Research On Technology Of Glueless Fiber Optic Acceleration Sensor

At present,our country's consumption energy is still dominated by fossil energy.The total consumption of oil and gas resources is increasing year by year,but the exploitation is difficult to improve,and it is extremely dependent on imports.In such a situation where supply exceeds demand,it is urgent to improve the exploration capability of oil and gas resources and the exploitation of unconventional oil and gas resources.Seismic wave exploration is one of the highly efficient and precise exploration technologies.Its technical principle is to invert the geological structure by receiving and analyzing the vibration signals from the stratum.Therefore,the detection performance of geophones affects the exploration level of oil and gas resources.Since seismic waves are mainly low-frequency signals after being filtered by the earth,and some geophones need to work in high-temperature wells,the geophones need to have good low-frequency response characteristics and high temperature resistance.In this paper,based on the fiber Bragg grating(FBG)sensing principle,a high-reliability FBG acceleration sensor that can be used for a long time in high temperature environment of the well is developed.The sensor uses the symmetrical inclined cantilever beam on both sides to produce micro-bending under vibration excitation to make the FBG deform.The magnitude of the vibration signal can be obtained by analyzing the change of the center wavelength of the FBG.After theoretical analysis and parameter optimization,the sensor has achieved a good low-frequency response.In addition,in order to improve the stability of the acceleration sensor in the harsh environment such as downhole,the FBG is packaged by glass welding technology,so that the packaged sensor can overcome the adhesion creep and maintain stable sensing performance in a long-term high temperature environment.At the same time,the sensor can quickly and accurately respond to the thermal shock and can also ensure that the packaging performance remains unchanged under the cyclic thermal shock,so as to maximize the measurement accuracy of the sensor in actual use.The research results show that the operating frequency range of the acceleration sensor is from 0.1 Hz to 30 Hz,the measurement sensitivity is 290 pm/g,the maximum lateral interference degree is 3.6%,and the maximum operating temperature is not less than 250 ?.It meets the frequency band requirements and temperature resistance requirements of acceleration sensors in the field of oil and gas resource exploration.