tubing is
lengthened in the production tubing with the sealing tool connected
at lower end up to the moment the sealing tool abuts against a stop
43 provided in the nipple 9, which is usually called no-go in the
wellbore field.
[0057] A safety valve 8 is usually secured in such a nipple 9 after
abutment against this stop 43. Securing the safety valve in the
nipple after abutment permits to adjust perfectly the subsurface
aperture 31 of the control line in the nipple in front of the
aperture of the chamber 21. The same occurs when setting the
releasing device inside the nipple.
[0058] The sealing tool 41 includes housing 44 with an abutment,
i.e. a greater diameter upper extend. This abutment abuts against
the no-go 43 of the nipple and the releasing device is secured by
well known techniques in snubbing or coil tubing. The sealing tool
41 perfectly fits the nipple bore so that it can not move. Securing
the releasing device in the nipple and production tubing after
abutment permits to adjust perfectly the subsurface aperture 31 of
the control line 10 in front of a fluid communication aperture 45
of the sealing tool 41. The fluid communication aperture 45 is for
example a recess in the outer circumference of the housing 44 that
extends as illustrated on FIGS. 4 to 8 on the whole outer
circumference of the sealing tool and along a large height, so as
to ease the adjustment of this aperture 45 in front of the
subsurface aperture 31 of the control line 10. The housing 44 of
the sealing tool presents on each side of the fluid communication
aperture 45 an annular location on its outer circumference in which
is arranged an O-ring seal 46, also know as a packing. These two
seals 46, disposed spaced apart from each other according to the
axial direction A of the production tubing, prevent fluid contained
in the fluid communication aperture 45 to escape between the outer
circumference of the housing and the inner cylindrical wall of the
nipple. The bottom 47 of the housing 44 is closed. The top of the
housing is sealingly connected to the mini tubing. A fluid
communication path inside the housing connects the fluid
communication aperture 45 and the top of the housing. The sealing
tool 41 defines consequently a sealed chamber sealingly connected
on one side to the mini tubing and on the other side to the control
line subsurface aperture 31. The nipple inside cylindrical wall
between the two seals 46 also defines this sealed chamber.
[0059] The releasing device of FIGS. 4 to 8 consists more
particularly of a pressure intensifier. But this releasing device
can also be used as a pressurized fluid transmitter, which also
enters the scope of the invention.
[0060] As illustrated in FIG. 4, in a first attempt to release the
control line, the releasing device is used as a pressurized fluid
transmitter. The releasing device comprises the mini tubing 42
extending up to the surface and a fluid communication path between
this mini tubing and the control line aperture 31 through the fluid
communication aperture 45. Liquid solvent, and more particularly
diesel oil is poured at the surface in the mini tubing so as to
fill the mini tubing and part of the fluid communication path. The
liquid solvent usually exhibits heat stability and low
compressibility abilities. Pressure is then supplied to the liquid
solvent using a controller connected at the surface to the mini
tubing. The controller is a means for flowing fluid such as a
pressure supplying pump controlled with a control panel. The liquid
solvent is then urged into the fluid communication aperture 45 of
the releasing device, into the control line subsurface aperture 31
and part into the control line 10. This pressure is then
transmitted to the blocked fluid in the control line and provides a
move of the blockage and a flow of liquid solvent in the control
line 10. Removal of the blockage is achieved because of the
resulting driving action which is reverse to the usual forces
acting on the blockage (such usual forces are hydrostatic pressure
and pressure generated through the surface aperture to open the
safety valve or to flush the blocked fluid). Furthermore, the
solvent helps to dissolve and disintegrate the blockage. The
blockage can also be expelled or flushed at the surface by
continuing flowing solvent through the releasing device or in the
well by withdrawing the releasing apparatus and applying a pressure
in the control line through the surface aperture. Consequently,
this method permits to move and then to unblock the blockage in
order to get rid of it.
[0061] Removal of the blockage in the control line can be detected
at the surface by the flow of fluid out of the control line through
the surface aperture.
[0062] Hydraulic pressure from the releasing device can be pulse
applied in order to unblock the blockage. Further, hydraulic
pressures can be applied alternatively onto the blockage through
the subsurface aperture and through the surface aperture of the
control line, thereby creating an oscillation effect onto the
blockage. The pressure of the fluid can also be increased
intermittently into the mini tubing or into the control line for
more efficiency. Additionally, higher hydraulic pressure than can
be supplied through the control line subsurface aperture may be
brought to bear upon the blockage by using a downhole pressure
intensifier.
[0063] The burst limit of the mini tubing 42 has to be taken into
account when applying pressure through the releasing device and
consequently, the pressure applied this above mentioned way on the
blockage is limited. To remain under this burst limit, the pressure
supplied by the controller depends on how deep the nipple is
placed, the pressure in the mini tubing being the sum of the
hydrostatic pressure and of the pressure supplied by the
controller, as it is well known in the art.
[0064] The pressure applied to the blockage might not be sufficient
to move and remove the blockage. In such cases, the method
according to the invention is continued, taking advantage of the
pressure intensification ability of the releasing device.
[0065] The fluid communication path goes through a bored piston and
is designed in order to permit the multiplication of the pressure
value between the mini tubing 42 and the fluid communication
aperture 45.
[0066] The releasing device comprises a piston 48 having two end
sides, an upper side 49 and a lower side 50, isolated from each
other by a seal assembly into the housing 44 providing at least two
sealed separate chambers, an upper chamber 51 and a lower chamber
52. The piston has a T-shape profile and is arranged to allow
movement, i.e. the upper and lower sides 49,50 have parallel fluid
contact surfaces S,S1 having different sizes. More particularly,
the fluid contact surface S of the upper side 49 is greater than
the fluid contact surface S1 of the lower side 50 and both fluid
contact surfaces S and S1 are perpendicular to the translation
direction of the piston. The upper and lower chambers 51,52 have
appropriate sizes to sealingly accommodate respectively the upper
and the lower sides 49,50 of the piston 48. The perfect seal
between the piston and the chambers is achieved with O-ring seals
53. The piston 48 is further bored so as to permit liquid solvent
flow from the upper chamber 51 to the lower chamber 52 through an
inner bore 54. The liquid solvent is prevented to flow the other
way, i.e. from the lower chamber to the upper chamber, by means of
a check valve 55 arranged into the piston inner bore 54. The upper
chamber 51 is open on the mini tubing 42 and the lower chamber 52
is open on the fluid communication aperture 45 through a duct 56.
The travel of this duct 56 is designed to minimize the size of the
sealing tool 41 that must fit into the nipple 9.
[0067] During the first attempt for releasing the control line as
described here in above, hydraulic pressure is applied on the
blockage by fluid communication through the mini tubing 42, part of
the upper chamber 51, the piston inner bore 54, the lower chamber
52, the duct 56, the apertures 45,31 and part of the control line
10. The piston remains in the upper position because of the
shearing forces caused by the O-ring seals 53 provided in the
piston and bearing against the upper and lower chamber inner
walls.
[0068] The solvent liquid and then the travel of the solvent liquid
is highlighted on FIGS. 4 to 8 with hatched lines.
[0069] The surface controller is stops applying pressure. The
pressure drops in the mini tubing, i.e. only the hydrostatic
pressure remains, whereas the pressure remains equal to P
downstream the check valve 55, i.e. in the lower chamber. The check
valve 55 indeed prevents the downstream pressurized liquid solvent
from flowing through the piston inner bore 54 to obtain a pressure
balance and thus preserves the pressure P.
[0070] As illustrated in FIG. 5, an heavy ball 57, for example made
of stainless steel or bronze, is then dropped in the mini tubing
and sinks until it obstructs the piston inner bore 54 on the upper
side 49. A hydraulic pressure P is after that applied in the upper
chamber 51. This hydraulic pressure P acts on the fluid contact
surface of the upper side 49 and forces the piston 48 to the lower
position. On the other side of the piston 48, the pressure of the
liquid solvent contained in the lower chamber 52 acts on the fluid
contact surface of the lower side 50, which can be considered as a
full surface because of the check valve 55 that obstructs the
piston inner bore 54 that way, and forces the piston to the upper
position. A balance of pressure is obtained resulting in a pressure
value P1 in the lower chamber such that P1=(P*S1)/S. Consequently,
as S1 is inferior to S, P1 is superior to P. This results in a
pressure multiplication effect.
[0071] The hydraulic pressure P1 in the lower chamber is greater
than during the first attempt without using the pressure
intensifier, and the hydraulic pressure applied on the blockage is
therefore greater. The sealing tool, as well as the nipple or the
control line can stand greater pressure than the mini tubing.
[0072] As a matter of example, a construction of the kind of the
mini tubing can stand about 8000 PSI whereas a nipple or a control
line can stand usually more than 25 000 PSI. Usable practical
parameters are then a hydraulic pressure P of about 6000 PSI and an
intensifier coefficient of 4, i.e. the surface S being four times
larger than the surface S1. The hydraulic pressure supplied in the
control line is consequently of about 24 000 PSI, which was not
possible without the pressure intensifier. Such a high hydraulic
pressure acting against the blockage moves this blockage. The
blockage is pushed and fluid flows into the control line while the
piston moves to the lower position. The piston can move in the
upper chamber because this upper chamber is in air communication
with the production tubing 3 through a bleed hole 58. The releasing
of the blockage can be detected because of fluid flowing out of the
control line surface aperture or because of a pressure drop in the
mini tubing. The hydraulic pressure is maintained and the piston 48
moves down to the lower position and allows a certain volume of
liquid solvent to circulate through the control line for cleaning
purpose.
[0073] FIG. 6 illustrates the piston 48 having completed its
stroke, which can be detected by the pressure increasing again in
the mini tubing 42.
[0074] The surface controller is then controlled so as to stop
applying pressure in the mini tubing and the pump 15 actuated by
the control panel 16 applies pressure in the control line 10 from
the surface aperture. Fluid flows through the unblocked control
line 10 up to the lower chamber 52 and pushes the piston 48 up to
the upper position against an abutment 59, as illustrated in FIG.
7. An increase of pressure in the control line indicates that the
piston is in upper position. The blockage, if it still partly
exists and obstructs the fluid flow in the control line, is then
pushed downwardly.
[0075] To confirm that the control line is unblocked, the control
line 10 is then flushed and cleaned. For that, as illustrated in
FIG. 8, a dart 60 having a bevel tip 61 is introduced in the mini
tubing so as to force the ball 57 out of the aperture of the piston
inner bore 54. The piston inner bore 54 is open for fluid
communication from the upper chamber 51 to the lower chamber 52.
The dart 60 is preferably bored. The controller is controlled to
flow liquid solvent into the mini tubing and the dart bore. Solvent
flows then through the piston inner bore 54, the lower chamber 52,
the duct 56, the control line aperture 31 and the control line 10
up to the surface aperture. The blockage, or parts of the
disintegrated blockage, is then flushed away from the control line.
This avoids the formation of an ensuing new blockage from old
blockage part settlements.
[0076] The control line 10 being clean and released, the releasing
device 40 can be retrieve with the snubbing or coil tubing machine.
The plug is removed and the safety valve reinstalled in the nipple
9 of the production tubing 3.
[0077] If the blockage does not move the first time the intensified
pressure is applied, the pressure can be bled off and reapplied in
the mini tubing. This operation can be repeated several times to
create high-pressure impulses and a jarring action to more
efficiently unblock the blockage. Further, hydraulic pressure can
also be applied alternatively on the blockage from the surface
aperture of control line and from the releasing device, creating an
oscillation effect on the blockage to facilitate its removal.
[0078] Instead of the steps with reference to FIGS. 7 and 8, the
releasing device can be retrieved of the production tubing as soon
as the blockage is unblocked and the control line cleaned and
flushed into the production well by applying an hydraulic pressure
through the control line surface aperture.
[0079] Preferable diesel is pumped through the mini tubing before
setting the releasing device in the nipple to ensure thoroughly
cleaned conditions but other fluids may be used.
[0080] Although the invention has been described in part by making
detailed reference to specific embodiments, such detail is intended
to be and will be understood to be instructional rather than
restrictive. It should be noted that while embodiments of the
invention disclosed herein are described in connection with a
specific safety valve, the embodiments described herein may be used
with any type of control line controlled safety valve and with any
type of control line used in subsurface safety valves.
[0081] For example, in some relatively deep subsurface safety valve
well, to compensate for the "active" control line's hydrostatic
pressure, a "balance" control line is used to negate the affect of
hydrostatic pressure from active control line. Such "balance"
control line can also be released using the method and the device
in accordance with the invention.
[0082] The device generating high pressure against a surface inner
wall of the production tubing through a down hole can also be used
for numerous other applications including communicating with a
tubing retrievable safety valve, so-called TRSV. Such TRSV are
safety valves incorporated into the production tubing and
authorizing an inner flow identical to the flow of the production
tubing, contrarily for example to a wireline retrievable safety
valve secured in the production tubing. The device described here
in above can be used with little modification to perforate weak
areas in a nipple arranged beforehand for TRSV, for example for
setting an insert valve inside the tubing retrievable safety valve
and still using the existing control system. For that, the fluid
communication aperture of the sealing tool must be narrow and well
oriented.
[0083] Whereas the present invention has been described in relation
to the drawings attached hereto, it should be understood that other
and further modifications, apart from those shown or suggested
herein, might be made within the scope and spirit of the present
invention.
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