What are the functions of optical fiber sensors?
1. Measuring fluid flow
Due to the intensity, phase, frequency, Characteristics such as wavelength will be modulated by the flow rate during the optical fiber transmission process. Using a certain light detection method to convert the modulation amount into an electrical signal, the flow rate of the fluid can be calculated. This is the working principle of the fiber optic flow meter.
2. Measure the temperature
The distributed optical fiber measurement system uses the temperature effect of optical fiber back-Raman scattering to monitor the temperature field of the optical fiber in real time.
3. Moisture content and density measurement
The transmission power of U-shaped optical fiber changes with the change of the refractive index of the external medium. Light waves serve as information carriers and are mixed with Fluid resistivity, flow pattern and water quality have nothing to do. The optical fiber retention/density sensor based on this principle essentially solves the existing retention rate problems of high water content, no resolution and the application of radioactive substances. For multi-phase fluids such as oil and water, The refractive index of oil, water and gas is different, so the refractive index of the mixed fluid will change with the change of the proportion of oil, water and gas. Therefore, this refractive index modulated optical fiber sensor can not only measure the fluid retention rate, but also measure the fluid density at the same time, and its accuracy is high.
4. Acoustic wave measurement
Seismic waves propagate in different media, and the received seismic wave waveforms will be different. According to different seismic wave shapes, it can be identified Stratigraphic sedimentary sequences and sedimentary structures are used to locate reservoirs, determine channeling, detect casing damage and fractures, perforate layers and determine fluid flow, etc. Downhole fiber optic three-component seismic measurement has high sensitivity and directionality, and can produce high-precision spatial images. It can not only provide near-wellbore images, but also provide images of the formations around the wellbore, with a measurement range of thousands of kilometers. It can withstand harsh environmental conditions, has no moving parts and downhole electronics, can withstand strong shock and vibration, and can be installed in extremely small spaces in complex completion strings.
How to debug optical fiber sensors
Different optical fiber sensors have different debugging methods, but their general operation methods are similar. Here is a brief introduction:
1. Fully automatic calibration
When the workpiece enters the sensitive area of the probe, press and hold the “SET” button for 3 seconds. The sensitivity value will be set and displayed in green
2 , two-point calibration
When the workpiece does not enter the sensitive area, press and hold the “SET” key for three seconds. A sensitive value will be memorized. Then place the workpiece in the sensitive area and press The “SET” key is held for three seconds, and another sensitive value is memorized. When the sensitive value changes from one value to another, the sensor produces a level change.
3. General calibration
General calibration can increase or decrease the sensitivity setting value by pressing the “select button” and the left and right keys.
4. Position calibration
When the workpiece does not enter the sensitive area, press and hold the “SET” key for three seconds, and then place the workpiece away from the probe. At a certain distance, press the “SET” button for three seconds, and a sensitive value will be memorized. Each time the workpiece reaches this position, the sensor level will change.
5. Normally open and normally closed setting
Press the switch selection button on the far right side of the sensor to select whether the internal switch is normally closed or normally closed. open.
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