Modification of composition

Abstract

A method and apparatus for modifying a composition of annulus fluid in at least one annulus region of a flexible pipe, and a flexible pipe are disclosed. The method comprises providing at least one alert signal indicating that a predetermined condition is satisfied associated with an annulus region in flexible pipe body of a flexible pipe; responsive to each alert signal, actuating at least one pump element selectively in fluid communication with a plurality of containers each holding a respective source of a respective counteractive fluid that is a fluid that counteracts a respective predetermined fluid condition; and providing at least one counteracting fluid into the annulus region thereby modifying a composition of annulus fluid in the annulus region.

Description

[0001] MODIFICATION OF COMPOSITION

[0002] The present invention relates to a method and apparatus for modifying a composition of annulus fluid in at least one annulus region of a flexible pipe. In particular, but not exclusively, the present invention relates to the provision of multiple sources of fluid that each have a respective counteractive effect upon fluid that collects in the annulus region of a flexible pipe. By monitoring an annulus region respective counteractive fluids can be selectively introduced to the annulus region in an automatic and real time fashion to constantly modify a composition of annulus fluid in that annulus region thereby helping to minimise any undesired effects caused by migration of gas through fluid retaining layers or outer sheath breach.

[0003] Flexible pipes are widely used in the oil and gas industry in offshore applications for the transportation of oil, gas, water, or other fluids from one location to another. Flexible pipe is particularly useful in connecting sea-level supporting structures and subsea locations (which may be deep underwater, say 1000 metres or more), where the pipe may act as a riser. A flexible pipe is generally formed as an assembly of flexible pipe body and one or more end fittings. Flexible pipe body may have an internal diameter of typically up to around 0.6 metres (e.g. diameters may range from 0.05 m up to 0.6 m). Due to their location, flexible pipes are exposed to a range of challenging conditions that may have high pressures, seawater, high tensile strain, and corrosive environments. Flexible pipe body is therefore composed of several concentric polymeric, metallic, and / or composite layers. For example, pipe body may include polymer and metal layers, or polymer and composite layers, or polymer, metal and composite layers. Layers may be formed from a single piece such as an extruded tube or by helically winding one or more wires at a desired pitch or by connecting together multiple discrete hoops that are arranged concentrically side-by-side. Depending upon the layers of the flexible pipe used and the type of flexible pipe some of the pipe layers may be bonded together or remain unbonded. The polymeric layers generally provide sealing from fluid ingress and the metallic layers structural rigidity.

[0004] Some flexible pipes have been used for deep water (less than 3,300 feet (1 ,005.84 metres)) and ultra-deep water (greater than 3,300 feet) developments. It is the increasing demand for oil which is causing exploration to occur at greater and greater depths (for example in excess of 8202 feet (2500 metres)) where environmental factors are more extreme. For example, in such deep and ultra-deep water environments, ocean floor temperature increases the risk of production fluids cooling to a temperature that may lead to pipe blockage. In practice, flexible pipes are conventionally designed to perform at operating temperatures of -30°C to +130°C and pipe body are being developed for even more extreme temperatures. Increased depths also increase the pressure associated with the environment in which the flexible pipe must operate. For example, a flexible pipe may be required to operate with external pressures ranging from 0.1 MPa to 30 MPa acting on the pipe. Equally, transporting oil, gas or water may well give rise to high pressures acting on the flexible pipe from within, for example with internal pressures ranging from zero to 140 MPa from bore fluid acting on the pipe. As a result, the need for high levels of performance and environmental resilience from certain layers such as a pipe carcass or a pressure armour or a tensile armour layer of the flexible pipe body is increased. It is noted for the sake of completeness that flexible pipe may also be used for shallow water applications (for example less than around 500 metres depth) or even for shore (overland) applications.

[0005] The innermost layers of flexible pipe body often include an inner sheath which can be an extruded non-porous polymer layer that confines a bore fluid to its internal circumference. An outermost sealed or fluid tight layer of a flexible pipe is typically the outer sheath, an extruded non-porous polymer layer that protects the pipe’s structural elements from the environment around the flexible pipe and prevents the ingress of seawater. An annulus region is defined between a radially outer surface of an inner fluid retaining layer and a radially inner surface of an outer fluid retaining layer.

[0006] For some flexible pipes that include intermediate polymer layers flexible pipe body may include multiple annuli. For many flexible pipes though only an outer and an inner polymer layer is included. A single annulus of such a flexible pipe is thus provided as a region between the innermost fluid containing layer and the outermost fluid containing layer. The innermost layer in a primary annulus region is a pressure armour layer. These are made of helically wound flattened metallic wires arranged at a lay angle close to 90°. Neighbouring wound wires in the pressure armour layer interlock to control the gap between windings. Pressure armour is designed to withstand hoop stress in the pipe wall, which is caused by the bore fluid pressure. Pairs of tensile armour layers can also be located in the annulus, and these are cross-wound radially outside the pressure armour layer. Tensile armour layers are often made of slightly flattened rectangular metallic wires arranged at a lay angle of about 30 - 55°. Tensile armour layers support the weight of all internal pipe layers and transfer the resulting tensile stress to the sea-level supporting structures. The annulus may also have other layers such as anti- wear and anti-birdcaging tapes, and thermally insulating layers. Carbon steel wires in the annulus are thus often a feature of flexible pipes for subsea environments.

[0007] During service life of a flexible pipe in a pipeline gases can permeate through various fluid retaining layers and partially or fully fill one or more annulus regions defined by the various layers. Amongst the many problems this can cause is the fact that these gases can cause an outer sheath of the pipeline to breach or the steel layers within an annulus region to corrode if the annulus is not vented sufficiently. It is know that collected gases and their concentrations vary depending upon the field where the flexible pipe is deployed and the service of the pipeline. From a corrosion point of view, methane, carbon dioxide, hydrogen sulphide, water and / or methanol are all fluids which are of interest. It has to date been considered advantageous to be able to control the levels of key target gas levels to ensure they stay below a desired level during operation of a flexible pipe. For example an aim has been to control a corrosive gas level to ensure they stay below an upper limit of so-called sweet service as defined in ISO 15156. Generally at any environment with a H2S partial pressure above 0.05 pounds per square inch absolute (PSIA) is considered as sour service. Conventionally vent valves in a riser system or other such pipeline system have had to be provided which open upon a desired differential pressure being reached. Other alternative ways of helping to vent or exhaust undesired fluid from an annulus region have been suggested.

[0008] Likewise WO2015 / 121616 proposes an alternative approach which provides a predetermined fluid in a void space of an annulus of a flexible pipe. The predetermined fluid can comprise water or grease or an oil which can optionally be dosed with an oxygen scavenger or a H2S scavenger or a pH buffer or a biocide. Whilst the solution proposed in WO2015 / 121616 works well in certain situations it is inappropriate for use under certain circumstances and its usage can prove operationally difficult to implement. A limitation offered by the solution proposed in WO2015 / 121616 is that the single predetermined fluid that can be introduced into an annulus region must be selected in advance. This has disadvantages in the circumstances where unexpected fluids find themselves being introduced into the void space of an annulus.

[0009] Likewise whilst currently liquid chemicals that are used for H2S removal, passivation of metal surfaces etc are known there has been little or no suggestion as to how these can be deployed in a way that optimises end result.

[0010] Certain previous solutions have tried to incorporate a neutralising chemical inside the inner sheath. The effectiveness of this has been limited due to the thickness of the inner sheath. It has also had to be incorporated with a specific contaminant in mind. As a result when other unexpected contaminants find their way into an annulus region there has to date been little solution to the problems that such unexpected fluids can cause.

[0011] It is an aim of the present invention to at least partly mitigate one or more of the above- mentioned problems.

[0012] It is an aim of certain embodiments of the present invention to provide a method of modifying a composition of annulus fluid in at least one annulus region of a flexible pipe.

[0013] It is an aim of certain embodiments of the present invention to provide a flexible pipe and ancillary equipment that can automatically and in real time modify a composition of annulus fluid in at least one annulus region in the flexible pipe.

[0014] It is an aim of the present invention to provide a chemical delivery system that can directly introduce counteractive fluids when needed and that optionally can be linked to a vent gas analysis system and / or the electronic flooding detection system.

[0015] It is an aim of certain embodiments of the present invention to provide a method of manufacturing flexible pipe body capable of selectively introducing desired fluids into one or more annulus regions within flexible pipe body whereby each introduced fluid can have a respective counteractive effect to undesired fluids which have built up in the annulus region.

[0016] It is an aim of certain embodiments of the present invention to provide a system for monitoring component constituents of annulus fluid in an annulus region of flexible pipe body during use of a flexible pipe.

[0017] It is an aim of certain embodiments of the present invention to provide the ability to inject passivating, inhibiting and / or scavenging chemicals and / or dilution gas into an annulus region at any time as and when any one of the possible source fluids that have such counteractive properties is needed.

[0018] According to a first aspect of the present invention there is provided a method of modifying a composition of annulus fluid in at least one annulus region of a flexible pipe, comprising the steps of: providing at least one alert signal indicating that a predetermined condition is satisfied associated with an annulus region in flexible pipe body of a flexible pipe; responsive to each alert signal, actuating at least one pump element selectively in fluid communication with a plurality of containers each holding a respective source of a respective counteractive fluid that is a fluid that counteracts a respective predetermined fluid condition; and providing at least one counteracting fluid into the annulus region thereby modifying a composition of annulus fluid in the annulus region.

[0019] Aptly the method further comprises determining a respective concentration level for a plurality of target fluids in a respective annulus region in flexible pipe body of a flexible pipe; determining that at least one determined concentration level satisfies a predetermined condition, indicating that a respective target fluid is a detrimental target fluid; and varying a concentration level of at least one detrimental target fluid thereby modifying the composition of annulus fluid in the annulus region.

[0020] Aptly determining a respective concentration level comprises determining if a target fluid is present in a sample of annulus fluid from the annulus region.

[0021] Aptly the method further comprises, if a target fluid is determined as present, determining a percentage total of the target fluid in the annulus fluid for each detrimental target fluid.

[0022] Aptly the method further comprises determining the respective concentration level via an analyser module in fluid communication with the fluid communication passageway and that is disposed to sample and identify a plurality of constituent target fluids in the annulus fluid.

[0023] Aptly the method further comprises modifying said a composition by varying a concentration level for each of at least one detrimental target fluid by selecting at least one injectable counteracting fluid from a plurality of possible injectable counteracting fluids and injecting a selected injectable counteracting fluid into at least one fluid communication passageway that extends along a portion of the annulus region and is in fluid communication with at least one region of the annulus region.

[0024] Aptly the method further comprises, for each detrimental target fluid, selecting at least one injectable counteracting fluid; and providing the injectable counteracting fluid from a respective counteracting fluid source into the annulus region. Aptly the method further comprises, via the pump element, urging fluid via a lumen that is disposed helically in the annulus region, and that provides a fluid communication passageway along the annulus region, into the annulus region at a positive pressure.

[0025] Aptly the method further comprises determining that at least one concentration level satisfies a predetermined condition by simultaneously and repeatedly determining a measured level for each detrimental target fluid of the plurality of detrimental target fluids is equal to or greater than a pre-set threshold value.

[0026] Aptly, the method further comprises providing each counteracting fluid by injecting a portion of passivating fluid and / or inhibiting fluid and / or scavenger holding fluid into the annulus region.

[0027] Aptly the method further comprises applying a negative pressure to the annulus region via a pump element thereby drawing annulus fluid selectively from the annulus region.

[0028] Aptly actuating at least one pump element comprises actuating a single pump element that is selectively in fluid communication with a plurality of containers that each holds a respective source of a respective counteracting fluid or actuating a plurality of pump elements each of which is selectively in fluid communication with at least one container that holds a respective source of a respective counteracting fluid.

[0029] Aptly said step of actuating a plurality of pump elements comprises simultaneously or one-by- one, actuating pump elements of the plurality of pump elements thereby simultaneously or in sequence injecting a respective counteracting fluid into an annulus region.

[0030] Aptly providing the alert signal comprises monitoring at least one fluid parameter of at least one of the plurality of target fluids.

[0031] Aptly the at least one fluid parameter is a plurality of fluid parameters.

[0032] Aptly the at least one of the plurality of target fluids is a plurality of target fluids.

[0033] Aptly the at least one fluid parameter is a concentration of at least one of the target fluids. Aptly the method further comprises providing the alert signal when, for at least one of the plurality of target fluids, the at least one fluid parameter exceeds a first predetermined threshold that optionally is a predetermined concentration of at least one of the plurality of target fluids in the annulus region.

[0034] Aptly the predetermined condition is satisfied when at least one fluid parameter of at least one of the plurality of target fluids exceeds a first predetermined threshold.

[0035] Aptly the method further comprises, responsive to the alert signal, providing at least one counteracting fluid into the annulus region for a predetermined period of time.

[0036] Aptly the method further comprises providing a predetermined quantity (that optionally is a volume) of the counteracting fluid responsive to the alert signal.

[0037] Aptly the method further comprises responsive to a further alert signal, providing at least one further counteracting fluid into the annulus region.

[0038] Aptly the method further comprises providing the further alert signal when the at least one fluid parameter (of the at least one of the plurality of target fluids) exceeds a further predetermined threshold that optionally is a further predetermined concentration of the at least one of the plurality of target fluids.

[0039] Aptly the further predetermined threshold is greater in magnitude that the first predetermined threshold.

[0040] Aptly the method further comprises, responsive to a cease signal, ceasing provision of the at least one counteracting fluid into the annulus region.

[0041] Aptly the method further comprises providing the cease signal when the at least one fluid parameter approaches, reaches or exceeds a predetermined cease threshold.

[0042] Aptly the predetermined cease threshold is greater in magnitude than the first predetermined threshold.

[0043] Aptly the method further comprises, responsive to a reactivation signal, providing the at least one counteracting fluid into the annulus region. Aptly the method further comprises providing the reactivation signal when the at least one fluid parameter approaches, reaches or falls below a predetermined reactivation threshold.

[0044] Aptly the predetermined reactivation threshold is greater in magnitude than the first predetermined threshold and / or is less than (in magnitude) than the predetermined cease threshold.

[0045] Aptly the method comprises substantially filling a void space of an annulus with a selection of predetermined fluids simultaneously.

[0046] Aptly the method provides for substantially filling a void space of an annulus region with only a single predetermined fluid and then removing the fluid from the void space via a negative pressure pump and subsequently reintroducing another different predetermined fluid into the void space.

[0047] Aptly the method comprises communicating fluid to a plurality of locations along a length of flexible pipe body substantially simultaneously. The fluid communicated can be a mixture of different fluids each of which has a counteractive effect on a respective undesired species or alternatively can be a single fluid selected from multiple options of injectable fluid.

[0048] Aptly the method further comprises providing fluid into the void space of an annulus region at a flow rate of at least about around 5 litres per minute and optionally at least about around 15 litres per minute and optionally at least about around 25 litres per minute.

[0049] Aptly the method provides injecting one or more predetermined fluids from multiple separate and distinct fluid sources. Optionally the one or more predetermined fluids are injected at a positive pressure of less than about around 50 PSI or around 50 PSI or more than 50 PSI. Optionally the positive pressure may be of the magnitude of 100 PSI or 1000 PSI or 10,000 PSI or 100,000 PSI or even higher.

[0050] Aptly the method provides injecting one or more predetermined fluids from a single fluid source.

[0051] According to a second aspect of the present invention there is provided apparatus for modifying a composition of annulus fluid in at least one annulus region of a flexible pipe, comprising: at least one positive pressure pump element selectively in fluid communication with a plurality of respective counteracting fluid containers each for storing a respective counteracting fluid; at least one alert generator units each for providing a respective at least one alert signal indicating that a predetermined condition is satisfied associated with an annulus region in flexible pipe body of the flexible pipe; wherein the positive pressure pump element is actuatable to selectively inject one or more fluid from said counteracting fluid containers into the annulus region thereby modifying a composition of annulus fluid in the annulus region.

[0052] Aptly the alert generator unit is an acoustic and / or electromagnetic monitor or is a distributed temperature sensing (DTS) sensor or is a distributed acoustic sensing (DAS) sensor or a real time sheath breach detection system.

[0053] Aptly the alert generator unit comprises a real time sheath breach detection (SPIRE) system or a pipeline electronic breach locator (PEBL).

[0054] Aptly the at least one positive pressure pump element comprises a single positive pressure pump element that is selectively in fluid communication with a plurality of containers of a respective counteracting fluid or the at least one positive pressure pump comprises a plurality of pump elements each selectively in fluid communication with at least one container of a respective counteracting fluid.

[0055] Aptly the at least one alert generator comprises a real time vent gas monitoring system for providing output data indicating a respective concentration level of at least one annulus fluid species and generating a respective alarm command when a concentration level is equal to or exceeds a respective predetermined threshold value.

[0056] Aptly the at least one alert generator further comprises a real time sheath breach detection system.

[0057] According to a third aspect of the present invention there is provided a flexible pipe body comprising an inner fluid retaining layer and a further fluid retaining layer radially outside the inner fluid retaining layer and spaced apart from the first fluid retaining layer to provide an annulus region therebetween; at least one conduit, extending along at least a portion of a whole length of the flexible pipe body from a fluid introduction end of the flexible pipe body, comprising at least one opening each disposed at a respective position along a length of the conduit for communicating counteracting fluid injected at a fluid injection end of the conduit into a void space in the annulus region; and an end fitting terminating the fluid introducing end of the flexible pipe body, comprising at least one fluid injection port connectable to an outlet of at least one positive pressure pump element.

[0058] Aptly the end fitting further comprises at least one fluid evacuation port connectable to a negative pressure pump element for selectively evacuating partly or entirely fluid from the annulus region; and the end fitting further comprises a gas vent port.

[0059] Certain embodiments of the present invention provide a method of modifying a composition of annulus fluid in at least one annulus region of a flexible pipe. The method includes providing alert signals indicating a predetermined condition is satisfied and responsive to an alert signal actuating one or more pumps each associated with a respective source of a respective counteractive fluid and injecting one or more different counteracting fluids into the annulus region thereby modifying a composition of annulus fluid.

[0060] Certain embodiments of the present invention provide an automated and real time monitoring and fluid introduction system for monitoring, over time, fluid building up in an annulus region of a flexible pipe body of a flexible pipe and selectively once or repeatedly or from time to time or constantly introducing one or more fluids which have a counteractive capacity to counteract detrimental effects posed by respective predetermined fluid conditions in the annulus region.

[0061] Certain embodiments of the present invention provide for real time vent gas monitoring to monitor a concentration of gas species in an annulus region of a flexible pipe. The gas species monitored can be one, two, three or more gas species each relating to a gas that can lead to a detrimental effect over time. For example, including gas species that can lead to stress corrosion cracking. Monitoring of gas species evolution over time within a flexible pipe annulus can occur over part or a whole of an entire service life.

[0062] Certain embodiments of the present invention provide a gas monitoring system that measures flow and pressure and other such annulus region parameters in the annulus as well as a concentration of gases such as carbon dioxide, methane, hydrogen sulphide and oxygen and the like. Continuous real-time data can be constantly measured and stored to enable gas to be analysed under in-situ conditions. Intermittent and / or scheduled data acquisition routines can also be adopted and measurements stored to similarly to enable the annulus gas to be analysed under in-situ conditions. Certain embodiments of the present invention provide very useful information when producing from fields in corrosive gases or susceptible to well souring. A system is provided that is a multiplex system or a single dedicated system. The multiplexing system can be connected to multiple flexible pipes such as multiple risers, multiple sections of the riser or alternatively a system can be dedicated in the sense of only being in fluid communication with a single annulus region of a single flexible pipe.

[0063] Certain embodiments of the present invention provide annulus fluid analysis on a continuous and real time basis and do not require the use of a human operator to monitor the evolution of gas species over a part or whole of the entire service life. The system may be automated in the sense of monitoring of gas species is automated and a control of injection of multiple optionally fluid species that each have a respective counteractive nature to one or more the undesired gas species in the annulus region can be injected.

[0064] Certain embodiments of the present invention provide for annulus fluid to be monitored over a period of time of hours or months or even years to monitor changes in annulus gases over life of field as a reservoir matures and optionally as additional wells are brought on-line. By contrast to legacy vent gas monitoring systems which require vent gas samples to be retrieved manually and sent to an onshore laboratory for analysis, certain embodiments of the present invention apply an approach which is in-situ and whereby analysis can be done effectively in real time.

[0065] Certain embodiments of the present invention utilise non-dispersive infrared (NDIR) spectrometry and / or electrochemical methods or the like to analyse a composition of permeated gases that exit an end fitting of a flexible pipeline. The pipeline may be a single flexible pipe perhaps arranged as a riser or may be formed from multiple flexible pipes arranged in an end to end configuration.

[0066] Certain embodiments of the present invention utilise an alarm-based system whereby alarms are set on a real time vent gas monitoring unit and when measure levels for one or more gas species reach or exceed a predetermined threshold a command is generated to open a valve and initiate injection of one or more of a multiple option of injectable gases. Optionally when a level of a target molecule such as hydrogen sulphide drops below the alarm level a valve is shut and injection is terminated. Certain embodiments of the present invention are useable regardless of whether a pipe annulus is flooded with condensed water (however sealed still) or if an outer sheath is breached in which case the pipe is flooded with seawater. Some injected gas is dissolved in such water but a remainder of the injected gas can bubble through a permeated water at the sag and make its way to the gas monitoring system.

[0067] Certain embodiments of the present invention provide for an initial dosage / injection of chemicals when an alarm level is reached on one or more annulus fluid gas species whereby the system thereafter monitors and intermittently doses. As an alternative merely a single initial intervention can be utilised.

[0068] Certain embodiments of the present invention provide for “maintenance free” riser health monitoring where gases are detected and counteractive fluids can continuously or repeatedly at periodic or non-periodic times be injected.

[0069] Certain embodiments of the present invention are applicable to single length risers.

[0070] Certain embodiments of the present invention provide for the installation of one or more tubes or other fluid communication passageways along a whole length or part of a whole length of a flexible pipe. Optionally the tube is added in a way that follows a helix of a tensile armour layer. Optionally the tube has holes along its length until it reaches an end fitting. This pipe end connects to the end fitting face which provides an opportunity to inject passivating / inhibiting or scavenging chemicals into a flexible pipe annulus at any time when they are required. This helps in delivering multiple chemical types depending on a particular issue that is faced. A pumping system can help control a gas composition by diluting the annulus gas with inert gas or where there is a sheath breach and flooding has been found, to inject chemicals to control either the corrosion rate by passivation of the metal or removal (scavenging) of dissolved oxidizing gases.

[0071] Certain embodiments of the present invention provide for a method for injecting chemicals by installing one or more tubes, optionally having holes along their length, into a flexible pipe annulus whereby injection can occur at any time, depending upon an issue, to control either a corrosion rate by passivation of a metal or scavenging of dissolved oxidizing gases, or by neutralizing annulus fluids, or by evacuating and / or drying the flexible pipe annulus. Certain embodiments of the present invention enable a concentration level of at least one detrimental target fluid to be varied thereby modifying the composition of annulus fluid in an annulus region.

[0072] Certain embodiments of the present invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings in which:

[0073] Figure 1 illustrates flexible pipe body;

[0074] Figure 2 illustrates an environment and usage of flexible pipes;

[0075] Figure 3 illustrates a cross section through flexible pipe body;

[0076] Figure 4 illustrates a void space of an annulus region;

[0077] Figure 5 illustrates schematically the introduction of a fluid in an annulus;

[0078] Figure 6 illustrates how via monitoring of at least one fluid parameter a chemical intervention can be provided to a pipe region which is then further controlled and adjusted over time;

[0079] Figure 7 illustrates how two concentration thresholds may be set which together act as both triggers for chemical intervention, when a fluid parameter in monitored data exceeds one or both of the thresholds, and / or as tolerance bounds for a range of acceptable concentration; and

[0080] Figure 8 illustrates wet chemical monitoring of a fluid concentration in evacuated annulus fluid.

[0081] In the drawings like reference numerals refer to like parts.

[0082] Throughout this description, reference will be made to a flexible pipe. It is to be appreciated that certain embodiments of the present invention are applicable to use with a wide variety of flexible pipe. For example, certain embodiments of the present invention can be used with respect to flexible pipe body and associated end fittings of the type which is manufactured according to API 17J. Such flexible pipe is often referred to as unbonded flexible pipe. Other embodiments are associated with other types of flexible pipe. It will be understood that the illustrated flexible pipes are an assembly of a portion of flexible pipe body and one or more end fittings in each of which a respective end of the pipe body is terminated. Figure 1 illustrates how pipe body 100 is formed from a combination of layered materials that form a pressure-containing conduit. Although a number of particular layers are illustrated in Figure 1 , it is to be understood that certain embodiments of the present invention are broadly applicable to coaxial pipe body structures including two or more layers manufactured from a variety of possible materials. The pipe body may include one or more layers comprising composite materials, forming a tubular composite layer. It is to be further noted that the layer thicknesses are shown for illustrative purposes only. As used herein, the term “composite” is used to broadly refer to a material that is formed from two or more different materials, for example a material formed from a matrix material and reinforcement fibres.

[0083] A tubular composite layer is thus a layer having a generally tubular shape formed of composite material. Alternatively, a tubular composite layer is a layer having a generally tubular shape formed from multiple components one or more of which is formed of a composite material. The layer or any element of the composite layer may be manufactured via an extrusion, pultrusion or deposition process, or by a winding process in which adjacent windings of tape which themselves have a composite structure are consolidated together with adjacent windings. The composite material, regardless of manufacturing technique used, may optionally include a matrix or body of material having a first characteristic in which further elements having different physical characteristics are embedded. That is to say elongate fibres which are aligned to some extent or smaller fibres randomly orientated can be set into a main body or spheres or other regular or irregular shaped particles can be embedded in a matrix material, or a combination of more than one of the above. Aptly the matrix material is a thermoplastic material, aptly the thermoplastic material is polyethylene or polypropylene or nylon or PVC or PVDF or PFA or PEEK or PTFE or alloys of such materials with reinforcing fibres manufactured from one or more of glass, ceramic, basalt, carbon, carbon nanotubes, polyester, nylon, aramid, steel, nickel alloy, titanium alloy, aluminium alloy or the like or fillers manufactured from glass, ceramic, carbon, metals, buckminsterfullerenes, metal silicates, carbides, carbonates, oxides or the like.

[0084] The pipe body 100 illustrated in Figure 1 includes an internal pressure sheath 110 which acts as a fluid retaining layer and comprises a polymer layer that ensures internal fluid integrity. The layer provides a boundary for any conveyed fluid. It is to be understood that this layer may itself comprise a number of sub-layers. It will be appreciated that when a carcass layer 120 is utilised the internal pressure sheath is often referred to by those skilled in the art as a barrier layer. In operation without such a carcass (so-called smooth bore operation) the internal pressure sheath may be referred to as a liner. A barrier layer 110 is illustrated in Figure 1 radially outside the carcass layer 120.

[0085] It is noted that a carcass layer 120 is a pressure resistant layer that provides an interlocked construction that can be used as the innermost layer to prevent, totally or partially, collapse of the internal pressure sheath 110 due to pipe decompression, external pressure, and tensile armour pressure and mechanical crushing loads. The carcass is a crush resistant layer. It will be appreciated that certain embodiments of the present invention are thus applicable to ‘rough bore’ applications (with a carcass). Aptly the carcass layer is a metallic layer. Aptly the carcass layer is formed from stainless steel, corrosion resistant nickel alloy or the like. Aptly the carcass layer is formed from a composite, polymer, or other material, or a combination of materials and components. The carcass layer is usually radially positioned within the barrier layer.

[0086] The carcass layer is a “layer” in the sense that a radially innermost and outermost surface are created in single pass at a single manufacturing node. The single manufacturing node may include multiple tape handling sections axially close together so that they are effectively a single node. The node aptly extends over an axial distance of less than 2.5m. Aptly the node has a length of 1m or less.

[0087] The pipe body includes a pressure armour layer 130 that is a pressure resistant layer that provides a structural layer that increases the resistance of the flexible pipe to internal and external pressure and mechanical crushing loads. The layer also structurally supports the internal pressure sheath. Aptly as illustrated in Figure 1 the pressure armour layer is formed as a tubular layer. Aptly for unbonded type flexible pipe the pressure armour layer consists of an interlocked construction of wires with a lay angle close to 90°. Aptly in this case the pressure armour layer is a metallic layer. Aptly the pressure armour layer is formed from carbon steel, aluminium alloy, stainless steel or the like. Aptly the pressure armour layer is formed from a pultruded composite interlocking layer. Aptly the pressure armour layer is formed from a composite formed by extrusion or pultrusion or deposition. A pressure armour layer is positioned radially outside the illustrated underlying barrier layer.

[0088] The flexible pipe body illustrated also includes a first tensile armour layer 140 and second tensile armour layer 150. Each tensile armour layer is used to sustain tensile loads and optionally also internal pressure. Aptly for some flexible pipes the tensile armour windings are metal (for example steel, stainless steel or titanium or the like). For some composite flexible pipes the tensile armour windings may be polymer composite tape windings (for example provided with either thermoplastic, for instance nylon, matrix composite or thermoset, for instance epoxy, matrix composite). For unbonded flexible pipe the tensile armour layer is formed from a plurality of wires (to impart strength to the layer) that are located over an inner layer and are helically wound along the length of the pipe at a lay angle typically between about 10° to 55°. Aptly the tensile armour layers are counter-wound in pairs. Aptly the tensile armour layers are metallic layers. Aptly the tensile armour layers are formed from carbon steel, stainless steel, titanium alloy, aluminium alloy or the like. Aptly the tensile armour layers have a microstructure that consists of orientated lamellae. Aptly the tensile armour layers are formed from a composite, polymer, or other material, or a combination of materials.

[0089] Aptly the flexible pipe body includes optional layers of tape 160 which help contain underlying layers and to some extent prevent abrasion between adjacent layers. A tape layer may optionally be a polymer or composite or a combination of materials, also optionally comprising a tubular composite layer. Tape layers can be used to help prevent metal-to-metal contact to help prevent wear. Tape layers over tensile armours can also help prevent “birdcaging” of the tensile armour wires.

[0090] The flexible pipe body also includes optional inner layers of insulation 165 and an outer sheath 170, which comprises a polymer layer used to protect the pipe against penetration of seawater and other external environments, corrosion, abrasion and mechanical damage. Any thermal insulation layer helps limit heat loss through the pipe wall to the surrounding environment. An annulus 180 is a region associated with the space between the internal pressure sheath 110 and the outer sheath 170. In other words, in the flexible pipe body illustrated in Figure 1 , the pressure armour layer 130, the first tensile armour layer 140, the further tensile armour layer 150, the layers of tape 160, and the I layers of insulation 165 are located in the annulus region 180. It will be appreciated that in some embodiments, the annulus region 180 may contain any or none of the layers present in the flexible pipe body illustrated in Figure 1 . The elements between opposed fluid retaining layers act as stand offs and a void space is between those elements in the annulus region.

[0091] The flexible pipe comprises at least one portion, referred to as a segment or section, of flexible pipe body 100 together with an end fitting located at least one end of the flexible pipe. A respective end fitting may be used to terminate each end of the flexible pipe body. An end fitting provides a mechanical device which forms the transition between the flexible pipe body and a connector. The different pipe layers as shown, for example, in Figure 1 are terminated in the end fitting in such a way as to transfer the load between the flexible pipe and the connector.

[0092] Figure 1 also helps illustrate one or more conduits 190 wound in place of a tensile armour winding so as to provide a fluid communication passageway that extends along the flexible pipe body. It will be appreciated that such conduits (described in more detail below) may optionally extend along a full length of the flexible pipe body being connected into both respective end fittings, or may extend from only one selected end fitting and terminate in an open end or sealed end at a desired length along the flexible pipe body. In the case of a conduit having a sealed end one or more openings in a wall of the conduit can be utilised as described in more detail below. Such conduits may have similar or different lengths. It will likewise be appreciated that whilst the fluid communication passageway 190 illustrated in Figure 1 is shown as an outermore tensile armour winding, fluid communication passageways could additionally or alternatively be provided by an innermost tensile armour winding or indeed by winding in another wound layer and / or combination of these options. Still furthermore a fluid communication passageway may not be helically wound but may optionally be formed from a pressure resistant tube that is provided between opposed layers within the flexible pipe body. That tube may be “straight” or may be wound round in a manner which is not necessarily a helix with a repeating pitch.

[0093] The pressure resistant body of a tube defines within it a lumen along which fluid can flow. This effectively provides a fluid communication passageway which is a way in which fluid can pass from one location to another thereby connecting two locations and enabling fluid communication between those connected locations.

[0094] Figure 2 illustrates a riser assembly 200 suitable for transporting production fluid such as oil and / or gas and / or water from a sub-sea location 210 to a floating facility 220. For example, in Figure 2 the sub-sea location 210 includes a sub-sea flow line 225. The flexible flow line 225 comprises a flexible pipe, wholly or in part, resting on the sea floor 230 or buried below the sea floor and used in a static application. The floating facility may be provided by a platform and / or buoy or, as illustrated in Figure 2, a ship. The riser assembly 200 is provided as a flexible riser, that is to say a flexible pipe 240 connecting the ship to the sea floor installation. The flexible pipe may alternatively be part of a pipeline including segments of flexible pipe body with connecting end fittings. It will be appreciated that there are different types of riser, as is well-known by those skilled in the art. Certain embodiments of the present invention may be used with any type of riser, such as a freely suspended (free-hanging, catenary riser), a riser restrained to some extent (buoys, chains), totally restrained riser or enclosed in a tube (I or J tubes). Some, though not all, examples of such configurations can be found in API 17J. Figure 2 also illustrates how portions of flexible pipe can be utilised as a jumper 250.

[0095] Figure 3 helps illustrate a cross section or view through the flexible pipe body illustrated in Figure 1 and helps illustrate how an outer surface 300 of the internal pressure sheath 110 is generally coaxial with and spaced apart from an inner surface 310 of the outer sheath 170. The outer surface 300 of the internal pressure sheath and the internal surface 310 of the outer sheath are spaced apart and substantially coaxial and thus define an annulus 180. The annulus is a region within the flexible pipe body. The annulus extends along a whole length of the flexible pipe. The annular region 180 is an annular shaped region. It will be appreciated that certain embodiments of the present invention are applicable to flexible pipe body which includes one or more intermediate fluid retaining layers. When such intermediate fluid retaining layers are utilised in flexible pipe body multiple annuli are defined. Each annulus is an annular shaped region between a radially outer inner layer that is fluid tight and radially inner surface of an outer fluid retaining layer.

[0096] Figure 3 also helps illustrate how wire in the inner tensile armour layer 140 and wires in the outer tensile armour layer 150 extend to form a metallic layer. Figure 3 helps illustrate how three wires in the outer tensile armour layer 150 may each be replaced by a respective tube 190 to provide respective fluid communication passageways along a length of the flexible pipe body. Aptly each of the fluid communication passageways 190 is a conduit provided, for example, by a pressure rated tube. The conduit is sufficiently crush resistant so that it is not crushed during manufacturing and so that it does not crack over an operational lifetime of the flexible pipe. Aptly the conduit is a steel tube or other metal tube or corrosion resistant alloy tube, or a crush resistant polymer composite tube. Aptly the conduit formed from a malleable material so that it can be wound. Aptly the conduit it a copper tube. Aptly the conduit is a pressure rated steel tube. Aptly the conduit is pressure rated.

[0097] As illustrated in Figure 3, three conduits can be provided along the length of the flexible pipe. It will be appreciated that as an alternative one, two, three, four or more conduits could be provided. These may optionally be evenly distributed circumferentially around the pipe or may be more closely packed at desired location circumferentially. It will also be appreciated that such fluid communication passageways can be provided in a mixture of layers such as one or more conduits in the outer tensile armour layer and one or more conduits in an inner tensile armour layer. As an alternative, as illustrated in Figure 3, all conduits that play a part in fluid communication can be provided in a common layer. The conduits are in fluid communication with the annulus region of the flexible pipe in which they are located.

[0098] Figure 4 helps illustrate in a schematic format a magnified view of a portion of a cross section through the flexible pipe body illustrated in Figure 3. The carcass layer 120 is provided by interlocking windings. The barrier layer 110 has a radially innermost surface 400 which defines in inner bore of the flexible pipe body in use. The radially outermost surface 300 of the barrier layer is also illustrated in Figure 4. A radially outermost surface 410 of the outer sheath 170 is also illustrated in Figure 4 as is the radially innermost surface 310 of the outer sheath 170.

[0099] Figure 4 helps illustrate how the annulus 180 defined by the spaced apart inner surface 310 of the outer sheath and outer surface 300 of the barrier layer is partially filled with the other components of the flexible pipe. Nevertheless, a void space 450 is defined in the annulus. The void space 450 is the volume of the annular region which remains free and is not filled with matter provided by the other elements / component parts of the flexible pipe body. Figure 4 helps illustrate how components of production fluids travelling down the bore will tend to permeate along the direction shown by arrow A through the barrier layer 110 in use and could otherwise collect in the void space 450 in the annulus 320 of the flexible pipe. As noted previously the collection of such permeated fluids can prove detrimental to the lifetime of the flexible pipe body if allowed to collect.

[0100] Figure 5 illustrates a system 500 for modifying a composition of annulus fluid in at least one annulus region of a flexible pipe. Figure 5 illustrates a section of flexible pipe body 100. An end fitting 505 terminates an end region 506 of the flexible pipe body 100 the flexible pipe body extends towards another end (not shown) where the flexible pipe body is terminated in a further end fitting (not shown). As illustrated in Figure 5 the flexible pipe body includes a fluid communicating conduit 190. This is wound like a tensile armour wire in the flexible pipe body. This is illustrated schematically in Figure 5. It will be appreciated that the conduit forming part of the tensile armour wire would be within an annulus region of the flexible pipe body. Figure 5 also illustrates how the conduit 190 can include apertures 510 at a lower region 515. That is to say the conduit 190 which can be provided by a pressure rated steel tube or the like has no apertures along an upper length near the upper end fitting 506 but includes apertures in a further region. It will be appreciated that as an alternative, apertures could be provided throughout an entire length or in different regions of the conduit 190.

[0101] By way of example Figure 5 illustrates a situation where an outer sheath breach has occurred. This has resulted in surrounding seawater invading the annulus 180 and the upper limit of that flooded area 520, illustrated by an upper surface of the flooded seawater 525, is illustrated in Figure 5. It will be appreciated that certain embodiments of the present invention can be used to monitor for issues other than outer sheath breach and thus flooding of one or more annuli in a flexible pipe. Figure 5 illustrates a flexible pipe in a somewhat vertical orientation. It will be appreciated that certain embodiments of the present invention are applicable to flexible pipes arranged in other configurations such as horizontal or oblique to a seabed or with one or more bends.

[0102] The system 500 illustrated in Figure 5 includes a first injection pump 530 and a further injection pump 535. Each of these are positive pressure pumps. That is to say when energised the pump can inject respective fluids from a respective source into a respective inlet of the end fitting 505 and, via respective fluid communication pathways through the end fitting, into the annulus 180.

[0103] The first positive pressure pump 530 illustrated in Figure 5 is in fluid communication with a nitrogen source 540. This is provided by a vessel containing nitrogen gas. The further positive pressure pump 535 illustrated in Figure 5 is connected fluidically to two different fluid sources, one is a source of corrosion inhibitor (e.g. chemicals under the Corrtreat name from Clariant Oil Services), and another is a fluid including a hydrogen sulphide scavenger. The fluid can be water or an oil or a grease. The fluid could be an oxygen scavenger, or a biocide for instance.

[0104] It will be appreciated that the corrosion inhibitor may include 2-Butoxy ethanol and / or 2- Mercaptoethanol and / or ethanediol and / or 2-Aminoethanol and / or the like. Aptly the corrosion inhibitor may not include 2-Butoxy ethanol and / or 2-Mercaptoethanol and / or ethanediol and / or 2-Aminoethanol. Figure 5 also helps illustrate how each respective pump receives a control signal to energise the pump and thereby selectively inject a respective fluid into the annulus of the flexible pipe body to thereby modify a composition of annulus fluid in at least one annulus region of the flexible pipe. In Figure 5 a real time vent gas monitoring system (RTVGM) is provided to provide a control signal to each respective positive pressure pump. The RTVGM system 540 monitors the concentration of gas species in an annulus. This may include monitoring for gas species that include those that can lead to stress corrosion cracking. Monitoring can take place once or periodically or constantly to allow monitoring of gas species evolution within a flexible pipe annulus over a given period or an entire service life. The RTVGM 540 provides continuous and / or scheduled and / or intermittent real / time data to enable gases to be analysed under in-situ conditions. Optionally the RTVGM 540 measures flow and pressure in the annulus as well as concentration of gases such as carbon dioxide, methane, hydrogen sulphide and oxygen. Chemical analysis can take place on permeated annulus gases in real time.

[0105] The RTVGM 540 includes an analyser 545 which interrogates data and provides trending and / or thresholding analysis. In this way in real time and in-situ respective alarm commands can be generated and provided to the positive pressure pumps 530, 535. For example when the RTVGM determines that a H2S level has reached a predetermined level an alarm signal is generated and provided to the further positive pressure pump 535. This initiates pumping of the fluid containing a H2S scavenger which is thus injected into the pipe annulus to help modify the composition and thereby moderate H2S levels.

[0106] Figure 5 also helps illustrate how a real time sheath breach detection system 550 may be included. This provides real time information. The sheath breach detection system 550 can determine a time and location of outer sheath breach. Aptly the sheath breach detection system can determine a location of annular water. Aptly the real time sheath breach detection system can detect a flooded annulus. Optionally the sheath breach detection system can utilise an electrically isolated existing load carrying tensile wire (not shown) to help determine in real time when a breach of an outer sheath of the flexible pipe body occurs. When an outer sheath breach is detected a respective command signal can be provided to the further positive pressure pump 535. This can be utilised to inject a respective counteracting fluid from a local fluid source into the annulus. It will be understood that other types of breach detection system may alternatively or also be integrated or connected to the system 500 to assess the annulus condition on a continuous, scheduled or intermittent basis. Examples of such breach detection systems are: distributed temperature sensing systems (DTS) which may detect small local temperature variations around a breach in the outer sheath of the flexible pipe body as fresh water floods into the annulus or is exchanged with water from the annulus; distributed acoustic system (DAS) incorporating one or more acoustic emitters and / or sensors; ultrasonic testing (UT) inspection system; movement - displacement I accelerometer I bending frequency monitoring systems, systems which may detect changes in the way a pipe moves or that provide information which may infer a change in the friction between pipe body layers or damage to the riser structure.

[0107] Figure 5 illustrates how a system 500 can also include a negative pressure pump 570. This can be utilised to selectively evacuate fluid from a pipe annulus via respective vent paths and vent orifices of the end fitting. This can be achieved via an injection conduit (effectively reversing the injection concept) or via one or more “dedicated” evacuation conduits. This can help facilitate the system 500 to be able to perform wet chemical experiments on the evacuated fluid and determine the pH or concentration of previously injected intervention chemicals in the evacuated fluid such that the system can stop, moderate or increase further chemical injections in order to bring the chemistry of the annulus fluid into a desired or acceptable range.

[0108] Figure 5 also helps illustrate how the system 500 can include a gas purge exhaust 580. This gas purge exhaust can help dispose of the venting gases from the pipe annulus, either by chemical neutralization and capture, or by routing the gases to be burned in the flare on the floating facility 220.

[0109] Figure 5 helps illustrate how fluid flow illustrated by the arrows 590 in Figure 5 can be introduced through orifices along at least a region of a conduit that runs through the flexible pipe body to modify composition of annular fluid. For example, passivation of metal surfaces can be achieved by injecting phosphate related chemicals.

[0110] The system 500 analyses an environment and determines when certain changes are found to have occurred. This helps induce pumps to inject respective chemicals and / or gases to bring the overall environmental conditions “under control”. An analysing unit, injection suite and one or more injector tubes installed during manufacturing of flexible pipe body, and that can optionally follow a helix in a tensile armour wire, can be utilised. The conduit or each conduit has one or more holes along a length and / or an open end. The system provides the ability to inject passivating and / or inhibiting and / or scavenging chemicals and / or a chemically passive purging fluid into an annulus at any time that they are required. This can be achieved without human operator assistance.

[0111] Figure 6 helps illustrate how the system 500 can take data from monitoring of at least one fluid parameter (temperature, concentration, etc.) and provide a chemical intervention which is then further controlled and adjusted over time. It will be appreciated that Figure 6 shows an example of how the system 500 may respond to a fluid parameter. The pressure or concentration 610 of an acidic gas species 620, such as H2S as shown in Figure 6, can be monitored at the end fitting vent and a trigger value set (programmed into the system) at which intervention can be automatically triggered by the system 500 or via a further monitoring system or the like that can communicate with the system 500. It will be understood that Figure 6 illustrates data 630 from monitoring the concentration 610, in parts per million (ppm), of H2S 620 against time 640 (that is the time in which the fluid parameter is monitored). It will be appreciated that the time illustrated in Figure 6 may be in years or months or days or hours or minutes or seconds or the like. As illustrated in the fluid monitoring example of Figure 6, a trigger level 650 of around 35ppm (that may be around 40ppm or may be between 35 and 40 ppm or around 35, 36, 37, 38, 39 or 40 ppm) of detected H2S (that may be a predetermined tigger level and / or may be a user defined or user programmed trigger level or the like) triggers the injection of a pre-determined volume of H2S scavenger, and / or a purge of nitrogen. That is to say, a measured concentration of H2S in the annulus at or above the trigger level causes the system 500 to inject the H2S scavenger and / or purge nitrogen. It will be appreciated that the injected volume of H2S scavenger may be calculated from the known free volume not taken up by armours or tapes within the annulus of the flexible pipe body.

[0112] As shown in Figure 6, shortly after the initial chemical injection is made, the on-going H2S monitoring detects a resulting drop in the H2S concentration 630 in the pipe annulus region and the H2S concentration again falls below the injection trigger level 660. It will be appreciated that, as shown in Figure 6, some time later the beneficial effect of the chemical injection has been overcome by further permeation of H2S 620, and as the concentration 630 of H2S increases again it reaches the trigger value 650, triggering another chemical intervention. This sequence may continue until the flexible pipe is deemed to have come to the end of its service life.

[0113] It will thus be appreciated how the system 500 can provide automatic control of aberrant fluid conditions in a pipe annulus region. Figure 7 illustrates how two concentration thresholds 710, 720 may be set which together act as both triggers for chemical intervention and / or as tolerance bounds for a range of acceptable concentration. In the example shown in Figure 7, the acceptable concentration relates to hydrogen in the annulus vent gas. It will be appreciated that the hydrogen concentration in the annulus vent gas is an example of a fluid parameter. It will further be understood that Figure 7 illustrates a plot of hydrogen concentration in the pipe annulus vent gas against time (in which the hydrogen concentration in the annulus vent gas is being measured) 725. As shown in Figure 7, after the increasing concentration of hydrogen in the annulus vent gas passes / exceeds 730 the lower, initial control trigger level 710 the system 500 provides an injection of a corrosion inhibitor to reduce corrosion (which in this instance is triggering production of hydrogen gas as a by-product of the corrosive activity). Subsequent to the injection of the corrosion inhibitor, the concentration of hydrogen continues to rise 730, albeit at a slower rate as prior to said injection, and as the detected concentration crosses 740 the higher, second control trigger level 720 a second intervention chemical injection is triggered. It will be appreciated that this second injection is provided by the system 500. The hydrogen concentration in the annulus vent gas then falls over time 750 and further intervention would only be triggered were it to rise again past one or both concentration thresholds 710, 720.

[0114] Figure 8 illustrates wet chemical monitoring of a fluid concentration in which the concentration 810 shown in Figure 8 is the concentration of phosphate-based inhibitor continuously or intermittently monitored in evacuated annulus fluid. That is to say the concentration 810 is an inhibitor concentration that optionally is a phosphate-based inhibitor. Aptly any other suitable inhibitor or fluid may instead be utilised. It will be appreciated that Figure 8 illustrates a plot of phosphate-based inhibitor concentration in an evacuated annulus against time (that is the time in which the evacuated annulus is monitored). Chemical intervention (provided by the system 500 in the form of a phosphate-based inhibitor in the Examiner of Figure 8, which has already been triggered prior to the concentration data shown in the plot of Figure 8 as a result of the detection of water in the annulus of the flexible pipe body) continues until the concentration of inhibitor in evacuated annulus fluid exceeds a first / initial control trigger level 820 and reaches (or exceeds) a higher, second control trigger level 830, at which point injection (of the phosphate-based inhibitor by the system 500) is stopped. Subsequent to the injection, the concentration of inhibitor gradually falls over time 840, and as it approaches the lower, initial control trigger level 820 further chemical intervention is activated (provided by the system 500) in the form of providing additional inhibitor to prevent the inhibitor concentration from falling below a lower bound / magnitude of the desired inhibitor concentration range in evacuated annulus fluid. Aptly, the further chemical intervention may be activated when the concentration of inhibitor falls below the lower (initial) control trigger level. As shown in Figure 8, the inhibitor concentration in evacuated annulus fluid thereby starts to rise again 850 until the concentration approaches the higher, second control trigger level 830 again, at which point the system moderates the further chemical intervention, as necessary, to maintain the inhibitor concentration in evacuated annulus fluid between the upper and lower bounds of acceptability, defined by the second control trigger level 830 and the initial control trigger level 820.

[0115] It will be appreciated that the chemical deployment lumen (the lumen in which the system 500 can provide chemicals such as the phosphate-based inhibitor to a pipe region) can also be utilised as a sampling means to withdraw liquid from the annulus and perform wet chemical analysis to establish for example the pH and or the phosphate concentration and / or determine if it is with the intended range and / or determine future chemical deployment parameters and the like.

[0116] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to” and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0117] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and / or steps are mutually exclusive. The invention is not restricted to any details of any foregoing embodiments. The invention extends to any novel one, or novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0118] The reader’s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS:1 . A method of modifying a composition of annulus fluid in at least one annulus region of a flexible pipe, comprising the steps of: providing at least one alert signal indicating that a predetermined condition is satisfied associated with an annulus region in flexible pipe body of a flexible pipe; responsive to each alert signal, actuating at least one pump element selectively in fluid communication with a plurality of containers each holding a respective source of a respective counteractive fluid that is a fluid that counteracts a respective predetermined fluid condition; and providing at least one counteracting fluid into the annulus region thereby modifying a composition of annulus fluid in the annulus region.

2. The method as claimed in claim 1 , further comprising: determining a respective concentration level for a plurality of target fluids in a respective annulus region in flexible pipe body of a flexible pipe; determining that at least one determined concentration level satisfies a predetermined condition, indicating that a respective target fluid is a detrimental target fluid; and varying a concentration level of at least one detrimental target fluid thereby modifying the composition of annulus fluid in the annulus region.

3. The method as claimed in claim 2, further comprising: determining a respective concentration level comprises determining if a target fluid is present in a sample of annulus fluid from the annulus region.

4. The method as claimed in claim 3, further comprising: if a target fluid is determined as present, determining a percentage total of the target fluid in the annulus fluid for each detrimental target fluid.

5. The method as claimed in claim 2 and any claim dependent thereon, further comprising: determining the respective concentration level via an analyser module in fluid communication with the fluid communication passageway and that is disposed to sample and identify a plurality of constituent target fluids in the annulus fluid.

6. The method as claimed in any preceding claim, further comprising: modifying said a composition by varying a concentration level for each of at least one detrimental target fluid by selecting at least one injectable counteracting fluid from a plurality of possible injectable counteracting fluids and injecting a selected injectable counteracting fluid into at least one fluid communication passageway that extends along a portion of the annulus region and is in fluid communication with at least one region of the annulus region.

7. The method as claimed in claim 2, further comprising: for each detrimental target fluid, selecting at least one injectable counteracting fluid; and providing the injectable counteracting fluid from a respective counteracting fluid source into the annulus region.

8. The method as claimed in any preceding claim, further comprising: via the pump element, urging fluid via a lumen that is disposed helically in the annulus region, and that provides a fluid communication passageway along the annulus region, into the annulus region at a positive pressure.

9. The method as claimed in claim 2 and any claim dependent thereon, further comprising: determining that at least one concentration level satisfies a predetermined condition by simultaneously and repeatedly determining a measured level for each detrimental target fluid of the plurality of detrimental target fluids is equal to or greater than a pre-set threshold value.

10. The method as claimed in the preceding claim, further comprising: providing each counteracting fluid by injecting a portion of passivating fluid and / or inhibiting fluid and / or scavenger holding fluid into the annulus region.

11. The method as claimed in any preceding claim, further comprising: applying a negative pressure to the annulus region via a pump element thereby drawing annulus fluid selectively from the annulus region.

12. The method as claimed any preceding claim, further comprising:actuating at least one pump element comprises actuating a single pump element that is selectively in fluid communication with a plurality of containers that each holds a respective source of a respective counteracting fluid or actuating a plurality of pump elements each of which is selectively in fluid communication with at least one container that holds a respective source of a respective counteracting fluid.

13. The method as claimed in claim 12, further comprising: said step of actuating a plurality of pump elements comprises simultaneously or one-by-one, actuating pump elements of the plurality of pump elements thereby simultaneously or in sequence injecting a respective counteracting fluid into an annulus region.

14. Apparatus for modifying a composition of annulus fluid in at least one annulus region of a flexible pipe, comprising: at least one positive pressure pump element selectively in fluid communication with a plurality of respective counteracting fluid containers each for storing a respective counteracting fluid; at least one alert generator units each for providing a respective at least one alert signal indicating that a predetermined condition is satisfied associated with an annulus region in flexible pipe body of the flexible pipe; wherein the positive pressure pump element is actuatable to selectively inject one or more fluid from said counteracting fluid containers into the annulus region thereby modifying a composition of annulus fluid in the annulus region.

15. The apparatus as claimed in claim 14, further comprising: the alert generator unit is an acoustic and / or electromagnetic monitor or is a distributed temperature sensing (DTS) sensor or is a distributed acoustic sensing (DAS) sensor or a real time sheath breach detection system.

16. The apparatus as claimed in claim 14 or claim 15, further comprising: the at least one positive pressure pump element comprises a single positive pressure pump element that is selectively in fluid communication with a plurality of containers of a respective counteracting fluid or the at least one positive pressure pump comprises a plurality of pump elements each selectively in fluid communication with at least one container of a respective counteracting fluid.

17. The apparatus as claimed in anyone of claims 14 to 16, further comprising: the at least one alert generator comprises a real time vent gas monitoring system for providing output data indicating a respective concentration level of at least one annulus fluid species and generating a respective alarm command when a concentration level is equal to or exceeds a respective predetermined threshold value.

18. The apparatus as claimed in claim 17, further comprising: the at least one alert generator further comprises a real time sheath breach detection system.

19. A flexible pipe, comprising: flexible pipe body comprising an inner fluid retaining layer and a further fluid retaining layer radially outside the inner fluid retaining layer and spaced apart from the first fluid retaining layer to provide an annulus region therebetween; at least one conduit, extending along at least a portion of a whole length of the flexible pipe body from a fluid introduction end of the flexible pipe body, comprising at least one opening each disposed at a respective position along a length of the conduit for communicating counteracting fluid injected at a fluid injection end of the conduit into a void space in the annulus region; and an end fitting terminating the fluid introducing end of the flexible pipe body, comprising at least one fluid injection port connectable to an outlet of at least one positive pressure pump element.

20. The flexible pipe as claimed in claim 19, further comprising: the end fitting further comprises at least one fluid evacuation port connectable to a negative pressure pump element for selectively evacuating partly or entirely fluid from the annulus region; and the end fitting further comprises a gas vent port.

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