Measuring apparatus

Abstract

A method of measuring solid content present in a solid-fluid flow through a tube, comprising: using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solidfluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a solid content present within the tube; and, providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube, wherein the signal processor is remotely located from the tube.

Description

[0001] MEASURING APPARATUS

[0002] Field of the invention

[0003] The present invention relates to measuring apparatus. The invention relates to for example to a solid content measuring apparatus for monitoring solid content in solidfluid flows. The invention also relates to for example monitoring water content in fluid flows wherein conditions for hydrate deposit formation can potentially arise. The present invention relates to methods of measuring such content in fluid flows. For example to methods of measuring solid or water content in fluid flows in conditions wherein hydrate deposit formation can potentially arise.

[0004] The present invention relates to methods of measuring water content in drilling mud mixture in conditions where a change in the content of water, solids and hydrocarbon may potentially arise.

[0005] The present invention relates to methods of measuring solid content in drilling mud mixtures in conditions where a change in the content of water, solids and hydrocarbon may potential arise.

[0006] Furthermore, the present invention concerns software products recorded on machine-readable media, wherein the software products are executable on computing hardware for implementing aforesaid methods.

[0007] Background of the invention

[0008] It is known to employ a pair of coils of wire exhibiting mutually different responses and excited with alternating signals for determining phase characteristics of a fluid region intersected by magnetic and electrical fields generated by the pairs of coils when excited. Such coils conventionally have relatively few turns, for example less than 10 turns each, and can determine fluid composition to within an accuracy of a few percent by way of measurement of their resonance characteristics, for example resonance Q-factor. The pair of coils is susceptible, for example, to being used to monitor fluids extracted from a production borehole when water, oil, sand particles and scum can potentially simultaneously be present in the fluids. Apparatus for determining phase characteristics of a fluid region are described in a published international PCT application no. W02004 / 025288A1 , "Method and arrangement for measuring conductive component current of a multiphase fluid flow and uses thereof", inventor Erling Hammer.

[0009] A contemporary issue is that geological oil reserves are becoming rapidly depleted, requiring oil companies to revert to difficult and expensive off-shore drilling and production to meet World demand for oil; the World demand is presently estimated to be 85 million barrels of oil equivalent per day. Many newly discovered oil and gas fields, for example in the Barrent Sea lying North of Norway, are found to contain a higher ratio of gas to oil than expected from earlier discovered oil and gas fields. Consequently, there is found to be a need to monitor to an increasing extent gas production in Northern latitudes which are often subjected to severe operating conditions, for example low ambient operating temperatures, for example below 0 °C.

[0010] A contemporary problem encountered with gas production is spontaneous formation of hydrate deposits which can block tubes completely and therefore threaten gas production with associated financial loss. Hydrate formation occurs when gas hydrocarbon molecules, for example on account of strong polarization of their hydrogen atoms, attract oxygen atoms of water molecules so that the hydrocarbon molecules become encapsulated in water molecules to form miniature hydrate ice crystals which can precipitate to cause aforementioned hydrate deposit blockages in tubes. The blockages grow initially on inside walls of tubes, and eventually obstruct a central region of the tubes. Once hydrate ice crystal deposition commences on the inside walls, hydrate crystal nucleation is enhanced such that hydrate blockages can potentially form rapidly, for example within minutes. Moreover, the blockages are also often rather difficult to remove when formed, sometimes requiring costly "pigging" or heat treatment to be performed. A conventional approach to hinder hydrate formation is to include additives in a flow of gas. However, using additives is expensive and can also potentially cause a degree of contamination in gas flows.

[0011] Contemporary sensors and associated measuring instruments for sensing hydrate formation in tubes are complex and costly, thereby limiting locations whereat they can be installed in gas production systems. Consequently, many locations along gas tubes and pipes which could beneficially be provided with measuring instruments capable of detecting potential formation of hydrate deposits are hindered from being accordingly equipped on account of cost of conventional hydrate measuring instruments.

[0012] It is also known that in well drilling operation, in the process of creating a wellbore into Earth’s surface to access and extract oil or natural gas, a specially formulated fluid, known as “drilling mud”, is pumped down the drill pipe during the drilling operation. The drilling mud is then circulated back up to the surface before being recirculated down the drill pipe.

[0013] The drilling mud serves multiple purposes, including cooling the drill bit, removing crushed or cut rock or general drilling debris (which is often referred to as “cuttings”), and maintaining pressure to prevent blow out. The quality and composition of the drilling mud is important in maintaining wellbore stability and to provide a safe and efficient drilling operation.

[0014] A contemporary issue during well bore operation is contamination of drilling mud. Drilling mud can be prone to contamination from various sources, including formation fluids, solids, and drill cuttings from the well bore operation. Monitoring the drilling mud allows detection, identification and correction of issues that may cause well bore instability and equipment damage.

[0015] Contemporary methods and techniques for assessing drilling mud quality use manual sampling and laboratory analysis. Contemporary methods take drilling mud samples at regular intervals, such as daily or over many hours.

[0016] Summary of the invention

[0017] The present invention seeks to provide an improved solid measuring system for analysis of drilling mud. The present system provides advantages over the prior art by providing greater responsiveness and improved ease of adjusting treatment of the drilling mud. The present invention also provides an improved method of water volume fraction measurement. According to a first aspect of the present invention, there is provided a method of measuring solid content present in a solid-fluid flow through a tube, comprising: using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solid-fluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a solid content present within the tube; and, providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube, wherein the signal processor is remotely located from the tube.

[0018] Contemporary systems do not provide real-time measurements of the solid content present in the solid-fluid flow. Instead, contemporary systems provide measurements only on very seldom basis. As noted above, this may be once per day or perhaps at most 3 or 4 times a day. Such measurements are labour intensive, requiring man power and therefore there are competing requirements for the use of the time of the man power. In this way, modem operations often minimise the number of measurements taken to reduce the man power impact of taking and analysing the measurements on other requirements.

[0019] Contemporary systems also use on-site analysis of the solid-fluid flow measurements. This means that greater man power is required on-site. In the example of off shore drilling operations however this is a significant and costly requirement. The present system allows off-site processing and therefore reduces this cost.

[0020] Of course, on site there may be located some communication device near the tube which is arranged to provide data from the generator to the signal processor which may be located remotely from the tube. In this way, the data may be obtained at the tube (on-site) and sent for analysis away from the tube (off-site).

[0021] The present system therefore saves significantly on cost and improves the safety of the operation. By taking regular measurements, in examples this is continuous and / or real time measurements, the operators are informed of changes in the solidfluid flow sooner and can therefore take action should action be required. Furthermore, by reducing the man power required on the measurements, such man power can be redirected towards the drilling operation, maintenance of equipment etc., thereby further increasing the safety of the overall operation.

[0022] Moreover, the process described herein not only increases the safety of the drilling operation but also the safety of the operators of the drilling operation. The present system does not need human interference to take measurements of the drilling mud. In contemporary systems, the operators are exposed to hazardous chemicals and dangerous environments when needing to take samples from the drilling mud in use. As such, the present system also protects the operators of the operation.

[0023] In an example, the method comprises on receiving the real-time measurements of solid content present in the solid-fluid flow, adjusting a treatment of the solid-fluid flow in the tube.

[0024] The treatment of the solid-fluid flow may include the speed of the flow, the constituent parts of the flow, how the flow is filtered etc. There are many ways that the flow can be treated. The analysis provided informs how the flow can best be treated to be optimal in the drilling process. This may be to increase flow to decrease the time required to complete the process (i.e. increasing the rate of attack against the rock), or may be to decrease the flow if solid removal equipment does not have sufficient capacity to handle the cuttings in the flow.

[0025] Broadly, the adjustment is based on the content provided to a user on the solid-fluid flow. The user is able to alter the work environment or the operation station around the data provided. This ultimately improves the safety and energy efficiency of the process. In this way, a greener drilling process may be provided.

[0026] In an example, adjusting a treatment of the solid-fluid flow in the tube comprises at least one of: altering solid removal from, solid input to or fluid input to the solid-fluid flow; and, updating flow speed of the solid-fluid flow.

[0027] As noted above, this may relate to altering an operator behaviour to prevent platform run-off water getting into the flow or the rate of attack against the rock. Platform runoff water may be present near the drilling operation due to cleaning of the platform during use. Additionally, undesired water may get into the solid-fluid flow from the reservoir during the drilling operation (for example an influx from a drill zone) or from possible leaks in the well bore system. Operators may not be as careful as is preferred during such cleaning and the method herein can account for difficulties that would otherwise be introduced in the drilling process from such user errors.

[0028] Any of the operational drilling properties may be updated based on the data provided in real time to a user by the present method. Allowing suitable action thereby improves the overall safety of the drilling process as users are informed sooner or deviations from normal operation.

[0029] In an example, altering solid removal from, solid input to or fluid input to the solid-fluid flow comprises: filtering out solids using a kinetic separator wherein the solids relate to the real-time measurements of solid content present in the solid-fluid flow through the tube.

[0030] Separating out cuttings from the drilling mud is a way to keep the consistency of the mud as expected. In doing this, the mud will perform in a more expected manner (typically a better manner). Therefore, by detecting the solids in the solid-fluid flow in real time and acting to remove those solids (by e.g. a kinetic separator), the consistency of the mud is better maintained and therefore the performance of the mud is higher overall. Any other method of removal of solid cuttings can be used additionally or alternatively. This step is acting on the data provided to maintain the consistency of the drilling mud. Contemporary systems cannot offer this as they do not offer real time measurements. Therefore, contemporary systems can act to remove solids however the accuracy of the present system is far superior. This accuracy leads to a greater accuracy in the removal of solids and therefore a greater consistency in drilling mud. In turn, this decreases the likelihood of issues arising such as overheating or the like that can lead to dangerous outcomes. Therefore, the safety of the overall system is improved.

[0031] In an example, the solids relating to the real-time measurements of solid content present in the solid-fluid flow through the tube are cuttings. This may be cuttings from a mud drilling operation. The cuttings may be rock and / or metal debris from material collected by the mud flow or from drill bits or the like used in the drilling operation.

[0032] In an example, the method further comprises performing calibration measurements on a first solid-fluid flow through a tube to obtain a first measurement of solid content present in the solid-fluid flow through the tube; and, comparing real-time measurements of solid content present in the solid-fluid flow through the tube to the first measurement.

[0033] In this way, the user may calibrate system parameters against the initial solid-fluid flow. This may be the mud as intended for use. The real-time measurements then allow a user to detect changed in the solid-fluid flow which necessarily are the result of changing circumstances since the calibration. In this way, the user can know how to provide a treatment to the solid-fluid flow to improve the performance or safety of the operation. The present system allows for a highly reactive and agile system that accounts for changes occurring during use.

[0034] In an example, providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube comprises providing real-time measurements to a user interface located proximally to the tube.

[0035] The system herein is user friendly and is designed to decrease the time required to obtain information on the changing status of the solid-fluid flow and therefore decrease the reaction time for changes to be made that may improve performance or safety or the like. By providing to a user interface near the tube, a user that can provide the treatment adjustments discussed (i.e. a user near the solid-fluid flow) is informed of the relevant information.

[0036] In an example, providing real-time measurements to a user interface comprises providing real-time measurements via an online connection. Such a connection is a reliable and robust method for providing analysis to the users that can impact the solid-fluid flow without requiring those same users to perform the measurements and analysis. The present system removes from these users method steps that would otherwise detract from tasks related to maintenance of performance and safety of the operation involving the solid-fluid flow.

[0037] In an example, the method is performed in an automated manner. The present system does not require user input to obtain the data. The present system does not require user input to analyse the data. Instead, the present system is a significant improvement over contemporary systems in the automation of the data measurement and analysis. The user need only review the analysis of the data and perform treatment adjustments to the solid-fluid flow based on the analysed data. In this way, man power time is most effectively and efficiently used.

[0038] In an example, remotely located control circuitry comprises the signal processor. Such control circuitry advantageously provides a large level of user-dissociation from the process. The control circuitry is able to perform the data obtaining and processing. This, as noted above, frees up man power at the operation.

[0039] In an example, the solid-fluid flow is a drilling mix for use in drilling operations. As discussed above, the process may be used in drilling operations. Such operations may take place off shore and therefore man power is very valuable. Use of automated processes are therefore highly advantageous in such situations.

[0040] In an example, the generator and tube are located off shore and wherein the signal processor is located on shore. In this way, the drilling operation may be off shore. The signal processing is located on shore and the communication between the two may occur via online communication. The present system provides greater analysis and data manipulation on shore such that the man power and man hours off shore can be focussed on the operation. In this way, the process allows for cheaper and safer operations.

[0041] In an example, providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube comprises: providing, by the signal processor, continual real-time measurements of solid content present in the solid-fluid flow through the tube. As there is no man power required for the obtaining and analysing of the data, the measurements may be performed continually by the control circuitry and signal processor. Such a method is not required as “continual” measurements are more taxing on processing power than interm ittent-but-regular measurements. Such interm ittent-but-regular measurements are sufficient to capture information on changing solids in the solid-fluid flow and provide a user with an opportunity to adjust a treatment of the flow. Continual measurements may be useful if the user expects to find significant changes in the solid-fluid flow over a small period of time and wishes to be informed immediately as to when such change occurs.

[0042] In an example, the method further comprises providing data on initial solid-fluid composition to signal processor. This may include data on the solid components, the liquid components. This may include percentage or weights of solids used in forming the initial solid-fluid flow. This may include percentage or weights of liquids used in forming the initial solid-fluid flow.

[0043] Drilling muds may be formed from solids being mixed with water and oil being added. The details of the formation of the original mud are useful to compare later data against. In that, the real time measurements of the solid-fluid flow can be compared against the “ideal” produced drilling mud prior to be inserted into the borehole for drilling. Therefore, the starting conditions can be those that a user strives to maintain throughout the use of the mud in the operation.

[0044] According to a second aspect of the present invention, there is provided a solid content measuring apparatus for measuring solid content present in a solid-fluid flow through a tube, wherein the apparatus includes a generator for generating in operation an excitation signal, a coil arrangement disposed around the tube adapted to be excited into resonance by the excitation signal and interact with the fluid flow through the tube, and a signal processor adapted to receive resonance signals from the coil arrangement for determining a solid content present within the tube, wherein the signal processor is remotely located from the tube.

[0045] In an example, the apparatus further comprises a solid-fluid flow treatment module for applying a treatment to the solid-fluid flow in the tube. In an example, the solid-fluid flow treatment module is arranged to at least one of: alter solid removal from, solid input to or fluid input to the solid-fluid flow; and, update flow speed of the solid-fluid flow.

[0046] The treatment module may include kinetic separators, controllable openings, sieving arrangements, or the like that may be used to separate out material.

[0047] In an example, remotely located control circuitry comprises the signal processor. As noted above, remote location of processing hardware is highly advantageous as providing a redistributed requirement for workload from the on-site users.

[0048] As used herein, remote and off site are synonyms and proximal and on site are synonyms.

[0049] In an example, the solid content measuring apparatus is for use in drilling operations. In an example, the generator and tube are located off shore and wherein the signal processor is located on shore.

[0050] According to a third aspect of the present invention, there is provided a method of measuring water volume fraction present in a solid-fluid flow through a tube, comprising: using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solidfluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a water volume fraction present within the tube; and, providing, by the signal processor, real-time measurements of water volume fraction present in the solid-fluid flow through the tube.

[0051] The present system is able to provide accurate measurements and calculations of the water volume fraction present in a solid-fluid flow. This is highly advantageous as these measurements can be compared against the expected water volume fraction measurements and action can be taken accordingly to alter the solid-fluid flow if the flow composition is different from expected. This allows great control over the flow and therefore over the safety and performance of the arrangement as explained above. In an example, the signal processor is remotely located from the tube. The signal processor may be located on site or off site, however there is a communication channel between the location where the data measurements are taken and the location where the data measurements are analysed. The data obtaining location is different to the data analysis location. In this way, the operational advantages provided by the present system can be realised.

[0052] In an example, the solid-fluid flow comprises at least a water fraction, a solid fraction and an oil fraction. The composition of the solid-fluid flow may include water, solids and oil. Data on these may be used to infer data on others. For example, a flow with very high water fraction will have a lower solid and oil fraction.

[0053] More relevantly, the water fraction value can be used by an operator of a drilling rig or the like to ascertain whether the composition of the drilling mud is optimal. If the water fraction is too high, the operator can add a greater amount of solid to the mix. In contrast, if the water fraction is too low, the operator can add more water.

[0054] The amount of water can vary during use due to e.g. rainfall or user error (e.g. user washing the platform of the rig and waste water entering the bore). The water is typically emulsified and therefore rather than approaching the issue attempting to remove water, it is preferable to add a greater solid mass to redress the balance of the drilling mix.

[0055] In an example, the method further comprises obtaining data relating to the density of the solid fraction and the oil fraction.

[0056] This data can be compared against known data of the composition in the solid-fluid flow. In this way, calculations can be performed to obtain data of the present drilling mix against the initial drilling mix. These calculations help identify possible issues as they arise. The present system is highly reactive and responsive to problems. This leads to a system that is robust and has vastly improved safety aspects to modern arrangements. According to a fourth aspect of the present invention, there is provided a computer readable medium comprising computer-implementable instructions for causing a processor to become configured to carry out the method of any of the preceding aspects or examples.

[0057] The invention is of advantage in that the apparatus is capable of measuring minute quantities of water present within the tube, for example indicative of potential early hydrate formation.

[0058] Optionally, the generator is operable to generate the excitation signal to include a temporal series of excitation pulses.

[0059] Optionally, the resonance coil employs at least 15 turns, more beneficially at least 20 turns, yet more beneficially at least 25 turns.

[0060] Optionally, the water content measuring apparatus is implemented so that the tube and its associated coil arrangement are surrounded by an electrostatic shield for screening the coil arrangement when in operation.

[0061] Optionally, the water content measuring apparatus further includes a sensor arrangement for sensing low-frequency electrical conductivity and temperature on an inside wall of the tube and for providing corresponding sensor signals to the signal processor for enabling the signal processor to compute the water content within the tube independently of the salinity of the water content.

[0062] Optionally, the water content measuring apparatus is implemented so that the coil arrangement includes excitation, resonance and pickup coils, wherein the excitation coil is coupled to the generator, the pickup coil is coupled to the signal processor, and the resonance coil is coupled to a tuning capacitor (C) for providing a resonance characteristic which is sensitive to water content within the tube. More optionally, the coils are fabricated from at least one of: individually insulated Litz wires, insulated metallic tape. More optionally, the coils are silver plated on their peripheral external surfaces to reduce their surface electrical resistance. Optionally, the water content measuring apparatus is implemented so that at least one of the generator and the signal processor are adapted to be spatially remote from the tube and its coil arrangement in operation.

[0063] Optionally, the water content measuring apparatus is adapted to monitor conditions in which potential hydrate formation within the tube can arise.

[0064] Optionally, the water content measuring apparatus is implemented so that the tube is fabricated from at least one of: polycarbonate polymer, acrylic polymer, PEEK polymer. PEEK polymers are obtained by step-growth polymerization by dialkylation of bisphenolate salts. Typically, PEEK is produced by way of a reaction of 4,4'-difluorobenzophenone with a diSodium salt of hydroquinone, which is generated in situ by deprotonation with Sodium Carbonate. PEEK manufacture employs a reaction which is conducted at a temperature of around 300 °C in polar aprotic solvents, for example such as diphenylsulphone. PEEK is a semicrystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. PEEK exhibits a Young's modulus of 3.6 GPa, and its tensile strength is in a range of 90 to 100 MPa. Moreover, PEEK has a glass transition temperatures at around a temperature of 143 °C and melts at a temperature around 343 °C. Furthermore, PEEK is highly resistant to thermal degradation as well as attack by both organic and aqueous environments. However, PEEK is attacked by halogens and strong Bronsted and Lewis acids as well as some halogenated compounds and aromatic hydrocarbons at high temperatures.

[0065] A method of measuring water content present in a fluid flow through a tube, characterized in that the method includes:

[0066] (a) using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the fluid flow through the tube; and

[0067] (b) receiving at a signal processor resonance signals from the coil arrangement for determining a water content present within the tube, wherein the coil arrangement includes a resonance coil having a length-to-diameter ratio which is at least 3:1 , and wherein the resonance coil include at least 10 turns. A software product recorded on a machine readable medium, wherein the software product is executable upon computing hardware for implementing a method pursuant to the above method of measuring water content present in a fluid flow.

[0068] Description of the diagrams

[0069] Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

[0070] FIG. 1 is an illustration of an embodiment of a water content measuring apparatus;

[0071] FIG. 2 is an illustration of signals to be analyzed in the apparatus of FIG. 1 ;

[0072] FIG. 3A is an illustration of a signal received from a pickup coil of the apparatus of FIG. 1 when a fluid flow tube of the apparatus is devoid of water;

[0073] FIG. 3B is an illustration of a signal received from the pickup coil of the apparatus of FIG. 1 when the fluid flow tube of the apparatus contains spring water;

[0074] FIG. 4 is an illustration of changes in a parameter (tau, T) representative of Cofactor as a function of a water content of the fluid flow tube of the apparatus of FIG. 1 ;

[0075] FIG. 5 is a graph illustrating sensitivity of the apparatus of FIG. 1 to saline solution; FIG. 6 is a graph illustrating sensitivity of the apparatus of FIG. 1 to salt weight in saline solution present within a sensing tube of the apparatus;

[0076] FIG. 7 is a schematic illustration of noise sources of a water content measuring apparatus;

[0077] FIG. 8 is a schematic illustration of an electronic circuit for use when implementing a water content measuring apparatus;

[0078] FIG. 9 is an illustration of a resonance characteristic of a sensing resonant coil arrangement of the apparatus associated with FIG. 7 and FIG. 8, illustrating a driven resonance coo and an undriven natural resonance con;

[0079] FIG. 10 is an illustration of a sample of measured Q-factor of a sensing coil arrangement of the apparatus associated with FIG. 7 and FIG. 8; and FIG. 11 is an illustration of a resonance characteristic of a sensing coil arrangement of the apparatus associated with FIG. 7 and FIG. 8.

[0080] In the accompanying diagrams, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is nonunderlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

[0081] Description of embodiments of the invention

[0082] It is well known that cylindrical conductor coils exhibit electrical resonances on account of inductance and distributed capacitances associated with such conductor coils; such “distributed capacitances” contributed to resonant circuit tuning capacitors pursuant to the present invention. The distributed capacitances correspond to interwinding capacitances. Moreover, the inductance arises on account of magnetic flux developed by the coils. However, as aforementioned, it is conventionally perceived that such coils are only capable of providing multiphase mixture measurement to an error deviation of a few percent. For measuring conditions of potential hydrate formation, it is necessary to measure water content to concentrations of a few parts per million (p.p.m.). Thus, it has been conventional practice to regard an electrical resonance coil as being quite unsuitable for use in making precision hydrate-related measurements.

[0083] Experimental studies associated with devising the present invention have surprisingly shown that suitable excitation of a coil having a sufficient number of turns and an adequate length in relation to its diameter allows water content measurements to be performed to concentrations as low as a few parts per million (p.p.m.). Such high accuracy measurement is feasible utilizing a water content measurement apparatus as illustrated in FIG. 1 ; the water content measurement apparatus is indicated generally by 10. The apparatus 10 includes a polymer material tube 20, for example fabricated from polycarbonate, acrylic-type or PEEK plastics materials; such polymer materials are chosen to exhibit relatively low dielectric losses at a frequency of several MHz. The tube 20 beneficially has an inside diameter d in a range of 70 to 90 mm, and a length provided with windings in a range of 280 mm to 320 mm; however, the apparatus 10 is susceptible to being adapted at larger diameters above 90 mm. The tube 20 is provided at its first end with an excitation coil 30A comprising a single turn. In a middle portion of the tube 20, there is provided a resonance coil 30B comprising in a range of 30 to 50 turns which is optionally terminated with a capacitor C of value 32 pF; for example, 34 turns for the coil 30B is found to function well in practice. The capacitor C is beneficially a high-quality capacitor exhibiting low dielectric losses at operating frequencies of a few MHz, for example a high-quality ceramic capacitor, Mica dielectric capacitor or sealed air-cored capacitor. The resonance coil 30B coupled to its associated capacitor C is operable to exhibit a resonance frequency in an order of a few MHz, for example in a range of 1 MHz to 5 MHz, although other operating frequencies can be employed if required. The resonance coil 30B is beneficially uniformly wound along the length I, such that the coil 30B has a diameter: length ratio in a range of 1 :3 to 1 :5. Ratios in excess of 1 :5 can optionally be employed. Beneficially, the coil 30B is wound from Litz wire (namely individually insulated wire strands) or from thin Copper tape with associated insulation to reduce conductor skin-depth effects in the coil 30B from adversely affecting its Q-factor to detriment of sensitivity of the apparatus 10 to minute quantities of water present in the tube 20. Optionally, an outer conducting surface of windings of the coil 30B is silver plated to increase a resonance Q-factor of the coil 30B. Moreover, the tube 20 also includes a pickup coil 30C comprising a single turn. The capacitor C is beneficially spatially located in close proximity to the coil 30B as illustrated for obtaining most accurate measurement of water content, for example in gases flowing in operation through the tube 20 in conditions in which hydrate deposition would be expected to arise. The tube 20 and its coils 30A, 30B, 30C are furnished with an outer peripheral screening shield 40 fabricated from Aluminium sheet, stainless steel or similar. Beneficially, the shield is designed to be able to withstand a pressure that is likely to be encountered within the tube 20. Optionally, the Aluminium sheet employed to fabricate the shield 40 has a thickness which is less than 1 mm, for preferably less than 0.5 mm. Alternatively, or additionally, outer fibre glass or carbon composite shielding for the tube 20 and its coils 30A, 30B, 30C is employed. The excitation coil 30A is coupled to a generator 50 which is operable, for example, to output a temporal series of pulses 60 having a pulse duration TPand a pulse repetition frequency fp. Beneficially, the pulse duration TPis much shorter than a period between pulses 60, namely — by at least an order of magnitude.

[0084] Z P

[0085] The pickup coil 30C is connected via two well-screened coaxial cables 70 to a signal processing unit 80 employing computing hardware executing software products for analyzing signals induced in operation in the pickup coil 30C to generate corresponding analysis results. The processing unit 80 is operable to present the analysis results on a display 90 indicative of concentration of water content present within the tube 20, for example potentially to trace levels as low as a few parts per million (p.p.m.) of water content being present within the tube 20. Optionally, the processing unit 80 is adapted to monitor water concentration, temperature and conductivity on an inside surface of the tube 20 for identifying conditions in which hydrate deposition is likely to arise.

[0086] Resonance characteristics of the coil 30B are strongly affected depending upon whether or not water present within the tube 20 is saline in nature. Salt content in a salt solution affects a freezing temperature of the solution, and therefore affects a temperature at which hydrate deposition can arise when the solution is present together with a hydrocarbon, for example methane or propane. On account of the highly conductive nature of saline solution, it is necessary for the apparatus 10 to include additionally a sensor arrangement 100 on an inside surface of the tube 20, wherein the sensor arrangement 100 includes a temperature sensor for measuring a temperature T of the inside surface of the tube 20 and a surface electrical conductivity sensor for measuring an electrical conductivity cr of a film formed in operation of the inside surface of the tube 20. Signals associated with the sensor arrangement 100 conveyed to the processing unit 80 are illustrated in FIG. 2. The processing unit 80 is programmed to perform a computation represented by Equation 1 (Eq. 1): w = F Q,fr,T, ,p) Eq. 1 wherein w = water concentration;

[0087] P = pressure within the tube 20;

[0088] Q = Q-factor of resonance of the coil 30B subject to excitation;

[0089] T = temperature of inside surface of the tube 20; cr= electrical low-frequency or d.c. conductivity of a moisture film formed on the inside surface of the tube 20; and

[0090] F = a conversion function determined from experimental calibration measurements.

[0091] The function F is beneficially implemented as a lookup table implemented in computer memory of the processing unit 80. Optionally, the function F is determined empirically by performing a series of experimental tests to derive measurement data, and then synthesizing intermediate measurements by mathematical extrapolation to provide the function F as a continuously variable function. Alternatively, the function F can be derived analytically from theoretical consideration of the sensor arrangement 100. The Q-factor Q is determined from an envelope of a temporal signal decay characteristic as illustrated in FIG. 3A and FIG. 3B wherein the signal is described substantially by Equation 2 (Eq. 2): wherein s = signal induced in the pickup coil 30C; vo = amplitude coefficient of the signal s;

[0092] T = exponential decay time constant of the response signal arising from electrical resonance of the coil 30B; o) - resonance frequency of the coil 30B; and t = time.

[0093] The sensor arrangement 100 can be implemented in various different ways. For example electrodes of the sensor arrangement 100 for measuring electrical conductivity can be implemented as annular ring electrodes around an inner circumferential surface of the tube 20 and disposed in a direction along an elongate axis of the tube 20. Alternatively, or additionally, electrodes of the sensor arrangement 100 for measuring electrical conductivity can be implemented as sectors of limited angular extent for sensing inhomogeneous deposition of hydrates onto the inner surface of the tube 20. Beneficially, the conductivity sensing electrodes are selected or treated to have a similar wetting characteristic to other parts of the tube 20 so that hydrate formation measurements provided by the apparatus 10 are as representative as possible for other tube connected to the tube 20. Similarly, the temperature sensor of the sensor arrangement 100 can be implemented as one or more individual temperature sensors which are spatially disposed for sensing temperature gradients within the tube 20. For purposes of computing Equation 1 (Eq. 1 ), an aggregate or average of the several temperature measurements from a plurality of temperature sensors of the sensing arrangement 100 can be used. The inside surface of the tube 20 is beneficially smooth for avoiding non-representative deposition of hydrate deposits onto the inside surface.

[0094] FIG. 3A and FIG. 3B are illustrations of resonance characteristics exhibited by the coil 30B as sensed using the pickup coil 30C. In a preferred embodiment of the invention, the coil 30B beneficially has 34 turns and is optionally tuned with a capacitor C having a capacitance value 32 pF. Alternatively, the coil 30B has 15 turns and is optionally tuned with a capacitor C having a capacitance value 100 pF. Correct impedance matching of the excitation coil 30A is highly beneficial for obtaining an uncluttered waveform as presented in FIG. 3A and FIG. 3B; the impedance matching corresponds to a filter which reduces excitation of higher-order resonances within the coil 30B, for example at frequencies approximately an order of magnitude above its main resonance frequency, for example at around 35 MHz when the coil 30B has a fundamental resonance around 3.5 MHz. Matching components as illustrated in FIG. 2 including a T-arrangement comprising a series connection of 50 , 33 resistors and a1000 pF capacitor to signal ground at a midpoint between the resistors has been found from experimental studies to function well for the apparatus 10. A relatively high Q-factor resonance of FIG. 3A corresponds to the tube 20 devoid of water; in contrast, FIG. 3B corresponds to a lower Q-factor response arising when the tube 20 contains a quantity of fresh water. By accurate measurement of Q-factor executed by the processing unit 80 when processing the pickup signal from the pickup coil 30C, the apparatus 10 is capable of detecting very small concentrations of water within the tube 20, for example to concentrations of a few parts per million (p.p.m.). The very high sensitivity of the apparatus 10 is also illustrated in FIG. 4 which is a graph having an abscissa axis representative of water fraction / 3 present within the tube 20, and an ordinate axis providing a measured parameter (tau, T) indicative of the Q-factor of resonance of the coil 30B a sensed via the pickup coil 30C.

[0095] As will be elucidated in greater detail later, by exciting the coil 30B to resonate, there is providing thereby an indication, via Q-factor measurement pursuant to the present invention, for establishing whether or not hydrate formation is likely to occur within a region encircled by the coil 30B. The Q-factor measurement is beneficially determined from a natural undriven Q-factor of the coil 30B, namely without disturbances arising from a finite driving impedance of the excitation coil 30A. The pickup coil 30C is beneficially arranged to represent a high impedance to the coil 30B, and thereby has a negligible influence upon the resonance of the coil 30B. Beneficially, the excitation coil 30A is driven momentarily to excite the coil 30B into resonance, and then the resonance of the coil 30B is allowed to decay naturally with the excitation coil 30A "open circuit" so that the excitation coil 30A does not influence the Q-factor of the coil 30B, namely permits the coil 30B to exhibit its natural resonance having a natural resonant frequency con. By monitoring the natural resonance of the coil 30B, an improved measurement accuracy can be achieved from the apparatus 10. In the apparatus 10, the Q-factor measurement of the coil 30B can either be performed in a continuous driven manner or in a pulse-resonant excited manner, or by employing a mixture of such measurement techniques.

[0096] The apparatus 10 provides a benefit that its pulse excitation manner of operation enables the generator 50 and the data processor 80 to be located spatially remotely from the tube 20 and its associated coils 30A, 30B, 30C and optional sensor arrangement 100. Such flexibility is highly beneficial when the tube 20 is required to operate at temperatures which would be hostile to electronic components associated with the data processor 80 and the generator 50. The apparatus 10 is susceptible to being employed in a large range of applications. For example, the apparatus 10 can be used in ocean-bed hydrate handling equipment, in separation tanks, down boreholes, in carbon dioxide capture and sequestration systems associated with climate change carbon tax funded facilities, in chemical industries, in space probes and similar. Measurement methods employed in the apparatus 10 will be described in more detail later.

[0097] It will be appreciated that the apparatus 10 is not operable to measuring a presence of hydrate deposits directly, but rather is able to provide an indication of a likelihood of hydrate deposit formation (hydrate ice crystals) based upon measured conditions of conductivity, temperature and pressure in combination with determining a concentration of water present within the tube 20. Optionally, the generator 50 is operable to excite the coil 30A by way of a repetitive burst of a plurality of pulses as an alternative to periodic single pulses; such burst excitation enables a better signal- to-noise (S / N) to be achieved in relation to electronically-generated noise arising within the apparatus 10, in combination with a reduced tendency to excite higher order resonances within the coil 30B.

[0098] In FIG. 1 , the peripheral screening shield 40 is described in the foregoing as being fabricated from Aluminium. Alternatively, the screen 40 is fabricated from a recognized type of steel which is able to withstand gas and liquids which the apparatus 10 will encounter during transportation and operation. A region between an outside surface of the tube 20 and the screen 40 is beneficially filled with a mechanical robust insulating material exhibiting a relative permeability of approximately unity; for example the coils 30A, 30B, 30C can beneficially be appropriately encapsulated (namely “potted”) in a hydrocarbon polymer materials resin, for example an epoxy or polyurethane material. Optionally, the screen 40 includes fibre glass, carbon fibre or other strong polymer structural components for example fabricated from stainless steel which can withstand a pressure within the tube 20 and thereby enable the instrument 10 to survive structurally in an unlikely event that the tube 20 ruptures in operation.

[0099] Referring again to Equation 1 (Eq. 1), the apparatus 10 operates to measure subtle characteristics whose nature is not generally appreciated. For example, a kink 500 in the curve of FIG. 4 is not a measurement inaccuracy, but rather a genuine relaxation effect resulting from spontaneous momentary alignments of groups of polarized water molecules to form larger momentary dipole moments which are many orders of magnitude larger than the dipole moments of individual water molecules. Such larger dipole moments are observed in the formation of ice crystals. In FIG. 5, there is a shown a graph pertaining to the Q-factor exhibited by the coil 30B as a proportion of saline solution within the tube 20 is varied. An abscissa axis 400 denotes a percentage of saline solution present in the tube 20 and an ordinate axis 410 denoting the time constant tau, r of resonance of the coil 30B; the Q-factor Q of the coil 30B is directly susceptible to being computed from the time constant tau, T . It will be observed in FIG. 5 that a minimum Q-factor occurs at a saline proportion of around 0.5% with a high sensitivity below 0.5%, namely below 5000 p.p.m., wherein discrimination of presence of saline solution to within tens’ of p.p.m. is achievable using the apparatus 10.

[0100] In FIG. 6, a response of the apparatus 10 to saline solution within the tube 20 is shown, wherein an abscissa axis 500 denotes percentage weight of salt within a saline solution present within the tube 20, and an ordinate axis 510 denotes the time constant tau, r. The resonance characteristic of the coil 30B exhibits a distinct peak 520 at around 3% salt (Sodium Chloride, NaCI) by weight present in the solution corresponding to greatest Q-factor, reducing with salt percentage above 3% as conductivity of the solution increases and also falling for concentrations below 3% on account of aforementioned relaxation effects caused by spontaneous momentary polarisation alignment of water molecules to create a large effective dipole moment. Between 0% salt weight content and 3% salt weight content, increasing salt content hinders spontaneous association of water molecules to form a large momentary effective dipole moment by way of Chlorine atoms screening highly polarized hydrogen atoms (protons), thereby resulting in a corresponding progressive increase in Q-factor. Both FIG. 5 and FIG. 6 exhibit a rapidly changing measurement characteristic near zero which imparts the apparatus 10 with excellent measurement characteristics for trace amounts of fresh water or saline solution. Such a measurement characteristic is well suited for identifying conditions where there is a potential risk of hydrate deposits being formed which can block tubes, for example in an offshore gas production and processing facility. In FIG. 7, sources of noise arising within the apparatus 10 are illustrated schematically. These noise sources influence an accuracy to which the Q-factor of the coil 30B can be measured. The Q-factor of the coil 30B is greatest when its encircled region is filled with dry gas; this is conveniently referred to as being Qdry. When traces of fresh water or saline water are introduced into the encircled region, the Q-factor of the coil 30B is reduced; this is conveniently referred to as being Qwet. The Q-factor Qdry is influenced by the temperature T, for example as a result of winding resistances of the coil 30B changing with the temperature T. Thus, inherent in Equation 1 (Eq. 1 ) is a subtraction function as described in Equation 3 (Eq. 3):

[0101] ><’ = F((Q T)-Q T) fr,T,a,P) Eq. 3

[0102] Qdry( T) can be determined by accurate measurement. Qwet(T) is determined as the apparatus 10 is employed in practice. It will be appreciated that Qdry and Qwet can be relatively large numbers, for example in an order of 100 or more, and hence need to be measured to high precision for detecting occurrence of water to a sensitivity in an order of p.p.m. Such precision is influenced by noise and drift effects occurring within the apparatus 10 when in use.

[0103] In FIG. 7, the sources of noise occurring within the apparatus 10 include a first noise source 600 affecting the Q-factor arising from flow turbulence within a spatial region surrounded by the tube 20 surrounded by the coil 30B. Such flow turbulence is quasi-constant within a time period of signal decay illustrated in FIG. 3A and FIG. 3B, but will vary from one measurement of Q-factor of the coil 30B to another thereof over a monitoring period of several seconds or minutes, for example. Electronic noise E1 arising in an electronic amplifier 610 receiving signals from the pickup coil 30C arises, but is relatively constant; however, the electronic noise E1 is influenced by an operating temperature of the amplifier 610. Beneficially, the amplifier 610 is cooled by Peltier elements or a cryogenic engine to reduce its electronic noise E1. Digital electronic circuits 620 which receive an output signal from the amplifier 610 cause electronic noise E2, for example quantization noise, which is beneficially reduced by suitable design choice of components, for example by employing high- resolution ADC components for converting amplified analog signals from the amplifier 610 into corresponding digital sampling data. Noise sources 630, 640, 650 are associated with conductivity measurements, temperature measurements and pressure measurements respectively and can arise from corrosion (i.e. drift effects), electrochemical effects and ageing of electronic components. In practice, the noise source 600 is dominant and beneficially requires novel approaches to measurement technique pursuant to the present invention to obtain p.p.m. measurement accuracy results when detecting a presence of water within the tube 20.

[0104] Measurements of resonance Q-factor of the coil 30B are beneficially performed using a circuit as illustrated in FIG. 8. The circuit is indicated generally by 700 and includes a gated phase-locked-loop (PLL) including the aforesaid amplifier 610 for receiving a signal from the pickup coil 30C, a phase detector 710 for receiving an output signal Si of the amplifier 610, a phase integrator 720 for receiving a phase error output signal S2 of the phase detector 710 wherein the phase integrator 720 is provided with an associated gating switch 730 for locking an output signal S3 of the integrator 720 when required, a voltage-controlled oscillator (VCO) 740 controlled by the output signal S3 of the phase integrator 720, a drive amplifier 750 for receiving an output signal S4 from the oscillator (VCO), and a switch 760 for receiving an output signal Ss of the drive amplifier 750 and coupled to the excitation coil 30A. There is also included a microprocessor 800 for providing a phase reference signal C|)K to the phase detector 710, for providing a gating signals G to the switches 730, 760, and for receiving the signal Si. The microprocessor 800 is operable to execute software products recorded on machine-readable data storage media to generate an output indicative of water content as measured by the apparatus 10.

[0105] The phase integrator 720 is implemented either by analog components or digitally, and is provided with the switch 730 for momentarily holding the output signal S3 of the integrator 720 constant, thereby maintaining an output frequency of the signal S4 momentarily constant. Optionally, the oscillator 740 synthesizes a sine-wave for the signal S4 and its output is derived from a stable high-frequency reference, for example derived from a high-stability quartz-crystal oscillator forming a part of the oscillator 720. In operation, the circuit 700 functions in two modes, namely a first excitation mode and a second measurement mode. In the first excitation mode, the oscillator 730 is swept to find a driven resonance frequency coo of the coil 30B and the phase signal c|)K is then adjusted by the microprocessor 800 so that the amplitude of the signal Si is adjusted to its maximum amplitude; this occurs with the switch 760 closed to couple the signal Ss to the excitation coil 30A. When a maximum amplitude for the signal Si is achieved, the coil 30B is resonating at its driven resonance frequency coo.

[0106] Thereafter, the circuit 700 is operated in its second mode, wherein the oscillator 730 is locked at the frequency coo via use of the switch 730 controlled from the microprocessor 800; optionally, the oscillator 740 is adjusted slightly down in frequency to an estimate of its natural undriven resonant frequency con, namely when the coils 30A, 30C are effectively open-circuit. The microprocessor 800, via the switch 760, then pulse excites the excitation coil 30A, and hence excites the coil 30B, using one or more pulses preferably at a frequency con and thereafter opens the switch 760, so that the coil 30B exhibits natural resonance at a frequency con with a decay envelope akin to that illustrated in FIG. 3A and FIG. 3B from which a measure of Q-factor may be derived using the microprocessor 800 to digitize and analyze the signal Si during the decay envelope for example as illustrated in FIG. 3A and FIG. 3B. The first mode followed by the second mode is beneficially implemented within a time period during which the noise source 600 on FIG. 7 is quasi-constant.

[0107] FIG. 9 illustrates a difference between the driven resonance frequency coo of the coil 30B in comparison to the natural resonance frequency con. An amplitude of the signal Si is denoted along an ordinate axis 830 and the driving frequency of the signal Ss is denoted along an abscissa axis 820.

[0108] By repeating the first mode followed promptly by the second mode a plurality of times, a series of Q-factor measurements Qi, ... Qm are obtained during a measurement time period. On account of turbulence noise arising within the tube 20 and electronic noise as aforementioned, the series of Q-factors fall generally within a Gaussian-bell frequency-of-occurrence distribution as illustrated in FIG. 10 as computed by the microprocessor 800. An abscissa axis 900 denotes frequency of resonance as approximately determined from the signal Ss, and an ordinate axis 910 denotes a frequency-of-occurrence of given Q-factors in the sample of Q-factor Qi, ... Qm. denoted by g(Q). In the results illustrated, the microprocessor 800 determines a most representative Q-factor to employ for Equation 1 (Eq. 1 ) by performing analytical processing on the series of measured Q-factors Qi, ... Qm. as will now be described.

[0109] In signal processing performed by the microprocessor 800, lower and upper results denoted by 920, 930 are beneficially ignore, namely truncated, and more central Q- factor results are in a region 940 are employed to derive a reliable measure of the Q- factor to employ for Equation 1 (Eq. 1 ). For example, the upper and lower results 920, 930 correspond to upper and lower quartiles of the Q-factor distribution of FIG. 10. In a first processing method, the results in the region 940 are averaged to derive a representative value of Q-factor at the natural resonant frequency con of the coil 30B. In an alternative second processing method, the Q-factor results in the region 940 are subject to one or more auto-correlations which defines very accurately a best measurement of Q-factor at an auto-correlation peak. By such an approach, the microprocessor 800 of the instrument 10 is capable of determining a representative value for the Q-factor of the coil 30B to extreme precision, which subsequently enables water factions present in the tube 20 in vicinity of the coil 30B to be measure to potentially p.p.m. accuracy using Equation 1 (Eq. 1 ).

[0110] In overview, the circuit 700 is beneficially operable to measure the Q-factor of the coil 30B at natural resonance ®n, and then process corresponding Q-factor measurements to remove stochastic errors which, in turn, enables Equation 1 (Eq. 1 ) to be employed to high accuracy to determine a water faction present within the tube 20, for example potentially to p.p.m. accuracy.

[0111] As an alternative, the circuit 700 is capable of being employed in other manners for measuring Q-factor of the coil 30B. For example, the circuit 700 is adjusted to find a driven peak resonance of the coil 30B at a frequency coo, and then a phase adjustment provided by way of the phase control C|)K is applied by the microprocessor 800 to switch between phase intervals below and / or above resonance of the coil 30B. for example corresponding to -3 dB points, and corresponding Q-factor measurements Qi, ... Qm obtained which are then optionally processed as aforementioned to correct for stochastic influences to derive a final measure of the Cofactor to employ in Equation 1 (Eq. 1 ) for computing the water faction w present in the tube 20. Such continuous non-pulse measurement is illustrated in FIG. 11 where an abscissa axis 950 denotes phase and an ordinate axis 960 denotes amplitude of the signal Si , for example for -3 dB, 0 dB, -3 dB points corresponding to operating control phases of -45°, 0°, +45° respectively, corresponding to excitation frequencies coi, coo, c u respectively; a measure of Q-factor of the coil 30B can be computed readily from the frequencies coi, coo, cou.

[0112] From the foregoing, it will be appreciated that operation of the instrument 10 to measure water content to an accuracy of p.p.m. requires that the coil 30B be appropriately designed together with advanced signal processing techniques being employed to reduce error sources so that a highly reliable and accurate measurement of Q-factor can be derived from which the water fraction w present can be accurately and reliably computed.

[0113] The above-described device can be used to detect properties of fluid flow and solidfluid flows. In particular, detecting and measuring water content is highly useful for many reasons in the drilling technology space. Similarly so is detecting, measuring and calculating water volume fraction. Similarly again, is detecting, measuring and calculating the solid content of a solid-fluid flow. Using a series of manipulations it is possible to obtain these properties.

[0114] These criteria are desirable to have because, in between the time of sampling, the quality of the drilling mud may change. In modern systems that sample only in a seldom manner (daily or a few times a day), the quality may change significantly during periods of non-sampling. As such, this may result in less optimal drilling operation or in unsafe drilling operation. The present invention increases significantly the sampling rate while reducing the workload required to perform that sampling. Real-time and continuous measurement of drilling mud parameters using sensors and automated systems can provide valuable information without the need for frequent manual sampling resulting in a safer and more efficient drilling operation.

[0115] Information can be provided to a control system such as composition of the mud for drilling (the solid-fluid flow). This may include the densities and weights of the constituent parts of the mud. This allows a density of the mix to be known at a starting condition.

[0116] Once the system is operating for a period of time, the mix may change due to inclusion of cuttings from the rock or the like. Rainfall or leaks in the well bore may change the liquid content of the solid-fluid flow. As such, use of the apparatus above enables measurements of the density of the components at a given time during operation.

[0117] A calculation can be performed to assess whether there is a difference between the starting values and the in-use detected values. If there is a greater density, for example, we can conclude that there is excess solid in the mud mix - i.e. that cuttings need to be removed.

[0118] As the properties of the cuttings can be calculated and the water content can be known (described above), it is possible to calculate the water volume fraction.

[0119] Comparing the detected and calculated measurements for solids and water in the mud mix to the known starting conditions allows a user to impact the solid-fluid flow to optimise performance of the drilling operation.

[0120] In particular, typically the mud mix will have been designed to provide an optimal performance in the expected conditions of the wellbore. As such, in the main, it is desirable for the components and composition of the mud to remain as close to starting conditions as possible. These change over time (rainfall, leaks, rock cuttings, drill cuttings etc.) and it is desirable to note these and adjust the mix to optimise performance. The above arrangement provides this flexibility in use by comparing the initial data taken against the data measured during use.

[0121] In an alternate arrangement, without calibration, the water content measuring apparatus described in this invention measures the water content present in the solid-fluid (mud mixture) without any initial user input or calibration performed on the initial solid-fluid. The measured Q-factor of the sensing coil will only relate to, and be affected by, the content (volume fraction) of the conductive medium in the mud mixture (i.e. the water fraction of the mud mixture). This is therefore independent of the fraction of hydrocarbon and solids. The water content can therefore be calculated by means of the described calculating unit. A change in water content in the returning solid-fluid flow (after drilling operation) will then be detected by the water content measured in real-time. Advantages associated with “real-time” measuring have been described in detail above. Broadly they include improved performance efficiency, reduced operating time, greener operation and reduced costs.

[0122] The remaining content in the water measuring apparatus will be the sum of the solid and the hydrocarbon fraction. The sum of water, hydrocarbon and solids tally to the full content of the solid fluid flow. This therefore provides a constant against which the calculations described herein can be performed.

[0123] In another example, by measuring the initial mixture density of the solid-fluid mixture, as well as the known densities and fractions of the components comprising the initial solid-fluid mixture and entering this information into the calculating unit of the water content measuring apparatus for the purpose of calibration, it is further possible to perform calculations of the solid fraction and the hydrocarbon fraction in the solidfluid using the described calculating unit. Said calculations may be performed online. This allows said calculations to be performed remotely to the drilling location. In an example, the drilling may be an off shore operation and the calculations may be performed on shore. Alternatively, both may be on shore but in different locations.

[0124] The calculating unit may be a controller or control circuitry that receives the data from the measurements taken on the solid-fluid flow. This may be on site or off site. The unit may be in communication with a communicating element that sends the data to the calculating unit. The calculating unit calculates the constituent fractions as per the above, using the techniques explained herein.

[0125] It is assumed that the returning solid-fluid mix may have an increase of density, typically because of the addition of well bore cuttings entering the solid-fluid mixture (drilling fluid). This is a common result of the drilling operation. This can then be measured by the water content apparatus provided that the density of the returning solid-flow is measured and entered as an input to the calculating unit.

[0126] By calculating the difference of the known density of the initial mixture of the solidfluid and the measured density of the returning solid-fluid mixture, combined with the water content measurement from the water content measurement apparatus, a change in solid content can be calculated. Since the initial solid content is well established as part of the calibration of the water content measuring apparatus the change in (or increase of) solid content (referred to as cuttings) can be calculated. By measuring the water content and calculating the solid content, it is further possible to calculate the remaining content which can be safely presumed to be hydrocarbon, since the sum of water content, solid content and hydrocarbon content equals 100% of the content inside the measurement volume of the water content measurement apparatus.

[0127] Measurement of the returning solid-liquid mixture can typically be done by means of on-line density apparatus, for example a coriolis measurement apparatus, a radioactive density measurement apparatus or other types of online density apparatus.

[0128] The present system allows for a large number of calculations to be done not necessarily on-site. There is no requirement for man power to be dedicated to taking measurements. This improves the safety of the work of the operators of the equipment. Furthermore, there are efficiency gains as those operators can focus on optimising the operation based on the measurements and calculations performed by the system described herein. This leads to a more consistent performance in the drilling operation, a decreased likelihood of damage to the equipment and therefore an increase in the lifetime of the drilling device. This is therefore an environmentally friendly improvement over previous systems.

[0129] By allowing off site calculations via a communication link between the operation site and the calculation site, less complex computing arrangements are required at site. In this way, maintenance of such computing arrangements is more straightforward and less equipment needs to be transported to the operation site. Again, this reduces the environmental impact of such operations.

[0130] The present system allows for real time, continual measurements of the condition of the solid-fluid drilling mix to be provided to users. This in turn allows users to optimise the performance of the operation. There are many improvements over previous systems disclosed herein. The invention described herein is broadly applicable, but ideally applicable to drilling operations and the like.

[0131] Modifications to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “consisting of”, “have”, “is” used to describe and claim the present invention are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. Numerals included within parentheses in the accompanying claims are intended to assist understanding of the claims and should not be construed in any way to limit subject matter claimed by these claims.

[0132] Further examples of feature combinations taught by the present disclosure are set out in the following numbered clauses:

[0133] First Set of Clauses

[0134] 1. A water content measuring apparatus (10) for measuring water content present in a fluid flow through a tube (20), wherein the apparatus (10) includes a generator (50) for generating in operation an excitation signal (60), a coil arrangement (30A, 30B, 30C) disposed around the tube (20) adapted to be excited into resonance by the excitation signal (60) and interact with the fluid flow through the tube (20), and a signal processor (80) adapted to receive resonance signals from the coil arrangement (30A, 30B, 30C) for determining a water content present within the tube (20), wherein the coil arrangement (30A, 30B, 30C) includes a resonance coil (30B) having a length-to-diameter ratio which is at least 3:1 , wherein the resonance coil (30B) includes at least 10 turns, and wherein the generator (50) generates pulses having a pulse duration much shorter than a period between pulses.

[0135] 2. A water content measuring apparatus (10) according to clause 1 , wherein said generator (50) is arranged to generate the excitation signal to be a temporal series of excitation pulses.

[0136] 3. A water content measuring apparatus (10) according to clause 1 or 2, wherein the tube (20) and its associated coil arrangement (30A, 30B, 30C) are surrounded by an electrostatic shield (40) for screening the coil arrangement (30A, 30B, 30C) when in operation.

[0137] 4. A water content measuring apparatus (10) according to clause 1 , 2 or 3, further including a sensor arrangement (100) for sensing low-frequency electrical conductivity and temperature on an inside wall of the tube (20) and for providing corresponding sensor signals to the data processor (80) for enabling the signal processor (80) to compute the water content within the tube (20) independently of the salinity of the water content.

[0138] 5. A water content measuring apparatus (10) according to clause 1 , 2, 3 or 4, wherein the coil arrangement (30) includes excitation, resonance and pickup coils (30A, 30B, 30C), wherein the excitation coil (30A) is coupled to the generator (50), the pickup coil (30B) is coupled to the signal processor (80), and the resonance coil (30B) is coupled to a tuning capacitor (C) for providing a resonance characteristic which is sensitive to water content within the tube (20). 6. A water content measuring apparatus (10) according to clause 5, wherein the coils (30A, 30B, 30C) are fabricated from at least one of: individually insulated Litz wires, insulated metallic tape.

[0139] 7. A water content measuring apparatus (10) according to any one of the preceding clauses, wherein at least one of the generator (50) and the signal processor (80) are adapted to be spatially remote from the tube (20) and its coil arrangement (30A, 30B, 30C) in operation.

[0140] 8. A water content measuring apparatus (10) according to any one of the preceding clauses, wherein the tube (20) is fabricated from at least one of: polycarbonate polymer, acrylic polymer, PEEK.

[0141] 9. A method of operating a water content measuring apparatus (10) according to any one of the preceding clauses, wherein the apparatus (10) is adapted to monitor conditions for potential hydrate formation within the tube (20), and wherein detection of minute quantities of water present within the tube is indicative of potential early hydrate formation.

[0142] 10. A method of measuring water content present in a fluid flow through a tube (20), characterized in that the method includes:

[0143] (a) using a generator (50) to generate in operation an excitation signal (60) for exciting a coil arrangement (30A, 30B, 30C) disposed around the tube (20) for interacting with the fluid flow through the tube (20); and

[0144] (b) receiving at a signal processor (80) resonance signals from the coil arrangement (30A, 30B, 30C) for determining a water content present within the tube (20), wherein the coil arrangement (30A, 30B, 30C) includes a resonance coil (30B) having a length-to-diameter ratio which is at least 3:1 , wherein the resonance coil (30B) include at least 10 turns; and wherein the pulses have a pulse duration much shorter than a period between pulses. 11. A software product recorded on a machine readable medium, wherein the software product is executable upon computing hardware (80; 800) for implementing a method as claimed in clause 10.

[0145] Second Set of Clauses

[0146] 1 . A method of measuring solid content present in a solid-fluid flow through a tube, comprising: using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solid-fluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a solid content present within the tube; and, providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube.

[0147] 2. A method according to clause 1 , wherein the signal processor is remotely located from the tube.

[0148] 3. A method according to clause 1 or 2, further comprising: on receiving the real-time measurements of solid content present in the solidfluid flow, adjusting a treatment of the solid-fluid flow in the tube.

[0149] 4. A method according to clause 3, wherein adjusting a treatment of the solidfluid flow in the tube comprises at least one of: altering solid removal from, solid input to or fluid input to the solid-fluid flow; and, updating flow speed of the solid-fluid flow.

[0150] 5. A method according to clause 4, wherein altering solid removal from, solid input to or fluid input to the solid-fluid flow comprises: filtering out solids using a kinetic separator wherein the solids relate to the real-time measurements of solid content present in the solid-fluid flow through the tube. 6. A method according to clause 5, wherein the solids relating to the real-time measurements of solid content present in the solid-fluid flow through the tube are cuttings.

[0151] 7. A method according to any of clauses 1 to 6, further comprising performing calibration measurements on a first solid-fluid flow through a tube to obtain a first measurement of solid content present in the solid-fluid flow through the tube; and, comparing real-time measurements of solid content present in the solid-fluid flow through the tube to the first measurement.

[0152] 8. A method according to any of clauses 1 to 7, wherein providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube comprises providing real-time measurements to a user interface located proximally to the tube.

[0153] 9. A method according to clause 8, wherein providing real-time measurements to a user interface comprises providing real-time measurements via an online connection.

[0154] 10. A method according to any of clauses 1 to 9, wherein the method is performed in an automated manner.

[0155] 11. A method according to any of clauses 1 to 10, wherein remotely located control circuitry comprises the signal processor.

[0156] 12. A method according to any of clauses 1 to 11 , wherein the solid-fluid flow is a drilling mix for use in drilling operations.

[0157] 13. A method according to any of clauses 1 to 12, wherein the generator and tube are located off shore and wherein the signal processor is located on shore. 14. A method according to any of clauses 1 to 13, wherein providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube comprises: providing, by the signal processor, continual real-time measurements of solid content present in the solid-fluid flow through the tube.

[0158] 15. A method according to any of clauses 1 to 14, further comprising providing data on initial solid-fluid composition to signal processor.

[0159] 16. A solid content measuring apparatus for measuring solid content present in a solid-fluid flow through a tube, wherein the apparatus includes a generator for generating in operation an excitation signal, a coil arrangement disposed around the tube adapted to be excited into resonance by the excitation signal and interact with the fluid flow through the tube, and a signal processor adapted to receive resonance signals from the coil arrangement for determining a solid content present within the tube, wherein the signal processor is remotely located from the tube.

[0160] 17. A solid content measuring apparatus according to clause 16, further comprising a solid-fluid flow treatment module for applying a treatment to the solidfluid flow in the tube.

[0161] 18. A solid content measuring apparatus according to clause 17, wherein the solid-fluid flow treatment module is arranged to at least one of: alter solid removal from, solid input to or fluid input to the solid-fluid flow; and, update flow speed of the solid-fluid flow.

[0162] 19. A solid content measuring apparatus according to any of clauses 16 to 18, wherein remotely located control circuitry comprises the signal processor.

[0163] 20. A solid content measuring apparatus according to any of clauses 16 to 19, wherein the solid content measuring apparatus is for use in drilling operations. 21 . A solid content measuring apparatus according to any of clauses 16 to 20, wherein the generator and tube are located off shore and wherein the signal processor is located on shore.

[0164] 22. A method of measuring water volume fraction present in a solid-fluid flow through a tube, comprising: using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solid-fluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a water volume fraction present within the tube; and, providing, by the signal processor, real-time measurements of water volume fraction present in the solid-fluid flow through the tube.

[0165] 23. A method according to clause 22, wherein the signal processor is remotely located from the tube.

[0166] 24. A method according to clause 22 or 23, wherein the solid-fluid flow comprises at least a water fraction, a solid fraction and an oil fraction.

[0167] 25. A method according to clause 24, further comprising obtaining data relating to the density of the solid fraction and the oil fraction.

[0168] 26. A method according to any of clauses 22 to 25, wherein on receiving the realtime measurements of water volume fraction present in the solid-fluid flow, adjusting a treatment of the solid-fluid flow in the tube.

[0169] 27. A method according to clause 26, wherein adjusting a treatment of the solidfluid flow in the tube comprises at least one of: altering solid removal from, solid input to or fluid input to the solid-fluid flow; and, updating flow speed of the solid-fluid flow. 28. A method according to clause 27, wherein altering solid removal from, solid input to or fluid input to the solid-fluid flow comprises at least one of: filtering out solids using a kinetic separator wherein the solids relate to the solid content present in the solid-fluid flow through the tube; providing additional water into the solid-fluid flow; and, providing additional solids into the solid-fluid flow.

[0170] 29. A method according to any of clauses 22 to 28, further comprising performing calibration measurements on a first solid-fluid flow through a tube to obtain a first measurement of water volume fraction present in the solid-fluid flow through the tube; and, comparing real-time measurements of water volume fraction present in the solid-fluid flow through the tube to the first measurement.

[0171] 30. A method according to any of clauses 22 to 29, wherein providing, by the signal processor, real-time measurements of water volume fraction present in the solid-fluid flow through the tube comprises providing real-time measurements to a user interface located proximally to the tube.

[0172] 31 . A method according to clause 30, wherein providing real-time measurements to a user interface comprises providing real-time measurements via an online connection.

[0173] 32. A method according to any of clauses 22 to 31 , wherein the method is performed in an automated manner.

[0174] 33. A method according to any of clauses 22 to 32, wherein remotely located control circuitry comprises the signal processor.

[0175] 34. A method according to any of clauses 22 to 33, wherein the solid-fluid flow is a drilling mix for use in drilling operations.

[0176] 35. A method according to any of clauses 22 to 34, wherein the generator and tube are located off shore and wherein the signal processor is located on shore. 36. A method according to any of clauses 1 to 34, wherein the generator and tube are located on shore at a first location and wherein the signal processor is located on shore at a second location, the first location being remote from the second location.

[0177] 37. A computer readable medium comprising computer-implementable instructions for causing a processor to become configured to carry out the method of any of clauses 1 to 15 and / or 22 to 36.

[0178] 38. A water volume fraction measuring apparatus for measuring water volume fraction present in a solid-fluid flow through a tube, wherein the apparatus includes a generator for generating in operation an excitation signal, a coil arrangement disposed around the tube adapted to be excited into resonance by the excitation signal and interact with the fluid flow through the tube, and a signal processor adapted to receive resonance signals from the coil arrangement for determining a solid content present within the tube.

[0179] 39 A water volume fraction measuring apparatus according to clause 38, wherein the signal processor is remotely located from the tube.

[0180] 40. A water volume fraction measuring apparatus according to clause 38 or 39, further comprising a solid-fluid flow treatment module for applying a treatment to the solid-fluid flow in the tube.

[0181] 41 . A water volume fraction measuring apparatus according to clause 40, wherein the solid-fluid flow treatment module is arranged to at least one of: alter solid removal from, solid input to or fluid input to the solid-fluid flow; and, update flow speed of the solid-fluid flow.

[0182] 42. A water volume fraction measuring apparatus according to clause 41 , wherein the solid-fluid flow treatment module is arranged to: filter out solids using a kinetic separator wherein the solids relate to the solid content present in the solid-fluid flow through the tube; provide additional water into the solid-fluid flow; and, provide additional solids into the solid-fluid flow.

[0183] 43. A water volume fraction measuring apparatus according to any of clauses 38 to 42, wherein remotely located control circuitry comprises the signal processor.

[0184] 44. A water volume fraction measuring apparatus according to any of clauses 38 to 43, wherein the water volume fraction measuring apparatus is for use in drilling operations.

[0185] 45. A water volume fraction measuring apparatus according to any of clauses 38 to 44, wherein the generator and tube are located off shore and wherein the signal processor is located on shore.

[0186] 46. A water volume fraction measuring apparatus according to any of clauses 38 to 44, wherein the generator and tube are located at a first location and wherein the signal processor is located at a second location, the first location being remote from the second location.

[0187] 47. A water volume fraction measuring apparatus according to clause 46, wherein the first location is off shore and the second location is on shore.

Claims

CLAIMS1. A method of measuring solid content present in a solid-fluid flow through a tube, comprising: using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solid-fluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a solid content present within the tube; and, providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube, wherein the signal processor is remotely located from the tube.

2. A method according to claim 1 , further comprising: on receiving the real-time measurements of solid content present in the solidfluid flow, adjusting a treatment of the solid-fluid flow in the tube.

3. A method according to claim 2, wherein adjusting a treatment of the solid-fluid flow in the tube comprises at least one of: altering solid removal from, solid input to or fluid input to the solid-fluid flow; and, updating flow speed of the solid-fluid flow.

4. A method according to claim 3, wherein altering solid removal from, solid input to or fluid input to the solid-fluid flow comprises: filtering out solids using a kinetic separator wherein the solids relate to the real-time measurements of solid content present in the solid-fluid flow through the tube.

5. A method according to claim 4, wherein the solids relating to the real-time measurements of solid content present in the solid-fluid flow through the tube are cuttings.

6. A method according to any of claims 1 to 5, further comprisingperforming calibration measurements on a first solid-fluid flow through a tube to obtain a first measurement of solid content present in the solid-fluid flow through the tube; and, comparing real-time measurements of solid content present in the solid-fluid flow through the tube to the first measurement.

7. A method according to any of claims 1 to 6, wherein providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube comprises providing real-time measurements to a user interface located proximally to the tube.

8. A method according to claim 7, wherein providing real-time measurements to a user interface comprises providing real-time measurements via an online connection.

9. A method according to any of claims 1 to 8, wherein the method is performed in an automated manner.

10. A method according to any of claims 1 to 9, wherein remotely located control circuitry comprises the signal processor.

11. A method according to any of claims 1 to 10, wherein the solid-fluid flow is a drilling mix for use in drilling operations.

12. A method according to any of claims 1 to 11 , wherein the generator and tube are located off shore and wherein the signal processor is located on shore.

13. A method according to any of claims 1 to 12, wherein providing, by the signal processor, real-time measurements of solid content present in the solid-fluid flow through the tube comprises: providing, by the signal processor, continual real-time measurements of solid content present in the solid-fluid flow through the tube.

14. A method according to any of claims 1 to 13, further comprising providing data on initial solid-fluid composition to signal processor.

15. A solid content measuring apparatus for measuring solid content present in a solid-fluid flow through a tube, wherein the apparatus includes a generator for generating in operation an excitation signal, a coil arrangement disposed around the tube adapted to be excited into resonance by the excitation signal and interact with the fluid flow through the tube, and a signal processor adapted to receive resonance signals from the coil arrangement for determining a solid content present within the tube, wherein the signal processor is remotely located from the tube.

16. A solid content measuring apparatus according to claim 15, further comprising a solid-fluid flow treatment module for applying a treatment to the solid-fluid flow in the tube.

17. A solid content measuring apparatus according to claim 16, wherein the solid-fluid flow treatment module is arranged to at least one of: alter solid removal from, solid input to or fluid input to the solid-fluid flow; and, update flow speed of the solid-fluid flow.

18. A solid content measuring apparatus according to any of claims 15 to 17, wherein remotely located control circuitry comprises the signal processor.

19. A solid content measuring apparatus according to any of claims 15 to 18, wherein the solid content measuring apparatus is for use in drilling operations.

20. A solid content measuring apparatus according to any of claims 15 to 19, wherein the generator and tube are located off shore and wherein the signal processor is located on shore.

21. A method of measuring water volume fraction present in a solid-fluid flow through a tube, comprising:using a generator to generate in operation an excitation signal for exciting a coil arrangement disposed around the tube for interacting with the solid-fluid flow through the tube; receiving at a signal processor resonance signals from the coil arrangement for determining a water volume fraction present within the tube; and, providing, by the signal processor, real-time measurements of water volume fraction present in the solid-fluid flow through the tube.

22. A method according to claim 21 , wherein the signal processor is remotely located from the tube.

23. A method according to claim 21 or 22, wherein the solid-fluid flow comprises at least a water fraction, a solid fraction and an oil fraction.

24. A method according to claim 23, further comprising obtaining data relating to the density of the solid fraction and the oil fraction.

25. A computer readable medium comprising computer-implementable instructions for causing a processor to become configured to carry out the method of any of claims 1 to 14 and / or 21 to 24.

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