EP2984278A1

EP2984278A1 - An arrangement and a method for removing debris in a well

Info

Publication number: EP2984278A1
Application number: EP14782848.7A
Authority: EP
Inventors: Bård Martin TINNEN
Original assignee: WTW Solutions AS
Current assignee: WTW Solutions AS
Priority date: 2013-04-09
Filing date: 2014-04-07
Publication date: 2016-02-17
Also published as: NO20130472A1; NO339623B1; WO2014168485A1

Abstract

The present invention regards an arrangement and a method for removing a portion of debris (300) settled on an upper side of a barrier (114), the arrangement and the barrier being integrated in a portion of a tubing (201), the barrier (114) isolating a first tubing section (2002, 2003) from a second tubing section (2001) containing the debris (300), the arrangement comprising: - an inlet (405) communicating with the first tubing section (2002, 2003); - at least one outlet (401, 402, 403) communicating with the second tubing section (2001); - a fluid conduit (400) connecting the inlet (405) with the at least one outlet (401, 402, 403); and - means (112, 113) for controlling fluid flow from the first tubing section (2002, 2003) to the second tubing (2001) via the flow conduit (400).

Description

AN ARRANGEMENT AND A METHOD FOR REMOVING DEBRIS IN A WELL

This invention relates to a well cleanout system associated with the use of downhole well barriers and other downhole well systems where debris may represent a problem.

More particularly the invention relates to an arrangement and a method for removing a portion of debris being on a first side of a barrier located in a section of tubing, the barrier isolating a first section of the tubing from a second section of the tubing.

In conjunction with the completion of wells, involving steps such as the installation of production casing, production liner (lower completion) and production tubing (upper completion), and also intermediate completion strings, barrier systems are commonly used.

In one scenario, a barrier is mounted in top of the lower completion (production liner), to isolate the reservoir whilst installing the production tubing (upper completion) in the upper section of the well.

In another scenario, a barrier is installed in the bottom of the production tubing during the installation thereof. Once the tubing is positioned correctly, pressure is applied on the inside to set the production packer. To form a sealed enclosure during such operation, to allow for pressurizing the internals of the tubing, the bottom of the tubing has to be sealed off. Most commonly, such seal is provided for by using a barrier device.

In even another scenario, a barrier is installed in an intermediate completion string. Typically, such intermediate completion string is installed subsequent to and on top of the lower completion (liner) and prior to running the upper completion (tubing). The reason for installing intermediate completion strings may vary, but a common reason is to mechanically seal off the reservoir of the well prior to running the upper completion. Such considerations may for instance apply if the well is drilled into a highly pressurized reservoir, and there is a large difference in density between the drilling mud (which is in place when running the liner) and the completion fluid (placed in the well in conjunction with running the production tubing), respectively.

A common requirement to the barrier systems described above is the ability to withhold relevant pressure induced forces during the stages where such barrier functionality is required. A second, equally important requirement is that the barrier can be opened or removed when barrier functionality is no longer required, to open the liner and/or production tubular so that fluids can flow through it.

Patent application PTC/NO2012/050020 filed by the present applicant, discloses one specific embodiment of said downhole barriers and is hereby included for reference.

Traditionally, temporary completion barriers were installed and retrieved using well service techniques such as wireline or coil tubing.

In many offshore fields, very costly drilling rigs are utilized for the purpose of dril ling and completing a well. In such cases, any time spent on wireline or coil tubing operations will contribute to making the completion of the well increasingly expensive as it increases the time the drilling rig has to be rented for the completion of the well. To remove the need to operate the above mentioned barrier systems on wireline or coil tubing, barriers that can be operated to open without the need for physical intervention into the well have been developed. Initial systems of such kind were ball valves, flapper valves, sliding sleeves or similar that were operated open by cycling well pressure using a pump at the surface of the well .

Cycling pressure means repeated pressurizing and depressurizing (bleeding down) the tubing (and/or liner top) pressure in order to operate mechanical counter systems associated with the downhole barrier. Typically, after a certain amount of pressure cycles, the mechanical counter system will engage with a barrier activation mechanism that causes the barrier/valve to open. Typically, such engagement is achieved by the counter mechanism ultimately operating a valve member of the activation system that allows well pressure to work against an atmospheric chamber via a piston . The resulting work is used to shift the valve member to an open position. In other versions, such engagement is achieved by the counter mechanism ultimately operating a mechanical lock of the activation system that releases a pre-tensioned spring mechanism in the activation mechanism, whereupon this causes the valve member to shift to an open position. Other similar methods of activating and shifting the valve member may be applied. Such methods would be appreciated by a person skilled in the art, and are not described further herein. Alternative barrier systems to metallic valves are barriers made of non-metallic materials such as for example glass, ceramics, salt or other more brittle materials. A common method for barrier removal in this respect is a mechanical cycle open mechanism that triggers an activation mechanism where an explosive charge is detonated inside or in close proximity to the brittle barrier. An alternative method entails the mechanical cycle open mechanism to operate a mechanical lock that holds a pre-tensioned spring system. When releasing the pre-tensioned spring, an impact device such as a spear will be driven into the brittle barrier to crush it. Even another method for removal is to lead a highly pressurized fluid in between brittle barrier components. Such methods are assumed known to someone skilled in the art, and not further referred to herein.

A well known problem with the above described remotely operated mechanical systems is that if the cycle open mechanism or activation mechanism fails to operate, or if the valve element fails to open for any other reason, alternatives for mechanical removal of the barrier are associated with a relatively high cost and risk. An example of alternative removal is to use coil tubing to shift open, or in the worst case mill out a ball valve or a steel flapper valve.

Typical causes of failure may be debris in the well that jams the cycle open mechanism, the activation mechanism or the valve element itself. It is known that the cleaning of a well can be problematic, and that it is difficult to guarantee that the environment where the cycle open mechanism operates is clean from debris, high viscous agents and similar that could cause problems.

Patent application PTC/NO2012/050084 filed by the present applicant, discloses embodiments of cycle open systems intended for use in wells with debris problems/potential and is hereby included for reference.

Despite having a debris tolerant cycle open system, the final opening of said barrier may still become a challenge should there be debris in the well. In particular, this may be the case should the barrier be covered by larger amounts of debris. In some cases, for example in the case of running the barrier in a well as part of an intermediate completion, with subsequent replacement of well fluid from drilling mud to completion fluid prior to setting the production packer, there is a risk of solids - typically remains from the drilling mud - falling out of suspension and settling on top of the barrier. In some cases, the column of settled solids is known to be as long as 40 meters. The combination of a partly opened/activated barrier with a significant debris column on the top of it may function as a standalone barrier to flow, hence prevent well production. In such cases, physical intervention (using wireline or coil tubing) may be required to remove the debris column and the partly activated barrier. Said physical intervention as well as the associated delay in the drilling rig program may result in a high extra cost.

The object of the invention is to remedy or reduce at least one of the drawbacks of prior art.

The object of the present invention is to provide for an integral well cleanout system that facilitates removal of at least a portion of a debris column that has settled on one side of a well barrier used during the completion of the well .

The object is achieved in accordance with the invention, by the characteristics stated in the description below and in the following claims.

According to a first aspect of the present invention there is provided a well

arrangement for removing a portion of debris settled on an upper side of a barrier, the arrangement and the barrier being integrated in a portion of a tubing, the barrier isolating a first tubing section from a second tubing section containing the debris, the arrangement comprising :

- an inlet communicating with the first tubing section;

- at least one outlet communicating with the second tubing section;

- a fluid conduit connecting the inlet with the at least one outlet; and

- means for controlling fluid flow from the first tubing section to the second tubing section via the fluid conduit.

Thus, the present invention provides an integral cleanout system that facilitates removal of at least a portion of a debris column that has settled on one side of the barrier used during for example a completion of a well.

In one embodiment the barrier is a dual body barrier comprising a first barrier element and a second barrier element, the barrier elements defining a cavity communicating with the inlet and forming part of the first section upon removal of the second barrier element so that said means for controlling fluid flow from the first tubing section to the second tubing section comprises the second barrier element.

Further aspects are provided in claims 2-4 and 6-9. The embodiments shown in the specific part of this document are related to a dual element barrier design where each of the two barrier elements being construed from a plurality of smaller elements to form a stable geometry, the barrier elements being designed to withstand pressure forces from a first and a second tubing portion, respectively. However, the invention herein may also be applied to other types of barrier design, such as frangible barriers (made from brittle materials such as glass or ceramics), metallic valves such as flapper and ball valves and other, and is not limited to use with dual body barrier systems, only. Sometimes, such other design barriers, single as well as plural body/element design, fail to fully open or activate due to the said debris column lying on top of them. Consequently, the herein described functionality for removal of debris upon barrier activation is deemed useful and relevant for most downhole barrier systems. This would be appreciated by a person skilled in the art.

In a preferred embodiment, the arrangement for removing a portion of debris settled on one side of a barrier is activated at the same time, or in a related timeframe to the activation of the barrier itself. By "related timeframe" it is meant at some related operative step, prior to or after activating the barrier to open. Preferably, for such applications, the debris removal system is activated prior to barrier activation, to avoid a large debris column causing malfunction during the barrier removal stage.

It is emphasised that the features of the present invention differ from the known concept of "equalizing" wireline retrievable bridge plugs, which is a common operational step in conjunction with the pulling of bridge plugs. Here, a pressure equalizing function is activated to prevent differential pressure forces acting on the plug at the instant of releasing it from the tubing wall, to avoid unwanted/uncontrolled movement of the plug. Should there be a debris column on top of a bridge plug, traditional equalizing methods (using a mechanical tool intervened on wireline) would not be able to engage with the plug. Irrespective of what technique being applied to equalize a bridge plug, prior art design would only provide for fluid communication path(s) limited to the distance between the bottom and the top of the bridge plug, which may not be suitable for the removal of debris accumulations being of the nature as described herein.

Finally, all known tubing integrated completion barriers are of a very different design and operated different than bridge plugs (which are interveneable barriers), hence traditional equalizing considerations don't apply.

The present invention discloses a system for sequential removal of debris that has settled on a barrier, such as a completion barrier, by providing fluid outlet points along the tubing mandrel above the barrier, and associated system components as well as methodology for controlling flow, hence obtaining as optimal a debris removal pattern as possible.

According to a second aspect there is provided a method for removing a portion of debris settled on an upper side of a barrier integrated in a portion of a tubing, the barrier isolating a first tubing section from a second tubing section containing the debris; the method comprising :

- arranging a fluid conduit bypassing the barrier, the fluid conduit having an inlet communicating with the first section and at least one outlet communicating with the second section; and

- - activating a means for controlling fluid flow from the first section via the fluid conduit and out of the at least one outlet in the second section, said means being activated at the same time, or in a related timeframe to the activation of the barrier itself.

Further aspects are provided in claim 11 et seq.

The following describes a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which :

Fig. la-lc illustrates an example of generic use of the invention;

Fig. 2a-2c illustrates one embodiment of a prior art barrier system with an associated cycle open and activation mechanism;

Fig. 3 illustrates one potential problem associated with the prior art design

shown in fig. 2a;

Fig. 4 illustrates one embodiment of a barrier system with an associated cycle open and activation mechanism, including a cleanout arrangement according to the present invention;

Fig. 5 illustrates a first operational step for the cleanout system shown in fig. 4;

Fig. 6 illustrates an alternative embodiment of the cleanout system shown in fig.

4;

Fig. 7 illustrates another alternative embodiment of the cleanout system shown in fig. 4; Fig. 8 illustrates a second/subsequent operational step for the cleanout system shown in fig. 4;

Fig. 9 illustrates another alternative embodiment of the cleanout system shown in fig. 4;

Fig. 10 illustrates another alternative embodiment of the cleanout system shown in fig. 4;

Fig. 11 illustrates an embodiment of the invention used for a single body barrier system; and

Fig. 12 illustrates a subsequent operational step to what is illustrated in fig. 11.

Figures la-lc illustrate a borehole 101. Casing 102 is used to prevent the borehole from collapsing during drilling and subsequent production, and to seal off the borehole wall to prevent unwanted leakage to or from strata/zones in the underground and ultimately to provide a barrier between the pressurized hydrocarbon reservoir and the open environment. In most cases, the casing is cemented to the rock wall as will be appreciated by any person skilled in the art and thus not illustrated herein. A generic well completion is illustrated. In figures la-lc the lower completion 1000 comprises a cemented production liner 103 which is open towards the hydrocarbon reservoir via perforations 104. A person skilled in the art will know that the design and configuration of the production liner 103 may vary significantly from what is illustrated herein. The production liner 103 is anchored to and forms a seal towards the casing 102 by means of a liner hanger system 105.

An intermediate completion 1001 forms part of the completion string and is stung into the lower completion by means of a seal stinger assembly 107. A sealing arrangement 108 comprising a barrier 114 is installed as an integral part of the intermediate completion 1001. Also, the intermediate completion 1001 includes a mechanical cycle open mechanism 112 that is associated with an activation module 113 that triggers the opening and/or removal of the barrier 114 when it has served its function in the completion process. Finally, a cleanout system or arrangement 117 according to the present invention is incorporated as part of the intermediate completion 1001.

The upper completion 1002 comprises the production tubing 106, which is stung into the intermediate completion 1001 by means of a seal stinger assembly 116. The upper completion 1002 includes the production packer 109. In the top of the well, the tubing 106 is terminated in the wellhead 110. The completion design may vary significantly from what is shown in fig. 1, and there are common completion components that are not illustrated herein, such as a downhole safety valve. These facts will be appreciated by a person skilled in the art. Similarly, the device according to the present invention can be used for other completion designs than what is shown herein, and fig ures laic is only an example.

When running the upper completion 1002 in the hole, the production packer 109 is not activated, as illustrated in fig. la.

The centerline 115 of the tubular is illustrated for reference. A debris column 118 is indicated on top of the barrier 114.

Now considering fig. lb, a pump 111 is set in fluid communication with the wellhead 110. The production packer 109 comprises mechanical anchors and seal elements as will be appreciated by a person skilled in the art. In order to set the production packer 109, meaning to expand the mechanical anchors and seal elements to engage with the casing 102, the pump 111 is used to apply high pressure to the fluid inside the tubing 106. This is possible due to the sealed enclosure formed by the tubing 106, the sealing arrangement 108, the wellhead 110 and the pump 111. After setting the packer 109, the barrier 114 is no longer required in the well. The next step is to remove the barrier 114 so that the well can be put on production or injection.

To remove the barrier 114, the fluid inside the tubing 106 is pressure-cycled as described earlier in this document, using the pump 111. For each complete pressure cycle, a mechanical cycle open mechanism 112 is operated one step. After a certain amounts of steps, the mechanical cycle open mechanism 112 will interact with an activation module 113 that triggers the opening and/or removal of the barrier 114. In summary, after a certain amount of cycles, i.e. pressurizing and de-pressurizing the tubing fluid, the barrier 114 opens. Fig. lc illustrates the well completion after the barrier 114 has been opened by being removed.

In a situation where the debris column 118 shown in figures la and lb prevents the barrier 114 from opening, or causes the barrier 114 to only partly open/activate, and where the debris column 118 forms a plug in the wellbore in combination with the partly activated barrier 114, or acts as a standalone plug, with the result that the well will not open for production, the cleanout system 117 provides for an arrangement and a method of flushing away the debris so that the wellbore fully opens. Fig. 2a illustrates an embodiment of the barrier 114, the cycle open mechanism 112 and the activation module 113 described above is mounted inside a pipe mandrel 201. In other embodiments, the pipe mandrel 201 may comprise two or more sub mandrels, i.e. that pipe mandrel 201 is an assembly construed by several mandrels.

For the illustrated embodiment, the barrier 114 comprises an upper barrier element 202 and a lower barrier element 204 covered by elastomer membranes 203 and 205, respectively. The barrier elements 202, 204 are terminated to the wall of the mandrel 201 via saw-tooth shaped interface profiles 210, 211 as shown. The saw-tooth profiles 210, 211 provides for a strong anchoring of the barrier elements 202, 204 to the wall of the mandrel 201, and at the same time, only small/shallow radial cuts/grooves are required in the mandrel for anchoring the barrier elements 202, 204. This is beneficial as the reduction of thickness; hence loss of strength of the mandrel 201 is reduced to a minimum by using this technique, emulating pipe threads but normally without the lead associated with threads.

As further elaborated on in patent application PTC/NO2012/050020, the upper barrier element 202 and lower barrier element 204 comprises a plurality of smaller elements 213 and 213', as indicated in figures 2b and 2c, respectively. When assembled, barrier elements 202, 204 are stable and capable of carrying high loads from a first direction, but weak against loads imposed from a second (opposite) direction. More specifically, the upper barrier element 202 combined with the upper elastomer membrane 203 is capable of withstanding very high delta pressures if the pressure of portion 2001 defined by the mandrel 201 and the upper barrier element 202 exceeds the pressure of the portion 2002 defined by the mandrel 201 and the upper barrier element 202 and lower 204 barrier element. On the contrary, if the pressure in portion 2002 exceeds that of the pressure in portion 2001, the upper barrier element 202 would tend to rapidly disintegrate in an upwards direction further to the orientation shown in the figure. Similar conditions apply for the lower barrier element 204 considering delta pressures between portion 2002 and 2003, respectively.

As further elaborated on in patent application PTC/NO2012/050084, the cycle open mechanism 112 is operated by cycling pressure inside the completion. As a function of rising and lowering pressure inside portion 2001 (using a pump 111 at the surface of the earth), the cycle piston 206 is shifted up and down and operates a counter mechanism inside the cycle open mechanism 112. The cycle piston 206 is located i nside an "open geometry" recess 207 of the mandrel 201. Said open geometry being intended to make the cycle open mechanism 112 more robust against debris than traditional, often "closed geometry" prior art designs.

After a designated number of pressure cycles, the cycle open mechanism 112 interacts with an activation mechanism 113 that serves the function to activate/ re move the barrier 114. In the embodiment shown in figures 2a-2c the activation mechanism 113 opens for flow between a communication port 208 provided in the mandrel 201 and a fluid communication line 209 running inside a wall of the mandrel 201, terminating in cavity 2002 between the barrier elements 202, 204. The cavity 2002 will also be denoted portion 2002.

As illustrated in fig. 2b, when opening for flow from portion 2001 to portion 2002 via the fluid communication line 209, pump action on surface can be used to disintegrate the lower barrier element 204, pumping the plurality of individual elements 213 downwards after rupturing the lower membrane 205. The reason for this is that the said pumping action will increase the pressure in portion 2002 (because of this now being in fluid communication with portion 2001) to a level exceeding the pressure in portion 2003, whereupon the lower barrier element 204 and membrane 205 will disi ntegrate and be flushed downwards in the wellbore 201.

As illustrated in fig. 2c, having removed the lower barrier element 204, the well can now be put on production, whereupon the pressure in portion 2002 and 2003 (which now are merged) will exceed the pressure in portion 2001, whereupon the upper barrier element 202 is disintegrated. In one embodiment, the plurality of individual elements 213' of the upper barrier element 202 are flushed upwards and out of their stable initial position shown in figures 2a and 2b, by the production flow 214 after rupturing the upper membrane 203. In one embodiment, the communication line 209 includes a one way valve 212 that prevents fluid flowing from portions 2002, 2003 to portion 2001, via line 209. Thus, a required delta pressure (between portion 2002 and 2001, respectively) sufficient to flush the upper barrier element 202 and membrane 203 away is established at this last stage of the operation.

Fig. 3 illustrates a scenario where a debris column 300 has formed on top of the upper barrier element 202 and corresponding membrane 203. Here, the lower barrier element 204 and membrane 205 have been flushed out of their original position by applying a pump at the surface of the earth, pumping fluid down the completion and into the fluid communication line 209 via communication port 208 after operating the activation system 112, 113. However, when attempting to put the well on production, the upper barrier 202 and membrane 203 cannot be pumped out of their position due to the weight and consistence of the debris column 300. In other words, for this embodiment, the combination of upper barrier 202, membrane 203 and the debris column 300 is capable of withstanding the pressure in cavity or lower portion 2002 provided by the productions flow and/or reservoir pressure.

Traditionally, such cases would require the removal of the debris column using intervention techniques such as wireline or coil tubing.

In one embodiment, the check valve 212 is removed from the line 209, so that a limited production flow could be established up fluid communication line 209 via communication port 208 and into the production tubing after removal of the lower barrier element 204. This could be relevant for verification purposes - i.e. pressure testing could be performed using a pump 111 at the surface to verify that fluid communication has been established between portion 2003, 2002 and 2001, respectively, meaning that the cycle open system 112 has been working properly (and that the reason for not obtaining subsequent production flow being debris 300 accumulated on top of the barrier 114). For prior art barrier systems, fluid communication may not be esta blished between portions above and below the barrier upon activation, preventing such verification of the cycle open system 112 being operated successfully.

Due to a limited cross-sectional area of line 209 and port 208, relevant production flow rates would be too low to be utilized for such purposes. Most prior art design barrier systems do not facilitate for production flow in conduits, such as fluid communication line 209, running inside the mandrel 201 wall as shown herein, i.e. they could not support said verification of fluid communication between portions 2003, 2002 and 2001, respectively.

It is also noted in conjunction with fig. 3 that for this embodiment, the cycle open system 112, the activation system 113 and the communication port 208 are elevated to a position relatively high above the upper barrier element 202, to extend above the top of the debris column 300. Such techniques are commonly used to minimize the debris impact on the cycle open system 112, but are somewhat uncertain as the exact height of the debris column 300 may be difficult to predict prior to completing the well.

Fig. 4 illustrates one embodiment of a cleanout system 117 according to the present invention. For this embodiment, the cleanout system 117 comprises a fluid conduit 400 running inside the wall of the mandrel 201 from an inlet 405 located in a centre cavity 2002 between upper barrier element 202 and lower barrier element 204, to exit points 401, 402, 403 spaced apart along the wall of the mandrel 201. The fluid line 400 will in the following also be denoted a flushing line 400. A check valve 404 is provided in the flushing line 400 for preventing flow from portion 2001 into portion 2002 via the flushing line 400. Thus, check valve 400 prevents unwanted/accidental activation of the barrier 114 via the flushing line 400. The check valve 404 could be of a large range of designs, as would be appreciated by a person skilled in the art.

For the embodiment shown in fig. 4, the flushing line 400 is illustrated as a standalone line, in the form of a drilled bore in the mandrel 201, isolated from other lines running through the mandrel 201, such as the fluid communication line 209. In other embodiments, there may be more lines running through the mandrel 201, and for some embodiments, the flushing line 400 serves a combined purpose. This could be required to minimize the need to provide a plurality of conduits in the wall of the mandrel 201, or in the case of spatial constraints during design and manufacture. In embodiments where lines 400, 209 should serve multiple purposes, selected valve arrangements are required to avoid conflict of purpose/operation. This would be appreciated by a person skilled in the art.

In the figures the fluid conduit or flushing line 400 is shown running inside the wall of the mandrel 201. In an alternative embodiment (not shown) the flushing line may be arranged on the outside of the mandrel 201. In such an alternative embodiment the at least one outlet 401, 402, 403 is in fluid communication with the flushing line 400 via bore(s) through the wall of the mandrel 201. The purpose of the flushing line is still to provide a line 400 bypassing the barrier 114 from the inlet 405, communicating with the first section 2002, 2003, to the at least one outlet 401, 402, 403 communicating with the second section 2001.

Fig. 5 illustrates a situation after removal of the lower barrier element 204 and membrane 205 as explained previously. The well is then put on production to remove the upper barrier element 202 and appurtenant membrane 203. The cleanout system 117 will provide a step-wise flushing process to remove the debris column 300 so that the upper barrier element 202 and membrane 203 can be removed after at least some of the debris column 300 is removed .

Upon opening for fluid flow in the flushing line 400 after removal of the lower barrier element 204 the fluid will initially flow from portion 2002, which is now merged with the lowermost portion 2003 to form a first portion, via the inlet 405, up the flushing line 400 and out through the uppermost exit point 403, where the effective flow restriction created by (alternatively; the delta pressure required to break through) the debris column 300 is the smallest. This is illustrated by arrows 5000 in fig. 5. This ini- tial flow will flush away an upper portion 5001 of the debris column 300, and this will enable subsequent flow via exit point 402, as the removal of overburden caused by flow through exit 403 has reduced the required delta pressure required to establish flow at exit 402, and the pattern will repeat itself, cascading downwards.

In one embodiment, a filter 405' is provided at the inlet 405 to prevent particles above a predetermined size from entering into the inlet 405 and cause plugging, see fig. 9.

In summary, the invention will allow gradually flushing away more and more of the debris column 300 by stepwise flushing away an upper part thereof by means of fluid flow from an upper exit point 403 and thereby preparing/facilitating for a subsequent fluid flow at a lower exit point 402 and finally out of lower exit point 401, until the majority of the debris column 300 has been flushed away, whereupon the overburden will be reduced to a level where the upper barrier element 202 and membrane 203 will be flushed out of its original position by the fluid in the first portion 2002, 2003 below the upper barrier element 202.

The exit points 401, 402, 403 will also be denoted outlets 401, 402, 403.

For the design shown in fig. 5, there may be a risk of not achieving the above described debris column 300 removal pattern. This could be the case if the flow rate through an upper exit point, such as exit point 403, is insufficient to flush the debris permanently away from its original position. This could also be the case if the pressure loss between first portion 2002, 2003 and second portion 2001 associated with the flow pattern through an upper exit point such as exit point 403 is so low that it prevents the establishment of flow via a lower exit point such as exit point 402. More specifically, if the pressure loss is sufficiently low, it may not be possible to achieve a high enough delta pressure between exit point 402 and portion 2001 to "break up" the portion of the debris column 300 running between exit point 403 and exit point 402.

In one embodiment of the invention, the exit points 403, 402, 401 are provided with a one way valve, a one way mechanic plug arrangement or similar to prevent debris from entering the exit points 403, 402, 401 during the completion process, hence preventing unwanted blocking of the exit points prior to operation.

Establishing communication between a portion below and above a barrier is known technique in conjunction with the retrieval of bridge plugs. Often, such plugs are equalized prior to pulling them, meaning that fluid communication is established between portions above and below the plug prior to disengaging its anchors from the pipe it is set in. The reason for the equalizing process being to avoid uncontrolled movement of the plug upon release due to differential pressure forces acting on it. For bridge plugs, communication is typically established by mechanical manipulation using a pulling tool. Moreover, the length and geometry of the equalizing conduits are limited by the dimensions of the plug itself, which is normally short, and in many cases substantially shorter than the length of debris 300 described in the embodiments herein. A main difference between the equalizing of bridge plugs and the technique described herein is that the inlet 405 is opened/accessed for flow upon activating the barrier 114, whereupon a flow pattern designed to remove a larger debris column 300 is established.

Fig. 6 illustrates the use of tailored nozzles 601, 602, 603 (defined by the hole geometry of exit points 401, 402, 403, or by means of physical inserts, such as ceramic inserts) in conjunction with the exit points 401, 402, 403 respectively. The purpose of said nozzles 601, 602, 603 is to create a controlled flow and delta pressure pattern associated with the cleanout flow through cleanout system 117. In the embodiment illustrated in fig. 6, the nozzles 601, 602, 603 are orifices with a designated size. In one embodiment the orifices has an inner diameter of 4 millimeters, equivalent with many ICD solutions (ICD - inflow control device) commonly used in lower well completions to provide an even flow distribution along the producing interval. The use and functionality of ICD devices, hence nozzles 601, 602, 603, would be appreciated by a person skilled in the art and is no further described herein.

In a preferred embodiment, ICD design nozzles 601, 602, 603 mounted in the exit points 401, 402, 403 will provide an optimal flow pattern and distribution (within a defined min-max flow rate and delta pressure range) between the exit points 401, 402, 403, whereupon the debris column 300 is flushed up and away in a cascading pattern, starting with its upper part and continuing downwards as a function of flow being established at lower exit points 402, 401, as a function of flushing away parts of the debris column 300 that is located adjacent to higher exit points 403, 402. Thus, the nozzles 601, 602, 603 utilized in the cleanout system 117 according to the present invention provide a step-wise removal of at least parts of the debris column.

Fig. 7 illustrates even another embodiment where the exit points 401, 402, 403 are provided with autonomous flow control devices 701, 702, 703. The autonomous flow control devices 701, 702, 703 could be in the form of AICD's (AICD - autonomous inflow control device), which are commonly used in conjunction with lower well completions, and that self-regulate as a function of flow rate and delta pressure (as well as other parameters - AICD devices can be set up to operate based on changes in fluid density, viscosity, salinity or a combination of parameters).

A desirable feature both in the case of using nozzles 601, 602, 603 or control devices 701, 702, 703, would be a nozzle/valve design that operated between zero flow and an upper flow rate defined as follows:

• The upper flow rate should be high enough to flush away debris 300, i.e. establish a flow pattern so that the debris 300 is removed from the area of interest.

• The upper flow rate established at an upper exit point 403, 402 should be low enough to represent a true choking effect within the cleanout system 117, so that the pressure differential between a lower exit point 402, 401 and the upper portion 2001 of the wellbore remains relatively high, and flow will be esta blished even if the overburden over a lower exit point 402, 401 is relatively large.

IDC and AICD design features would be known to a person skilled in the art and is no further commented herein.

Fig. 8 illustrates a situation further to the embodiment shown in fig. 6, where flow has been established at exit point 402 after the flow from exit point 403 has removed a sufficiently large portion 5001 of the debris column 300. This again will entail further removal of debris column 300, whereupon flow will be established from exit point 401, and, finally, the upper barrier element 202 and membrane 203 can be flushed away by the production flow of the well.

Fig. 9 illustrates a filter 405' located adjacent to inlet 405, to prevent impurities in the production flow 5000 from plugging the inlet 405.

Fig. 10 illustrates the exit points 401', 402', 403' being oriented in upwards and downwards angles relatively to the direction of the wellbore. Upward directed exit points 402' could be better suited to lift portions of debris 300 during the "brea kthrough" stage when initial flow from the exit point 402' in question is being established. Downward directed exit points 401', 403' could be suited to flush out a portion of debris 300 being located below the exit point 401', 403', hence easing the process of establishing initial flow at an lower lying exit point. In a preferred embodiment, a combination of upward, downward and horizontal exit points 401, 402, 403, 401', 402', 403' are used to obtain an optimized, cascading pattern of flushing away at least a part of the debris 300 required to initiate and establish full production flow from the well.

Fig. 11 illustrates an alternative embodiment of the invention, where a single body barrier 1101, a cycle open mechanism 112 and an activation module 113 is mounted inside a pipe mandrel 201. In fig. 11 the single body barrier 1101 separates a lower portion 2003 from an upper portion 2001 of the well. The activation module 113 is functionally connected to the barrier 1101, illustrated by dotted line 1103. For this embodiment, the flushing line 400 is initially closed by a valve 1102, and the activation module 113 is functionally connected to the barrier 1101, illustrated by dotted line 1104.

In fig. 12 an operation of the cycle open mechanism 112 and activation module 113 has resulted in manipulating barrier 1101 to open (or disintegrate), and also manipulating valve 1102 to open so that fluids can flow through the flushing line 400.

The cycle open mechanism 112, activation module 113, barrier 1101 and the valve 1102 can be arranged to facilitate simultaneous opening of barrier 1101 and valve 1102, or they can be operated at different time periods/sequential operational steps/ pressure cycles. Also, additional, independent cycle open and/or activation mechanism could be used to operate valve 1102, meaning that barrier 1101 and valve 1102 may be operated by fully independent cycle open mechanisms and activation modules. Such a cycle open and/or activations mechanism would be appreciated by a person skilled in the art and is therefore not discussed in any further details.

Claims

P a t e n t C l a i m s

1. A well arrangement for removing a portion of debris (300) settled on an upper side of a barrier (114), the arrangement and the barrier being integrated in a portion of a tubing (201), the barrier (114) isolating a first tubing section (2002, 2003) from a second tubing section (2001) containing the debris (300), the arrangement comprising :

- an inlet (405) communicating with the first tubing section (2002, 2003);

- at least one outlet (401, 402, 403) communicating with the second tubing section (2001);

- a fluid conduit (400) connecting the inlet (405) with the at least one outlet (401, 402, 403); and

- means (112, 113) for controlling fluid flow from the first tubing section (2002, 2003) to the second tubing section (2001) via the fluid conduit (400).

2. The arrangement according to claim 1, wherein the at least one outlet comprising two or more outlets (401, 402, 403) spaced apart in a longitudinal direction of the tubing (201).

3. The arrangement according to claim 1 or 2, wherein the fluid conduit (400) is arranged in a wall of the tubing (201).

4. The arrangement according to claim 1, wherein said means for controlling fluid flow is a cycle open system (112) interacting with an activation system (113).

5. The arrangement according to any of claim 1 to 4, wherein the barrier (114) is a dual body barrier comprising a first barrier element (202) and a second barrier element (204), the barrier elements (202, 204) defining a cavity (2002) communicating with the inlet (405) and forming part of the first section (2002, 2003) upon removal of the second barrier element (204) so that said means for controlling fluid flow from the first tubing section (2002, 2003) to the second tubing section (2001) comprises the second barrier element (204).

6. The arrangement according to claim 5, wherein the second barrier element (204) is removed by means of a cycle open system (112) interacting with an activation system (113).

7. The arrangement according to claim 2, wherein the outlets (401, 402, 403) are further provided with flow regulating means (601, 602, 603; 701, 702, 703) for regulating fluid flow out of the at least one outlet (401, 402, 403) .

8. The arrangement according to claim 7, wherein the flow regulating means (601, 602, 603) is an inflow control device, ICD, for providing an optimal flow pattern and distribution within min-max flow rate and a delta pressure range between the outlets (401, 402, 403).

9. The arrangement according to claim 7, wherein the flow regulating means

(701, 702, 703) is an autonomous inflow control device, AICD, being self- regulating as a function of selected parameters.

10. A method for removing a portion of debris (300) settled on an upper side of a barrier (114) integrated in a portion of a tubing (201), the barrier (114) isolating a first tubing section (2002, 2003) from a second tubing section (2001) containing the debris (300); the method comprising :

- arranging a fluid conduit (400) bypassing the barrier (114), the fluid conduit (400) having an inlet (405) communicating with the first section (2002, 2003) and at least one outlet (401, 402, 403) communicating with the second section (2001); and

- activating a means (112, 113) for controlling fluid flow from the first section (2002, 2003) via the fluid conduit (400) and out of the at least one outlet (401, 402, 403) in the second section (2001), said means (112, 113) being activated at the same time, or in a related timeframe to the activation of the barrier (114) itself.

11. The method according to claim 10, further comprising arranging a flow regulating means (601, 602, 603; 701, 702, 703) in a portion of the fluid conduit (400).

12. The method according to claim 11, wherein the flow regulating means is an inflow control device (601, 602, 603) arranged at the outlet (401, 402, 403).

13. The method according to claim 11, wherein the flow regulating means is an autonomous inflow control device (701, 702, 703), AICD, arranged at the outlet (401, 402, 403).