GB2472083A

GB2472083A - Apparatus and methods for determining the location of an interface in a medium

Info

Publication number: GB2472083A
Application number: GB0912882A
Authority: GB
Inventors: Wayne Rudd; Laurie Linnett
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-07-24
Filing date: 2009-07-24
Publication date: 2011-01-26
Also published as: GB0912882D0; WO2011010096A1

Abstract

Apparatus and methods for determining the location of an interface region such as an interface region defined between first and second layers in a multi-layered medium' for example, an interface region defined between oil and water layers in pipeline. The location is determined by using a time of flight of an interface signal having been communicated across a transmission path of known distance passing through the multi-layered medium having the first layer, second layer and the interface region, together with the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the location of the interface region along the transmission path. A conduit 100 forms part of a pipeline, a multi layer medium considered to have laminar flow comprises first layer 110 and second layer 120 separated by interface region 115. Apparatus 200 comprising ultrasonic transmitter 210a and receiver 210b is configured such that interface signal passes through layers 110 and 120 to determine the time of flight of the interface signal travelling across transmission path 50.

Description

A method for determining the location of an interface region in a medium and associated apparatus

Technical Field

The invention relates to a method for determining the location of an interface region in a medium, and associated apparatus. In particular, the invention relates to a method for determining the location of an interface region defined between first and second layers of a multi-layer medium, and associated apparatus.

Background

In certain industries it is desirable to measure features or properties of a medium, such as properties of solids, liquids or gases (or combinations thereof). Such mediums may be provided in a container, pipeline, reservoir, conduit, or the like. An example of a medium might be a coolant in a cooling system conduit, or a flow of hydrocarbons in a transportation/production pipeline. In some instances, mediums can comprise two or more layers, each layer being a different density and/or different phase. Such mediums may be considered to be multi-layered.

An example of a multi-layered medium may be hydrocarbon gas and oil, provided in a pipeline, in which the gas and oil are provided as different layers due to the difference in their relative densities. In an alternative example of a multi-layered medium, a conduit comprising a deposited build-up of matter on the inner wall may be considered to be a first layer, while the material passing through the conduit may be considered to be a second layer of the multi-layer medium.

An interface region may be provided between such layers. An example of an interface region may be a boundary layer defined at the interface between two immiscible layers (e.g. at the interface provided between water and oil), or as an interface layer provided between a layer of deposition in a pipeline and material flowing through a pipeline, for example. It can be desirable to determine the location of the interface region so as to, for example, determine the height, or hold-up, of a particular material in a layer (or deposit), determine a flow regime, determine component ratios or the like. It can be helpful to determine the profile of the interface region. That is to say it can be helpful to determine the height over a particular area, or volume, of interface region.

Inaccurate measurement of the location of an interface region can often be provided in the oil and gas exploration and production industry, such as when monitoring the fluid flow in a multi-fluid/multi-layered pipeline, which can result in serious processing hazards, and/or an undesirable increase in operational costs.

Summary

According to a first aspect of the invention there is provided a method for determining the location of an interface region defined between first and second layers in a multi-layered medium, the method comprising: using a time of flight of an interface signal having been communicated across a transmission path of known distance passing through the multi-layered medium having the first layer, second layer and the interface region, together with the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the location of the interface region along the transmission path.

The first and second layers may comprise adjacent layers. The first and second layers may be stratified, or substantially stratified. The first and second layers may be substantially continuously stratified such that said layers are of a substantially equivalent dimension in at least one direction, such as the direction of the interface region. The first and second layers may be discretely stratified. In this arrangement one of the first and second layer may be at least partially contained within the other of the first and second layer. For example, one of the first and second layers may comprise a bubble, core, slug, droplet, bead, ball or the like contained within the other of the first and second layer.

The interface region may comprise an interface layer, boundary layer or the like. The interface region may comprise a region of emulsion. The interface region may comprise a region of gas and liquid foam defined between the first and second layers.

The location of the interface region may be provided with respect to a location of receipt of the interface signal. The location of the interface region may be provided with respect to a location of transmission of the interface signal. The location of the interface region may be an approximate location. The location may be provided as a particular distance along the transmission path.

Determining the location of the interface region may provide for determining the height, or hold-up, of at least one of the first and second layer. For example, by using the determined location of the interface region and the known distance of the transmission path. The height may be the height of at least one of the first and second layer in a conduit, container, pipeline, reservoir, tubular, or the like.

Determining the location of the interface region may provide for determining the height of both the first and second layer (e.g. in a conduit, etc.).

The interface signal may comprise a reflected signal (e.g. a signal transmitted across the transmission path and reflected at a target, or object).

The method may comprise using the time of flight of two or more interface signals.

The two or more interface signals may have been communicated across two or more transmission paths.

The two or more transmission paths may have the same known distance, or may have different known distances. At least two of the two or more interface signals may have been transmitted from a common transmitter. At least two of the two or more interface signals may have been received at a common receiver. One, some or all of the transmission paths may intersect. This may provide for using the time of receipt associated with two or more transmission paths for every one transmitted/received interface signal.

The determined location of the interface region along different transmission paths may provide for determining the location (or relative location) of the interface region at different regions in the medium, for example, different regions of a medium in a conduit, container, reservoir, or the like. The determined location of the interface regions along different transmission paths may provide for determining a profile of the interface region of a multi-layer medium, such as a profile of the interface region provided in a conduit, etc. The profile may be a cross-sectional profile. The profile may be a two-dimensional profile, or may be a three dimensional profile. The profile may be time variant. That is to say, the profile may change as the medium/interface region changes.

The method may comprise providing a visual representation of the change in profile For example, a visual representation may be provided on a user interface, such as an output user interface (e.g. Liquid Crystal Display, Organic Light Emitting Diodes, etc.). The method may comprise providing for flow visualisation (e.g. visualisation of the flow of a medium, such as real time visualisation).

The speed of the interface signal in the first layer may be associated with the speed of the interface signal at the location of transmission of the interface signal (i.e. for transmission across a transmission path). The speed of the interface signal in the first layer may be the speed of the interface signal at the location of transmission.

The speed of the interface signal in the second layer may be associated with the speed of the interface signal at the location of receipt of the interface signal (i.e. receipt across a transmission path). The speed of the interface signal in the second layer may be the speed of the interface signal at the location of receipt.

The speed of the interface signal in the first layer may be different from the speed of the interface signal in the second layer, or the same, similar, roughly the same, or the like.

The method may comprise determining the location of an interface region in a conduit. The method may comprise using the time of flight of two or more interface signals having been communicated across a conduit. The conduit may comprise or at least partially define a pipeline, such as an oil and gas pipeline (e.g. production and/or exploration pipeline). The method may comprise using the time of flight of two or more interface signals having been communicated across transmission paths of a conduit at different interval orientations. For example, transmission paths spaced at every 30 degrees, 45 degrees, around a conduit, and/or 0.1 m, 0.2 m, etc. along a conduit, or the like. The intervals may be regular or irregular, or combination of regular and irregular intervals.

The method may comprise using the time of flight of four interface signals having been communicated across four transmission paths through a multi-layered medium to determine the location of the interface region (e.g. through a multi-layered medium in a conduit).

The known distances of one, some or all of the transmission paths may be measured known distances, estimated known distances, evaluated known distances, approximated known distances, or the like. The distances may include configured known distances.

That is to say that, in some instances a particular distance may have been measured prior, during, or after transmitting of the interface signal, or may have been estimated, evaluated, or approximated. In further instances, the interface signal may have been transmitted a configured distance.

A time of receipt of the interface signal may be used to provide for determining the time of flight. The method may comprise determining the time of flight from a time of receipt of the interface signal. The time of receipt may be considered to be the time of flight.

The multi-layer medium may comprise a single phase. The multi-layer medium may comprise multiple phases. The multi-layer medium may comprise any one or combination of: solid, liquid and/or gas component phase. The first layer may comprise any one, or more, of solid, liquid or gas component phases. The first layer may comprise a single component phase. The first layer may comprise multiple component phases. The first layer may comprise different or the same component phases. The first layer may comprise water, oil, hydrocarbon gas, hydrates, asphaltenes, salts, etc. The second layer may comprise any one, or more, of solid, liquid or gas component phases. The second layer may comprise a single component phase. The second layer may comprise multiple component phases. The second layer may comprise different or the same component phases. The second layer may comprise water, oil, hydrocarbon gas, hydrates, asphaltenes, etc. The first layer and the second layer may comprise different or the same component phases.

At least one of the first and second layer may comprise two or more sub-layers, such as three, four, five, ten, twenty sub-layers, or any number therebetween. Each sub-layer may be adjacent, such as being adjacently stratified, or the like.

Each sub-layer may serve to define a sub-interface region between respective sub-layers. The sub-interface region may be provided as an interface layer, boundary layer, region of emulsion, foam, etc. The speed of an interface signal in at least one of the first and second layer comprising sub-layers may be provided as the average speed of an interface signal through the cumulative sub-layers. That is to say that the interface region, whose location is to be determined, may be selected from a plurality of interface regions (or sub-interface regions), by providing the average speed of a interface signal through the cumulative sub-layers that define an interface region with another layer (or other sub-layers).

The method may be for determining the presence, and/or change in deposition in a conduit, pipeline, etc. For example, the interface region may be the region provided between material flowing in a pipeline and hydrates, asphaltenes, salts, etc. deposited in a pipeline. The method may be for determining the presence, and/or change in corrosion in a conduit, pipeline, etc. For example, the interface region may be the region provided between material flowing in a conduit and a wall of a conduit.

The method may comprise providing the speed of the interface signal in the first and/or second layer. Providing the speed of the interface signal in the first layer and/or second layer may be provided by having knowledge of the first and/or second layer. For example, if it were known, guessed, assumed, or the like, that the first layer was water, and the second layer was oil, the speed of interface signals in those layers may be determined, such as determined from look-up tables, or the like. The method may comprise using the temperature of at least one of the first and second layer to provide the speed of an interface signal in the first/second layer.

The speed of a particular interface signal in the medium may be dependent upon the particular interface signal species that is used. Examples of interface signal species are acoustic interface signals, such as ultrasonic interface signals, electromagnetic interface signals, such as Radio Frequency interface signals, optical interface signals, or the like.

The method may comprise determining the speed of the interface signal species in at least one of the first and second layer of a multi-layer medium. The method may comprise determining the speed of the interface signal species in both the first and second layer of the multi-layer medium. The method may comprise determining the speed of the interface signal species in at least one of the first and second layer of a multi-layer medium so as to provide for determining the location of the interface region.

The speed of the interface signal species may be determined by transmitting one or more signals across one or more distances (e.g. one or more transmission paths).

Interface signals may be used (e.g. additionally used) for determining the speed of the signal species.

The method may comprise receiving one or more interface signals. The method may comprise transmitting one or more interface signals. The method may comprise using one or more transmitter/receivers, such as acoustic transducers, for transmitting and/or receiving. The method may comprise using one or more transducers. The method may comprise using one or more common transmitters/receivers (e.g. for transmitting/receiving two or more interface signals). The method may comprise using one or more transceivers for transmitting and receiving.

The method may comprise using four transmitter-receiver pairs to provide twenty-four transmission paths (e.g. twenty-four transmission paths in a conduit). The method may comprise using movable/adjustable apparatus to provide configured known distances of transmission paths. The method may comprise using moveable/adjustable transmitters/receivers/transceivers.

The method may comprise determining the presence of an interface region along one or more particular transmission paths associated with one or more particular interface signals. The method may comprise determining the lack of an interface region along one or more particular transmission paths. The presence or lack of an interface region may be used to provide for determining the location of the interface region.

For example, a determined presence or lack of an interface region may allow for determining that there is no location of an interface region along a particular transmission path, and/or that a determined location is spurious.

The method may comprise using the speed of a particular interface signal in the first and second layer in order to determine the presence or lack of an interface region along the associated particular transmission path. The speed of the particular interface signal in the first layer may be compared with the speed of the particular interface signal in a second layer to determine the presence or lack of an interface region. For example, when the speed of the particular interface signal in the first and second layer is considered to be similar, the same, or substantially similar/the same, it may be determined that no interface regions exists along that particular transmission path. For example, if the speed of the interface signal in the first and second layer is considered roughly the same, it might be considered that the first layer and the second layer are the same material, density, phase, etc. The determination of the presence or lack of an interface region may be for use in providing a profile (e.g. a profile of the interface region).

The method may comprise not using, or discarding, a determined location of an interface region derived from the time of flight of an interface signal having been communicated across a transmission path having a lack of interface region (or a determined lack of interface region). The method may comprise not determining the location of an interface region derived from the time of flight of an interface signal having been communicated across a transmission path having a lack of interface region (or a determined lack of interface region). For example, the location of an interface region used for providing a profile along transmission paths may be disregarded if no interface region exists, is determined to exist (e.g. for the purposes of providing a profile).

According to a second aspect of the invention there is provided a method for determining the location of an interface region defined between first and second layers in a multi-layered medium, the method comprising: transmitting an interface signal across a transmission path of a known distance, the transmission path passing through a multi-layered medium having a first layer and a second layer, the first and second layer having an interface region defined between the first layer and the second layer; determining the time of flight of the interface signal travelling across the transmission path; providing the speed of the interface signal in the first layer and the speed of the interface signal in the second layer; using the time of flight of the interface signal, the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the location of the interface region along the transmission path.

According to a third aspect of the invention there is provided a computer program stored, or storable, on a computer readable medium, the computer program configured to provide the method of any of the features of the first and second aspect.

According to a fourth aspect of the invention, there is provided apparatus for determining the location of an interface region defined between first and second layers in a multi-layered medium, the apparatus configured to use a time of flight of an interface signal having been communicated across a transmission path of known distance, such a transmission path passing through a multi-layered medium having a first layer, second layer and an interface region, such an interface region being defined between a first layer and a second layer, together with the speed of an interface signal in a first layer and the speed of an interface signal in a second layer in order to provide for determining the location of an interface region along a transmission path.

The apparatus may be configured to determine the location of an interface region with respect to a location of receipt and/or transmission of an interface signal. The location may be an approximate location.

The apparatus may be configured to determine the location of an interface region to provide the height, or hold-up, of at least one of a first and second layer. For example, by using a determined location of an interface region and a known distance of a transmission path. The height may be the height of at least one of the first and second layer in a conduit, container, pipeline, reservoir, tubular, or the like.

The apparatus may comprise a transmitter configured to transmit an interface signal.

The apparatus may comprise a receiver configured to receive an interface signal.

The transmitters/receiver may be configured to provide the transmission path. The transmitter/receiver may be configured to provide the known distance of the transmission path.

The apparatus may be configured to use the time of flight of two or more interface signals (e.g. having been communicated across two or more transmission paths).

The apparatus may comprise two or more transmitters and/or receivers to provide two or more transmission paths. The two or more transmission paths may have the same known distance, or may have different known distances.

The apparatus may comprise a common transmitter for transmitting two or more interface signals. The apparatus may comprise a common receiver for receiving two or more interface signals. The apparatus may be configured such that one, some or all of the transmission paths intersect. The apparatus may comprise one or more transceivers configured to transmit and receive interface signal(s).

A determined location of an interface region along different transmission paths may provide the location (or relative location) of an interface region at different regions in a medium, for example, different regions of a medium in a conduit, container, reservoir, or the like. The apparatus may be configured to determine the interface regions along different transmission paths to provide a profile of an interface region of a multi-layer medium, such as a profile of an interface region provided in a conduit, etc. (e.g. a cross-sectional profile). The profile may be a two-dimensional profile, or may be a three dimensional profile. The profile may be time variant. That is to say, the profile may change as the medium/interface region changes.

The apparatus may further comprise a user interface, such an output user interface (e.g. Liquid Crystal Display, Organic Light Emitting Diodes, etc.). The apparatus may be configured to provide flow visualisation (e.g. visualisation of the flow of a medium, such as real time visualisation). The apparatus may be configured to provide a visual representation of a change in profile of an interface region.

The speed of an interface signal in a first layer may be associated with the speed of an interface signal at the location of transmission of that interface signal (i.e. for transmission across a transmission path). The speed of an interface signal in a first layer may be the speed of that interface signal at the location of transmission. The speed of an interface signal in a second layer may be associated with the speed of that interface signal at the location of receipt of that interface signal (i.e. receipt across a transmission path). The speed of an interface signal in a second layer may be the speed of that interface signal at the location of receipt.

The apparatus may be configured for use with a conduit. The apparatus may comprise a conduit, such as a conduit configured for use with a multilayered medium.

The apparatus may be configured to communicate two or more interface signals across the conduit. The conduit may be a pipeline, such as an oil and gas pipeline.

The apparatus may be configured to communicate the two or more interface signals at different interval orientations with respect to the conduit, such as spaced at every degrees, 45 degrees, around a conduit, and/or 0.1 m, 0.2 m, 0.5 m, etc. along the conduit, or the like. The intervals may be regular or irregular, or combination of regular and irregular intervals.

The apparatus may be configured to use the time of flight of four interface signals having been communicated across four transmission paths through a multi-layered medium to determine the location of the interface region (e.g. a multi-layered medium in a conduit).

That is to say that, in some instances a particular distance may be measured prior, during, or after transmitting of the interface signal, or may be estimated, evaluated, or approximated. In further instances, the apparatus may be configured/configurable to transmit an interface signal a configured distance. For example, the apparatus may be movable/adjustable to provide a configured known distance, such as providing movable/adjustable transmitters, and/or receivers.

A time of receipt of the interface signal may be used to provide for determining the time of flight. The apparatus may be configured to determine the time of flight from a time of receipt. The time of receipt may be considered to be the time of flight.

The apparatus may be configured for use with a multi-layer medium comprising any one or combination of: solid, liquid and/or gas component phase. The first layer may comprise any one, or more, of solid, liquid or gas component phases. The first layer may comprise a single component phase. The first layer may comprise multiple component phases. The first layer may comprise different or the same component phases. The first layer may comprise water, oil, hydrocarbon gas, hydrates, asphaltenes, etc. The second layer may comprise any one, or more, of solid, liquid or gas component phases. The second layer may comprise a single component phase. The second layer may comprise multiple component phases. The second layer may comprise different or the same component phases. The second layer may comprise water, oil, hydrocarbon gas, hydrates, asphaltenes, salts, etc. The first layer and the second layer may comprise different or the same component phases.

At least one of the first and second layers may comprise two or more sub-layers, such as three, four, five, ten, twenty sub-layers, or any number therebetween. Each sub-layer may be adjacent, such as being adjacently stratified, or the like.

The location of the interface region may be determined by evaluating the difference between two of more interface signals.

The apparatus may be configured to determine the presence, and/or change in deposition in a conduit, pipeline, etc. For example, the interface region may be the region provided between material flowing in a pipeline and hydrates, asphaltenes, etc. deposited in a pipeline. The apparatus may be configured to determine the presence, and/or change in corrosion in a conduit, pipeline, etc. For example, the interface region may be the region provided between material flowing in a conduit and a wall of the conduit.

The apparatus may be configured to provide the speed of an interface signal in a first and/or second layer. Providing the speed of the interface signal in the first layer and/or second layer may be provided by having knowledge of the first and/or second layer. For example, the apparatus may be configured to from look-up table based on secondary data to provide the speed of an interface signal. The secondary data may comprise the temperature of at least one of a first and second layer.

The apparatus may be configured to use one or more of: acoustic interface signals, such as ultrasonic interface signals, electromagnetic interface signals, such as Radio Frequency interface signals, optical interface signals, or the like.

The apparatus may be configured to determine the speed of an interface signal species in at least one of a first and second layer of a multi-layer medium. The apparatus may comprise one or more measurement sensors to provide for determining the speed. The one or more measurement sensors may determine the speed directly (e.g. by transmitting a signal in the first/second layer and determining speed), or indirectly (e.g. by measuring one or more of the layer's characteristics, such as density, temperature, etc., to provide for determining the speed, such as by using look-up tables).

The apparatus may be configured to determine the presence of an interface region along one or more particular transmission paths associated with one or more particular interface signals. The apparatus may be configured to determine the lack of an interface region along one or more particular transmission paths. The presence or lack of an interface region may be used to provide for determining the location of the interface region. For example, a determined presence or lack of an interface region may allow for determining that there is no location of an interface region along a particular transmission path, and/or that a determined location is spurious.

The apparatus may be configured to use the speed of a particular interface signal in a first and second layer it order to determine the presence or lack of an interface region along that associated particular transmission path. The speed of a particular interface signal in a first layer may be compared with the speed of that particular interface signal in a second layer to determine the presence or lack of an interface region along that particular transmission path. For example, when the speed of a particular interface signal in a first and second layer is considered to be similar, the same, or substantially similar/the same, the apparatus may be configured to determine that no interface regions exists along that particular transmission path. For example, if the speed of an interface signal in a first and second layer is considered roughly the same, it might be considered that that first layer and that second layer are the same material, density, phase, etc. The determination of the presence or lack of an interface region may be for use in providing a profile (e.g. a profile of the interface region).

The apparatus may be configured to not use, or discard, a determined location of an interface region derived from a time of flight of an interface signal having been communicated across a transmission path having a lack of interface region (or a determined lack of interface region). The apparatus may be configured to not determine the location of an interface region derived from the time of flight of an interface signal having been communicated across a transmission path having a lack of interface region (or a determined lack of interface region). For example, the location of an interface region used for providing a profile along transmission paths may be disregarded if no interface region exists, is determined to exist (e.g. for the purposes of providing a profile).

The apparatus may be comprised with a conduit, container, pipeline, or the like. The apparatus may be attachable/detachable with a conduit, container, pipeline, etc. The apparatus may be mountable/demountable with a conduit, container, pipeline, etc. The apparatus may be configured for attachment/mounting with the outer side of a conduit, container, pipeline, and/or the inner side of a conduit, pipeline, container, etc. The apparatus may be configured to be retro-fit to a conduit, container, pipeline, etc. The apparatus may be provided with a conduit for use as a modular component of a pipeline, and/or further conduit. For example, the apparatus may be comprised with a portion of pipeline, conduit, flow circuit, or the like, for use with other modular parts of a pipeline, conduit, etc. Such other modular parts may not comprise apparatus, but merely act to complete a flow circuit, or the like.

The apparatus may be configured such that one or more interface signals may be transmitted from transmitters implanted, or embedded, in a multi-layered medium, which may be a multi-layered medium in a conduit, reservoir, pipeline, etc. That is to say that the apparatus may be configured such that one or more signals might be transmitted and received (and/or reflected and received) from regions within a medium, such as a medium in a conduit, pipeline, reservoir, or the like. The apparatus may comprise one or more locators to allow location of the apparatus within a medium.

According to a fifth aspect of the invention there is provided apparatus for determining the location of an interface region defined between first and second layers in a multi-layered medium, the apparatus comprising: a transmitter and receiver configured to transmit and receive an interface signal across a transmission path of a known distance, such a transmission path passing through a multi-layered medium having a first layer and a second layer having an interface region defined between first layer and second layer; the apparatus configured to determine the time of flight of an interface signal travelling across a transmission path and to use the speed of an interface signal in a first layer and a speed of an interface signal in a second layer in order to provide for determining the location of an interface region along a transmission path.

According to a sixth aspect of the invention there is provided a measurement device comprising an apparatus of the fourth or fifth aspect. The measurement device may be a flow meter. The measurement device may be an oil and gas flowmeter. The measurement device may be comprised with a conduit (e.g. a pipeline).

According to a seventh aspect of the invention there is provided a pipeline, such as an oil and gas pipeline, comprising an apparatus of the fourth or fifth aspect, or a device of the sixth aspect.

According to an eight aspect of the invention, there is provided a device for determining the location of an interface region, the device comprising: one or more conduits for permitting passage of a multi-layered medium; and apparatus according to any of the features of the fourth or fifth aspects.

According to a ninth aspect of the invention there is provided a method for determining the presence of an interface region defined between first and second layers in a multi-layered medium, the method comprising: using a time of flight of an interface signal having been communicated across a transmission path of known distance passing through the multi-layered medium having the first layer, second layer and the interface region, together with the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the presence of the interface region along the transmission path.

According to a tenth aspect of the invention there is provided a method for determining the location of an interface region defined between first and second layers in a multi-layered medium, the method comprising: using a time of flight of an interface signal having been communicated across a transmission path of known distance, the transmission path passing through a multi-layered medium having a first layer, second layer and an interface region, the interface region defined between the first layer and the second layer, together with the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the location of the interface region along the transmission path.

The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations with of aspects whether or not specifically stated (including claimed) in that combination or in isolation. It will be appreciated that one or more embodiments/features/aspects may be useful in stimulating subterranean target material.

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

Brief description of the figures

These and other aspects of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows an exemplary embodiment, comprising a conduit, and apparatus for determining the location of an interface region; Figure 2 shows a further embodiment of the invention for determining the location of an interface at different locations along a conduit; Figure 3 shows an embodiment of apparatus comprising measurement sensors; Figure 4 shows an embodiment of exemplary apparatus with a cross-section of a pipeline; Figure 5 shows an embodiment of exemplary apparatus with a pipeline; Figure 6 shows an exemplary embodiment of apparatus for use in flow visualisation.

Figure 7 shows an embodiment of apparatus for use with a reflected interface signal; Figure 8 shows an embodiment of the invention for use with sub-layers in a multi-layered medium; Figure 9 shows a further exemplary embodiment of apparatus; and Figure 10 is a diagrammatic representation of the arrangement of layers within a conduit.

Detailed description of the figures

Figure la shows a diagrammatic longitudinal section of a conduit 100 forming part of a pipeline, which comprises a multi-layer medium having a first layer 110 and a second layer 120 separated by an interface region 115. Figure lb shows a cross-section of the exemplary conduit 100 as a tubular pipeline.

The conduit 100 is provided in a horizontal configuration, such that the first layer 110 rests on the second layer 120. Here, the first layer 110 is a liquid hydrocarbon, such as oil, while the second layer 120 is water.

Alternatively, the first and/or second layer may be any liquid, gas or solid. For example, the first layer 110 may be a mixture water and oil in an emulsion, while the second layer may be asphaltene, such as an asphaltene deposit, or the like. The first layer 110 may be a coolant, while the second layer 120 is a deposit, or the first layer 110 may be a gas, while the second layer 120 is a liquid or solid, etc. In this example, the first layer 110 and the second layer 120 each have a flow rate in a particular direction, and can be considered to have a laminar flow.

The conduit 100 cross-section is a known distance, 0'. The height, or so-called hold-up, of the first layer 110 at the first known distance can be considered to be h'. The height, or so-called hold-up, of the second layer 120 can be considered to be D-h'.

Figure 1 a further shows apparatus 200 comprising a transmitter 21 Oa and a receiver 21 Ob. The transmitter 21 Oa and receiver 21 Ob are configured to transmit and receive respectively an interface signal of a particular signal species across a transmission path 50. Here, the transmission path 50 is provided across the known distance, D'.

Figure lb shows the relative positions of the respective transmitter 21 Oa and receiver 21 0b as indicated by arrows. Although shown such that the transmitter/receiver 21 0a, 210b are perpendicular to the interface region 115, in alternative embodiments that need not be the case.

The apparatus 200 is configured such that the interface signal passes initially through the first layer 110, and then through the second layer 120 in order to reach the receiver 210b. The transmitter 210a is a distance h from the interface region 115, while the receiver 210b is a distance D-h' from the interface region 115.

Here, the transmitter 210a and receiver 210b are configured to transmit and receive ultrasonic signal species. The apparatus 200 is configured to determine the time of flight of an interface signal travelling across the transmission path 50. The time of flight may be measured by observing the difference in time between transmitting an interface signal and receiving an interface signal. Alternatively, the apparatus 200 may be configured to only observe the time of receipt. In such cases, the time of flight may be determined from further information regarding the time of transmission.

In this example, the apparatus 200 is configured to be mountable/demountable with the conduit 100, however in alternative configurations the apparatus 200 may be comprised with the conduit 100, or portion of the conduit, or the like.

It will be appreciated that the time of flight of the interface signal travelling across the transmission path 50 can be considered to be the cumulative time of flight of the interface signal passing through the first layer 110, and then the second layer 120.

This can be represented algebraically by the following: (1) where t, is the cumulative time of flight of an interface signal passing through the first layer 110 and through the second layer 120, (t0+ t). Assuming an average velocity or speed of signal species in each layer 110, 120, the cumulative time of flight can be considered as: (2) where V0 and V are the speed of the interface signal species in the first layer 110 and the second layer 120 respectively. That is to say that in this example V0 is the speed of the interface signal passing through oil, while V is the speed of the interface signal passing through water.

Consider the situation when: D=101.6mm V0 = 1410 m/s V = 1450 m/s t = 70.656 p5 By substituting these values into (2) it can be shown that, h (D-h) t. --j-0 W h (101.6mm-h) 70.656us + 1410m/s l450m/s h30mm Therefore, it can be determined that the interface region is 30 mm from the transmitter 21 Oa, and 71.6 mm from the receiver 21 Ob.

It will readily be appreciated that in the above example, the interface signal of the apparatus 200 mounted, for example to the outer side of a conduit, will additionally pass through the wall of the conduit. However, in embodiments when the wall thickness might not be considered to be negligible, the apparatus 200 is configured to remove from the time of flight the time taken for the interface signal to pass through the wall of the conduit.

For example, if it is known that the wall thickness is 10 mm of steel, the time taken for the interface signal to pass into the first layer 110 through the conduit 100, and for it to pass from the second layer 120 through the wall to the receiver 210b can be determined. This time can be removed from the time of flight in order to determine the location of the interface region 115 from the wall of the conduit 100, and/or the location of the interface region 115 with respect to the transmitter 210a or receiver 2 lOb.

Figure 2 shows a further embodiment of apparatus 300, similar to that described above, comprising two transmitters 310a, 310c and two receivers 310b, 310d. The apparatus 300 is configured to determine the location of the interface region 115 along two transmission paths 350a, 350b. Here, the location of the interface region 115 is provided with respect to the transmitters 310a, 310c, hi' and h2'. In a similar manner to that described above, hi' and h2' can be determined.

It will be appreciated that the flow velocity of the first and second layer 110, 120 may be determined by observing the location of the interface region 115, or time rate of change of location of an interface region 115, at a first transmitter/receiver 310a, 31 Ob and comparing this with the observations of a second transmitter/receiver 31 Oc, 310d, spaced at a distance from the first transmitter/receiver 310a, 310b (e.g. along the conduit). The time taken for the location of the interface region 115 (or time rate of change of interface region 115) to be observed as the same, or similar, can be used, along with the distance between the first and second transmitters/receivers 310a-310d to determine the flow velocitylrate, such as the flow velocity/rate of the first and second layers 110, 120.

Figure 2b shows a similar embodiment in which a common transmitter 3iOe is configured to transmit an interface signal along two transmission paths 350c, 350d for receipt by two receivers 310b, 310b. The location of the interface region 115 with respect to the transmitter 310e and receivers 310b, 310d can be determined in a similar manner to that above. In addition, by knowing the angle, p, the location of the interface region 115 with respect to the conduit wall (e.g. h') can be determined. In such a configuration, a profile of the interface region 115 can again readily be provided.

While the apparatus 300 shown in Figure 2 have only a first and second transmitter/receiver 3iOa-310d, or a common transmitter 310e, and two receivers 310b, 310d, in alternative embodiments, the apparatus 300 may comprise any number of transmitters/receivers, one, some or all of which may act as common transmitters/receivers. It will also be appreciated that a profile of the location of the interface region 115 may be determined for a length of the conduit 100, and/or for a cross-section of the conduit 100.

Figure 3 shows a further exemplary apparatus 400, similar to that described in relation to Figure 1. Here, the apparatus 400 comprises a transmitter 410a, and receiver 410b, configured to transmit and receive an interface signal across a transmission path 45 of known distance.

The apparatus 400 further comprises measurement sensors 430a, 430b configured to measure one or more characteristics of the first and second layer 110, 120. Here, the measurement sensors 430a, 430b are configured to be in direct communication with the first and second layer 110, 120, but in other embodiments that need not be the case. The measurement sensors 430a, 430b may be in communication indirectly with the first and second layer 110, 120 such as via the wall of the conduit 100.

Here, the measurement sensors 430a, 430b are configured to determine the speed of an interface signal in the first and second layer 110, 120 respectively. For example, each measurement sensor 430a, 430b may comprise two displaced transducers, configured to transmit and receive a signal of the same species as the interface signal so as to measure the speed of an interface signal in the first or second layer 110, 120. Alternatively, each measurement sensors 430a, 430b may be provided by a thermocouple, or the like, configured to determine the temperature of the first and/or second layer. The temperature may then provide the speed of the interface signal species in the first/second layer (e.g. by using a look-up table and knowledge of the first/second layer).

Here, the apparatus 400 is configured such that when the speed of an interface signal is determined to be the same, or similar, in the first and second layer 110, 120 the apparatus determines that no interface region is present. This allows for determining that the first and second layer are provided as an emulsion, or are substantially the same (e.g. homogenous). For example, in a conduit 100 in which a particular transmission path passes only through one of the first or second layer, the apparatus 400 is configured to determine the lack of interface region, and may discard using any determined interface region for the purposes of providing a profile.

Alternatively, when the apparatus 400 determines that the speed of an interface signal in the first and second layer 110, 120 is different, it uses these determined values in order to determine the location of the interface region 115 (as provided by equation 2).

While in Figure 2 the apparatus 300 was show to be provided along the conduit 100, it will be appreciated that the apparatus 300 may additionally or alternatively positioned around the conduit 100.

Figure 4a shows a cross-section of a conduit 100 comprising apparatus 450 having a plurality of transceivers 50a-50f for determining the location of an interface region. In this example, each transceiver 50a-50f is configured to transmit and receive interface signals in order to determine the location of the interface region 115. Figure 4b exemplifies the transmission paths for an interface signal being transmitted from one of the transceivers 50a. In this example, each transceiver 50a-50f is located at a regular interval around the conduit (e.g. 30 degrees, 45 degrees, etc). However, the transceivers 50a-50f may be configured at irregular intervals. Additional, transmitters/receivers may be used rather than transceivers.

In this case, a cross-sectional, or two-dimensional, profile of the interface region 115 may be provided. This can be achieved by providing the location to the interface region 115 along each transmission path. It will readily be appreciated that, for example, the apparatus 450 is configured to discard (or not use) the determined interface region 115 provided by transceiver 50a and SOb, or 50a and 50f. In such cases, the apparatus 450 would determine that the speed of the interface signal in the first layer and second layer would be the same, because, in effect, the signal passes only through the first layer.

Figure 5 shows a conduit comprising apparatus 500 for determining the location of an interface region 115, in which the apparatus 500 is provided with a plurality of transceivers 50a-50f, 60a-60f, 70a-70f, spaced not only around a conduit 100, but also along the conduit 100 (some of the transceivers are not shown for clarity). As is shown by example, each particular transceiver 60a is configured to communicate an interface signal to not only further transceivers 60d across the conduit, but to transceivers 70d along the conduit. Of course, in certain circumstances, the apparatus 500 may be configured to communicate interface signals only across, or only along the conduit 100.

Figure 6 shows an exemplary apparatus 900 similar to the apparatus 500 described above, comprising a plurality of transmitters/receivers 910a-910n, 920a-920n for use with the conduit 100. Again, each of the transmitters/receivers are configured to transmit/receive an interface signal across a first/second layer. It will be appreciated that the apparatus 900 may be configured with 2, 3, 4, 5, 10, 20 or more transmitters/receivers (or transceivers), or any number therebetween.

Here, the apparatus 900 further comprises a remote controller 930 comprising a processor 940 and a memory 950, the processor 940 and memory 950 being configured in a known manner. The processor/memory 940, 950 may be provided by a microcontroller, such as provided by a field programmable gate array, application specific integrated circuit, programmable intelligent computer, or the like. Here, the controller 930 is configured to operate the transmitters/receivers so as to provide the interface signals. The controller 930 is further configured to determine the time of flight of respective signals, and determine the location of the interface region (i.e. along each respective transmission path).

By being remote, the controller 930 is configured to communicate with the transmitters/receiver from a distance (i.e. not located at a multi-layer medium). In this embodiment, the controller 930 is configured to communicate with the respective transmitterslreceivers by wired communication, but in alternative embodiments, the controller may be configured to communicate with the transmitters/receivers by wireless, optical, acoustic (i.e. using the layer in the conduit as a vehicle for signals) or any combination thereof.

The controller 930 is configured to provide an output 960. The output 960 is in communication with a user interface 965, such as a Liquid Crystal Display output.

The profile (or data associated with the profile) of the interface region is provided from the controller to the user interface 965 so as to provide a display of the profile of the interface region 115 (e.g. flow visualisation). Such a configuration allows for a three-dimensional profile to be displayed. Of course, two dimensional (or cross-sectional) profiles would be equally possible.

In some embodiments, the output 960 is configured to be in communication with a different apparatus, such as a multiphase flow meter. Alternatively, the controller 930 and output 960 are comprised with a multiphase flow meter.

Although the apparatus 900 is described as being provided with a remote controller 930, this need not always be the case. In some instances the controller 930 and/or user interface 965 may be provided locally (i.e. local to the medium, conduit, etc.).

While in the above embodiments, the apparatus has been shown to provide a transmission path from a transmitter to a receiver (or transducer to transducer, etc.), it will readily be appreciated that in other embodiments, the apparatus may be configured to use a reflected interface signal.

Figure 7 shows a further exemplary embodiment of apparatus 600, similar to that described in relation to Figure 1. However, in this configuration, the apparatus 600 is provided with a transducer 610, which can be used to transmit and receive the interface signal (i.e. a transceiver) across a transmission path 55. In this case, the transmission path 55 is twice that of Figure 1.

Following the similar analysis to above, it can be shown that the cumulative time of flight can be considered as: (3) Thus when: o = 101.6mm V0 = 1410 m/s V=1450m/s t = 141.312 ps By substituting these values into (3) it can be shown that t again is 30 mm. The same analysis can be derived for the embodiments shown in the further Figures (i.e. Figures 2 to 6). That is to say some or all of the transmission paths may be provided for reflected interface signals.

Figure 8a shows a further embodiment on the invention provided with a chamber 10, such as a container, barrel, drum, or the like (although this is exemplary, and embodiment may equally be provided with a conduit 100, such as a pipeline, reservoir, etc. and vice versa). The chamber 10 contains a first layer 111 and a second layer 121 in a similar manner to that described above. However, in this embodiment, the second layer 121 has two sub-layers 121a, 121b, which are separated by a second interface region 117. In a similar manner to that described above, the location of the interface region 115 may be evaluated. That is to say, that the speed of the interface signal in the sub-layers 121a, 121b, may be considered to be an average speed of signal in the second layer 121. The time of flight of the interface signal passing through the second layer 121 can be considered to be a cumulative average. Additionally, or alternatively, the location to the second interface 117 may be determined by considering the speed of the interface signal in the first layer 111 and the top sub-layer 121a together (e.g. as an average speed).

Figure 8b shows an embodiment of the chamber 10 in which the lower sub-layer 121b is a deposit of material, such as a hydrate, asphaltene, etc. In some embodiments, the second layer 121 may be entirely, or substantially, provided by a deposit. Similar deposits may be formed/measured in the above exemplary conduits in Figures ito 7.

Figure 9 shows a further embodiment of the invention, comprising apparatus 800 in a similar configuration to that described in relation to Figure 1, whereby the apparatus 800 is immersed in a multi-layered medium having the first layer 110, second layer 120, and interface 115. Here, the apparatus 800 is provided such that it is not comprised with a conduit or the like, but is provided with locators 810, configured such that the apparatus 800 can be located in a medium, so as to transmit an interface signal through the first and second layers.

Here, the apparatus 800 is immersed in a reservoir comprising the multi-layer medium, but in alternative configurations that apparatus may be for use in a conduit, in the like. The locators 810 may be configured such that the apparatus can be embedded in deposits, or located in liquid/gas, such as flowing liquid/gas, as will be appreciated. The apparatus 800 may be configured such that the interface region is maintained, or controlled, to be a particular distance between receiver/transmitter.

Figure 9b shows the apparatus 800 is a similar configuration to Figure 2b.

A similar configuration may be provided in relation to any of the further apparatus described above. For example, the configuration of any of the Figures 1 to 5, 7 and 8may be provided with locators 810, rather than being provided with a conduit/chamber.

In the above described exemplary embodiments the first and second layers are shown to be continuously stratified. However, in alternative arrangements, as illustrated in Figure 10, the first layer 11 Oa may be at least partially contained within the second layer 120 with an interface region 115a defined therebetween. Further, the first layer IlOb may be entirely contained within the second layer 120 with an interface region 115b defined therebetween.

While in some of the above exemplary embodiments, the apparatus/conduit is consider to have a wall of negligible thickness, or that the transmitters/receivers are in (direct) communication with the respective layer, it will be appreciated by the skilled reader that wall thickness, such as pipe thickness may easily be accounted for in any of the above embodiments (e.g. when the transmitters/receivers are not in direct communication with the layer).

For instance, consider the embodiment of Figure 1, in which the interface signal must travel through a conduit wall. In such a configuration, the interface signal must pass through this wall thickness twice in order to be passed initially into the layer, then again when being passed into the receiver (irrespective of whether or not a reflected signal is used) In such an arrangement, by having knowledge of the conduit wall construction, for example, steel, and the wall thickness, the time taken for the signal to travel across the wall can be approximated/evaluated accounted for in any subsequent evaluation.

In some embodiments, a temperature sensor, such as a thermocouple, may be provided with the conduit in order to determine accurately the speed of a signal in the wall.

While in the above embodiments, layers such as oil and water have been described, it will readily be appreciated that the apparatus/method may be applicable for any layer, which may be a solid, liquid or a gas. For example, in some embodiments the apparatus may be configured to location of an interface in a combination of liquid and gas, such as oil and a hydrocarbon gas, or an emulsion of a number of fluids. In alternative embodiments, the apparatus may be configured to determine the location of an interface in other layers in a conduit, such as coolants, or the like.

In addition, and in view of the foregoing description, it will be evident to a person skilled in the art that various modifications to any of the embodiments may be made within the scope of the invention. Similarly, the apparatus and/or methods disclosed may have other functions/steps, in addition to those described.

It will be appreciated to the skilled reader that the features of particular apparatus may be provided by apparatus arranged such that they become configured to carry out the desired operations only when enabled, e.g. switched on, or the like. In such cases, they may not necessarily have the appropriate software loaded into the active memory in the non-enabled state (e.g. switched off state) and only load the appropriate software in the enabled state (e.g. on state). The apparatus may comprise hardware circuitry and/or firmware. The apparatus may comprise software loaded onto memory.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

While there have been shown and described and pointed out example embodiments of the invention, it will be understood that various omissions and substitutions and changes in the form and details of the apparatus and methods described may be made by those skilled in the art without departing from the scope of the invention. For example, it is expressly intended that all combinations of those apparatus and/or method steps that perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

CLAIMS1. A method for determining the location of an interface region defined between first and second layers in a multi-layered medium, the method comprising: using a time of flight of an interface signal having been communicated across a transmission path of known distance passing through the multi-layered medium having the first layer, second layer and the interface region, together with the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the location of the interface region along the transmission path.

0)
2. The method according to claim 1, wherein the location is provided as a particular distance along the transmission path.

0)
3. The method according to claim 1 or 2, wherein the method comprises determining a height of at least one of the first and second layer by using the determined location of the interface region and the known distance of the transmission path, wherein the height is the height of at least one of the first and second layer in a conduit.
4. The method according to any preceding claim, wherein the interface signal comprises a reflected signal.
5. The method according to any preceding claim comprising using the time of flight of two or more interface signals, the two or more interface signals having been communicated across two or more transmission paths.
6. The method according to claim 5, wherein the two or more interface signals have been transmitted from a common transmitter, or received at a common receiver.
7. The method according to claim 5 or 6, wherein determining the location of the interface regions along different transmission paths provides for determining a profile of the interface region of a multi-layer medium.
8. The method according to claim 7, wherein the profile is a cross-sectional profile.
9. The method according to claim 7 or 8, wherein the profile is time variant.
10. The method according to any of the claims 5 to 9, comprising providing a visual representation of the change in profile to provide for flow visualisation. a)
11. The method according to any of claims 5 to 10, wherein the method comprises using the time of flight of two or more interface signals having been communicated across transmission paths of a conduit at different interval orientations.
12. The method according to claim 11, wherein the intervals are regular intervals.
13. The method according to any preceding claim, wherein a time of receipt of the interface signal is considered to be the time of flight.
14. The method according to any preceding claim, wherein the multi-layer medium comprises multiple phases, the multi-layer medium comprising any one or combination of: solid, liquid and/or gas component phase.
15. The method according to any preceding claim, wherein at least one of the first and second layer comprises two or more sub-layers, wherein the speed of an interface signal in at least one of the first and second layer comprising sub-layers is provided as the average speed of an interface signal through the cumulative sub-layers.
16. The method according to any preceding claim, wherein the method is for determining the presence, and/or change in deposition or corrosion in a conduit. 0)
17. The method according to any preceding claim comprising determining the presence or lack of an interface region along one or more particular transmission 0) paths associated with one or more particular interface signals.
18. The method according to claim 17 comprising using the speed of a particular interface signal in the first and second layer in order to determine the presence or lack of an interface region along the associated particular transmission path.
19. The method according to claim 18, wherein the speed of the particular interface signal in the first layer is compared with the speed of the particular interface signal in a second layer to determine the presence or lack of an interface region.
20. A method for determining the location of an interface region defined between first and second layers in a multi-layered medium, the method comprising: transmitting an interface signal across a transmission path of a known distance, the transmission path passing through a multi-layered medium having a first layer and a second layer, the first and second layer having an interface region defined between the first layer and the second layer; determining the time of flight of the interface signal travelling across the transmission path; providing the speed of the interface signal in the first layer and the speed of the interface signal in the second layer; using the time of flight of the interface signal, the speed of the interface signal in the first layer and the speed of the interface signal in the second layer in order to provide for determining the location of the interface region along the transmission path. a)
21. A computer program stored on a computer readable medium, the computer i program configured to provide the method of any of the claims 1 to 20. a)
22. Apparatus for determining the location of an interface region defined between first and second layers in a multi-layered medium, the apparatus configured to use a time of flight of an interface signal having been communicated across a transmission path of known distance, such a transmission path passing through a multi-layered medium having a first layer, second layer and an interface region, such an interface region being defined between a first layer and a second layer, together with the speed of an interface signal in a first layer and the speed of an interface signal in a second layer in order to provide for determining the location of an interface region along a transmission path.
23. The apparatus according to claim 22, wherein the apparatus is configured to use the time of flight of two or more interface signals, the two or more interface signals having been communicated across two or more transmission paths.
24. The apparatus according to claim 22 or 23, comprising one or more transmitters configured to transmit an interface signal and one or more receiver configured to receive an interface signal, the transmitters/receiver configured to provide the transmission path(s).
25. The apparatus according to any of the claims 22 or 24 comprising a user interface configured to provide a visual representation of a change in a profile of an interface region, the profile being provided by location of interface regions along 0') different transmission paths.i
26. The apparatus according to any of the claims 22 to 25, wherein the apparatus 0) is configured for use with a conduit.
27. The apparatus according to claim 26, wherein the apparatus is configured to communicate two or more interface signals at different interval orientations with respect to a conduit.
28. The apparatus according to any of the claims 22 to 27, wherein the apparatus is configured to determine the presence, and/or change in deposition or corrosion in a conduit.
29. The apparatus according to any of the claims 22 to 28, wherein the apparatus is configured to use acoustic interface signals.
30. The apparatus according to any of the claims 22 to 29, wherein the apparatus is configured to determine the presence or lack of an interface region along one or more particular transmission paths associated with one or more particular interface signals.
31. A measurement device comprising an apparatus according to any of the claims 22 to 30.
32. The measurement device according to claim 31, wherein the device is comprised with an oil and gas flowmeter.
33. A pipeline, such as an oil and gas pipeline, comprising an apparatus 0) according to any of the claims 22 to 30.
34. A device for determining the location of an interface region, the device 3) comprising: one or more conduits for permitting passage of a multi-layered medium; and apparatus according to any of the claims 22 to 30.
35. Apparatus substantially as described with reference to the description and/or the figures.
36. Methods for determining the location or presence of an interface region substantially as described with reference to the description and/or figures.