Pressure management system for sensors

A pressure management system for sensors is provided. The system includes a sampling assembly. The sampling assembly is configured to hold a first portion of a test fluid. Further, the system includes at least one sensor disposed proximate to the sampling assembly. The sensor is configured to determine at least one property of the test fluid. The system also includes a housing that is disposed around the sampling assembly. The housing defines a fluid chamber that houses a balancing fluid. Furthermore, the system includes a flexible device disposed in the fluid chamber that draws a second portion of the test fluid. The flexible device is configured to balance pressure exerted by the test fluid on the sampling assembly by exerting pressure on the balancing fluid with the second portion of the test fluid.

BACKGROUND

The present invention relates generally to sensors, and more particularly, to a system for management of pressure being exerted on sensors in harsh environments.

Wells are being used currently to utilize resources available under the surface of the earth. Natural resources such as oils, minerals, and gases are obtained through these wells with the help of pumps and valve configurations. The pressure present in the wells enables natural resources to be pulled up to the surface of the earth from where the natural resources are transported to refineries or storage containers. Pump and valve configurations are also utilized in other systems such as desalination plants, wastewater management systems and the like. Since the equipment required to produce output from these systems are located deep under the surface of the earth, it becomes difficult to check their condition periodically. Sensors are placed alongside such equipment to monitor their health and provide well managers with adequate time to fix ill-functioning equipment.

Sensing systems are also deployed in systems such as separators, desalters, wastewater management systems, and oil quality control systems to analyze compositions of the fluid being extracted from under the surface of the earth. Further, flow meters are also installed in wells to analyze the flow dynamics of available resources. Chemicals are also injected into the wells to protect them from corrosion, and ill-effects caused by foam and other such materials. Injection of chemicals in wells is generally carried through chemical-injection management systems that are controlled using flow meters.

It has been observed that operating efficiency of sensing systems, such as flow meters, and solenoid-coil based sensors deteriorates with increase in operating temperature and pressure. Temperature effect on sensing systems is compensated with the use of insulation material in the sensing system vicinity.

However, for pressure compensation the use of isolation layers does not yield the same results. It has been observed that the response from sensing systems is affected in the presence of metallic absorption shields. To avoid the metallic shield to interfere with the response from sensing systems, sensing systems are wrapped in radio-frequency (RF) absorbing materials and shielded. However, RF absorbing materials that can be utilized in deep environments where the operating frequency is less than 10 MHz are not easily available.

Hence, there is a need for a system that compensates for pressure exerted on sensing systems deployed in harsh environments.

BRIEF DESCRIPTION

In one embodiment, a system including a sampling assembly is provided. The sampling assembly is configured to hold a first portion of a test fluid. Further, the system includes at least one sensor disposed proximate to the sampling assembly. The sensor is configured to determine at least one property of the test fluid. The system also includes a housing that is disposed around the sampling assembly. The housing defines a fluid chamber that houses a balancing fluid. Furthermore, the system includes a flexible device disposed in the fluid chamber that draws a second portion of the test fluid from the first portion of the test fluid. The flexible device is configured to balance pressure exerted by the test fluid on the sampling assembly by exerting pressure on the balancing fluid with the second portion of the test fluid.

In another embodiment, a system including a vessel system is provided. The vessel system is configured to hold a test fluid. The system further includes a sampling assembly that is coupled with the vessel system. The sampling assembly is configured to draw a first portion of the test fluid from the vessel system. The system also includes at least one sensor that is disposed proximate to the sampling assembly. The sensor is configured to determine at least one property of the test fluid. Furthermore, the system includes a pressure balancing device configured to protect the at least one sensor from pressure change. The pressure balancing device includes a housing and a flexible device. The housing is disposed around the sampling assembly and is configured to define a fluid chamber that houses a balancing fluid. The flexible device is disposed in the fluid chamber and is configured to draw a second portion of the test fluid from the first portion. The flexible device is configured to balance pressure exerted by the test fluid on the sampling assembly by exerting pressure on the balancing fluid with the second portion of the test fluid.

DETAILED DESCRIPTION

Reference will be made below in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals used throughout the drawings refer to the same or like parts.

Sensing systems are utilized in wells that are dug to recover natural resources from under the surface of the earth. Sensing systems are utilized to sense a plurality of properties pertaining to equipment installed to recover the natural resources. Sensing systems are also installed to analyze the resources being recovered from the well. Sensing systems determine a plurality of properties pertaining to the resources. The properties being determined by the sensing systems include, but are not limited to, temperature, composition of the emulsion, level of a particular component in the composition and the like. Similarly, sensing systems are utilized to analyze fluids being utilized in systems such as waste water management systems, or desalination systems. To utilize the sensing systems excitation signals are provided to the sensing systems. A response of the sensing systems to the interaction between the excitation signal and the fluid is captured to determine one of the plurality of properties. To allow for the excitation signal to interact with the fluid, the fluid is drawn from storage vessels and stored in sampling assemblies. Examples of storage vessels include, but are not limited to desalters, biochemical reactors, containers, and others known in the art. Samples of the fluid are drawn from the vessels with the help of sampling assemblies such as try-line assembly, or a swing arm assembly, or a dipstick. The sensing systems are placed proximate to the sampling assemblies to generate the response required for analysis and determination. In certain cases, the sensing systems include solenoid coil based sensors. The solenoid coil based sensors are wound around the sampling assembly. One coil from the sensing system is provided with the excitation signal and the response is collected from another coil. The pressure exerted by the environment on the sensing system, when the sensing system is disposed with the sampling assembly, can cause the sensing system to malfunction. A pressure management system, as will be described in greater detail in forthcoming paragraphs, provides for balancing the pressure being exerted on the sensing system. The pressure management system includes a housing. The housing, typically, is of cylindrical shape and may be defined by a sheet of metallic material. The housing defines a fluid chamber in which balancing fluid is disposed. The sampling assembly, that holds test fluid from the vessel, is enclosed within the housing. A flexible device is disposed in the fluid chamber to be proximate to the sampling assembly. The housing is sealed from both sides with end caps. One of the end caps includes a plurality of apertures to couple exit ports of the vessels with input ports of the sampling assembly and also provide for input ports to the housing to allow for balancing fluid to enter the fluid chamber. The volume of the housing is filled with the balancing fluid. During operation, the test fluid is simultaneously made to enter the sampling assembly and the flexible device. The test fluid enters both, the flexible device and the sampling assembly, through a connecting device such as a tee-connector. When the test fluid enters the flexible device, the flexible device expands and the pressure exerted by the entering test fluid is distributed to the walls of the housing through the balancing fluid. The sampling assembly thus sees a simple flow channel of the test fluid without experiencing the high pressures at which the test fluid enters the housing. The system for pressure management is explained in greater detail in the following paragraphs.

FIG. 1illustrates a schematic view of a typical sensing system deployed to measure at least one property of the test fluid. The sensing system100typically includes a sampling assembly102, and a sensor assembly104. The sampling assembly102, as shown inFIG. 1, receives test fluid from vessels that are configured to store and process fluid extracted from under the surface of the earth. Nonlimiting examples of vessels include reactors, chemical reactors, biological reactors, storage vessels, containers, and others known in the art. The fluid present in the vessel may, for example, be a mixture of oil, water, and a demulsifier. A portion of the fluid is obtained from the vessel and stored in the sampling assembly102as the test fluid. The test fluid is drawn from the vessel using multiple configurations such as try-line assembly, dipstick assembly, or a swing-arm assembly. The sampling assembly102may be at least one output conduit of these configurations that are used to draw the test fluid from the vessel. Exemplary embodiments of vessels with configurations to draw the test fluid are explained in greater detail inFIGS. 2 and 3.

According to certain embodiments, the sampling assembly is a baffle tube. The sampling assembly102may be made of material that is resistant to fouling such as Polytetrafluoroethylene (PTFE), a synthetic fluoropolymer of tetrafluoroethylene. The sensor assembly104is placed proximate to the sampling assembly102such that walls of the sampling assembly102separate the sensor assembly104from the test fluid present in the sampling assembly102.

The sensor assembly104may be designed to determine at least one of a plurality of properties associated with the test fluid. The plurality of properties include, but are not limited to, temperature, pressure, composition, level of a particular component in the composition and the like. According to one embodiment, the sensor assembly104configured to determine a composition of the test fluid includes a solenoid-coil based assembly. The sensor assembly104, as illustrated inFIG. 1, is a coil-based sensor.

The sensor assembly104, as illustrated inFIG. 1, includes a primary coil106, and at least one secondary coil108. The primary coil106and the secondary coil108, according to certain embodiments, are wound around a holding area of the sampling assembly102. The sampling assembly102acts as a layer of dielectric material between the test fluid and the sensing assembly104. The layer of dielectric material plays an important role in creating a response at the secondary coil108.

The primary coil106and the secondary coil108are made from metallic wires. According to certain embodiments, number of turns of the primary and secondary coils are selected based on a desired range of response that the sensor assembly104is expected to cover. The primary and secondary coils106and108are made from metallic material such as copper, and aluminum. The primary coil106and the secondary coil108, according to one embodiment, are disposed proximate to each other. In the illustrated embodiment, the primary coil106encapsulates the secondary coil108.

The primary coil106and the secondary coil108are further coupled with a capacitive element107to create an inductive capacitive resonant circuit from the primary and secondary coil106and108. The primary coil106is further coupled with a power source that provides excitation signals. The secondary coil108, according to certain embodiments, is coupled with an analyzer. The secondary coil108and the analyzer may be coupled through wired or wireless communication channels. The analyzer, according to certain embodiments, is an impedance analyzer. According to certain embodiments, the analyzer is at least one of dual channel vector voltmeter, or a vector network analyzer. The analyzer is configured to measure responses induced in the secondary coil108when excitation signal is provided to the primary coil106. The properties determined by the analyzer include, among others, changes in capacitance, inductance, and resistance of the secondary coil108, and the resonant frequency of the secondary coil108. The properties measured by the analyzer are communicated to a processing sub-system through wired or wireless communication channels. The processing sub-system is configured to determine a relationship between the parameters determined by the analyzer and one of a plurality of properties associated with the test fluid present in the sampling assembly102.

According to certain embodiments, the sensor assembly104includes more than one secondary coil108. Multiple secondary coils are coupled to the primary coil106. Each secondary coil is configured to respond to different components present in the test fluid present in the sampling assembly102.

FIG. 2is a schematic diagram of an embodiment of a desalter. The sensor assembly104, as illustrated inFIG. 1is disposed in the desalter to determine at least one property of the fluid stored in the desalter. The desalter200is an embodiment of a vessel in which embodiments of the present technique may be disposed. The desalter200includes a desalter vessel202. Fluid such as raw oil enters the desalter200through input204and is mixed with water from water input206. The combination of the fluid and water flows through mixing valve208and into the desalter vessel202. The desalter200includes a treated oil output210and a wastewater output212. Disposed within the desalter vessel202are an oil collection header214and a water collection header216. Transformer218and transformer220provide electricity to top electrical grid222and bottom electrical grid224. Disposed between top electrical grid222and bottom electrical grid224are emulsion distributors226.

In operation, crude oil mixed with water enters the desalter vessel202and the two fluids are mixed and distributed by emulsion distributors226thereby forming an emulsion. The emulsion is maintained between the top electrical grid222and the bottom electrical grid224. Salt containing water is separated from the oil/water mixture by the passage through the top electrical grid222and bottom electrical grid224and drops towards the bottom of the desalter vessel202where it is collected as waste water from the wastewater output212.

Control of the level of the emulsion layer and characterization of the contents of the oil-in-water and water-in-oil emulsions is important in the operation of the desalter200. Determination of the level of the emulsion layer may be accomplished by placing the sensor assembly proximate to a sampling assembly such as a try-line assembly228coupled to the desalter vessel202. The sensor assembly104is disposed on at least one try-line output conduit230. The sensor assembly104may be coupled to a data collection component232. In operation, the sensor assembly104may be used to measure the level of water and the oil and to enable operators to control the process. The try-line assembly228may be a plurality of pipes open at one end inside the desalter vessel202with an open end permanently positioned at the desired vertical position or level in the desalter vessel202for withdrawing portions of the fluid in the vessel202such that test fluid is obtained. There are generally a plurality of sample pipes in a processing vessel, each with its own sample valve, with the open end of each pipe at a different vertical position inside the unit, so that test fluid can be withdrawn from a plurality of fixed vertical positions in the unit. Another approach to drawing portions of the fluid in the vessel202is to use a swing arm sampler. A swing arm sampler is a pipe with an open end inside the desalter vessel202typically connected to a sampling valve outside the unit. It includes an assembly used to change the vertical position of the open end of the angled pipe in the desalter200, by rotating it, so that test fluid can be withdrawn (or sampled) from any desired vertical position.

Another method to measure the properties of the fluid in the vessel is to dispose at least one sensor assembly104on a dipstick234. The dipstick234may be a rod with a sensor assembly104that is inserted into the desalter vessel202. Measurements are made at a number of levels. Alternately, the dipstick234may be a stationary rod having a plurality of multiplexed sensor assemblies104. The sensor assembly104may be coupled to a data collection component232that collects data from the various readings for further processing.

Another embodiment of a fluid processing system where the sensor assembly104may be disposed is a separator300illustrated inFIG. 3. The separator300includes a separator vessel302having an input conduit304. Fluid such as crude oil flowing from input conduit304impacts an inlet diverter306. The impact of the crude oil on the inlet diverter306causes water particles to begin to separate from the crude oil. The crude oil flows into the processing chamber308where it is separated into a water layer310and an oil layer312. The crude oil is conveyed into the processing chamber308below the oil/water interface314. This forces the inlet mixture of oil and water to mix with the water continuous phase in the bottom of the vessel and rise through the oil/water interface314thereby promoting the precipitation of water droplets which are entrained in the oil. Water settles to the bottom while the oil rises to the top. The oil is skimmed over a weir316where it is collected in oil chamber318. Water may be withdrawn from the system through a water output conduit320that is controlled by a water level control valve322. Similarly oil may be withdrawn from the system through an oil output conduit324controlled by an oil level control valve326. The height of the oil/water interface may be detected using a try-line assembly328having at least one sensor assembly104disposed in a try-line output conduit330and coupled to a data processor332. Alternately a dip stick334having at least one sensor assembly104coupled to a processor336may be used to determine the level of the oil/water interface314. The determined level is used to control the water level control valve322to allow water to be withdrawn so that the oil/water interface is maintained at the desired height.

When the sensor assembly104is disposed on the try-line assembly, or the swing-arm assembly, or the dipstick as illustrated inFIGS. 2 and 3, the pressure exerted by the fluid present in the vessels such as the separator vessel and the desalter vessel may cause damage to the sensor assembly104. The try-line output conduit, the swing-arm sampler, or the dipstick may be disposed within the pressure management system, as illustrated inFIG. 4, to protect the sensor assembly104from damages caused by the fluid pressure.

FIG. 4illustrates a pressure management system400for a sensor assembly104to be disposed in fluid vessels such as desalters, and fluid separation vessels. The pressure management system400includes a housing402. The housing402, typically, is of cylindrical shape. In one embodiment, one end of a sheet made from metal is joined to another end of the sheet to define a hollow cylindrical structure. The hollow cylindrical structure may be utilized as the housing402. The hollow portion of the housing402defines a fluid chamber404. The fluid chamber404is configured to house a balancing fluid406. Sampling assembly408, on which the sensor assembly104is disposed is enclosed within the housing402. A flexible device410is also disposed within the housing402. The sampling assembly408may be a tube configured to hold a test fluid. The test fluid may be a portion of fluid stored in the fluid vessels. For example, the test fluid may be an oil-water emulsion stored in a desalter as illustrated inFIG. 3. The sampling assembly408may be, in other embodiments, an output conduit of sampling assembly configurations such as the try-line assembly, or the swing arm sampler as illustrated inFIGS. 2 and 3. In some other embodiments, the sampling assembly408may be a dipstick, such as dipstick234, which is configured to be placed in the fluid. The sampling assembly408is configured to hold a first portion of the test fluid. In some embodiments, the sampling assembly408is surrounded by protective material424such as thermal insulation material, or shock absorption material.

The flexible device410is configured to expand and contract on application of pressure. The flexible device410is configured such that it is sealed from all sides except one, thus allowing for an enclosed space to be defined. The flexible device410, according to certain embodiments, includes a diaphragm that includes flexible material. According to certain other embodiments, the flexible device410is a bellow made from metallic material.

The pressure management system400further includes at least one end cap. In the illustrated embodiment, the pressure management system400includes end caps412and414. The end caps412and414are placed on the open ends of the housing402such that the housing402is sealed from all ends. Further, the sampling assembly408and the flexible device410are coupled with at least one of the end caps412and414. In the illustrated embodiment, the sampling assembly408and the flexible device410are sealed with the end cap412. The end cap412includes a plurality of apertures416. The apertures416are configured to couple the sampling assembly408with the fluid vessel. For example, the sampling assembly408may be coupled with at least one of the try-line output conduits230. The test fluid drawn from the fluid vessel is configured to enter the sampling assembly408through the apertures416coupled with the sampling assembly408. The open end of the flexible device410is also coupled with one of the apertures416in the end cap412. According to certain embodiments, O-ring seals are fitted on those ends of the housing402that are coupled with the end caps412and414.

The end cap412further includes a connecting device418. According to certain embodiments, the end cap412may be manufactured to have a built-in connecting device418. In other embodiments, the connecting device418may be retrofitted into the end cap412. The connecting device418is coupled with an input port of the fluid vessel on one side, and the apertures416that are coupled with the sampling assembly408and the flexible device410on the other side. The connecting device418is configured to divert the first portion of the test fluid to the sampling assembly408and a second portion of the test fluid into the flexible device410. In the illustrated embodiment, the connecting device418is a tee-connector.

The end cap414also includes a plurality of apertures420that are configured to couple the sensor assembly104with external power source and processing systems. One of the apertures420is also configured to drain the fluid chamber404in the housing402. The sampling assembly408is fixed to the end cap414and is coupled with one of the plurality of apertures420to allow for the first portion of the test fluid to leave the sampling assembly408.

The end caps412and414are coupled with each other through a plurality of rods422that are placed along the length of the housing402. In some embodiments, a protective layer may be disposed between the plurality of rods422to reduce the impact of pressure changes on the housing402.

During operation, when the fluid from the fluid vessel enters the connecting device418, a first portion of the test fluid enters the sampling assembly408and a second portion of the test fluid simultaneously enters the flexible device410. The second portion of the test fluid that enters the flexible device410causes the flexible device410to expand thereby exerting pressure on the balancing fluid406. The differential pressure created by the entering test fluid in the sampling assembly408is thus distributed across the walls of the housing402. The sampling assembly408thus experiences a simple flow of the first portion of the test fluid while the pressure being exerted by the test fluid is distributed to the walls of the housing402.

In case of a sensor assembly104failure or any other operational problems with the pressure management system400, the balancing fluid406is withdrawn from one of the plurality of apertures420present in the end cap414.

The balancing fluid406is a fluid selected based on the test fluid entering the sampling assembly408. In one embodiment, the balancing fluid406is a mineral oil based fluid. The balancing fluid406is selected such that the balancing fluid406does not interrupt with the operations of the sensor assembly104.