Doppler shift flow meters[ edit ] Another method in ultrasonic flow metering is the use of the Doppler shift that results from the reflection of an ultrasonic beam off sonically reflective materials, such as solid particles or entrained air bubbles in a flowing fluid, or the turbulence of the fluid itself, if the liquid is clean. Doppler flowmeters are used for slurries , liquids with bubbles, gases with sound-reflecting particles. This type of flow meter can also be used to measure the rate of blood flow, by passing an ultrasonic beam through the tissues, bouncing it off a reflective plate, then reversing the direction of the beam and repeating the measurement, the volume of blood flow can be estimated. The frequency of the transmitted beam is affected by the movement of blood in the vessel and by comparing the frequency of the upstream beam versus downstream the flow of blood through the vessel can be measured.
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Last year, when I was asked about the publication date of the 5th edition of my handbook, I answered, Today, my answer is late , and if you ask me next year, my answer might also shift. Because of the explosion of inventions and international competition during the past decade to meet the needs of the new processes from deep-sea drilling to solar hydrogen, from high-density batteries to bitumen and fracking processes, or in automating new nuclear power plants that will operate underwater a design that as-yet exists only on paper.
Here I will give only one example of this advance in only one area of measurement, an area about which, a decade ago I would have said that everything that can be discovered, already has. Well, I was wrong! The area I am talking about is flow measurement. I will describe only one new flow detector, but in future columns I might continue.
Also read related The Latest in Instrument Technology. We Have Entered a New Age The stone age ended, not because we ran out of stone, but because we discovered that bronze tools were better than stone ones. Yet, it will take another generation or two to make this transformation. So what is the challenge for our profession? It is to help both tribes. We can help the smart ones make their green processes cost-effective, and we can help the less intelligent ones make their outdated processes safer and less damaging.
Here I will concentrate on the processes of this second group and will focus only on the oil and gas flow measurement advances that are occurring in fracking and undersea production processes.
Offshore Drilling and Fiber-Optic Flowmeters Oil or natural gas production is a multiphase stream consisting of oil, water, gas and sand.
This is very important for safety reasons. The BP accident was caused by methane blow-out that was discovered too late. You might have also have heard of groundwater contamination because fracking fluid escaped and was not discovered in time. Measurement of the multiphase fluid rate and fluid composition is also important for production efficiency reasons and for zonal allocation of gas production in multi-zone completions.
It also supports identification and localization of injection or production anomalies in real time, determination of well productivity index, reduction of the need for surface well tests and surface facilities, etc. The Old Way In the past, the flow rate and composition of the product was determined by above-ground separators and after separation, the oil, water and gas flows were separately measured Figure 1.
These separators were not only slow often intermittent , but they usually separated only a small bypass stream, which was not necessarily representative. In addition to being slow, this technique was also expensive and took up a lot of space.
Figure 1: Conventional production uses above-ground separation to measure flows of oil, water and gas. This method is slow to determine what the well is producing. Therefore, replacing the separators with in-line subsea multiphase flowmeters Figure 2 was a major advance both in terms of safety and efficiency. They have no moving parts, do not require much maintenance and use sophisticated flow models to interpret the multiple measurements flow, density, pressure and temperature into dynamic multiphase flow and composition determinations.
Fiber-Optic Flowmeters The latest technology in subsea flow metering uses downhole fiber-optic FO cables mounted on the surface of the production pipe. On the right of Figure 3, the FO cable connecting the distributed optical temperature sensors DTS is shown in red, and the cable connecting the distributed optical pressure sensors DPS is shown in blue.
They interrogate multiple pressure and temperature sensors mounted on the outside surface of the production pipe. Figure 3. Left A smart, fiber-optic FO subsea flowmeter has distributed optical pressure detector elements for multivariable, multiphase product flow measurements.
Right The downhole FO cable mounted on the surface of the production pipe has distributed temperature sensor DTS, red and distributed pressure sensor DPS, blue cables serving to interrogate the optical pressure and temperature sensors. Courtesy of Weatherford These optical sensors take advantage of the fact that light in vacuum travels at velocity C, and when it reaches the surface of a substance, it slows to velocity V.
Therefore, the refractive index determines how much the light is bent or refracted back when reaching the interface with a substance.
The refractive index also determines the critical angle of reflection, the angle at which total reflection occurs, and the material starts behaving like a mirror. Therefore, if one is able to prepare an optical filter grating element that transmits all wavelengths except one, a wavelength-specific mirror is obtained.
A fiber Bragg grating FBG is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others.
A fiber Bragg grating can therefore be used to provide inline optical filters, each of which blocks or reflects a different specific wavelength. This system is usually referred to as a Distributed Bragg reflector. Figure 4 shows the structure of a fiber Bragg grating system. The refractive index profile of the fiber core shows the change of the refractive indexes n0, n1, n Thereby, the receiver algorithm "knows" which wavelengh is coming from which optical sensor and can read many sensors at the same time.
Optical Pressure and Temperature Sensors The fluid a mix of gas, water and oil passing through the production pipe travels at some average temperature and pressure. Both of these variables oscillate around some average value. These fluctuations the noise superimposed over the average values of the pressure and temperature of the fluid carry valuable information, because they are caused by eddy currents, gas bubbles, specific gravity changes and composition variations, etc.
The differential pressure between two detectors, for example, is related to the volumetric flow passing through the pipe, while the time it takes for a particular fluctuation to travel from one detector to another relates to the velocity of the fluid.
Figure 5: The cross-section of the fiber optic cable with the fast optical pressure and temperature sensors 1. Courtesy of Weatherford In my next column I will describe other new flowmeter designs, unless in the meanwhile, an even more interesting topic comes up.
He can be reached at liptakbela aol. Related Content.
Gas[ edit ] Gases are compressible and change volume when placed under pressure, are heated or are cooled. A volume of gas under one set of pressure and temperature conditions is not equivalent to the same gas under different conditions. Gas mass flow rate can be directly measured, independent of pressure and temperature effects, with thermal mass flowmeters , Coriolis mass flowmeters , or mass flow controllers. Liquid[ edit ] For liquids, various units are used depending upon the application and industry, but might include gallons U. Primary flow element[ edit ] A primary flow element is a device inserted into the flowing fluid that produces a physical property that can be accurately related to flow.
The Incredible Fiber-Optic Flowmeter
Last year, when I was asked about the publication date of the 5th edition of my handbook, I answered, Today, my answer is late , and if you ask me next year, my answer might also shift. Because of the explosion of inventions and international competition during the past decade to meet the needs of the new processes from deep-sea drilling to solar hydrogen, from high-density batteries to bitumen and fracking processes, or in automating new nuclear power plants that will operate underwater a design that as-yet exists only on paper. Here I will give only one example of this advance in only one area of measurement, an area about which, a decade ago I would have said that everything that can be discovered, already has.
Ultrasonic flow meter
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