WO2017089000A1

WO2017089000A1 - Assembly and method of injecting a solidifiable fluid into a well

Info

Publication number: WO2017089000A1
Application number: PCT/EP2016/071978
Authority: WO
Inventors: Oddbjørn BJERKVIK; Eivind Christoffer EIKE HALVORSEN; Dag Jostein INGOLFSRUD KLEVER
Original assignee: Fmc Kongsberg Subsea As
Priority date: 2015-11-23
Filing date: 2016-09-16
Publication date: 2017-06-01

Abstract

An assembly (20) for riserless light well intervention, and associated method, for injecting a solidifiable fluid, such as cement, into a well, the assembly being submergible to a subsea location and is connectable to a subsea well for performing an operation on the subsea well before the assembly is retrieved back to a topside location, the assembly comprises: - a connection means for connecting the assembly to a bore (154) of the subsea well, - pressure control means (PCH) for providing pressure control of the subsea well and the assembly, - launch means (138,139) for launching at least one separating element (5,6) from within the assembly into the bore of the subsea well, and - means for injecting (7) a liquid through the assembly and into the bore of the subsea well.

Description

Assembly and method of injecting a solidifiable fluid into a well

The invention relates to an assembly and method for injecting a solidifiable fluid into a bore of a subsea well, as well as deployment of separating elements into the bore, e.g. wiper plugs or darts, from the assembly arranged at a subsea location. Background of the invention

Traditional well intervention and well abandonment in subsea wells have been conducted using drilling rigs and workover riser systems, where typically cement wiper plugs or darts are launched from topside, through the riser, and down into the well. This is time consuming and requires costly drilling rigs to perform the operations.

Therefore, Riserless Light Well Intervention (RLWI) has been evolved, which involves use of a Riserless Light Well Intervention (RLWI) stack, comprising a subsea lubricator to optimize this type of subsea well intervention where permitted by the scope of work to be performed in the well. The RLWI stack can be run from an intervention vessel without the use of a workover riser or a conventional marine riser. The RLWI stack is used when performing inspection and maintenance of subsea wells, i.e. without using a riser (Riserless), and is conducted by inserting downhole tools into the well under full pressure by the use of wireline. Such methods reduce the cost per operation by 40 to 60 % compared to the cost for performing well intervention on subsea wells when using drilling rigs and traditional equipment.

The RLWI Stack normally comprises the Well Control Package (WCP) connected to the X-mas tree, the Lubricator Section (LS), and the Pressure Control Head (PCH) that is installed together with the wireline tools. All operations are controlled from the Work Over Control System on deck. The RLWI Stack is adaptable to any existing subsea production system on the market. A one-piece XT-adaptor connects the RLWI stack to the X-mas tree.

Although the evolvement and introduction of RLWI systems have rendered possible the use of lighter equipment, i.e. equipment not requiring full-scale conventional drilling and intervention rigs, there are none prior art solutions available which can perform cementing operations without this full-scale rigs.

Cement is introduced into wells to provide support for the downhole casing and to prevent fluid migration between subsurface formations. In the prior art solutions, this is performed using drilling or intervention rigs where all operations are performed topside. Such operations include running or launching a first wiper/dart plug from topside and down into the well, injecting cement behind said first wiper/dart plug, and running or launching a second wiper/dart plug behind the cement.

It is an objective of the present invention to overcome the drawbacks in the prior art solutions. More specific, one objective of the invention is to launch wiper/dart plugs into subsea wells without using a conventional drilling and intervention rig, i.e. by using smaller vessels such as Light Well Intervention (LWI) vessels.

A further objective of the invention is to perform a well sealing operation without the use of a conventional riser extending from the surface to a subsea location. Another objective is to render possible plug launching from a subsea location.

Summary of the invention

These and other objectives of the invention are solved by the independent claims, wherein the dependent claims describe other features of the invention. The invention can be used in well operations, typically in wells used for

hydrocarbon production, but also in water wells, wells producing geothermal heat, storage wells for radioactive material or CO2 etc. The well operations may include abandonment operations, well intervention operations, maintenance operations etc. If used in well abandonment operations, i.e. in operations where the well is to be closed permanently, usually after production operations have drained the

hydrocarbon reservoir or after well logs have determined that there is insufficient earnings potential, plugging material (usually cement) is injected into the well in a sufficient amount to forever prevent leakage from the well. Any well intervention or well maintenance operation may include operations where a poor cement job is repaired, e.g. cement refill, improve cement job, or other typical

maintenance/intervention operations. Thus, the assembly is mainly used for temporary well operations, i.e. it is lowered to the seabed, then the operation is conducted, before the assembly is retrieved back to surface for use on another well or in another location. The invention relates to an assembly for injecting a solidifiable fluid into a well, the assembly being submergible to a subsea location and is connectable to a subsea well for performing an operation on the subsea well before the assembly is retrieved back to a topside location, the assembly comprises:

- a connection means for connecting the assembly to a bore of the subsea well, - pressure control means for providing pressure control of the subsea well and the assembly, - launch means for launching at least one separating element from within the assembly into the bore of the subsea well, and

- means for injecting a liquid through the assembly and into the bore of the subsea well. The solidifiable fluid shall be understood as the material used to permanently seal annular spaces between casing and borehole walls or alternatively to squeeze cement into the reservoir. The solidifiable fluid is also used to seal formations to prevent loss of drilling fluid and for operations ranging from setting kick-off plugs to plug and abandonment. The solidifiable fluid may be a cement, where the most common type is API Oilwell Cement, known informally as Portland cement. In general, oilfield cement is thinner and exhibits far less strength than cement or concrete used for construction due to the requirement that it be highly pumpable in relatively narrow annulus over long distances. Various additives are used to control density, setting time, strength and flow properties. Additionally, special additives are often used to reduce the occurrence of annular gas flow. The cement-slurry, commonly formed by mixing cement, water and assorted dry and liquid additives, is pumped into place and allowed to solidify (typically for 12 to 24 hours) before additional drilling or plugging activity can resume. The cement usually must reach a strength of 5000 psi [34,474 KPa] before drilling or perforating. More advanced oilfield cements achieve higher set-cement compressive strengths by blending a variety of particle types and sizes with less water than conventional mixtures of Portland cement, water and chemical additives. The solidifiable fluid may, as an alternative to cement, be e.g. epoxy, or any other alternative pumpable fluid.

The separating element may be a cementing plug or a rubber plug used to separate the cement slurry from other fluids, reducing contamination and maintaining predictable slurry performance. Two types of cementing plugs are typically used on a cementing operation. A bottom plug is launched ahead of the cement slurry to minimize contamination by fluids inside the casing or production tubing/pipe prior to cementing. A diaphragm in the plug body ruptures to allow the cement slurry to pass through after the plug reaches the landing collar. A top plug has a solid body that provides positive indication of contact with the landing collar and bottom plug through an increase in pump pressure. Alternatively, a pre-set collar might be needed at the setting depth of the solidifiable fluid to stop the first plug/dart. A second plug/dart is released behind the solidifiable fluid, whereafter a liquid is forcing the second plug/dart into the well.

The at least one separating element may be a wiper plug, a dart or a foam ball.

The connection means may be configured for connecting the assembly to a vertical X-mas tree (VXT) or to a horizontal X-mas (HXT) tree if a HXT is used instead of a VXT, either directly to the VXT or the HXT, or via a VXT adapter or a HXT adapter. However, the connection means is adapted to connect the assembly to a variety of subsea structures present subsea other than X-mas trees, such as wellheads, BOPs, manifolds, well slots etc.

The pressure control means may be any means adapted to establish pressure control of a subsea well, including, but not limited to e.g. a pressure control head (PCH). The PCH is normally attached on top of the lubricator and serves as a pressure barrier by sealing the well bore during for example wireline operations, allowing intervention access to wells under pressure. The Pressure Control Head (PCH) normally represents the primary seal when wireline is run into the well.

Alternatively, it may serve as an additional seal, such as a secondary, tertiary seal etc. The pressure control means may be actuated using a ROV, electric, mechanic, hydraulic or acoustic.

When using RLWI for cementing there is a possibility for squeezing reservoir with cement, as well making lower abandonment of wells possible (primary reservoir barriers provide good cement behind 9-5/8" casing can be documented/achieved). The separating elements, i.e. the wiper/dart plugs, are provided to protect the solidifiable fluid from contamination and ensure correct location of the solidifiable fluid, and may advantageously be provided with one plug in front of the solidifiable fluid and one behind. Further, a plug in plug profile may be provided to protect the RLWI stack from contamination of the solidifiable fluid.

The assembly may comprise at least one storage position for the at least one separating element, and launch means for selectively launching the at least one separating element. The at least one storage position may be arranged in a separately retrievable module, and the assembly may further comprise lubricating means for lubricating the at least one separating element into the bore of the subsea well. Such retrievable modules may be any module which is accessible from the surface such that it may be retrieved and installed separate of other subsea equipment. Examples of retrievable modules may be a container or other module, which may e.g. be installed by wire line and/or ROV. The lubricating means may comprise any means which can apply friction reducing compositions, such as lubricators used in lubrication of oil or other lubricating compositions.

However, it is clear that the at least one storage position may be in the retrievable module or in an integrated module, such as a cartridge, in a side bore or branch bore relative the bore of the subsea well.

The assembly may have first and second separating elements releasably arranged in a first position in the assembly. The first position may be in a cement adapter. The cement adapter may have a chamber provided in a cartridge. This may be the initial position of the separating elements. It shall be noted that even though the cement adapter is disclosed as a separate adapter (e.g. in a retrievable module), which is connected to the assembly (e.g. a RLWI stack) subsea, and provides for the possibility of submerging the adapter including the separating elements

independently of the assembly, it is clear that the cement adapter may alternatively be formed as an integral part of the assembly such that it can be installed and/or retrieved together with the assembly.

The cartridge storing the at least one separating element in the cement adapter can be oriented essentially at an angle of 45°, but other orientations may be possible for launching of the at least one separating element e.g. darts or wiper plugs into the solidifying fluid flow (e.g. cement flow or epoxy flow).

The launch means, also referred to as releasing means, may comprise first and second releasing valves arranged to be operated to an open position by for instance an ROV. The ROV may be connected to an ROV interface at each valve for operation of the valves. An accumulator containing pressurized gas, for instance a Nitrogen accumulator, may supply a driving fluid to the chamber/cartridge for launching of the first and second separating elements, e.g. darts or wiper plugs into the cement flow when the valves are in open position. Thus, the launch means releases the first separating element (and any additional separating elements) from the first position in the cartridge into the bore and to a second position in the subsea well.

The assembly may further comprise lubricating means for lubricating additional tools to be used in the well. This comprise any wireline tool, typically tools for logging, milling, punch, tractor.

The assembly may further comprise launch means or releasing means for injecting an activation fluid, the activation fluid having a pressure sufficient to force the at least one separating element into the bore of the subsea well. The activation fluid can be pressurized by hydraulic fluid, MEG, via an umbilical to the surface, from another subsea location, e.g. compressor, a well stream, etc.

The launch means or releasing means may comprise a wireline tool, or be actuated by any electrical, mechanical or hydraulic means. The liquid which is injected through the assembly and into the bore of the subsea well may be a solidifiable liquid, such as cement, epoxy or other sealant material. However, the liquid may also be any other liquid which is used in the relevant operation, such as water, brine, MEG, diesel, mud or any relevant fluid for well- treatment. The liquid may for example be other liquids than the solidifiable fluid if used for pressing a second separation element down the well. E.g. in operation, first a first separation element is launched, then cement is filled behind the first separation element, then a second separating element is launched, and a liquid is used for pushing the second separation element into the well.

The means for injecting liquid may further comprise an inlet, which inlet is connected to a supply arrangement arranged either topside or subsea, for injection of the solidifiable fluid or liquid into the bore after releasing the first separating element into the bore. The other features of these means for injecting solidifiable fluid or liquid may comprise pumps, valves, pressure sensors etc.

The assembly may comprise at least one parking position for each of the at least one separating elements and at least one fluid connection for the liquid to be injected, wherein the at least one fluid connection is arranged upstream of at least one of the parking positions. For example, if there are two separating elements, the fluid connection may be arranged upstream the parking position of the first or second separating element.

The invention further relates to a method of injecting a solidifiable fluid into a well, comprising the steps of:

a) submerging an assembly to a subsea location,

b) connecting the assembly to a subsea well using connection means, the

assembly comprising pressure control means for providing pressure control of the subsea well and the assembly,

c) running additional tools or liquid treatment through the assembly for

preparation of the subsea well,

d) operate launch means for launching at least one separating element from

within the assembly into a bore of the subsea well,

e) injecting a solidifiable fluid into the bore of the subsea well,

f) continue the operation according to program or retrieving the assembly to a topside location after finishing the operation.

The operational safety method of the invention will be integrated to the existing shut down modes i.e. Primary Shut Down (PSD), Emergency shut Down (ESD) and Emergency Quick Disconnect (EQD).

A primary method for shutting in the well may be provided by the regular

Emergency Shut Down (ESD) sequence. However, a surface controlled disconnect of the toolstring will be done and the upper part of the tool pulled back to the lubricator prior to closing the Well Control Package (WCP). Contingency method may be provided by shearing the tool with Safety Head (SH). A proper space out of the wireline toolstring will be required to ensure that the parts going through the Safety Head can be sheared when the plugs/darts are installed and ready to use in the cement adapter.

Various arrangements may be provided as launch means for forcing the darts/plugs into the cement flow. A Welltec stroker tool or similar tool adapted to correct lengths may be used, alternatively MEG may be used or any tools rendering possible moving the darts/plugs into the cement flow. The stroker tool may be a mechanical or electrical wireline stroker tool. Alternatively, the plugs/darts can be pumped into the cement flow by pressurizing the RLWI lubricator

When using MEG to pump dart/wiper plug into cement flow the following pumping sequence may be carried out:

1. Pressurize lubricator to break shear pins and pump first dart into cement flow in front of cement

2. Drop ball to seal in bottom of second plug

3. Run and install insert with check valve

4. Pressurize lubricator to break shear pins and pump second plug into cement flow behind cement

Alternative location and use of cement stinger:

Avoid 2^nd inlet below Safety Head (SH). Cement stinger must be possible to shear with Safety Head (SH) and preferable Upper Process Isolation Valve (UPIV) / Lower Process Isolation Valve (LPIV).

Purpose of cement stinger is to protect valves and be a flow path for cement. The Inner Diameter (ID) of cement stinger is equal to Inner Diameter (ID) of tubing hanger.

It is further possible to communicate with the wireline tool inside stack through IWOCS. This enables near wellhead work without wireline through the water column. Further, this solution enables more power to be available inside the lubricator.

Power and communication cable may be guided through Pressure Control Head (PCH) and connected to the IWOCS. The wireline tool may be installed in the lubricator. According to the invention, there may be arranged a space for at least one independent separating element above an inlet for liquid or solidifiable fluid in the cement adapter. The separating elements can be installed either in the cement adapter or in the Well Control Package (WCP). The separating elements can either be pre-installed with the cement adapter, or be inserted in the cement adapter or WCP by use of a wireline tool at any natural stage in the plugging process. A typical cementing process comprises pumping a spacer fluid in front of the cement, then pumping the cement before pumping another round with spacer fluid after the cement. This takes place in a continuous pumping process. The two darts/plugs can either be injected in the beginning of the pumping process when the cement from surface reaches the cement adapter, or one plug/dart can go before the cement and one after the cement, or both plugs/darts can go after the cement.

Summarized, the invention may have provisions for launching separating elements, such as darts or wiper plugs from inside a RLWI Stack. This may be carried out by use of wireline tools, wireline installable/retrievable plugs with integrated or connected darts/wiper plugs and/or Mono Ethylene Glycol (MEG)/hydraulic fluid. The protection plug or cartridge may be arranged with integrated darts/ or wiper plugs wherein

— dart/wiper plug release mechanism can be electrical, mechanical or hydraulic,

— Operation with MEG and/or wireline tools.

These and other characteristics of the invention will be clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein;

Brief description of the drawings

Fig 1 A shows an example of a RLWI stack with a cement rig up for launching a separating element into a cement flow;

Figure IB shows a first alternative position of the first and second separating element, with a protection plug positioned between an upper xt con and a lower xt con;

Figure 1C shows a second alternative position of the first and second separating element, with a protection plug positioned above both an upper xt con and a lower xt con;

Figure 2 shows details of Figures IB and 1C, showing a lower part of the wireline toolstring and plug/dart assembly going through the Well Control Package (WCP); Fig 3A shows a first embodiment using Mono Ethylene Glycol (MEG) as pressurized fluid to pump the first and second separating elements into the bore of the subsea well.

Figure 3B shows details of one embodiment of the first and second separating elements and the protection plug in the embodiment of Figure 3 A;

Fig. 4 shows a second embodiment using MEG as pressurized fluid for pumping the separating elements into the bore of the subsea well, where the first and second separating elements are arranged in a cartridge;

Figure 5 shows an alternative location of the wireline tool, protection plug and darts/plugs above the barrier elements in a bore of the subsea well;

Detailed description of preferred embodiments

In the following, with reference to the figures, the features of the invention is disclosed in relation to the inventive assembly. However, it is clear that the different features are also valid for the inventive method.

Fig. 1 A shows an example of a subsea temporary assembly 20, exemplified as a RLWI stack with a cement rig up for launching separating elements, e.g. wiper/dart plugs 5, 6 into the cement flow of a passage, i.e. bore 154, in the subsea well.

A possible operational setup of the assembly 20 for performing intervention or abandonment operations is disclosed. The assembly 20 has been submerged to a subsea location 22 and connected to a subsea well 21 for performing an operation on the subsea well 21 , before the assembly is retrieved back to a topside location (not shown in the drawings). The assembly 20 comprises pressure control means for providing pressure control of the subsea well 21 and the assembly. Further, the assembly comprises a connection to a bore 154 of the subsea well 21. The connection may be to a vertical X-mas tree (VXT) 150 (or to a horizontal X-mas tree if a horizontal X-mas tree is used instead of a VXT), either directly to the vertical X-mas tree 150 or via a vertical X-mas tree adapter 144.

The assembly 20 has first and second separating elements 5, 6 releasably arranged at a first position in the assembly 20. The first position is in Figure 1A in a cement adapter 141 arranged with a chamber 160 provided in a cartridge 162 wherein the dart/plugs 5, 6 are arranged in an initial position. It is to be noted that even though the cement adapter 144 is disclosed as a separate adapter which is connected to the assembly 20 (e.g. a RLWI Stack), which provides for the possibility of submerging the adapter including the separating elements 5, 6 independently of the assembly 20, the cement adapter 144 may also be formed as an integral part of the assembly 20 such that it is submerged and retrieved together with the assembly 20. In Fig. 1A, the cartridge 162 in the cement adapter 141 is oriented essentially at an angle of 45° relative the vertical bore of 154 of the well, but other orientations may be possible for launching of the at least first and second separating elements, e.g. darts or wiper plugs 5, 6, into the solidifying fluid flow (e.g. cement flow or epoxy flow).

Launch means, for example first releasing valve 138 and second releasing valve 139, are arranged to be operated to an open position by for instance an ROV. The launch means may further comprise means for injecting an activation fluid, the activation fluid having a pressure sufficient to force the at least one separating element 5, 6 into the bore 154 of the subsea well. Alternatively, the launch means may comprise a wireline tool, and/ or electrical, mechanical or hydraulic means. The ROV may be connected to an ROV interface at each valve 138, 139 for operation of the valves 138, 139. An accumulator 140 containing pressurized gas, for instance a Nitrogen accumulator, supplies a driving fluid to the chamber 160 for launching of the first and second separating elements 5, 6 into the cement flow when the valves 138, 139 are in open position. Thus, the launch means releases the first separating element 5 (and any additional separating elements) from the first position in the cartridge 162 into the bore 154 and to a second position in the subsea well 154. There is provided means for injecting a liquid into the bore 154. In the embodiment in Figure 1A, these means for injecting liquid comprises an inlet 7, which inlet 7 is connected to a supply arrangement arranged either topside or subsea, for injection of solidifiable fluid or liquid into the bore 154 after releasing the first separating element 5 into the bore 154. The other features of these means for injecting solidifiable fluid comprises pumps, valves, pressure sensors etc. The inlet 7 may thus be used both for injecting of a solidifiable fluid and a liquid.

Examples of such solidifiable fluid and liquid are exemplified earlier. In the event that the liquid is different from the solidifiable fluid, the inlet 7 may be used for injecting both the liquid and the solidifiable fluid, which may both be injected through a line running to a surface location or a subsea fluid storage reservoir.

It shall be noted that throughout the description, the term first and second separating elements and wiper/dart plugs have a similar meaning and refer to the same elements on the drawings. The only differences are in the particular embodiments where wiper plugs and darts are explicitly disclosed. Generally, they may be interchanged in each of the embodiments, meaning that if wiper plugs are described also darts may be used, and vice versa.

Figure IB shows a first alternative position of the first and second separating elements 5, 6, with a protection plug 3 positioned between an upper xt con and a lower xt con. The protection plug 3 is used in protecting the RLWI stack above. Figure 1C shows a second alternative position of the first and second separating elements 5, 6, with a protection plug 3 positioned above both an upper xt con and a lower xt con, but below the lowermost main bore element (in Fig. 1C being the Lower Process Isolation Valve, LPIV, 133) such that all main bore elements are protected from contamination by any injected liquid or solidifiable fluid.

The operational procedure of the embodiments disclosed in Figs. IB and 1C are similar to the embodiment in Fig. 1 A. The only difference being the initial positions of the first and second separating elements 5, 6.

Primary method for shutting in the well may be provided by the regular Emergency Shut Down (ESD) sequence. Usually, in an emergency situation, the normal practice is to cut or shear any tools or pipes running through the well barriers, i.e. to cut and damage any tool located at the well barrier. However, according to the present invention a controlled disconnect of the wireline tool will be triggered from the surface and the upper part of the tool pulled back to the lubricator prior to closing the WCP, allowing a lower part of the tool to be left in the well. Contingency method may be provided by shearing the tool with Safety Head 130. A proper space out of the wireline toolstring 159 will be required to ensure that the parts going through the Safety Head 130 can be sheared when the first and second separating elements 5, 6 are installed and ready to use in the cement adapter 141 , and retract any elements obstructing the Lower Process Isolation Valve, LPIV, 133 and Safety Head 130. Thus, the invention enables the possibility of reconnect back onto the protection plug 3 and first and second separating elements 5, 6 once recovered from an emergency situation.

Figure 2 shows details of Figures IB and 1C, and shows the lower part of the wireline toolstring 159 running through the Well control Package, WCP, and further details of the location of the separating elements 5, 6, protection plug 3 and Safety Head 130. It is disclosed cutting devices comprising the Upper Process Isolation

Valve (UPIV) 128, safety head 130 and Lower Process Isolation Valve (LPIV) 133. Dart #1 , reference 5, shall be released into the bore 154 in front of solidifiable fluid, e.g. cement, epoxy or other sealant material. A pre-set collar might be needed at cement setting depth to stop the dart. Dart number #2, reference 6, shall be released behind the solidifiable fluid. The solidifiable fluid, and any liquid, is injected through inlet 7.

Fig 3A shows a first embodiment using Mono Ethylene Glycol (MEG) as

pressurized fluid to pump the first and second separating elements into the bore of the subsea well. It is disclosed an inlet 7 on the left hand side, and a bore of the subsea well 154 where a first and second separating elements 5, 6 are arranged. Above said separating elements 5, 6, a protection plug 3 is arranged. Details of one embodiment of the first and second separating elements 5, 6 and the protection plug 3, is disclosed in the operational setup in the Figure 3B. The first separating element 5 is shown partly surrounding the second separating element 6. The second separating element 6 has a ball seat 163 provided therein. A protection plug 3 with a second seat 166 for receiving an insert with check valve 4 is shown connected to the second separating element 6. A first shear pin 1 is arranged between the first separating element 5 and the second separating element 6. Similarly, a second shear pin 2 is arranged between the second separating element 6 and the protection plug 3. In order to pump the first and second separating elements 5, 6 into the flow of solidified fluid, the following pumping sequence may be carried out, with reference to Figs. 3 A and 3B:

1. Pressurize lubricator, i.e. the MEG inside the lubricator, to break first shear pin(s) 1 , resulting in that the first separating element 5 is separated from the second separating element 6 and allowed to be released from its first position. Pump the first separating element 5 into the bore 154 of the subsea well until it reaches its allocated seat or setting depth in the well bore 154.

2. After the first separating element 5 has reached its position in the well, pump solidifiable fluid through inlet 7 into the bore 154 of the subsea well.

3. After finishing pumping of solidifiable fluid, drop ball 161 to enter ball seat

163 of the second separating element 6 and thus seal off the fluid passage

164 extending from the permanent plug 3 and through the second separating element 6.

4. Run and install insert 165 with check valve 4 until it lands in the second seat 166 in the protection plug 3.

5. Pressurize lubricator, i.e. the MEG inside the lubricator, to break second shear pin(s) 2 such that the second separating element 6 is separated from the protection plug 3 and allowed to be released from its first position. Pump the second separating element 6 into the bore 154 of the subsea well behind the solidifiable fluid using a liquid flowing through the inlet 7 until the second separating element 6 reaches its desired setting depth. After finishing the operation, the check valve 4 in the insert 165 of the protection plug 3 will prevent any pressurized fluids from entering areas above the insert 165 (thus protecting the elements in the RLWI stack above the protection plug 3).

Fig. 4 shows a second embodiment using MEG as pressurized fluid for pumping the first and second separating elements 5, 6 into the bore 154 of the subsea well. The first and second separating elements 5, 6 are arranged in a wiper cartridge 12. The cartridge 12 is connected to a protection plug 3, which protection plug has a check valve 1 1 therein. The protection plug 3 has a passage or chamber 16 for Mono Ethylene Glycol (MEG). The first separating element 5, shown as a lower wiper plug in Fig. 4, is provided in the lower part of the cartridge 12 and is configured to be launched first, i.e. in front of the solidifiable fluid. The second separating element 6, shown as an upper wiper plug in Fig. 4, is provided in the middle part of the cartridge 12 and is configured to be launched into the bore 154 of the subsea well behind the solidifiable fluid. The wiper cartridge 12 is arranged with first and second burst discs 13, 14 at different set points. The first burst disc 13 is arranged in fluid connection with the first separating element 5, whereas the second burst disc 14 is arranged in fluid connection with the second separating element 6. The burst discs 13, 14 break at different threshold pressures and are designed such that the first burst disc 13 ruptures at a lower pressure than the second burst disc 14.

Example of pumping sequence of the arrangement in Fig. 4, i.e. where the first and second separating elements 5, 6 are arranged in the wiper cartridge 12:

1. Pressurize lubricator, i.e. the MEG in the chamber or passage 16, to a first threshold pressure, e.g. 1000 psi (68,9 bar), to break the first burst disc 13. When the first burst disc 13 breaks, the pressurized MEG enters the first fluid line 8 and is guided to the lower MEG chamber 17 in said first fluid line 8. The lower MEG chamber 17 is in contact, either directly or indirectly, with the first separating element 5. Continued pumping of MEG will force the first separating element 5, shown as wiper plug #1 , into the bore 154 of the subsea well. The pumping is then continued until the first separating element 5 reaches its desired setting depth.

2. Pump solidifiable fluid, e.g. cement or epoxy or other sealant, e.g. through the inlet 7, behind the first separating element 5.

3. When the solidifiable fluid has been pumped, pressurize lubricator, i.e. the MEG, to a second threshold pressure, e.g. 2000 psi (137,9 bar), to break the second burst disc 14. When the second burst disc 14 breaks, the pressurized MEG enters the second fluid line 9 and is guided to the upper MEG chamber 18 in said second fluid line 9. The upper MEG chamber 18 is in contact, either directly or indirectly, with the second separating element 6. Continued pumping of MEG will force the second separating element 6, shown as wiper plug #2, into the bore 154 of the subsea well. The pumping is then continued until the second separating element 6 reaches its desired setting depth. Thus, the second separating element 6 is pumped behind the solidifiable fluid (e.g. cement or epoxy). The cartridge 12 may be lowered or submerged to a subsea location either individually of the submerging/installation of the assembly 20, or alternatively as part of the assembly 20. The arrangement may be provided by other units or arrangements than a cartridge, these units or arrangements being capable of bringing the first and second separating elements 5, 6 into the flow of solidifiable fluid.

Figure 5 shows an alternative location of the wireline tool, protection plug 3 and first and second separating elements 5, 6 above the barrier elements LPIV and UPIV 128, 133 in a bore of the subsea well. In this situation an alternative inlet 7 for cement is required. A cement stringer 157 which protects the main bore elements UPIV 128, Safety head 130 and LPIV 133 and side bore inlets from cement contaminations during operations is disclosed in the bore.

The solution in accordance with this embodiment avoids 2^nd inlet below Safety Head 130. The Lubricator Section is shown at LS, while the Well Control Package is shown at WCP. Cement stinger 157 must be possible to shear with Safety Head 130 and preferably Upper Process Isolation Valve (UPIV) 128 and/or Lower Process Isolation Valve (LPIV) 133.

The purpose of cement stinger 157 is to protect valves and be a flow path for cement. The cement stinger 157 should not contain pressure. The Inner Diameter (ID) of cement stinger 157 is preferably equal to the Inner Diameter (ID) of the tubing hanger. It is arranged a seal 158 below the LPIV 133 to protect the WCP.

The invention provides a solution to the drawbacks of the prior art by providing an assembly and associated method which render possible launching of separating elements from a subsea location.

By the above described embodiments, the objective of the invention is achieved, i.e. to provide an assembly and associated method rendering possible launching of separating elements from an assembly. This may be carried out by use of wireline tools, wireline installable/retrievable plugs with integrated or connected darts/wiper plugs and/or Mono Ethylene Glycol (MEG)/hydraulic fluid.

The invention is herein described in non-limiting embodiments. A person skilled in the art will understand that there may be made alterations and modifications to the embodiments that are within the scope of the invention as described in the attached claims. Reference list

1 First Shear pins

2 Second shear pins

3 Protection plug

4 Check valve

5 First separating element

6 Second separating element

7 Inlet

8 First fluid line

9 Second fluid line

11 Check valve

12 Wiper cartridge

13 Burst disc #1

14 Burst disc #2

15 Second burst disc

16 Chamber or passage for MEG

17 Lower MEG chamber

18 Upper MEG chamber

20 Assembly

21 Subsea Well

22 Subsea Location

100 USB

101 DSB

102 UGI

103 GIV

104 eGPU

106 LGI

107 DSBI

108 TCATCH

109 UCIRC

110 CBV

111 CIU

112 UTH1

113 UTH2

114 CI SEL

115 CDV

116 XOCK

1 17 UCIV

118 CIV

119 XOV, UXOV

120 UAIV

121 WK CON

122 HV1

123 TCI2

124 Test, Tl, T2

125 LOXOV 126 LIXOV

127 LCIRC, Lost Circulation

128 UPIV, Upper Process Isolation Valve

129 LCIV

130 SSR, SH, Safety Head

131 LBV

132 BLEED SEL

133 LPIV, Lower Process Isolation Valve

134 LAIV

35', 135 " XT CON

136 WL PLUG, Wire Line Plug

137 CEMENT CON

138 First Releasing Valve

139 Second Releasing Valve

140 Accumulator, e.g. N₂

141 Cement Adapter

142 First Release valve

143 Second Release Valve

144 VXT Adapter, Vertical X-mas Tree Adapter

145 X-over VXT Adapter, X-over Vertical X-mas Tree Adapter

146 VXT CON,

147 PSV, Production Swab Valve

148 ASV, Annulus Safety Valve

149 PWV, Production Wing Valve

150 VXT, Vertical X-mas Tree

151 PMV, Production Master Valve

152 AMV, Annulus Master Valve

153 XOV, X-over Valve

154 bore of the subsea well

155 AWV, Annulus Wing Valve

157 Cement Stinger

158 Seal to protect WCP

159 Wireline toolstring

160 Chamber for cement

161 Ball

162 Cartridge

163 Ball seat

164 Fluid passage

165 Insert (with check valve)

166 Second seat

LS Lubricator section

WCP Well Control Package

167 PAXV

168 SCSSV, Surface Controlled Subsurface Safety Valve

Claims

1. An assembly for injecting a solidifiable fluid into a well, the assembly being submergible to a subsea location and is connectable to a subsea well for performing an operation on the subsea well before the assembly is retrieved back to a topside location, the assembly comprises:

- a connection means for connecting the assembly to a bore of the subsea well,

- pressure control means for providing pressure control of the subsea well and the assembly,

- launch means for launching at least one separating element from within the assembly into the bore of the subsea well, and

- means for injecting a liquid through the assembly and into the bore of the subsea well.

2. Assembly according to claim 1 , wherein the assembly comprises at least one storage position for the at least one separating element, and launch means for selectively launching the at least one separating element.

3. Assembly according to claim 1 or 2, wherein the at least one storage position is arranged in a separately retrievable module, and the assembly further comprises lubricating means for lubricating the at least one separating element into the bore of the subsea well.

4. Assembly according to one of the previous claims, wherein the assembly comprises lubricating means for lubricating additional tools to be used in the well.

5. Assembly according to any of the preceding claims 2-4, wherein said at least one storage position is in a cartridge, in a side bore or branch bore relative the bore of the subsea well.

6. Assembly according to any of the preceding claims 2-5, wherein the launch means further comprises means for injecting an activation fluid, the activation fluid having a pressure sufficient to force the at least one separating element into the bore of the subsea well.

7. Assembly according to any of the preceding claims 1-5, wherein the launch means comprises a wireline tool, and/ or electrical, mechanical or hydraulic means.

8. Assembly according to any of the preceding claims, wherein the liquid comprises a solidifiable liquid, such as cement, epoxy or other sealant material.

9. Assembly according to one of the preceding claims, wherein the assembly comprises at least one parking position for each of the at least one separating elements and at least one fluid connection for the liquid to be injected, wherein the at least one fluid connection is arranged upstream of at least one of the parking positions.

0. Method of injecting a solidifiable fluid into a well, comprising the steps of: g) submerging an assembly to a subsea location,

h) connecting the assembly to a subsea well using connection means, the

i) running additional tools or liquid treatment through the assembly for

preparation of the subsea well,

j) operate launch means for launching at least one separating element from within the assembly into a bore of the subsea well,

k) injecting a solidifiable fluid into the bore of the subsea well,

1) retrieving the assembly to a topside location after finishing the operation.