System and method for forced fluid circulation through annulus of tube

Abstract

Systems and related methods configured to force fluid circulation through an annular space between an inner barrier and an outer cover of a tube, and methods of detecting leaks in an annular space between an inner barrier and an outer cover of a tube. The tube comprises segments (T1, T2, T3, TN) joined together by connectors, where each segment of the tube has an injector tube (I1, I2, I3, IN) for injecting fluid into the annular space at a first end of the segment, and a return tube (R1, R2, R3, RN) for removing fluid from the annular space at a second end of the segment. The system and method can effectively remove any corrosive fluid accumulated in the annular space of the flexible tube.

Description

[0001] This divisional application is based on Chinese Invention Patent Application No. 201880046118.4 (International Application No. PCT / GB2018 / 051463), entitled "System and Method for Forced Fluid Circulation Through Annular Space of Flexible Tube", filed on May 30, 2018.

[0002] Cross-references to related applications

[0003] This application claims the benefit of priority to BR 10 2017 011384-1, filed on May 30, 2017, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This invention relates to piping and riser technology. More particularly, this invention relates to piping with a control system and forced circulation of fluid through the annular space of the piping. Background Technology

[0005] In offshore oil production, riser systems are widely used. Such systems, consisting of risers and flow lines anchored to the seabed and connected to the risers, can be flexible or rigid. They function to collect oil produced from subsea wells, transport the oil to floating units or platforms, and then transfer the oil to tankers or directly to onshore facilities. Riser systems and flow lines are also used to inject gases, chemicals, and other fluids from floating units or platforms into wells for various purposes, such as enhancing well production or storing corrosive gases in tanks.

[0006] "Non-bonded" flexible conduits designed according to standards API Spec 17J and API RP 17B (the descriptions of which are incorporated herein by reference) have an armor typically made of carbon steel and carbon manganese steel, which is confined within an annular space between two permeable polymer layers. These two layers are a first layer (referred to as a "barrier") for isolating the fluid transported within the conduit and a second layer (referred to as an "outer cover" or "outer sheath") for isolating the surrounding environment. That is, the barrier and the outer cover can be considered as the inner and outer sheaths of the conduit. In this document, the term "annular space" is used to refer to this space between the barrier and the outer cover.

[0007] The armor is susceptible to corrosion from corrosive gases (CO2 and H2S) and water that permeate from the inside of the tube through the polymer barrier. Any loss of airtightness in the annulus also results in the presence of water within the annulus.

[0008] Corrosion can lead to failure mechanisms such as stress corrosion cracking (SC-CO2) and pitting corrosion. SC-CO2 stress corrosion cracking is a failure mechanism not covered by the current versions of the international standards for flexible conduits (API Spec 17J and ISO-13628-2). The content of standard ISO-13628-2 is also relevant and is incorporated herein by reference.

[0009] Currently, flexible tubes are typically constructed without an integrated system (to the tube body and connectors) for forced circulation within the annular space between the external cover and the barrier. This integrated system would enable the removal of corrosive gases that may be present in its annular space, thereby reducing the concentration or fugacity of the corrosive gases and preventing or minimizing their corrosive effects.

[0010] In the petroleum industry, in some cases, sections or segments of flexible conduits (with flanges at their ends) are interconnected to allow for the reduction of corrosive gas concentrations. However, this conventional technical solution is insufficient to prevent corrosion caused by condensation of water in the annulus or loss of annular integrity due to seawater intrusion. Typically, the annular space is very limited, making the circulation of already permeated gases and other fluids difficult. Therefore, without forced circulation or changes to the design characteristics of the flexible conduit, it is also difficult to remove or dilute corrosive fluids to acceptable levels.

[0011] Currently available flexible tubes have layers in their annular space that make fluid circulation difficult, and droplets or bubbles of CO2 and dissolved water may be trapped in these layers due to the geometry of certain metal layers (e.g., “Z-shaped,” “T-shaped,” or “C-shaped” layers, as shown in Figure 7 of Utility Recommendation API RP 17B), as well as in the gaps between the metal layers and the polymer layers or in elements (e.g., abrasion-resistant or buckling-resistant bands) arranged between these layers.

[0012] For example, document US20130068465A1 discloses a method for circulating fluid through the annular space of a flexible riser, which requires the use of an umbilicus with a tube to allow, for example, corrosion inhibitors to circulate in the annular space. However, this document does not provide the necessary structural changes to the flexible tube or connector to allow for mitigation of corrosion problems, such as SC-CO2 corrosion and pitting corrosion, in the armor of the flexible tube. The document only considers a single continuous riser, not a riser composed of multiple segments.

[0013] Thus, document US20130068465A1 does not consider how to mitigate corrosion in the armor of the flexible tube in cases where the airtightness of the annulus is lost, for example, due to damage to areas of the external covering (e.g., specific sections when the flexible tube is composed of multiple segments). In such a case, circulation would be interrupted in areas of the annulus that are flooded with seawater. Moreover, the method taught in US20130068465A1 requires additional supports in the platform for the connection of each umbilical cord that would allow necessary circulation in the annulus of the riser.

[0014] Document US2011153225A1 discloses a system and method for volumetric and compositional analysis of ventilation gases in the annulus of flexible tubing structures used in the oil and gas industry, as well as for detecting water flooding. One or more sensors are installed in the pipeline, connected to the ventilation inlet of the flexible tubing and linked to a data logging unit via a software interface, to monitor and record the level and type of the generated gases. The software can be used to analyze the level and type of the generated gases to detect whether the integrity of the pressure jacket has been compromised, whether seawater has entered the annulus, whether the armor or pressure layer has been corroded, and whether the outer jacket has been damaged.

[0015] Therefore, the method and system disclosed in document US2011153225A1 are used for indirect measurement of the water volume in the annular space of a flexible tube (based on calculations of the flow rate, pressure, and temperature of the discharged gas). Since it does not mention modifications to the flexible tube or direct or indirect interconnections of the annular spaces of adjacent sections, it only monitors the first section or a single section of the flexible tube connected to the SPU. Furthermore, the technique is limited to monitoring only and does not envision solutions for forcing fluid circulation in the annular space to prevent failure due to stress corrosion or pitting corrosion caused by corrosive gases such as CO2 and H2S.

[0016] Document WO2015087044A1 relates to a system for real-time monitoring of annular regions of flexible tubes using a sampling chamber based on a sample of the concentration of a target gas in a defined area of ​​the tube. However, this document does not propose a method for preventing corrosive wear of the armor of the flexible tube.

[0017] As will be explained in more detail below, this disclosure addresses the aforementioned problems of the prior art in a practical and effective manner. Summary of the Invention

[0018] This disclosure provides a system and method for forcing fluid circulation through the annular space of a flexible tube, the system and method being able to effectively remove any corrosive fluid that accumulates in the annular space of the flexible tube.

[0019] This disclosure also provides a system and method for forced fluid circulation through the annular space of a flexible tube, the system and method enabling fluid to circulate independently of other sections within each segment of the flexible tube.

[0020] This disclosure also provides a system and method for forced fluid circulation through the annular space of a flexible tube, the system and method allowing leak tests to be performed separately in each segment of the flexible tube, thereby allowing the detection of damaged sections.

[0021] This disclosure also provides a system and method for forced fluid circulation through an annular space of a flexible tube, the system and method allowing the injection of an inert fluid to remove corrosive agents from the annular space or fluid to maintain the tensile armor inside the annular space.

[0022] This disclosure also provides a system and method for forcing fluid circulation through an annular space of a flexible tube, the system and method allowing sampling of fluid present inside the annular space for subsequent analysis of its quality.

[0023] According to a first aspect of the invention, a system is provided that is configured to force fluid circulation through an annular space between an internal barrier and an external cover of a tube, the tube being divided into at least two segments joined together by at least one connector, wherein the system includes one or more of the following: for each segment of the tube, an injector tube is configured to inject circulating fluid substantially at a first end of the annular space of the segment, the injector tube being in fluid communication with the annular space of the segment via an inlet point; and for each segment of the tube, a return tube is configured to remove circulating fluid from the annular space of the segment, the return tube being positioned at a second end of the annular space of the segment of the tube, the return tube being in fluid communication with the annular space via an outlet point.

[0024] Optionally, the outlet point is located on a first connector at the first end of the segment of the pipe.

[0025] Optionally, the inlet point is located on a second connector at the second end of the segment of the tube.

[0026] Optionally, the system is configured to allow fluid communication between the annular spaces of two adjacent segments.

[0027] Optionally, the system further includes an annular valve between adjacent segments of the pipe, the annular valve being configured to allow closure of fluid communication between the annular spaces of two adjacent segments.

[0028] Optionally, the segments are configured such that fluid communication between the annular spaces of two adjacent segments is impossible.

[0029] Optionally, each segment includes a connector at each end, and adjacent segments are connected to each other via the connector.

[0030] Optionally, the system includes at least two injector tubes for each segment of the tube and at least two return tubes.

[0031] Optionally, the first injector tube and the first return tube are a primary set of injector tubes and return tubes, and the second injector tube and the second return tube are a backup set of injector tubes and return tubes.

[0032] Optionally, the system further includes at least one sampler configured to receive recirculated fluid returning from inside the annular space.

[0033] According to a second aspect of the invention, a method is provided for forced fluid circulation through an annular space between an internal barrier and an external cover of a tube, the tube being divided into at least two segments joined together by at least one connector, wherein the method comprises one or more of the following steps: for each segment, injecting circulating fluid through an injector tube substantially at a first end of the annular space of the segment, the injector tube being in fluid communication with the annular space of the segment via an inlet point; and for each segment, removing circulating fluid from the annular space of the segment through a return tube substantially located at a second end of the annular space of the segment, the return tube being in fluid communication with the annular space via an outlet point.

[0034] Optionally, the method further includes, in a return pipe communicating with the segment that has lost its integrity due to regional damage to the outer covering, allowing fluid to flow in the opposite direction to the removal step, thereby causing the return pipe to act as an injector pipe to facilitate the removal of any corrosive fluid in the annular space through the damaged area of ​​the outer covering of the segment to the outside of the annular space or to reduce any corrosive fluid in the annular space.

[0035] Optionally, the method further includes the step of allowing fluid communication between the annular spaces of two adjacent segments.

[0036] Optionally, the method further includes the step of closing the fluid communication between the annular spaces of two adjacent segments by means of an annular valve.

[0037] Optionally, the method further includes the additional step of preventing fluid communication between the annular spaces of two adjacent segments.

[0038] Optionally, the method further includes the step of guiding recirculated fluid from inside the annular space to at least one sampler.

[0039] According to a second aspect of the invention, a method is provided for detecting a leak in an annular space between an internal barrier and an external cover of a tube, the tube being divided into at least two segments joined together by at least one connector, wherein the method detects a segment of the tube in which a leak exists, and each segment is provided with an injector tube and a return tube for circulating fluid through the segment, the method comprising one or more of the following steps: for each segment, changing the pressure within the annular space using the injector tube and the return tube; monitoring the response to the pressure change in each segment and determining whether the response indicates a leak.

[0040] Optionally, changing the pressure includes pressurizing the segment via the return pipe or performing a vacuum test.

[0041] Optionally, monitoring the response to pressure changes in each segment and determining whether the response indicates a leak includes one or more of the following steps: measuring the pressure in the injection line; visually identifying a gas leak; or monitoring the local pressure level in the annular space of each segment.

[0042] According to another aspect, a system is provided for forcing fluid circulation through an annular space of a flexible tube, the flexible tube being divided into at least two segments joined together by at least a pair of connectors, the system comprising (i) at least one injector tube adapted to inject circulating fluid at a first end of the annular space of a designated segment of the flexible tube, the injector tube being in fluid communication with the annular space of the segment via at least one inlet point, and (ii) at least one return tube adapted to remove circulating fluid from the annular space of the segment, the return tube being positioned at a second end of the annular space of the segment of the flexible tube opposite to the first end, and the return tube being in fluid communication with the annular space via at least one outlet point, wherein at least one injector tube and at least one return tube are provided for each segment of the flexible tube.

[0043] A method for forcing fluid circulation through an annular space of a flexible tube divided into at least two segments joined together by at least a pair of connectors is also provided, the method comprising the steps of: (i) injecting circulating fluid at a first end of the annular space of a designated segment of the flexible tube through at least one injector tube in fluid communication with the annular space of the segment via at least one inlet point; and (ii) removing circulating fluid from the annular space of the segment through at least one return tube positioned at a second end of the annular space of the segment of the flexible tube opposite to the first end, the return tube in fluid communication with the annular space via at least one outlet point, wherein at least one injector tube and at least one return tube are provided for each segment of the flexible tube.

[0044] According to another aspect of the invention, a system is provided for forced fluid circulation through an annular space A of a flexible conduit 10, the flexible conduit 10 being divided into at least two segments T1, T2, T3, TN joined together by at least one connector C1a, C1b, C2a, C2b, C3a, C3b, wherein the system comprises: at least one injector tube I1, I2, I3, IN adapted to inject circulating fluid 30 substantially at a first end of the annular space A of a designated segment T1, T2, T3, TN of the flexible conduit 10, the at least one injector tube I1, I2, I3, IN being in fluid communication with the annular space A of the segment T1, T2, T3, TN via at least one inlet point IP, the at least one inlet point preferably located at the point furthest from the offshore facility. The flexible conduit 10 is located at the far end of the annular space A of the segment T1, T2, T3, TN, and at least one return pipe R1, R2, R3, RN is suitable for removing circulating fluid 30 from the annular space A of the segment T1, T2, T3, TN, said at least one return pipe R1, R2, R3, RN is located at the second end of the annular space A of the segment T1, T2, T3, TN opposite to the first end, said at least one return pipe R1, R2, R3, RN is in fluid communication with the annular space A via at least one outlet point OP, said at least one outlet point is preferably located at the end of the segment farthest from the offshore facility; wherein each segment T1, T2, T3, TN of the flexible conduit 10 is provided with at least one injector pipe I1, I2, I3, IN and at least one return pipe R1, R2, R3, RN.

[0045] Optionally, at least one outlet point OP is located on the first connectors C1a, C2a, C3a at the first end of segments T1, T2, T3, TN of the flexible tube 10.

[0046] Optionally, at least one entry point IP is located on the second connectors C1b, C2b, C3b at the second end of the flexible tube 10, which is opposite to the first end, of the segments T1, T2, T3, TN.

[0047] Optionally, the system allows fluid communication between two adjacent annular spaces of segments T1-T2 and T2-T3.

[0048] Optionally, the fluid communication between the annular spaces of two adjacent segments T1-T2 and T2-T3 can be closed by at least one annular valve.

[0049] Optionally, the system includes a case where there is no fluid communication between two adjacent annular spaces of segments T1-I2 and T2-T3.

[0050] Optionally, each segment T1, T2, T3, TN includes connectors C1b and C2b at each end, which are connected to another connector C2a and C3a located at one end of an adjacent segment T1-T2 or T2-T3.

[0051] Optionally, the system includes at least two injector tubes and at least two return tubes for each segment T1, T2, T3, TN of the flexible tube, i.e., a primary first set of injector tubes and return tubes and a backup second set of injector tubes and return tubes.

[0052] Optionally, the system further includes at least one sampler 40, which is adapted to receive recirculated fluid from inside the annular space A.

[0053] According to another aspect of the invention, a method is provided for forced fluid circulation through an annular space A of a flexible tube 10, the flexible tube 10 being divided into at least two segments T1, T2, T3, TN joined together by at least a pair of connectors C1a, C1b, C2a, C2b, C3a, C3b, characterized in that the method comprises the steps of: injecting circulating fluid 30 substantially at a first end of the annular space A of a designated segment T1, T2, T3, TN of the flexible tube 10 through at least one injector tube I1, I2, I3, IN, at least one injector tube I1, I2, I3, IN being in fluid communication with the annular space A of the segment T1, T2, T3, TN via at least one inlet point IP; and removing the circulating fluid 30 from the annular space A of the segment T1, T2, T3, TN through at least one return tube R1, R2, R3, RN, at least one return tube R1 R1, R2, R3, RN are generally located at the second end of the annular space A of the flexible tube 10, which is opposite to the first end. At least one return tube R1, R2, R3, RN is in fluid communication with the annular space A via at least one outlet point OP. Each segment T1, T2, T3, TN of the flexible tube 10 is provided with at least one injector tube I1, I2, I3, IN and at least one return tube R1, R2, R3, RN. In the annular space of a segment that has lost its integrity, at least one return tube R1, R2, R3, RN is used as an injector tube to allow flow in the opposite direction in addition to the regular flow through at least one injector tube I1, I2, I3, IN, thereby causing the corrosive fluid to be removed to the outside of the annular space of the segment or reducing the content of the corrosive fluid through the damaged area of ​​the outer cover of the segment.

[0054] Optionally, the method further includes the step of allowing fluid communication between two adjacent annular spaces of segments T1, T2, T3, TN.

[0055] Optionally, the fluid communication between the annular spaces A of two adjacent segments T1, T2, T3, TN can be closed by at least one annular valve.

[0056] Optionally, the method includes the additional step of preventing fluid communication between the annular spaces of two adjacent segments T1-T2 and T2-T3.

[0057] Optionally, the method includes the additional step of directing recirculated fluid from inside the annular space A to at least one sampler 40. Attached Figure Description

[0058] The specific description presented below is with reference to the accompanying drawings and their corresponding reference numerals.

[0059] Figure 1 A schematic diagram of the piping system is shown.

[0060] Figure 2 Show Figure 1 Detail A of the diagram presented in the image.

[0061] Figure 3 Show Figure 1 Detail B of the diagram presented in the image. Detailed Implementation

[0062] First, it should be emphasized that the following description is based on preferred embodiments. However, it will be apparent to those skilled in the art that the invention is not limited to these specific embodiments.

[0063] Figure 1 A schematic diagram of a system according to a preferred embodiment is shown. Figure 2 and 3 Show each Figure 1 Details A and details B of the diagram presented in the image.

[0064] As can be seen, a system for forced circulation of fluid is applied in the flexible conduit 10, which is divided into at least two segments T1, T2, T3, and TN. Segments T1, T2, T3, and TN are connected to offshore facilities, to each other, or to underwater equipment via multiple pairs of connectors (i.e., connectors located at each of the two ends of the segments). Figure 1 As shown, there will be at least one pair of connectors C1a, C1b; C2a, C2b; C3a, C3b. Figure 1 In the embodiment shown, the flexible tube 10 includes three segments T1, T2, T3, and therefore includes three pairs of connectors.

[0065] As can be seen, the first segment T1 is connected to the offshore facility 20 via its upper connector C1a. The offshore facility 20 can be a floating facility. The offshore facility 20 can be a stationary production unit (SPU).

[0066] The lower connector C1b of the first segment T1 is connected to the upper connector C2a of the second segment T2. Similarly, the lower connector C2b of the second segment T2 is connected to the upper connector C3a of the third segment T3. In a configuration with... Figure 1 In the case of a tube with more segments as shown, these connections continue successively until the nth segment TN of the flexible tube 10. The last segment of the flexible tube ( Figure 1 The T3 in the above is preferably connected to at least one underwater device, such as a manifold, wet tree, rigid pipe or subsea well W.

[0067] A system for forcing fluid circulation through the annular space of the flexible conduit 10 (i.e., the space between the internal barrier and the external covering) may include at least one injector tube I1, I2, I3, IN, preferably at least one injector tube for each segment. The injector tubes I1, I2, I3, IN are adapted to inject circulating fluid 30 at the first end of the annular space A of designated segments T1, T2, T3, TN of the flexible conduit 10. Therefore, the injector tubes I1, I2, I3, IN are in fluid communication with the annular space A of the designated segments T1, T2, T3, TN via at least one inlet point IP.

[0068] The annular space A is defined as the space between the inner polymer barrier IB and the outer polymer covering OC, such as Figure 2 As shown in the diagram, a tensile armor TA with an F is positioned inside the annular space, spaced apart from the pressure armor PA or the outer polymer cover OC.

[0069] The system for forced fluid circulation through the annular space of the flexible conduit 10 may further include at least one return conduit R1, R2, R3, RN, adapted to remove circulating fluid 30 from the annular space A of segments T1, T2, T3, TN, which has been injected via injector conduits I1, I2, I3, IN. The return conduits R1, R2, R3, RN are located at the second end of the annular space A of segments T1, T2, T3, TN of the flexible conduit 10, opposite the first end. The return conduits R1, R2, R3, RN may be in fluid communication with the annular space A via at least one outlet point OP.

[0070] In other words, a given segment TN may have an inlet point IP connected to the injector tube IN and located at one end of the segment, and an outlet point OP connected to the return tube RN and located at the other opposite end of the segment.

[0071] Taking segment T1 as an example, the injector tube I1 injects circulating fluid 30 into the annular space A of segment T1 via an inlet point IP located at one end of segment T1. The inlet point IP can be located on one of the connectors of segment T1 of the flexible tube 10. Figure 1 In one embodiment, the entry point IP is located on the lower connector C1b of segment T1 of the flexible tube 10.

[0072] Once the circulating fluid has been injected into the annular space A of segment T1 via inlet point IP, the fluid will travel along the entire length of segment T1 until the opposite end where the upper connector C1a is located. Outlet point OP is located at the end of segment T1 opposite to inlet point IP. Outlet point OP is in fluid communication with annular space A and the corresponding return pipe R1. Return pipe R1 returns the circulating fluid to offshore facility 20.

[0073] In the arrangement shown, the circulating fluid injected into the annular space A will have an upward flow through the annular space A in the riser section.

[0074] As shown in the figure, the outlet point OP is located closer to the offshore facility 20 relative to the inlet point IP. In this way, the flow within the annular space A will be directed towards the offshore facility 20. Alternatively, the outlet point OP can be located further away from the offshore facility 20 relative to the inlet point IP. In this way, the flow within the annular space A will be directed from the offshore facility 20 towards the well W.

[0075] The outlet point OP can be located at the first connectors C1a, C2a, and C3a at the first ends of segments T1, T2, and T3 of the flexible conduit 10. The outlet point OP can be located at the second connectors C1b, C2b, and C3b at the second ends of segments T1, T2, and T3 of the flexible conduit 10. As a result, the circulating fluid does not flow through the entire length of the flexible conduit 10 to return to the end of the flexible conduit 10 (e.g., to offshore facility 20) via the annular space. Instead, the circulating fluid exits the annular space of the flexible conduit 10 from each segment at the outlet point, and the fluid is then returned via a return pipe different from the annular space of the flexible conduit 10 (e.g., to offshore facility 20). For the segment closest to the return end (e.g., closest to offshore facility 20), this return pipe can be constructed into the final connector C1a.

[0076] The at least one inlet point IP and at least one outlet point OP can be configured as ports in each of connectors C1a, C1b, C2a, C2b, C3a, C3b, which are axially symmetrically distributed with material taken from injector tubes I1, I2, I3, IN and returned to return tubes R1, R2, R3, RN. The inlet and outlet ports can be interconnected to allow circulating fluid to be forcibly injected into the annular space A of the flexible tube 10.

[0077] The fluid circulating within annular space A carries corrosive gases such as CO2 and H2S, as well as water that has seeped through the internal polymer barrier IB from the flexible tube, back to offshore facility 20. This prevents corrosion of the tension armor TA and pressure armor PA located within annular space A by avoiding the accumulation of corrosive chemicals in annular space A.

[0078] The circulating fluid 30 may be selected from the group consisting of inert gases (e.g., N2), non-corrosive gases (e.g., CH4), and liquids used to regulate the annular space (e.g., ethanol, MEG, or chemicals). Optionally, the circulating fluid 30 may be a combination of at least two of the above fluids. However, it should be emphasized that those skilled in the art will be able to determine the optimal fluid to use, and therefore the selection does not constitute a limitation on the scope of protection of the present invention.

[0079] Preferably, the same subsystem described for segment T1 is also provided for each of segments T2 to TN. Thus, each segment has an injection system and return device for circulating fluid independent of the other segments.

[0080] Optionally, all return pipes R1, R2, R3, and RN are combined into a single return line. This combination can occur upon arrival at offshore facility 20. This reduces the number of pipes in the offshore facility and simplifies the system.

[0081] Optionally, gas recirculation via injector tubes I1, I2, I3, IN and return tubes R1, R2, R3, RN ensures the evaporation of H2O molecules (including molecules trapped in the gaps between the tension and pressure armors or in the layers below) that permeate from the inside of the flexible tube, preventing condensation or saturation and the resulting aqueous phase (condensate), which constitutes a necessary condition for the corrosion process.

[0082] like Figure 1 As shown, return pipes R1, R2, R3, and RN also allow sampling of the fluid present in the annular space of each segment by directing the fluid to sampler 40. In this case, isolation valve IV can be opened or closed to direct the recirculated fluid to sampler 40 or for processing and / or disposal.

[0083] Alternatively, return pipes R1, R2, R3, and RN can operate as injectors for recirculated fluid, optionally shared by all sections. That is, the return pipes can be operated in reverse to their normal operation to supply fluid to the sections. This might be desirable, for example, if the integrity of the annular space is compromised. Specifically, in the event of damage to the outer covering of a section, pumping recirculated fluid to the section via both the injector pipes and the return pipes can facilitate the removal of any corrosive fluid from the annular space to the outside of the section's annular space, or reduce any corrosive fluid within the annular space, through the damaged area. This will minimize further damage to the section (and, in the case of fluid communication between the annular spaces of adjacent sections, possibly the remaining portions of the pipes) until it can be repaired.

[0084] This system further envisions the possibility of performing individualized leak tests on the annular spaces of each segment T1, T2, T3, TN. The tests include pressurizing the annular space of each segment T1, T2, T3, TN, and detecting any pressure drop in the corresponding annular space due to a lack of integrity. Such pressurization and testing can be performed on a single segment or a subset of segments. Alternatively, the entire flexible conduit 10 can be pressurized, for example, by simultaneously pressurizing all segments via return pipes R1, R2, R3, RN or injector pipes I1, I2, I3, IN. Alternatively, the integrity of the annular space can be tested by means of a vacuum test (similar to the test specified in Section 9.6.2 of API Spec 17J-4th Edition): via injector pipes I1, I2, I3, IN obtained from lines near sampler 40 and injection lines LI1, LI2 or return pipes R1, R2, R3, RN into the annular space of the segment.

[0085] Defective sections can be identified by measuring pressure using at least one pressure sensor PI-1, PI-2 located in the injection lines LI1, LI2. The injection lines LI1, LI2 can be arranged such that the first injection line LI1 supplies the injector tube I1 of the first section T1, while the second injection line LI2 supplies all other injector tubes I2, I3, IN of the other sections T2, T3, TN of the flexible tube 10. Alternatively (not shown), there are separate injection lines for each injector tube I1, I2, I3, IN.

[0086] During leak testing, defective sections can also be identified by: (i) visual indications of gas leaks (e.g., via ROV); (ii) visual indications of the local pressure levels in the annular space A of sections T1, T2, T3, and TN; or (iii) pressure or vacuum testing conducted via offshore facility 20.

[0087] Optionally, fluid communication between the annular spaces of two adjacent segments is permitted. Fluid communication between the annular spaces of two adjacent segments can be closed by at least one annular valve (not shown). In this way, a choice can be made between allowing or disallowing communication between the annular spaces A of the different segments T1, T2, T3, TN of the flexible conduit 10.

[0088] Alternatively, fluid communication between the annular spaces A of the different segments T1, T2, T3, TN of the flexible conduit 10 is not permitted. That is, the system may not even allow the possibility of fluid communication between the annular spaces A of the different segments T1, T2, T3, TN.

[0089] Each segment T1, T2, T3, TN includes connectors C1a, C1b, C2a, C2b, C3a, and C3b at each end. Within the flexible conduit 10, each connector C1b, C2a, C2b, and C3a is connected to another connector C1b, C2a, C2b, and C3a located at one end of an adjacent segment T1, T2, T3, or TN. At the end of the flexible conduit 10, each connector C1a and C3b is connected to surrounding equipment—namely, offshore facility 20 or well W. Each connector C1a, C1b, C2a, C2b, C3a, and C3c can be connected via… Figure 2 and 3 The flange connector FU shown is connected to an adjacent device (another connector C1b, C2a, C2b, C3a or offshore facility 20 or oil well W).

[0090] To ensure the durability of the solution, spare injection and return lines (not shown) can be interconnected in each segment T1, T2, T3, TN via interconnecting channels present in the connectors and valves (holding and / or pressure control). The spare lines can be put into use if a fault is detected in the main pipe or if the integrity of the annular space in any segment of the pipeline is lost.

[0091] To prevent the annular space A from being flooded, if the tubing (injector tubing or return tubing) has been damaged during installation, it can be isolated before operation of the flexible tubing begins by means of at least one shut-off valve (not shown), for example, actuated by the ROV. This shut-off valve can be opened only after the tubing's airtightness and integrity have been verified. Alternatively, a one-way valve (check valve) can be installed on the return tubing, eliminating the need for opening via the ROV. The shut-off valve or check valve can be installed in the connector.

[0092] To ensure the durability of the solution, at least one spare injection tube and at least one spare return tube (not shown) are interconnected in each segment T1, T2, T3, TN via interconnecting channels present in connectors C1a, C1b, C2a, C2b, C3a, C3b and valves (holding and / or pressure control). The spare tube can be activated if a fault is detected in the main tube or if the integrity of the annular space A of any segment of the flexible tube 10 is lost.

[0093] Therefore, the system may include at least two injector tubes and at least two return tubes for each segment T1, T2, T3, TN of the flexible tube 10, namely, a primary first set of injector tubes and return tubes and a backup second set of injector tubes and return tubes.

[0094] This disclosure further provides a method, as described above, for forced fluid circulation through the annular space A of the flexible tube 10. The method may include one or more of the following steps:

[0095] (a) Circulating fluid 30 is injected substantially at the first end of the annular space A of a designated segment T1, T2, T3, TN of the flexible tube 10 through at least one injector tube I1, I2, I3, IN, the at least one injector tube I1, I2, I3, IN being in fluid communication with the annular space A of the segment T1, T2, T3, TN via at least one inlet point IP.

[0096] (b) Circulating fluid 30 is removed from the annular space A of segment T1, T2, T3, TN through at least one return pipe R1, R2, R3, RN, which is located at the second end of the annular space A of segment T1, T2, T3, TN of the flexible tube 10 opposite to the first end, and the at least one return pipe R1, R2, R3, RN is in fluid communication with the annular space A via at least one outlet point OP.

[0097] (c) wherein each segment T1, T2, T3, TN of the flexible tube 10 is provided with at least one injector tube I1, I2, I3, IN and at least one return tube R1, R2, R3, RN.

[0098] Optionally, the method includes the step of allowing fluid communication between the annular spaces A of two adjacent segments T1, T2, T3, TN. In this case, optionally, the fluid communication between the annular spaces A of two adjacent segments T1, T2, T3, TN can be closed by at least one annular valve (not shown).

[0099] Alternatively, the method includes the step of disallowing fluid communication between two adjacent segments T1, T2, T3, TN in the annular space A. Therefore, only the injector and return pipes of that specific segment T1, T2, T3, TN allow the circulating fluid 30 to circulate through the annular space A.

[0100] Optionally, the method further includes the step of directing recirculated fluid from inside the annular space A to at least one sampler 40.

[0101] Therefore, this disclosure provides a system and method for forced fluid circulation through the annular space of a flexible tube, the system and method being capable of effectively removing any corrosive fluid accumulated in the annular space of the flexible tube, and allowing fluid to circulate independently of other sections within each segment of the flexible tube. Additionally, the system allows for individualized leak testing in each segment of the flexible tube, thereby allowing for the detection of damaged segments. Furthermore, this disclosure envisions injecting an inert fluid to remove corrosives from the annular space or fluid to maintain the tensile and pressure armor within the annular space. Finally, the system allows for sampling of the fluid present within the annular space for subsequent quality analysis.

[0102] Numerous variations are permitted to fall within the scope of this application. This reinforces the fact that the invention is not limited to the specific construction / embodiment described above. Thus, modifications to the above-described apparatus and methods, combinations of different possible variations, and variations of aspects of the invention (which will be obvious to those skilled in the art) are within the spirit and scope of the claims.

Claims

1. A system configured to force fluid circulation through an annular space between an internal barrier and an external cover of a pipe, said pipe being divided into at least two segments joined together by at least one connector, wherein, The system includes: For each segment of the tube, an injector tube is configured to inject circulating fluid substantially at a first end of the annular space of that segment of the tube, the injector tube being in fluid communication with the annular space of the segment via an inlet point; and For each segment of the tube, a return tube is configured to remove circulating fluid from the annular space of the segment, the return tube being located at a second end of the annular space of the segment of the tube, and the return tube being in fluid communication with the annular space via an outlet point.

2. The system according to claim 1, wherein, The outlet point is located on the first connector at the first end of the segment of the pipe.

3. The system according to claim 1 or 2, wherein, The inlet point is located on the second connector at the second end of the segment of the tube.

4. The system according to any one of claims 1 to 3, wherein, The system is configured to allow fluid communication between two adjacent segments of annular space.

5. The system according to any one of claims 1 to 4, the system further comprising an annular valve between adjacent segments of the pipe, the annular valve being configured to allow closure of fluid communication between the annular spaces of two adjacent segments.

6. The system according to any one of claims 1 to 3, wherein, The segment is constructed such that fluid communication between the annular spaces of two adjacent segments is impossible.

7. The system according to any one of claims 1 to 6, wherein, Each segment includes a connector at each end, and adjacent segments are connected to each other via the connector.

8. The system according to any one of claims 1 to 7, wherein, The system includes at least two injector tubes for each segment of the tube and at least two return tubes.

9. The system according to claim 8, wherein, The first injector tube and the first return tube are the main set of injector tubes and return tubes, and the second injector tube and the second return tube are the spare set of injector tubes and return tubes.

10. The system according to any one of claims 1 to 9, wherein, The system also includes at least one sampler configured to receive recirculated fluid returning from inside the annular space.

11. A method for forcing fluid circulation through an annular space between an internal barrier and an external cover of a pipe, said pipe being divided into at least two segments joined together by at least one connector, wherein, The method includes the following steps: For each segment, circulating fluid is injected through an injector tube substantially at the first end of the annular space of the segment, the injector tube being in fluid communication with the annular space of the segment via an inlet point; and For each segment, circulating fluid is removed from the annular space of the segment via a return pipe located approximately at the second end of the annular space of the segment, and the return pipe is in fluid communication with the annular space via an outlet point.

12. The method according to claim 11, wherein the method further comprises: In a return pipe connected to a segment that has lost its integrity due to damage to the area of ​​the outer covering, fluid is allowed to flow in the opposite direction to the removal step, thereby causing the return pipe to act as an injector pipe to facilitate the removal of any corrosive fluid in the annular space through the damaged area of ​​the outer covering of the segment to the outside of the annular space or to reduce any corrosive fluid in the annular space.

13. The method of claim 11 or 12, the method further comprising the step of allowing fluid communication between the annular spaces of two adjacent segments.

14. The method according to any one of claims 11 to 13, the method further comprising the step of closing the fluid communication between the annular spaces of two adjacent segments by means of an annular valve.

15. The method according to any one of claims 11 to 14, the method further comprising the additional step of preventing fluid communication between the annular spaces of two adjacent segments.

16. The method according to any one of claims 11 to 15, the method further comprising the step of directing recirculated fluid from inside the annular space to at least one sampler.

17. A method for detecting leakage in an annular space between an internal barrier and an external cover of a tube, said tube being divided into at least two segments joined together by at least one connector, wherein, The method detects the presence of leaking sections in the tube, and each section is provided with an injector tube and a return tube for circulating fluid through the section. The method includes the following steps: For each segment, the pressure within the annular space is changed using the injector tube and the return tube; Monitor the response to pressure changes in each segment and determine whether the response indicates a leak.

18. The method according to claim 17, wherein, Changing the pressure includes pressurizing the segment via the return pipe or performing a vacuum test.

19. The method according to claim 17 or 18, wherein, Monitoring the response to pressure changes in each segment and determining whether the response indicates a leak includes one or more of the following steps: measuring the pressure in the injection line; visually identifying a gas leak; or monitoring the local pressure level in the annular space of each segment.

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