Embodiments of the present disclosure relate to mid-infrared sensing, and more particularly but not by way of limitation to a mid-infrared sensor for monitoring hydrate inhibitors.
The analysis of chemical composition of fluid samples from hydrocarbon wells for the determination of phase behaviour and chemical composition is a critical step in the monitoring and management of a hydrocarbon well as well as the evaluation of the producibility and economic value of the hydrocarbon reserves. Similarly, the monitoring of fluid composition during production or other operations can have an important bearing on reservoir management decisions. Similarly, determination of phase behaviour and chemical composition is important in pipelines and the like used to convey/transport hydrocarbons from the wellhead, including subsea pipelines.
Several disclosures have described analysis of specific gases in borehole fluids in the downhole environment using near-infrared (e.g. λ=1−2.5 μm) spectral measurements. For example, U.S. Pat. No. 5,859,430 describes the use of near-infrared spectroscopy to determine quantitatively the presence of methane, ethane and other simple hydrocarbons in the gas phase. The gases were detected using the absorption of near-infrared radiation by the overtone/combination vibrational modes of the molecules in the spectral region 1.64-1.75 μm.
More recently, U.S. Pat. No. 6,995,360 describes the use of mid-infrared radiation with a wavelength λ=3−5 μm to monitor gases in downhole environments, and U.S. Patent Publication No. 2012/0290208 proposes the use of mid-infrared radiation to monitor sequestered carbon dioxide dissolved into the liquid solutions of saline aquifers.
There are however many technical problems with using mid-infrared sensors in the hydrocarbon industry and processing information from such sensors. Additionally, much of the utility of mid-infrared spectroscopy for hydrate inhibitor monitoring has not previously been recognized.
Embodiments of the present disclosure are at least partly based on the recognition that hydrate inhibitors used to reduce or prevent formation of gas hydrates at high pressures and low temperatures may be monitored using a sensor based on mid-infrared radiation absorbance.
Accordingly, in a first aspect, an embodiment of the present disclosure provides a sensor for monitoring a hydrate inhibitor dissolved in a liquid, the sensor comprising:
As discussed below, the sensor may be part of a sensor arrangement with a further similar sensor for obtaining a reference intensity.
In a second aspect, embodiments of the present disclosure provide for the use of the sensor, or sensor arrangement, of the first aspect to determine an amount of a hydrate inhibitor dissolved in a liquid. For example, a method of monitoring a hydrate inhibitor dissolved in a liquid may include: providing the sensor of the first aspect such that the internal reflection window is in direct contact with the liquid; and operating the sensor to determine an amount of the hydrate inhibitor dissolved in the liquid.
In a third aspect, an embodiment of the present disclosure provides a well or pipeline tool including the sensor, or sensor arrangement, of the first aspect. The internal reflection window can be flush with an outer casing of the tool such that the attenuated internal reflection at the interface between the window and the liquid produces an evanescent wave which propagates into the liquid away from the tool. Thus, advantageously, the tool does not require a bypass channel for the sensed liquid.
Optional features of embodiments of the present disclosure will now be set out. These are applicable singly or in any combination with any aspect of the embodiments of the present disclosure.
In embodiments of the present disclosure, the liquid may be, or may be a component of, a production fluid.
By “mid-infrared radiation,” it is meant that in embodiments of the present disclosure the radiation has a wavelength in the range from about 2 to 20 μm, and in some embodiments from about 3 to 12 μm or from about 3 to 10 μm.
In an embodiment of the present disclosure, the first narrow bandpass filter may be configured such that its wavelength transmission band is substantially temperature invariant over all temperatures in the range from −25 to 25° C. Temperatures in subsea environments can vary, e.g. from about −25 to 25° C. By using such a temperature invariant filter, the sensitivity of the sensor to shifts in temperature of its surroundings can be greatly reduced, improving the accuracy with which the amount of the dissolved hydrate inhibitor is determined.
By “substantially temperature invariant,” it is meant herein that the variance in embodiments of the present disclosure is at most about 0.1 nm/° C. In some embodiments, the variance is at most about 0.05, 0.03, 0.02 or 0.01 nm/° C.
In embodiments of the present disclosure, each filter may comprise an interference filter.
Merely by way of example, in some embodiments of the present disclosure, each filter may include a substrate, formed of Si, SiO2, Al2O3, Ge or ZnSe and/or the like, and at each opposing side of the substrate alternating high and low refractive index layers may be formed. In some embodiments of the present disclosure, the high refractive index layers can be formed of PbTe, PbSe or PbS and the low refractive index layers can be formed of ZnS, ZnSe and/or the like.
In embodiments of the present disclosure, each filter may have three or more half wavelength cavities. Many conventional filters display unacceptably high band shifts with increasing temperature. For example, shifts in the range of 0.2 to 0.6 nm/° C. are typical in prior filters. Transmissivities also tend to reduce with increasing temperature. These properties, have prevented/limited development of mid-infrared sensors, especially in the petrochemical industry.
However, in accordance with embodiments of the present disclosure, by using a PbTe-based, a PbSe-based, a PbS-based interference filter and/or the like it is possible to substantially reduce band shifts and transmissivity reductions. For example, a PbTe-based interference filter, in accordance with an embodiment of the present disclosure, may have a band shift of only about 0.03 nm/° C. or less. As an alternative to PbTe, PbSe, PbS or the like, the high refractive index layers can be formed, in some embodiments of the present disclosure, of Ge or the like.
In embodiments of the present disclosure, a reference intensity may be used in the determination of the amount of the hydrate inhibitor in the liquid. Thus a sensor arrangement may include the sensor of the first aspect and a further similar sensor which can be used to obtain this reference intensity. The further sensor can have the same features as the first sensor except that its narrow bandpass filter transmits mid-infrared radiation over a band of wavelengths corresponding to a reference portion of the absorbance spectrum of the liquid. In such a scenario, the processor arrangement can be a shared processor arrangement of both sensors.
Another option, however, is to obtain the reference intensity using the first sensor. For example, the sensor may further include a second narrow bandpass filter transmitting mid-infrared radiation over a band of wavelengths corresponding to a reference portion of the absorbance spectrum of the liquid, the or a further infrared detector detecting filtered mid-infrared radiation transmitted through the second filter, and the processor arrangement measuring the reference intensity of the detected mid-infrared radiation transmitted through the second filter and using the measured reference intensity in the determination of the amount of the hydrate inhibitor in the liquid. The first and second filters may be selectably positionable between a single detector and the window, or each of the first and second filters can have a respective detector. Optional features of the first narrow bandpass filter pertain also to the second narrow bandpass filter.
In embodiments of the present disclosure, the sensor may be able to measure the amounts of more than one hydrate inhibitor dissolved in the liquid. For example, the sensor may include a plurality of the first narrow bandpass filters, each transmitting mid-infrared radiation over a band of wavelengths corresponding to an absorbance peak of a respective hydrate inhibitor, the or a respective further infrared detector detecting the filtered mid-infrared radiation transmitted through each first filter, and the processor arrangement measuring the intensity of the detected mid-infrared radiation transmitted through each first filter and determining therefrom an amount of each hydrate inhibitor dissolved in the liquid. The first filters may be selectably positionable between a single detector and the window, or each first filter can have a respective detector.
When the sensor is able to monitor more than one hydrate inhibitor, the determined amounts of the hydrate inhibitor in the liquid can be in the form of a ratio of the concentrations of the inhibitors.
In embodiments of the present disclosure, the beam of mid-infrared light may be pulsed. This can be achieved, for example, by providing a mechanical chopper between the source and the window, or by pulsing the source.
In embodiments of the present disclosure, the source can be a broad band thermal source or a narrower band source such as a light emitting diode or a laser.
In some embodiments of the present disclosure, the window may comprise a diamond window or a sapphire window. In some embodiments of the present disclosure, the diamond windows can be formed by chemical vapour deposition. Sapphire has a cut off for mid-infrared radiation at wavelengths of about 5 to 6 microns, but sapphire windows can generally be formed more cheaply than diamond windows. Thus, for absorption peaks below the cut off (such as the CO2 absorption peak at about 4.3 microns), sapphire may be a useful alternative to diamond. In particular, for a given cost a larger window can be formed.
In some embodiments of the present disclosure, the sensor may further include a heater which is operable to locally heat the window, thereby cleaning the surface of the window in contact with the fluid. For example, in some embodiments of the present disclosure, if the window includes a conductive or semiconductive material (e.g. an area of semiconductive boron-doped diamond), the heater may comprise an electrical power supply that may send a current through the window to induce resistive heating thereof For example, in some embodiments of the present disclosure, a diamond window can have a central mid-infrared transmissive (e.g. undoped) area and an encircling area of semiconductive boron-doped diamond. The heater can induce resistive heating of the encircling area, and the central area can then be heated by conduction of heat from the encircling area. In some embodiments of the present disclosure, the heater may heat the window to a peak temperature of at least about 400° C. In some embodiments of the present disclosure, the heater may maintain a peak temperature for less than one microsecond.
Alternatively or additionally, in some embodiments of the present disclosure, the sensor may further include an ultrasonic cleaner which is operable to ultrasonically clean the surface of the window in contact with the fluid. As another option, the sensor may be provided with a pressure pulse arrangement which is operable to produce a pressure pulse in the fluid at the window, thereby cleaning the surface of the window in contact with the fluid. In some embodiments of the present disclosure, the arrangement may produce a pressure pulse of at least about 1000 psi (6.9 MPa) in the fluid.
In an embodiment of the present disclosure, the sensor may be located subsea, e.g. on a subsea pipeline.
The inhibitor may be a thermodynamic inhibitor such as methanol, ethanol, monoethylene glycol or diethylene glycol, or it may be a kinetic inhibitor such as polyvinylpyrrolidone or polyvinylcaprolactam. In embodiments of the present disclosure, the positions and heights of the mid-infrared absorbance peak(s) of such compounds tend to be insensitive to salt content in the (typically water-based) liquid. Thus, in embodiments of the present disclosure, the sensitivity of the determination of the amount of the inhibitor to salt concentration is reduced. In an embodiment of the present disclosure, the first narrow bandpass filter may preferentially transmit mid-infrared radiation over a band of wavelengths corresponding to a 1040 cm−1 or a 1084 cm−1 absorbance peak for monoethylene glycol, a 1020 cm−1 absorbance peak for methanol, a 1045 cm−1 absorbance peak for ethanol, a 1085 cm−1 absorbance peak for ethanol, or a 1295 cm−1 absorbance peak for polyvinylpyrrolidone.
In embodiments of the present disclosure, the monitored hydrate inhibitor can be:
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
The ensuing description provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the invention. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements without departing from the scope of the invention.
Specific details are given in the following description to provide a thorough understanding of the embodiments. However, it will be understood by one of ordinary skill in the art that embodiments maybe practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques may be shown without unnecessary detail in order to avoid obscuring the embodiments.
Also, it is noted that the embodiments may be described as a process which is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed, but could have additional steps not included in the figure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function.
Moreover, as disclosed herein, the term “storage medium” may represent one or more devices for storing data, including read only memory (ROM), random access memory (RAM), magnetic RAM, core memory, magnetic disk storage mediums, optical storage mediums, flash memory devices and/or other machine readable mediums for storing information. The term “computer-readable medium” includes, but is not limited to portable or fixed storage devices, optical storage devices, wireless channels and various other mediums capable of storing, containing or carrying instruction(s) and/or data.
Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof When implemented in software, firmware, middleware or microcode, the program code or code segments to perform the necessary tasks may be stored in a machine readable medium such as storage medium. A processor(s) may perform the necessary tasks. A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, etc.
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact.
As the detector 6 changes its output with its temperature, even small changes in temperature can cause a large drift in signal output. However, pulsing the beam 3 allows the output signal of the detector to be frequency modulated, enabling removal of the environmental temperature effects from the signal. More particularly, the environment effects can be largely removed electronically by a high pass filter, because the time constant for environment effects tends to be much longer than the signal frequency. Typically, the detector output is AC-coupled to an amplifier. The desired signal can then be extracted e.g. electronically by lock-in amplification or computationally by Fourier transformation.
Instead of the thermal source 1 and the mechanical chopper 2, the pulsed beam 3 may be produced e.g. by a pulsable thermal source, light emitting diode or laser source. Pulsing the source in this way can give the same benefit of frequency modulation measurement, plus it can reduce resistive heating effects.
The beam 3 enters at one edge of the window 4, and undergoes a number of total internal reflections before emerging from the opposite edge. The total internal reflection of the infrared radiation at the liquid side of the window is accompanied by the propagation of an evanescent wave into the liquid. As the liquid preferentially absorbs certain wavelengths, depending on its chemical composition, this causes the emerging beam to have a characteristic variation in intensity with wavelength.
In some embodiments of the present disclosure, a window 4 is mechanically able to withstand the high pressures and temperatures typically encountered downhole and subsea. In embodiments of the present disclosure, the window is chemically stable to fluids encountered downhole and subsea and is transparent in the mid-IR wavelength region. In embodiments of the present disclosure, the window may comprise diamond, sapphire and/or the like.
In an embodiment of the present disclosure, the first narrow bandpass filters 5 each transmit mid-infrared radiation over a band of wavelengths corresponding to an absorbance peak of a respective hydrate inhibitor in the liquid, while the second narrow bandpass filter 5′ transmits mid-infrared radiation over a band of wavelengths corresponding to a reference portion of the absorbance spectrum of the liquid. The beam 3 then passes through a selected one of the narrow bandpass filters and is detected at the respective detector 6. Instead of having a plurality of detectors, each movable with its corresponding filter (as indicated by the double-headed arrow), a further option is to have a single detector in front of which the filters are selectively movable.
The detector 6 may comprise semiconductor photo-diodes (particularly in subsea applications), thermopiles or pyroelectric detectors.
In an embodiment of the present disclosure, the processor arrangement 7 receives a signal from the respective detector 6, which it processes to measure the intensity of the detected mid-infrared radiation transmitted through each filter 5, 5′, and, as discussed in more detail below, determines therefrom an amount of the respective hydrate inhibitor in the liquid.
Also discussed in more detail below, the sensor may include a heater 8 which is operable to locally heat the window 4, thereby cleaning the surface of the window in contact with the liquid. Other options, however, are to clean the window ultrasonically (as described for example in U.S. Pat. No. 7,804,598), or with a mechanical wiper.
In embodiments of the present disclosure, the narrow bandpass filters 5, 5′ may be based on Fabry-Perot interferometry. As shown in
The optical thickness ndcosθ of the substrate S, where n is the refractive index of the substrate, is equal to an integer number of half wavelengths λm, where λm is the peak transmission wavelength, corresponding approximately to the centre wavelength of the pass band of the filter. The condition for the transmission of radiation of wavelength λm through the filter is thus mλm/2=ndcosθ, where m is an integer.
The spectral region of conventional narrow bandpass dielectric filters designed to operate in the mid-infrared spectral regions shifts systematically to longer wavelengths with increasing temperature. The origin of the change in λm with temperature is a change in the material properties with temperature of the dielecric materials that comprise the layers of the filter.
However, an approach described below, in accordance with an embodiment of the present disclosure, provides for the configuration and fabrication of mid-infrared narrow bandpass filters that have substantially temperature invariant optical properties over a wide temperature range.
The approach can be considered by the design of the filter:
(LH)x1(LL)y1(HL)x2(LL)y2 . . . (LL)yN(HL)xN+1
consisting of a total of y half wavelength spacers (cavities) LL of low refractive index material in N cycles (y=Σyi), LH being the stacks of xi quarter wavelength layers of alternating of high and low refractive index material in the N cycles. The reflections wavelength of the quarter wavelength reflector stack (which is the only reflection to undergo constructive interference), irrespective of the values of x, and N, can be expressed as:
λm=2(nLdL+nHdH)
for first order reflections (m=0). The temperature variation of the wavelength in the reflector stack dλm/dT|s can be expressed as:
where CL and CH are the coefficients of linear expansion of the low and high refractive index materials, respectively. From eqn.[1] for first order reflection and normal incidence (i.e., m=1 and θ=0° , the corresponding temperature dependence dλm/dT|c of the cavity layer of low refractive index material is given by:
noting that y is the total number of half wavelength cavity layers. The total change in wavelength with temperature d□m/dT|T is given by the sum of dλm/dT|c and dλm/dT|s:
noting that nLdL=nHdH at the temperature for which the filter is designed for use. Clearly dλm/dT|T can only be zero if the value of dn/dT for one of the materials is negative. This condition can be fulfilled by high refractive index materials such as PbTe, PbSe or PbS. For close matching of the value of dλm/dT|T to zero, the wavelength dependence of n, temperature and wavelength dependence of dni/dT can be taken into account.
The condition dλm/dT|T=0 is given approximately by:
noting that C, is considerably smaller than dni/nidT for most materials used in mid-infrared filters. The term (1+y) can be chosen to satisfy the above expression depending on the choice of low refractive index material. For example, with ZnSe and PbTe for the low and high refractive index materials, respectively, and using the material values of bulk phases nL=2.43, nH=6.10, dnL/dT=6.3×10−5 K−1 and dnH/dT=−2.1×10−3 K−1 for λm=3.4 □m, the expression is satisfied with y=13.3, i.e., approximately 13 half wavelength cavity layers are required to achieve the condition dλm/dT|T=0.
There is considerable variation in the values of the material properties (nH, dnH/dT, CH, etc.) that appear in for thin films in a multilayer structure and therefore in the predicted value of dλm/λmdT or the value of y required to achieve the condition dλm/λmdT=0. The uncertainty is particularly severe for the value of dnH/dT for PbTe in view of its magnitude and influence on the value of y. For example, the value of dn/dT for PbTe at λm=5 □m has been reported to be −1.5×10−3 K−1 by Zemel, J. N., Jensen, J. D. and Schoolar, R. B., “ELECTRICAL AND OPTICAL PROPERTIES OF EPITAXIAL FILMS OF PBS, PBSE, PBTE AND SNTE”, Phys. Rev. 140, A330-A343 (1965), −2.7×10−3 K−1 by Piccioli, N., Besson, J. M. and Balkanski, M., “OPTICAL CONSTANTS AND BAND GAP OF PBTE FROM THIN FILM STUDIES BETWEEN 25 AND 300° K”, J. Phys. Chem. Solids, 35, 971-977 (1974), and −2.8×10−3K−1 by Weiting, F. and Yixun, Y., “TEMPERATURE EFFECTS ON THE REFRACTIVE INDEX OF LEAD TELLURIDE AND ZINC SELENIDE”, Infrared Phys., 30, 371-373 (1990). From the above expression, the corresponding values of y (to the nearest integer) are 9, 17 and 18, respectively.
In view of the uncertainties in the value of dn/dT for PbTe and therefore the number of low refractive index half wavelength spacers required to achieve dλm/dT=0, a more useful approach is to determine the experimental value of dλm/dT as a function of the optical thickness of the low refractive index cavities for a suite of filters fabricated by the same method.
The approach illustrated by
The Beer-Lambert law applied to the sensor of
A=−log10(I/I0)
where A is the absorbance spectrum by a species in a fluid having an absorbance peak at a wavelengths corresponding to the pass band of the filter 5, I is the intensity spectrum of the infrared radiation detected by the detector 6, and I0 is a reference intensity spectrum. For example,
Other species can be monitored in this way. For example,
A mid-infrared sensor, of the type discussed above, may, in accordance with embodiments of the present disclosure, be used to monitor hydrate inhibitor concentrations, for example in subsea locations, such as subsea pipelines.
In the subsea environemnt, gas hydrates can form, particularly, in production pipelines. This is undesirable as the hydrates can agglomerate and block the flow in the pipeline and/or cause equipment damage. Two solutions are generally proposed. One is to add thermodynamic inhibitors, such as methanol, ethanol, monoethylene glycol or diethylene glycol, to the flow. These compounds may be recovered and recirculated. Although such thermodynamic inhibitors are cheap, they usually have to be added in large quantities in order to have a thermodynamic effect of lowering the hydrate formation temperature and/or delaying hydrate formation. The second is to add kinetic inhibitors, such as polyvinylpyrrolidone or polyvinylcaprolactam, to the flow. These work by slowing down the rate of hydrate nucleation and/or reducing hydrate agglomeration. The kinetic inhibitors can be effective in lower doses, but are more expensive than most thermodynamic inhibitors.
With both types of inhibitor, it is important to be able to measure the concentration of inhibitor in the liquid. In the subsea environment, salt can be present in the liquid, sometimes in varying amounts. However, in a mid-infrared sensor, in accordance with embodiments of the present disclosure, the positions of mid-infrared absorption peaks of many inhibitors are not sensitive to salt concentration. As such, a mid-infrared sensor, in accordance with an embodiment of the present disclosure, provides for measuring inhibitor concentration in fluids with varying salt concentrations.
As mentioned above, the sensor of
Cleaning the window in this manner may be particularly effective, compared to other techniques such as ultrasonic cleaning or mechanical wiper cleaning.
The window 4 can be formed, for example, in some embodiments of the present disclosure, of diamond (e.g. by chemical vapour deposition). A central (typically undoped) area of the window may be mid-infrared transmissive, while an annular encircling area of the window may be made semiconductive, e.g. by boron doping that part of the window. The heater 8 can then be a simple electrical power source which sends a current through the window to induce resistive heating of the encircling area. The central area of the window is then heated by thermal conduction from the encircling area. Boron-doping of diamond components is discussed in U.S. Pat. No. 7,407,566.
In some embodiments of the present disclosure, the heater 8 may be able to heat the window to at least 400° C. This is higher than the 374° C. super-critical point for water, where super-critical water comprises a good cleaner and oxidiser. In some embodiments of the present disclosure, it is unnecessary to keep the window at high temperature for a long time period. In particular, less than a microsecond at peak temperature may be enough for cleaning purposes, with longer periods requiring more power and increasing the risk of overheating of other parts of the sensor.
In addition, or as an alternative, to the above heater, cleaning of the window 4 may, in some embodiments of the present disclosure, be performed by providing the sensor with a pressure pulse arrangement. For example, the sensor may be located on a fluid flow line between a pump for the fluid and an exit port from the flow line. With the exit port in a closed position, the fluid pressure can be increased in front of the window to above hydrostatic pressure by the pump. Subsequent of opening the exit port creates a sudden pressure difference that flushes the flowline fluid, e.g. to the borehole. The sudden movement of dense fluid in front of the window dislodges and carries away window contamination. A 1000 psi (6.9 MPa) pressure pulse is generally sufficient in most cases.
All references referred to above are hereby incorporated by reference.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from such scope.
Number | Date | Country | Kind |
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1416258.0 | Sep 2014 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/US15/49070 | 9/9/2015 | WO | 00 |