FIELD OF THE INVENTION

The present invention concerns a subsea well intervention system and method for inserting tubing from a floating vessel into a subsea well .

BACKGROUND OF THE INVENTION

During production phase , subsea wells require maintenance and/or remediation to improve flow or production of hydrocarbon fluid . The intervention process often needs to lower a tubing inside the well .

The tubing is lowered into the well through a lubricator module , a blowout preventer module , and the subsea tree .

The subsea tree is a system located on the top of the well at the sea floor, i . e . at the wellhead, such system comprising a plurality of valves for controlling the well flow during production phase .

The blowout preventer module , commonly named as a BOP, is a security system comprising valves that are able to seal the well in case of emergency and to avoid leak of hydrocarbon fluid in the environment .

Such blowout preventer module can be installed above the subsea tree via a running adapter module that is designed to adapt the blowout preventer module mechanical interface to the subsea tree mechanical interface . Thanks to this running adapter module a blowout preventer module from a first supplier can be connected to a subsea tree from a second supplier . Additionally, such running adapter module helps the automatic secured connection of said blowout preventer module on top of subsea tree in vertical direction at the deep-sea floor via a remotely operated vehicle .

The lubricator module is a system located on the top of the blowout preventer module that provides sealing of a wire line and/or a tubing and that keeps the fluids pressure inside the well during the use and displacement of a tool suspended bellow the wire line or during the use and displacement of a tubing inside the well .

Usually, a subsea intervention uses a workover string connected above the blowout preventer module to run down the blowout preventer module inside sea water down to the subsea tree . However, such system and method require a large floating vessel having a derrick and a storing of a lot of risers for assembling and deploying the workover string inside sea .

Another method is to use a subsea lubricator to eliminate the use of a workover riser . The blowout preventer module and the lubricator module are run down to the subsea tree by a cable line that is deployed via a crane and a winch, located on the floating vessel . A remotely operated vehicle helps the guiding and the secured connection of this subsystem above the subsea tree . A control umbilical is also installed between the floating vessel and the subsystem of the blowout preventer module and the lubricator module for providing power fluids to the blowout preventer module and to the lubricator module . For example , it provides fluids that circulate in the lubricator module , and the power to actuate various valves inside this subsystem .

Then, the wire line and/or tubing can be run down through the lubricator and the blowout preventer module .

However, due to well fluid pressure and/or due to well eruptivity, in certain circumstances , the tubing may be pushed out of the subsea well by the fluid pressure inside the subsea well . This may occur when the tubing weight cannot counterbalance (being higher than) the fluid pressure from the subsea well , for example at the end of an intervention and when the tubing is pulled out from the well . This may also occur because of overpressure or increase of well fluid pressure .

Usually, such problem is solved by an inj ector mechanism installed on the floating vessel and/or on the well head at sea floor .

Patent document US 5 309 990 gives an example of a coiled tubing inj ector for inj ecting and withdrawing a length of flexible , cylindrical tubing into and from a well bore . This inj ector comprises first and second sets of gripper shoes , and drive mechanism for moving the sets of grippers . The grippers shoes are pressed against the tubing with sufficient force to hold the tubing therebetween .

Patent document US 8 720 582 illustrates a subsea well system including a surface inj ector and an underwater in j ector .

These inj ectors systems are satisfying . But , they are heavy and complex in use . They still need to be improved to control the tubing displacement with a better user-friendliness .

OBJECTS AND SUMMARY OF THE INVENTION

A first object of the present invention is to provide improved subsea intervention system for a subsea well including a floating vessel . The floating vessel may be a small vessel , and/or may not comprise a derrick and therefore the intervention system can be called rigless or derrickless or towerless or riserless intervention system .

The system for inserting tubing from a floating vessel into a subsea well comprises : a subsea tree installed upon the well , a blowout preventer module connected onto the subsea tree , a lubricator module connected onto the blowout preventer module , a tubing extending from the floating vessel down to the well and through the lubricator module , the blowout preventer module and the subsea tree , wherein the lubricator module includes a pushing device inside a cavity of said lubricator device , and said pushing device being adapted to force the tubing to move down inside the well .

Thanks to the above features , the lubricator module is now a security device that prevents the tubing to move in an uncontrolled manner . The lubricator module is able to push the tubing inside the well .

Moreover, the floating vessel has no need of a derrick, and it has no additional control umbilical reel as is uses the remotely operated vehicle features . There is no need of riser on the floating vessel as the tool is ran directly by a wire line .

Therefore , the floating vessel equipments are less numerous , simpler, more easily used, and more independent from the various suppliers equipments .

Then, the subsea well intervention system is implemented with more secure/safe manner and more quickly . This system is then less expensive in use .

In various embodiments of the system, one and/or other of the following features may optionally be implemented .

According to an aspect of the system, the pushing device comprises : a piston device dividing cavity of lubricator module into an upper volume and a lower volume , said piston device being able to sealingly slide inside the lubricator module and around the tubing, and a holding device , and the lubricator module further comprises an input port communicating with upper volume for feeding the upper volume with a control fluid by a conduit , the pressure and feed volume of said control fluid being controlled by repeated sequences to move down the piston device inside the cavity of lubricator module and to force the tubing to move down inside the well , and to move up the piston device inside the cavity while the tubing is kept in position by the holding device . According to an aspect of the system, the piston device further comprises an actuation mechanism including : a plurality of coupling pads located inside the piston device around inner circumference of said piston device , and facing the tubing, and a plurality of rods adapted to actuate said coupling pads for tightening the tubing .

According to an aspect of the system : when the control fluid pressure inside upper volume is lower than well fluid pressure inside lower volume, the piston device being positioned at upper end of lubricator module , the rods being fully retracted and positioned inside the braking device to avoid contact between the coupling pads and the tubing, so that the tubing is free to move up and down inside the lubricator module , and when the control fluid pressure inside upper volume is equal or higher than well fluid pressure inside lower volume , and when a feed volume of control fluid pumped into the upper volume is higher than a limit volume , the rods are fully extended and actuate full coupling of tubing to move down the tubing together with the piston device .

According to an aspect of the system, each rod comprises : a rod elastic member compressed between upper end of said rod and piston body of braking device to naturally push the rod to extension outside of said piston body, and an opening elongated along the rod and associated to a coupling pad, each coupling pad comprises : a transversal axis articulated into rotation relative to the piston body, a transversal pin protruding into the opening for limiting rotation of coupling pad around the transversal axis , and a pad elastic member compressed between the coupling pad and piston body to naturally push the coupling pad towards tubing for braking or coupling .

According to an aspect of the system, the opening is wider at lower end and comprises an adapted shape to control the displacement of coupling pad towards the tubing when the actuation mechanism is actuated for progressively braking the tubing on the basis of feed volume .

According to an aspect of the system, the piston device comprises a plurality of levels of coupling pads and associated openings in the rods .

According to an aspect of the system : the lubricator module further comprises a locking mechanism to fasten the holding device at lowest position inside the lubricator module , the holding device further comprises a holding mechanism including a plurality of braking pads located inside the holding device around inner circumference of said holding device , and facing the tubing, and wherein the holding mechanism is adapted to actuate the braking pads to prevent the tubing to move up and to only allow the tubing to move down inside the well .

According to an aspect of the system, the locking mechanism actuates the braking pads .

A second object of the present invention is to provide improved subsea intervention method for inserting tubing from a floating vessel into a subsea well , the method comprising the steps of : - providing : a subsea tree installed upon the well , a blowout preventer module connected onto the subsea tree , a lubricator module connected onto the blowout preventer module , a tubing extending from the floating vessel down to the well and through the lubricator module , the blowout preventer module and the subsea tree , wherein the lubricator module includes a pushing device inside a cavity of said lubricator device , and

- controlling the pushing device to force the tubing to move down inside the well .

In various embodiments of the method, one and/or other of the following features may optionally be implemented .

According to an aspect of the method, the pushing device comprises : a piston device dividing cavity of lubricator module into an upper volume and a lower volume , said piston device being able to sealingly slide inside the lubricator module and around the tubing, and a holding device , and the lubricator module further comprises an input port communicating with upper volume for feeding the upper volume with a control fluid by a conduit , and the piston device is pushed down inside the cavity of lubricator module by repeated sequences of controlled pressure and feed volume of said control fluid to force the tubing to move down inside the well , and the piston device is pulled up inside the cavity of lubricator module while the tubing is kept in position by the holding device .

According to an aspect of the method, the piston device further comprises an actuation mechanism including : a plurality of coupling pads located inside the piston device around inner circumference of said piston device , and facing the tubing, and a plurality of rods adapted to actuate said coupling pads for tightening the tubing, and wherein the actuation mechanism is actuated by : when the control fluid pressure inside upper volume is lower than well fluid pressure inside lower volume , the piston device being positioned at upper end of lubricator module , the rods being fully retracted and positioned inside the braking device to avoid contact between the coupling pads and the tubing, so that the tubing is free to move up and down inside the lubricator module , and when the control fluid pressure inside upper volume is equal or higher than well fluid pressure inside lower volume , and when a feed volume of control fluid pumped into the upper volume is higher than a limit volume , the rods are fully extended and actuate full coupling of tubing to move down the tubing together with the piston device .

According to an aspect of the method, wherein the lubricator module further comprises a locking mechanism to fasten the holding device at lowest position inside the lubricator module , and the holding device further comprises a holding mechanism including a plurality of braking pads located inside the holding device around inner circumference of said holding device , and facing the tubing, and wherein the holding mechanism actuates the braking pads to prevent the tubing to move up and to only allow the tubing to move down inside the well .

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from the following detailed description of two of its embodiments given by way of non-limiting example , with reference to the accompanying drawings . In the drawings :

- Figure 1 is schematic view of the subsea well intervention system,

- Figure 2 is a schematic cutting view of lubricator module of intervention system of figure 1 including an example of pushing device comprising a piston device and a holding device ,

- Figures 3A to 3C are schematic cutting views of lubricator module of figure 2 in five states of operation,

- Figures 4A to 4C are more detailed views of figures 3A to 3C showing an exemplary of braking device , and

Figure 5 is detailed view of holding device included in the pushing device .

MORE DETAILLED DESCRIPTION

The figure 1 illustrates a subsea well intervention system used offshore in sea water 300 , said system including :

- a floating vessel 100 being at sea surface 301 ,

- a well 200 equipped with a subsea tree 201 above wellhead at sea floor 302 .

A blowout preventer module (BOP) 202 is connected above the subsea tree 201 . A lubricator module 203 is connected above the blowout preventer module (BOP) 202 . A pressure control head 204 substantially closes the top of the lubricator module 203 .

The blowout preventer module (BOP) 202 may correspond to an emergency disconnect package (EDP) and a low riser package (LRP) . For example , the EDP may include security valves in case of any uncontrolled displacement of the floating vessel that may lead to its disconnection from the well . For example , the LRP may include valves or any other devices to isolate the well from environment , e . g . in case of excessive pressure inside the well .

The floating vessel 100 comprises :

- a first crane 101 and optionally a second crane 102 ,

- a first reel 103 for winding a tubing 104 ( a cable ) , said tubing 104 being run down inside the well 200 , by going through the pressure control head 204 , the lubricator 203 , the blowout preventer module 202 and the subsea tree 201 .

The tubing 104 according to the disclosure can be any kind of tubing : tubing or pipe or coiled tubing . According to embodiment of figure 1 , the tubing 104 is a coiled tubing wrapped around the first reel 103 . But , the tubing 104 can be assembled via tubing sections on the floating vessel 100 . The tubing 104 may be composed of any material : metallic or synthetic or composite material . The floating vessel 100 may also comprise :

- a second reel 105 for winding a remotely operated vehicle umbilical 106 , said remotely operated vehicle umbilical 106 being connected between a control unit 107 located in the floating vessel 100 and a remotely operated vehicle (ROV) 206 .

The remotely operated vehicle 206 might control the various features of BOP 202 and/or subsea tree 201 . For example , the ROV 206 may open or close any valves of said BOP and/or subsea tree .

The obj ect of present disclosure system and/or method is to control the displacement and/or braking of the tubing inside the well 200 , and to push the tubing in the well in a controlled manner : e . g . controlled speed . It can also prevent the tubing to be pushed out from the well 200 by the well pressure . To this end, the lubricator module 203 includes a pushing device 500 adapted to force the tubing 104 to move down inside the lubricator module 203 , and therefore inside the well .

Figure 2 illustrates an enlarged view of an embodiment of the lubricator module 203 according to present disclosure . The lubricator module 203 comprises an upper cap 203a, a lubricator body 203b and a lower cap (not represented) . The tubing 104 is crossing through the entire lubricator module 203 in a sealed manner . The lubricator module 203 includes several seals to ensure the sealing of the outside surface 104a of tubing 104 so that to prevent leak of well fluid outside of the subsea well 200 and outside of the system .

The lubricator body 203b is a cylindrical tube having an inner cavity C . Inside said inner cavity, wherein the pushing device 500 is installed .

The pushing device 500 of illustrated embodiment comprises :

- a piston device 400 adapted to push the tubing downwards into the well , and

- a holding device 450 adapted to prevent the tubing 104 to move up and to allow the tubing to move down when a locking mechanism 459 is engaged, and to allow to move up and down when the locking mechanism 459 is not engaged .

The piston device 400 is substantially a piston comprising :

- a piston body 401 extending along a main axis ,

- an outer seal 402 for sealing the piston body 401 relative to the inner surface 203s of the lubricator body 203b, and

- an inner seal 403 for sealing the piston body 401 relative to the outside surface 104a of the tubing 104 .

The piston body 401 has an annular shape with an inner passage 404 for the crossing of tubing 104 through the lubricator module 203 . The inner passage 404 is formed by an inner surface 401a of piston body 401 . The piston body 401 surrounds the tubing 104 .

The piston body 401 may be composed of one part or a plurality of parts assembled together to form the totality of said piston body, each part being annular with a hole being a portion of the inner passage 404 of piston body . The plurality of parts is preferably coaxial to the main axis of piston device 400 .

The piston device 400 divides the cavity C of lubricator module 203 into two sealed volumes ; an upper volume VI located upper the piston device 400 and a lower volume V2 located bellow the piston device 400 . It is supposed the lubricator module 203 is installed vertically, the main direction of cylindrical lubricator body oriented in vertical direction, the upper volume being in a direction wherein the tubing 104 is entering the lubricator module 203 from the floating vessel , and the lower volume being in the opposite direction towards the subsea well .

The lubricator module 203 further comprises an input port 203c located at the upper end of the lubricator module 203 , said input port 203c communicating with the upper volume VI of the cavity C . The input port 203c is adapted for plugging a conduit , said conduit feeding the upper volume VI with a control fluid having a controlled pressure and/or a feed volume tuned by a control device or an operator . The control fluid pressure may push the piston device 400 downwards inside the cavity C of lubricator module 203 .

The lower volume V2 is at hydrocarbon well fluid pressure from inside the subsea well . The well fluid pressure may push the piston device 400 upwards ins ide the cavity C of lubricator module 203 , as illustrated by arrow on figure 2 .

The piston device 400 is therefore a piston inside the lubricator module that is subj ected on one side ( lower volume V2 ) to the well fluid pressure that tends to push it upwards , and that is also subj ected on the other side (upper volume V2 ) to the control fluid pressure that tends to push it downwards . The piston device 400 is then subj ected to equilibrium of pressure from well and from input port .

The piston device 400 further comprises an actuation mechanism including at least :

- a plurality of coupling pads 405 located around circumference of inner surface 401a of piston body 401 , and

- a plurality of rods 406 adapted to actuate the coupling pads .

By "actuate" , it is meant that the rods 406 can control the coupling pads 405 to tighten the tubing 104 so as to brake any displacement of tubing 104 relative to the piston device 400 (piston) and/or so as to cancel any relative displacement for coupling the tubing 104 to the piston device 400 . Reciprocally, the rods 406 can free the coupling pads 405 from the tubing 104 . An example of such mechanism will be detailed later in present disclosure in reference to figures 4A-4C .

For example , the rods 406 extend in the direction of main axis inside the piston device 400 , and comprise upper ends 406a extending outside of the piston device and inside the upper volume VI . These upper ends 406a may contact an inner surface of upper cap 203a, as illustrated on figure 2 . These rods 406 are themselves pushed upwards by rods elastic member, such as coil springs , or any other kind of springs .

The holding device 450 comprises a holding body 451 extending along the main axis . But , contrary to the piston device 400 , the holding device 450 has no seal and the well fluid can go through the holding device 450 , in the lower volume V2 , below the piston device 400 .

Similarly to piston device 400 , the holding body 451 has an annular shape with an inner passage 454 for the crossing of tubing 104 through the lubricator module 203 . The inner passage 454 is formed by an inner surface 451a of holding body 451 . The holding body 451 surrounds the tubing 104 .

The holding body 451 may include one or a plurality of parts coaxial to the main axis , and stacked in the direction of the main axis .

The holding device 450 further comprises a holding mechanism including at least a plurality of braking pads 455 located around circumference of inner surface 451a of holding body 451 , and adapted to be actuated by the locking mechanism 459 (when it is engaged) .

By "actuate" , it is meant the same technical effect than the one previously explained for the rods 406 of actuation mechanism in the piston device 400 : the locking mechanism 459 can control the braking pads 455 to tighten the tubing 104 so as to brake any displacement of tubing 104 relative to the holding device 450 and/or so as to cancel any relative displacement for coupling the tubing 104 to the holding device . Reciprocally, it can free the braking pads 455 from the tubing 104 . An example of such mechanism is illustrated on figure 5 .

Additionally, the holding device 450 might be a device designed so that it allows only a one way displacement ( in one direction, i . e . downwards direction) of the tubing 104 relative to the holding device 450 when the holding mechanism is actuated, i . e . when the locking mechanism 459 is engaged . Reciprocally, the holding device 450 allows a two way displacement (up and down) of the tubing 104 when the holding mechanism is not actuated, i . e . when the locking mechanism 459 is not engaged .

To this end, the braking pads 455 of holding device 450 may be dissymmetric in the direction of main axis : the braking pads 455 are wider at their bottom end than at their upper end to cause a coin effect and to increase the braking device in the upward direction of tubing displacement then in the downward direction of tubing displacement . Such dissymmetry can be designed to only allow a displacement of tubing 104 in the downward direction .

The lubricator module 203 includes a locking mechanism 459 adapted to firstly secure the holding device 450 to the lubricator body 203b, so that the holding device 450 is maintained at a predetermined position inside the cavity C of lubricator module . The predetermined position is for example a lower position inside the lubricator body 203b, and for example the lowest possible position inside the lubricator body 203b so that a distance between the piston device 400 and the holding device 450 is maximi zed .

The locking mechanism 459 comprises :

- a first portion 459a belonging to the lubricator body 203b and adapted to actuate the locking mechanism from outside of lubricator module 203 , and

- a second portion 459b belonging to the holding device 450 and corresponding to the first portion 459a, the first and second portions assuming securing of holding device 450 relative to lubricator body 203b upon engagement .

For example , as illustrated on the figures and according to an example of embodiment , the first portion 459a is composed of a lateral pin extending laterally trough the lubricator body 203b . Reciprocally, the second portion 459b of holding device 450 may be a groove adapted to receive said pin . Therefore , the pin ( first portion) can be engaged from outside of lubricator module 203 into the groove ( second portion of locking mechanism) to secure the holding device 450 to the lubricator body 203b . The first portion is disengaged from second portion to free the holding device 450 .

Other embodiments of locking mechanism 459 can be designed . The locking mechanism can be a mechanical part , electromechanical part , a hydraulic part , a electrohydraulic part , a magnetic part , or any else known actuation device .

The locking mechanism 459 also actuates the holding mechanism and its braking pads 455 . The braking pads 455 tighten the tubing 104 when the locking mechanism 459 is engaged to prevent the tubing 104 to move up . The braking pads 455 do not tighten the braking pads 455 when the locking mechanism 459 is not engaged to allow the tubing to move up and down, or reciprocally to allow the holding device 450 to move up and down .

The operation of pushing device 500 inside the lubricator module 203 is now explained in view of various states of pushing device illustrated on figures 3A-3E .

In figure 3A, the piston device 400 of pushing device 500 is located in an upper position inside the cavity C of lubricator module 203 .

In this case , no pressure or a low pressure is applied inside the upper volume VI by the input port 203c . For example , the pressure is substantially the atmospheric pressure . The well fluid pressure inside lower volume V2 being higher than the control fluid pressure inside upper volume VI (unbalanced upwards ) , the piston device 400 is pushed upwards by the higher pressure inside the second volume V2 , and is put into contact with the upper cup 203a . The upper volume VI is at its minimum value . The coupling pads 405 of piston device 400 are not applied onto the tubing 104 ( fully retracted) .

The first state of piston device 400 on figure 3A is a "free state" or "initial state" ; in which the tubing 104 is free to move up and down inside the lubricator module 203 . However, if a tubing force caused by the tubing weight (downwardly oriented) ) is lower than a force caused by the well pressure (upwardly oriented) , the tubing 104 cannot go down in the well by itself .

The piston device 400 is then in the "initial state" of figure 3A, when the control fluid pressure inside upper volume VI is lower than well fluid pressure inside lower volume V2 , the piston device being positioned at upper end of lubricator module , the rods 406 being fully retracted and positioned inside the piston device to avoid contact between the coupling pads 405 of piston device and the tubing 104 , so that the tubing 104 is free to move up and down inside the lubricator module .

In figure 3B, the piston device 400 moves down inside the lubricator module 203 of a distance relative to the upper cup 203a such that the rods 406 of said piston device are no more in contact with the upper cup 203a .

In this case , control pressure is applied inside the upper volume VI , and more and more control fluid is pumped to this upper volume VI , so that the upper ends 406a of rods 406 are not in contact with the upper cup 203a . The control pressure inside the upper volume VI is at least equal to the well fluid pressure inside the lower volume V2 . This equilibrium is controlled or tuned by a control device or an operator . This control device or operator may use a pressure measure from well fluid .

The rods 406 are fully actuating the coupling pads 405 to the tubing 104 and are fully braking and fully tightening the tubing 104 : the coupling pads 405 are coupled to the tubing 104 .

Then, the increase of control fluid volume inside the upper volume VI moves down the piston device 400 together with the tubing 104 coupled to it .

The coupling pads 405 and actuation mechanism of braking pads may be designed to couple the tubing according to a non-linear curve : more they are engaged to the tubing 104 more they tend to engage more . Therefore , the tightening force increases a lot according to a convex function .

The coupling pads 405 and actuation mechanism of coupling pads may be designed to be dissymmetric in view of displacement direction of tubing .

The tubing 104 is then forced to move down inside the well by the upper volume VI increasing pushing the piston device 400 downwards . Consequently, this pushes the tubing 104 down inside the well .

The piston device 400 moving down is going into contact with the holding device 450 , and pushes the holding device 450 down inside the lubricator body 203b, as illustrated by the arrows at the lower portion of figure 3B .

The second state of pushing device 500 on figure 3B is then a "pushing state" ; during which the tubing 104 is pushed inside the well .

The piston device 400 is then in the "pushing state" when the control fluid pressure inside upper volume is equal or higher than well fluid pressure inside lower volume , and when a feed volume of control fluid pumped into the upper volume is higher than a limit volume , the rods are fully extended and actuate full braking or full coupling of tubing with the piston device , so that the coupling pads 405 are tightening the tubing 104 , and the tubing 104 is then fasten to the piston device 400 so that the piston device 400 drag the tubing 104 it down into the well .

The limit volume corresponds approximately to a volume in the cavity C of a height equal to the height of the rods 406 fully extended inside the upper volume VI . In figure 3C, the piston device 400 and holding device 450 have reached the lowest position inside the lubricator body 203b, thanks to the increase of upper volume VI controlled by the feeding of control fluid by the input port .

Then, the locking mechanism 459 is actuated or engaged . In the illustrated embodiment , the first portion 459a ( lateral pin) is engaged to the second portion 459b (groove ) of holding device 450 .

Moreover, the holding mechanism can be simultaneously actuated so that the tubing 104 is hold : it allows the tubing 104 to move only down inside the well .

The holding device 450 is then securely positioned ( fastened or fixed) inside the lubricator body 203b at a predetermined position ( lowest ) . It cannot move up and down inside the lubricator 203 .

The third state of pushing device 500 on figure 3C is then a "locking state" ; during which the piston device 400 is at a lowest position inside the lubricator module 203 , the holding device 450 also secured at this lowest position inside the lubricator module 203 and the tubing 104 can only move down inside the well and can no more move up .

In figure 3D, the piston device 400 moves back upwards inside the lubricator body 203b (without the holding device 450 ) as the control pressure in upper volume VI is reduced lower to the well pressure . The well pressure inside the lower volume V2 pushes the piston 400 upwards .

The coupling pads 405 of piston device 400 might be one way acting pads as above explained for the braking pads 455 of holding device 450 . Therefore , the piston device 400 does not push upwards the tubing 104 .

The tubing 104 is maintained or kept in position while the piston device 400 moves upwards back to the upmost position near the upper cup 203a .

The upper volume VI is progressively reduced while the piston device 400 is going back to upmost position .

The fourth state of pushing device 500 is then a "return state" ; during which the piston device 400 is going back at the upmost position while the tubing is maintained immobile by the holding device 450 .

In figure 3E, the piston device 400 is back at the upmost position and the upper volume VI is lowest . This figure 3E is similar to figure 3A, except that the holding device 450 is at the lowest position, and maintaining the tubing 104 fixed in position .

The fifth state of pushing device 500 is then an "holding state" ; during which the tubing 104 is maintained or kept in position by the holding device 450 and the upper volume VI is small and the control fluid pressure inside upper volume VI is lower than well fluid pressure inside lower volume V2 .

The operation steps of figures 3B to 3E can be iterated one , two or more sequences , each sequence including the operation steps of "pushing state" of figure 3B, "locking state" of figure 3C, "return state" of figure 3D and "holding state" of figure 3E . The tubing 104 is progressively pushed a sequence after another sequence down inside the well , during each "pushing state" during which the tubing 104 is tightened by the piston device 400 and pushed down by the control fluid increasing upper volume VI , whereas during the other states the tubing 104 is maintained in position by the holding device 450 . Consequently, the tubing 104 is forced to move down inside the well by a plurality of repeated sequences . The tubing 104 moves step by step of repeated lengths . Each length corresponds to the length of travel of piston device 400 inside the lubricator module 203 . This displacement of tubing alternates displacement down inside the well of this length and no displacement during the return of piston device 400 at his upmost position .

At the end of the sequences , the locking mechanism 459 is disengaged to free the holding device 450 and/or to free the tubing 104 . The tubing 104 is then again free to move up and down . But , the downward force caused by the weight of tubing 104 is now higher than the upwards force caused by well pressure , and the tubing 104 is maintained in position by his weight and intervention mechanism on the floating vessel .

Figures 4A-4C illustrate an embodiment of a piston device 400 , and more specifically an actuation mechanism that control the operation of coupling pads 405 ins ide the piston device 400 . Figures 4A-4C are schematic views of this embodiment in states of operation as explained by reference to figures 3A-3B .

Figure 4A is showing two rods 406 belonging to the piston device 400 , said rods 406 being located around the tubing 104 . A first rod 406 is in a front position ( 0 ° in circumference around tubing) , and a second rod 406 is in a lateral position ( 90 ° in circumference around tubing) , so as to appreciate the features of these rods 406 and associated coupling pads 405 .

Each rod 406 comprises :

- an upper end 406a biased to extension upwards by a rod elastic member 406b compressed between the upper end 406a and piston body 401 of braking device 400 , and

- one or several openings 406c elongated along the rod, each opening corresponding to a coupling pad 405 , each opening 405 being wider at a lower end compared to an upper end .

Each coupling pad 405 comprises :

- a transversal axis 405a protruding from coupling pad into piston body 401 of piston device 400 so that each coupling pad 405 is articulated into rotation around said transversal axis 405a relative to piston body 401 of piston device , said transversal axis being located near upper end of the coupling pad 405 ,

- a transversal pin 405b protruding from coupling pad into an opening 406c of rod 406 , for limiting rotation of coupling pad 405 around its transversal axis 405a, and

- a pad elastic member 407 located at lower end of coupling pad 405 , and between said coupling pad and piston body 401 of braking device for naturally pushing the coupling pad 405 towards the tubing 104 for braking or coupling .

When the rod 406 is in the position of figure 4A, corresponding to above "initial state" of piston device 400 , the rod 406 is in a lower position inside the piston body 401 of piston device 400 , and the transversal pin 405b of coupling pad 405 is then in the upper end of opening 406c . The opening 406c comprises a shape that puts the transversal pin 405b away from the tubing 104 , i . e . the coupling pad 405 rotates in a contraclockwise direction around its transversal axis 405a to move away the lower end of coupling pad 405 from the tubing 104 . The pad elastic member 407 is then more compressed .

When the rod 406 is going from "free state" of figure 4A to "braking state" of figure 4B, the upper volume VI is increased, and the rods 406 are progressively exiting from the piston body 401 in an upwards direction, releasing partially the rod elastic member 406b .

The coupling pad 405 is moving downwards together with the piston body 401 , and the transversal pin 405b of coupling pad 405 is therefore moving down inside the opening 406c . As the opening 406c is wider in its lower portion, and thanks to its shape , this frees the transversal pin 405b and consequently the coupling pad 405 . The coupling pad 405 is then pushed towards the tubing 104 by the pad elastic member 407 , which comes into contact with the tubing 104 for braking displacement of said tubing . In this movement , the coupling pad 405 rotates in a clockwise direction around its transversal axis 405a to move the lower end of coupling pad 405 to the tubing 104 .

More the upper volume VI increases (more the rods 406 are exiting the piston body 401 ) , more the coupling pads 405 are pushed by the pad elastic members 407 towards the tubing 104 for braking or coupling the tubing relative to the piston device .

When the rod 406 is fully extended and in "stop state" of figure 4C, corresponding to a "pushing state" of pushing device 500 , the upper volume VI is increased and rods 406 are no more contacting the upper cup 203a . The transversal pin 405b is then positioned at the lowest portion of opening 406c, and the coupling pad 405 provides the highest force on the tubing 104 thanks to the pad elastic member 407 . This highest force is designed by shape of opening 406c and pad elastic member 407 . This highest force should correspond to a full braking and therefore a stop of displacement of tubing 104 inside the piston device 400 .

The above disclosed actuation mechanism is controlled by the control fluid pressure and volume of control fluid pumped inside the upper volume VI of lubricator module 203 as explained in description of figures 3A-3E .

Moreover, as illustrated on the figures , the piston device 400 may comprise a plurality of levels of coupling pads and associated openings in the rods to increase the number of coupling pads 405 in the system and to increase by design the maximum braking force of piston device 400 .

Thanks to this feature , the maximum braking force can be obtained inside the small diameter of lubricator module 203 . Moreover, the piston device 400 is modular and can be assembled with standardi zed modules connected together to reach a desired maximum braking force .

Moreover, the piston device 400 may be installed in the lubricator module 203 in the opposite direction than the direction as explained above and as illustrated on figures . In that case , the input port 203c is located at a lower end of the lubricator module 203 , and the input port is communicating with the lower volume V2 of cavity C . The input port 203c is also adapted for plugging a conduit , feeding the lower volume V2 with control fluid ( controlled pressure and/or feed volume ) . In that case , the control fluid pressure is able to push the piston device 400 upwards inside the cavity C .

A skilled person may then adapt all features and methods as disclosed in the above illustrated disclosure .

Figure 5 illustrates an embodiment of a holding device 450 , and more specifically a holding mechani sm that control the operation of braking pads 455 inside the holding device 450 .

The first portion 459a (pin) is able to fasten the holding device 450 to the lubricator body . It can also actuate the holding mechanism and to push the braking pads 455 towards the tubing 104 to brake or tighten the tubing 104 . The braking pads 455 can be dissymmetric, such as a wider width at bottom to ensure that the tubing 104 can move only in the downwards direction ( one way) , i . e . down inside the well . This is holding the tubing 104 when the piston device 400 is returning to the upmost position of figure 3E .

Additionally, the holding device 450 may comprise holding rods 456 so that the piston device 400 can catch the holding device at the end of processing thanks to an appropriate catching mechanism .