Patent Description:
To help manage reservoir production and maximise recovery factor, the oil and gas industry sometimes adopts multi-zone intelligent completion technology, which allows production from particular reservoir "zones" to be controlled, often independent from one another. This may be achieved by selectively operating control valve or ports at the sections of tubing at some or all of the "zones". To provide effective zonal isolation, sometimes each zone may be isolated using annular barriers between sections of tubing. In order to understand present conditions at the formation and well infrastructure - and operate and/or maintain the well appropriately - aspects of the zones or completion may be monitored, e.g. from surface.

However, to provide effective control/maintenance of intelligent completion or the like, there may be a desire to monitor conditions accurately. Additionally, such monitoring may be desired for much of the lifespan of any well, e.g. from installation through to production, etc..

<CIT> is directed to an annular barrier system for proving a testable annular barrier.

<CIT> is directed to downhole tools and systems that can be actuated chemically by placing a chemical sensor downhole and introducing a chemical slug into fluids being pumped downhole.

<CIT> is directed to an apparatus for monitoring at least a portion of a wellbore.

This background serves only to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the invention may or may not address one or more of the background issues.

The invention concerns a method as defined in independent claim <NUM>, as well as an associated monitoring system, as defined in independent claim <NUM>, for performing said method and an associated computer program product, as defined in independent claim <NUM>, for performing said method. Further, optional embodiments of the invention are set forth in the dependent claims.

In described examples, there are systems and methods for use determining conditions at a well. Particular examples may be for use in determining conditions at barriers associated with well infrastructure, for example, with intelligent completions. The systems and methods may provide effective control/maintenance of the well (e.g. and such completions), and may help monitor conditions accurately. Additionally, such systems and methods may be usable for much of the lifespan of any well, e.g. from completion through to production, etc..

In some examples, there is described a method for determining the condition of a barrier in a well infrastructure. The method comprises receiving sensor data derived from a sensor arrangement at a barrier. That barrier is positioned at a location in a well infrastructure. The sensor data is associated with measured conditions at the barrier. The method comprises receiving composition data derived from measurements of fluid composition within the well. Such composition data may be indicative of the location at which fluid has been in the well. The method further comprises analysing the received sensor data and composition data to determine the condition of the barrier.

The sensor data and/or composition data may be received from time to time, for example, during completion and/or production from the well. The sensor/composition data may be received periodically, e.g. hourly, daily, weekly or the like.

The sensor data may comprise pressure and/or temperature data associated with the barrier, or in the location of the barrier (e.g. at a particular zone). The composition data comprises data associated with identifiable properties of fluid composition (e.g. product), considered to be location-based identifiable properties. Such identifiable properties may be markers, such as chemical markers, or the like. The identifiable properties of fluid composition may be uniquely identifiable properties (e.g. specific to one location at the well). The composition data may comprise data associated with a plurality of identifiable properties (e.g. each of which may be associated with locations of fluid production in the well).

The barrier is used to provide zonal isolation, i.e. isolation of one zone of the well infrastructure from another zone. In similar words, the barrier may be configured to isolate a first zone from a second zone. Such isolation may prevent or inhibit the movement of fluids or gases or the like from the first zone to the second zone, and vice versa. The barrier may be for use with tubing, such as production tubing, casing, completion tubing, such as casing, etc. The barrier may be formed between well tubing and the corresponding formation or reservoir. The barrier may be considered to be an annular barrier. The barrier may comprise one or more packers (e.g. two packers, axially spaced on tubing). The or each packer may comprise elements that activate, or have activated, in the presence of particular well conditions, such as particular fluid in an annulus, for example, an annulus formed between tubing and formation (e.g. swellable packers).

The barrier may be configured to prevent or inhibit fluid from flowing from a first zone at one side of the barrier to a second zone at another side of the barrier. The sensor data may provide data informing as to the barrier capability (e.g. barrier integrity). In similar words, the sensor data may inform on whether the fluid may be flowing from a first zone at one side of the barrier to a second zone at another side of the barrier, or not. Such information may be determined from monitoring fluid pressure and/or temperature at the barrier. The first zone may be intended to be an isolated zone, whereas the second zone may be intended to be a production zone.

The method may comprise authenticating, or otherwise validating, sensor data associated with the barrier when additionally the composition data confirms the location at which fluid is being produced as being from the first, or isolated, zone. The method may comprise discarding sensor data associated with the barrier when the composition data confirms the location at which fluid is being produced as being from the second, or production, zone. The method may comprise attributing sensor data associated with the barrier to flow conditions in the well, when the composition data confirms the location at which fluid is being produced as being from the second, or production, zone.

The method may further comprise signalling an alert status. Such an alert status may be signalled in the event that composition data confirms the location at which fluid is being produced as being from the first, or isolated, zone.

The method comprises initially using essentially the received sensor data to determine conditions at the barrier, and then subsequently using composition data to determine conditions at the barrier. The method comprises initially using essentially received sensor data during installation/completion and subsequently using composition data during production (e.g. later during production).

The sensor data may be received from a signal path that is wired, wireless or combination thereof. The sensor arrangement may comprise one or more sensors, each sensor configured to measure conditions at or in the location of the barrier. The sensor arrangement may be provided with well tubing (e.g. integrated with or otherwise affixed to well tubing). The sensor arrangement may be provided on an outer surface of such tubing. The sensor arrangement may comprise a power source, such as a battery pack, for powering a transmitter, etc., for communicating signals to surface, or the like.

The received sensor data may have been communicated using a signal path comprising some of the well tubing (e.g. the completion and/or production tubing, etc.). The sensor data may be received or otherwise extracted from the well tubing. The sensor data may have been communicated to, or otherwise injected into, the well tubing, for subsequent receipt. In other similar words, the sensor data may have been communicated from an isolated zone, for subsequent receipt, using the tubing. The received sensor data may be received at surface.

The fluid composition may be indicative of the location at which fluid has been in the well by virtue of an interaction (or lack of) of the fluid with one or more tracer elements at the barrier. Such tracer elements may be configured to release markers into the fluid when in contact with the fluid. The tracer elements may be provided at a first side of the barrier (e.g. at an isolated side). The tracer elements may be provided together with the sensor arrangements.

The method may additionally comprise receiving sensor data from the well infrastructure (e.g. directly). The method may comprise measuring the composition of fluid (e.g. produced fluid) to provide composition data. Alternatively, the method may comprise receiving sensor/composition data remotely.

The method may additionally comprise communicating the sensor data from a barrier location for subsequent receipt and analysis (e.g. at surface).

In some examples, there are described methods for determining condition of multiple barriers in one or more well infrastructures.

The method may comprise collecting fluid samples for obtaining composition data from measurements of fluid composition within the well. That composition data may be indicative of the location at which fluid has been in the well.

The method may comprise communicating collected sensor data, fluid samples, and/or composition data in order to permit subsequent determination of the condition of the barrier using the communicated sensor data and composition data.

Any of the fluid samples, composition data and/or sensor data may be collected locally at the well infrastructure, and communicated to a remote location for subsequent analysis and determination of barrier condition.

In an example not forming part of the claimed invention, there is described a method for determining the condition of a barrier in a well infrastructure, the method comprising:.

There is described a monitoring system for performing the described method, configured to determine the condition of a barrier in a well infrastructure. The monitoring system is configured to receive sensor data derived from a sensor arrangement at a barrier positioned at a location in a well infrastructure. That sensor data is associated with measured conditions at that barrier. The system is configured to receive composition data derived from measurements of fluid composition within a well. That composition data is indicative of the location at which fluid has been in the well. The monitoring system is configured to analyse received sensor data and composition data to determine the condition of a barrier.

The monitoring system may be configured to receive sensor data and composition data at the well infrastructure, or remotely from the infrastructure (e.g. received data via a network connection, or the like). In some examples, the sensor data together with composition data may be collected at the well infrastructure, and subsequently communicated remotely to the monitoring system for receipt and analysis in order to determine conditions associated with a barrier.

There is described well infrastructure comprising at least one barrier, intended to provide zonal isolation, together with a sensor arrangement and tracer elements both positioned at the barrier. The sensor arrangement is configured to monitor conditions at the barrier and communicate sensor data associated with those conditions for subsequent receipt. The tracer elements are configured to interact with fluid at the location of the barrier so as to impart identifiable properties to the composition of the fluid. The infrastructure further comprises a monitoring system configured to receive sensor data from the sensor arrangement and to monitor the composition of fluid being produced by the well infrastructure so as to provide composition data associated with the composition of fluid in the well. The data system may be further configured to analyse sensor data and composition data to determine the condition of the at least one barrier.

The barrier may be an annular barrier provided by one or more packers. The barrier may be provided together with well-completion tubing, or the like. The sensor and elements may be provided at an isolated side of the barrier, e.g. isolated from production inflow.

In an example not forming part of the claimed invention, there is described well apparatus. The apparatus may comprise a barrier configured in use to provide isolation, such as zonal isolation. The apparatus may comprise a sensor arrangement configured to monitor conditions at the location of the barrier. The apparatus may comprise one or more tracer elements configured to interact with fluid at the location of the barrier, for example, so as to impart identifiable properties to the composition of fluid.

The sensor arrangement may be configured to measure pressure and/or temperature at the barrier. The tracer elements may be configured to impart uniquely identifiable properties to the composition of the fluid. Such identifiable properties may be markers, such as chemical markers, or the like, which may provide uniquely identifiable properties of the composition.

The apparatus may be comprised with, or otherwise mounted to, tubing.

The barrier may be configured to provide zonal isolation in use, i.e. isolation of one zone of a well infrastructure from another zone. In similar words, the barrier may be configured to isolate a first zone from a second zone. The tubing may be completion tubing, casing, production tubing or the like.

The barrier may be configured to activate from the tubing, such as casing, towards any corresponding formation, e.g. in order to seal one section of the well from another. The barrier may be considered to provide an annular barrier. The barrier may comprise one or more packers (e.g. two packers, axially spaced on tubing). The or each packer may comprise elements that are configured to activate in the presence of particular well conditions, such as particular fluid in the annulus formed between tubing and formation (e.g. swellable packers), or such as a particular pressure in the tubing and/or annulus (e.g. pressure applied from surface).

The barrier may be configured to prevent or inhibit fluid from flowing from a first zone at one side of the barrier to a second zone at another side of the barrier. The first zone may be intended to be an isolated zone, whereas the second zone may be intended to be a production zone.

The sensor arrangement may comprise one or more sensors, each sensor configured to measure conditions at or in the location of the barrier. The sensor arrangement may be provided with well tubing (e.g. integrated with or otherwise affixed to well tubing). The sensor arrangement may be provided on an outer surface of the tubing. The sensor arrangement may comprise a power source, such as a battery pack, e.g. for powering a transmitter to communicate signals to surface, or the like.

The sensor arrangement may be configured for wireless communication in as much as there the arrangement need not transmit data using a dedicated wired communication path. In similar words, the sensor arrangement may be configured to communicate wirelessly through the barrier. In some examples, the sensor arrangement may be configured to communicate using a signal path comprising the tubing (e.g. the completion and/or production tubing, etc.). The sensor arrangement may be configured to communicate to, or otherwise injected into, the tubing, for subsequent receipt. In other similar words, sensor data may be communicated from an isolated zone, for subsequent receipt, using the tubing. The received sensor data may be received at surface.

The fluid composition may be indicative of the location at which fluid has been in the well by virtue of an interaction (or lack of) of the fluid with one or more tracer elements at the barrier. Such tracer elements may be configured to release markers into the fluid when in contact with the fluid. The tracer elements may be provided at a first side of the barrier (e.g. together with the sensor arrangements).

In an example not forming part of the claimed invention, there is described well tubing, such as casing, comprising:.

In an example not forming part of the claimed invention, there is described a method for validating data from a sensor associated with an annular barrier in a well, comprising:.

In an example not forming part of the claimed invention, there is described a kit of parts comprising tubing, sensor arrangements and tracer elements configured, when assembled, to provide any of the systems/apparatus above. The kit of parts may be accompanying with assembly/use instructions.

In some examples, there is described a computer program product that when programmed into a suitable controller configures the controller to perform the methods according to the invention. There may be provided a carrier medium, such as a physical or tangible and/or non-transient carrier medium, comprising the computer program product. The carrier medium may be a computer readable carrier medium.

As will be appreciated, features associated with particular recited embodiments relating to systems may be equally appropriate as features of embodiments relating specifically to methods of operation or use, and vice versa.

It will be appreciated that one or more embodiments/aspects may be useful in effective control/maintenance of a well (e.g. and such completions), and may help monitor conditions accurately, for example, over the lifespan of any well, e.g. from completion through to production, etc..

The above summary is intended to be merely exemplary and non-limiting.

A description is now given, by way of example only, with reference to the accompanying drawings, in which:-.

<FIG> shows an exemplary representation of a multi-zonal well infrastructure <NUM>, in which sections of the well infrastructure <NUM> may be considered to be isolated from one another so as to permit controlled inflow of product or injection of fluids/gases from/to a formation <NUM>.

For ease of reference, some of the following examples have been described specifically in relation to well infrastructures <NUM> using non-cemented barriers between casing and formation, and the monitoring of the condition of such barriers. However, a skilled reader will appreciate that in other examples the systems and methods described herein may also be used with monitoring of other barriers, such as those provided between other or multiple well annuli (e.g. barriers between production tubing and casing, or other such tubing). Similarly, while the well infrastructure <NUM> of <FIG> may be considered to show a deviated or horizontal well configuration, it will be appreciated that in other examples, the systems and methods may be used in vertical, or near-vertical sections of well, and indeed in mother bores and/or laterals.

Further, the examples described have been given with reference to oil and gas production, but of course in other examples, the systems and methods may be used with other fluid being produced and/or injected.

<FIG> shows a simplified representation of the well infrastructure <NUM> that comprises tubing <NUM> running from surface to a subterranean hydrocarbon bearing formation <NUM>. At various sections of the infrastructure <NUM>, there may be multiple annuli, as will be appreciated. However, for ease of representation, only a single tubing <NUM> is shown - albeit this may comprise production tubing, casing, etc. In the examples described below, attention is focused on the use of barriers that may be formed between tubing <NUM> and the formation. In such examples, such tubing <NUM> can be considered to be the casing of the well infrastructure, as will be appreciated by the skilled reader.

In this example, the tubing <NUM> runs horizontally through a section of the formation <NUM>, as shown, and permits selective flow of product from the formation <NUM> to the tubing <NUM> for production to surface <NUM>. In this case, rather than a cemented annulus between the tubing <NUM> (e.g. casing) and the formation <NUM>, non-cemented annular barriers <NUM> are provided, which define a plurality of zones 140a, 140b, 104c, along some of the length of the tubing <NUM>, and in this example between the tubing <NUM> and the formation <NUM>.

Here, the formation <NUM> may be considered to be a carbonate formation, or fractured formation, or the like. As will be appreciated, such formations <NUM> can present particular challenges when achieving effective cement placement and bonding between the tubing (e.g. casing) and formation <NUM>. These challenges are further accentuated where the well infrastructures <NUM> are deep and have complex trajectories. Problems to achieving effective cement placement include contaminated cement, channelling through the cement, and lost circulation of the cement into fractures in the formation.

Therefore, in this case, rather than providing conventional cement, alternative non-cemented barriers <NUM> are provided. Here, each barrier <NUM> may be considered to comprise swellable packers, configured to expand in the presence of specified fluids, such as water or oil. However, alternative/additional mechanically-actuated packers may be used, that are set by the application of pressure or by other mechanical means.

During installation and production, each barrier <NUM> is intended to provide zonal isolation. In doing do, production and/or injection at each zone can be controlled (e.g. using control valves or ports at the tubing <NUM>, as is known). However, for such multi-zone intelligent completions to be effective, then the integrity of the barriers <NUM> should be maintained, where possible. Otherwise, any breach of the integrity of these barriers <NUM> may result in the high cost intelligent completion systems being ineffective.

For at least that reason, it may be helpful to monitor the condition of barriers (and zonal isolation), for example, in order to ensure integrity is being maintained. This may be desirable during early stage installation, production and injection testing and for longer term observation extending over several years.

Consider now <FIG>, which shows a section of tubing <NUM> from the well infrastructure <NUM> of <FIG>. Here, the barriers <NUM> may be considered to be provided on the outer surface of the tubing <NUM> (e.g. casing) and are configured to activate from the tubing <NUM> towards the formation <NUM> in order to seal one section of the well <NUM> from another. Here, barriers <NUM> provide an annular barrier. The barriers may comprise swellable packers or the like, configured to activate in the presence of particular well conditions, such as particular fluid in the annulus formed between tubing <NUM> and formation <NUM>.

Here, the barriers <NUM> are configured to prevent or inhibit fluid from flowing from a first zone <NUM> at one side of a barrier <NUM> to a second zone <NUM> at another side of the barrier <NUM> (or indeed to a third zone). In this example, the first zone <NUM> can be considered to be an isolated zone, whereas the second zone <NUM> can be considered to be a production zone.

Here, a sensor arrangement <NUM> is positioned within the first zone <NUM> and is configured to measure conditions, such as pressure and/or temperature, at the barrier <NUM> (e.g. at the first zone <NUM>), and provide sensor data accordingly. It will be appreciated that the sensor arrangement <NUM> may comprise one or more sensors, with each sensor being configured to measure particular conditions at or in the location of the barrier <NUM>/zone <NUM>. In some examples, the sensor arrangement <NUM> will be provided with well tubing <NUM> (e.g. integrated with or otherwise affixed to well tubing) prior to running into the well. As shown here, the sensor arrangement <NUM> is provided on an outer surface of the tubing <NUM>. The sensor arrangement <NUM> may comprise a power source, such as a battery pack, e.g. for powering a transmitter to communicate signals to surface, or the like.

In this example, the sensor arrangement <NUM> is configured for communication to surface using at least a wireless connection across the barrier <NUM>. As such, there is no need to transmit data using a dedicated wired communication path, which may otherwise penetrate or extend through the barrier <NUM>, potentially reducing effectiveness, increasing risk or compromising lifespan of the barrier <NUM>. While many methods of wireless communication may be possible, in this case the sensor arrangement <NUM> is configured to communicate sensor data using a signal path across the barrier <NUM> comprising the metallic tubing <NUM> itself (e.g. the casing and/or production tubing, etc.). In doing so, the sensor arrangement <NUM> is configured to communicate signals to, or otherwise injected signals into, the metallic tubing <NUM>, for subsequent receipt from the tubing <NUM>.

In some examples, the signal path may have a wireless connection across the barrier and the remainder, or at least most of the remainder, of the signal path to surface or otherwise may be wired. It will be appreciated that in this context, "wired" can include optical communication paths, or the like, as well as intermediate forms or apparatus for transferring data. In such cases, the signal path may be wired, wireless or combination thereof.

For example, data may initially be communicated wirelessly from the sensor arrangement located in the annular void, and received at a receiver or pick-up device positioned proximate the sensor arrangement. Subsequently, data may be communicated from the receiver to surface using wireline, or the like (or indeed wireless communication). In such cases, nonetheless, wireless communication can be used across the barrier helping maintain integrity. Of course, in other examples, wireless communication may be used from the barrier <NUM> to surface <NUM> (e.g. using the tubing to surface).

It will be appreciated that data may be communicated in real time, or may be communicated from time to time, and/or in response to a transmit request, for example, initiated from surface. In some cases, the data may be communicated in batch mode.

In any event, sensor data (i.e. data from the sensor arrangement that is associated with measured conditions at the barrier <NUM>, zone <NUM>) can be readily communicated from an isolated zone <NUM>, for subsequent receipt at surface <NUM>, using the tubing <NUM>. Here, electromagnetic data communications technology, which transmits low frequency electromagnetic signals from downhole to surface, or surface to downhole, using the well's tubing or casing as the transmission medium may be used.

In use, detailed sensor data regarding conditions, such as pressure and/or temperature can be measured and communicated to surface <NUM>. Such data may be desired when initially setting the barriers to ensure appropriate positioning instalment. Also, however, as will be appreciated, certain variations in measured conditions may be linked with a change in barrier integrity over the life of the well, suggesting that in some cases the barrier <NUM> may have been compromised and that a flow path <NUM> has been established from the first zone <NUM> to the second zone <NUM> (or third zone <NUM>).

In the event of barrier <NUM> failure, remedial action may be required, and potentially this action may be considered vitally urgent if the barrier <NUM> failure could result in loss of control of the well. Therefore, it will be appreciated that accurate monitoring of conditions, and the variations thereof, can be key to identifying barrier <NUM> failure and expeditiously taking appropriate action.

However, while conditions varying in the first zone <NUM> give rise to variations in measured conditions, the inventors have also discovered that, from time to time, variations in production fluids or injection fluids passing through the tubing <NUM> (or other thermally-driven fluctuation) can lead to measurement readings at the sensor arrangement <NUM> that spuriously suggest that the barrier <NUM> integrity may be compromised. In other words, accurate measurement of conditions - which may be required - can be difficult to achieve as the veracity of the data, or the confidence in that data, maybe in question. In some circumstances, this may lead to remedial action being performed that was otherwise not required.

Consider now therefore, the tubing of <FIG>. Here, in addition to the sensor arrangement <NUM>, tracer elements <NUM> are additionally provided at the location of the tubing <NUM>, at the first or isolated zone <NUM>. Here, the tracer elements <NUM> are configured to impart identifiable properties to the composition of the fluid. Such identifiable properties may be markers, such as chemical markers, or the like, which may provide uniquely identifiable properties of the composition. It will be appreciated that a section of tubing <NUM>, one or more barriers <NUM>, together with sensor arrangement <NUM> and tracer elements <NUM> may be provided as complete sections for deployment in the well (e.g. a part of, or to complement, an intelligent completion system).

The fluid composition in the tubing <NUM> (e.g. being produced to surface <NUM>) may be indicative of the location at which fluid has been in the well by virtue of an interaction (or lack of) of the fluid with tracer elements <NUM> at the barrier <NUM>. In other words, if a barrier <NUM> has been compromised, then the fluid composition at surface <NUM> should indicate as much (albeit it may not provide suitably sufficient data regarding that condition, as per the sensor data).

<FIG> shows a monitoring system <NUM> for use with the sensor arrangement <NUM> and tracer elements <NUM> of <FIG>. Here, the monitoring system <NUM> comprises a processor <NUM> and memory <NUM>, configured in a known manner. The system <NUM> further comprises a receiver <NUM> for receiving sensor data communicated by the sensor arrangement. In this case, the receiver is configured to extract signals communicated in the metallic tubing <NUM> itself. Of course, in other examples the receiver may be configured to receive signals from wireline (e.g. e-line), or the like, or other signal path, from the sensor arrangement. Additionally, the monitoring system <NUM> comprises a composition analyser <NUM> configured to measure fluid composition within the well, and provide corresponding composition data. That composition data may be indicative of the location at which fluid has been in the well, as will be appreciated.

While in this example, the monitoring system <NUM> is configured to receive sensor data and composition data at the well infrastructure <NUM>, in other examples the system <NUM> may be configured to receive such data remotely from the infrastructure (e.g. received data via a network connection, or the like). In some examples, the sensor data together with composition data may be collected at the well infrastructure <NUM>, and subsequently communicated remotely to the monitoring system <NUM> for receipt and analysis in order to determine conditions associated with a barrier <NUM>. In some examples sensor data may be collected at the well infrastructure and communicated remotely for subsequent analysis. Similarly, fluid samples of fluid composition within the well may be collected and communicated to a remote location for analysis, or indeed composition data may be collected and communicated to a remote location. In such examples, collected sensor data, fluid samples and/or composition data may be communicated remotely in order to permit subsequent determination of the condition of the barrier using the sensor data and composition data.

In use, in order to determine the condition of a barrier <NUM> at a location in a well infrastructure <NUM>, the system <NUM> (be it remote or local to the infrastructure, or combination thereof) initially receives sensor data associated with measured conditions at the barrier <NUM>, or zone <NUM>. Additionally, composition data of the fluid composition within the well <NUM> is obtained. The sensor data and/or composition data may be received from time to time, for example, during completion and/or production from the well. The sensor/composition data may be received periodically, e.g. hourly, daily, weekly or the like.

Here, the system <NUM> is configured to analyse the received sensor data and composition data to determine the condition of the barrier <NUM>. In some examples, in the event that the sensor data suggests that an isolated zone <NUM> (e.g. a barrier <NUM>) may be compromised, then the system <NUM> is configured to authenticate, or otherwise validate, the sensor data associated with that zone/barrier when the received composition data confirms the location at which fluid is being produced as being from the isolated zone (e.g. behind the barrier). In those cases, the system may be further configured to issue or otherwise signal an alert status in the event that composition data confirms the location at which fluid is being produced as being from the first, or isolated, zone. Alternatively, the system may be able to determine from the detailed sensor data that the compromise remains within acceptable limits, and take no immediate action.

Alternatively still, the system <NUM> may be configured to discard sensor data associated with the barrier <NUM> when the composition data confirms the location at which fluid is being produced as being from the second, or production, zone. In such cases, the system <NUM> may be configured to attribute sensor data associated with the barrier to flow conditions in the well, when the composition data confirms the location at which fluid is being produced as being from the second, or production, zone.

Additionally or alternatively it will be appreciated that in the above example, that the system <NUM> may be used for a period of the life of the well infrastructure <NUM>. In doing, however, the power supply for the sensor arrangement <NUM> may deplete over time. Therefore, in some examples, the system <NUM> may be configured to initially use essentially the received sensor data to determine conditions at the barrier <NUM>, and then subsequently use essentially composition data to determine conditions at the barrier <NUM>. For example, the system <NUM> may be configured to use initially essentially received sensor data during installation/completion and subsequently using composition data during production. In doing so, detailed data can be obtained from the well during installation (e.g. detailed sensor data), while long term integrity can be monitored accordingly (using composition data).

Claim 1:
A method for determining the condition of a barrier and the condition of zonal isolation provided by the barrier (<NUM>) in a well infrastructure (<NUM>), the method comprising:
receiving sensor data derived from a sensor arrangement (<NUM>) within an isolated zone provided by the barrier (<NUM>) positioned at a location in the well infrastructure (<NUM>), that sensor data associated with measured conditions at the barrier (<NUM>) and within the isolated zone;
initially using the received sensor data to determine conditions at the barrier (<NUM>) during installation or completion of the well infrastructure (<NUM>);
receiving composition data derived from measurements of fluid composition from the isolated zone within the well infrastructure (<NUM>), the composition data comprising data associated with location-based identifiable properties of fluid composition indicative of the location at which fluid has been in the well infrastructure (<NUM>); and
subsequently using the received composition data to determine conditions at the barrier (<NUM>) during production at the well infrastructure (<NUM>).