| Pressure and temperature are important parameters in the exploration and development of oil and gas resources.Real-time monitoring of pressure and temperature is required during the exploration,drilling,and production stages of oil and gas wells.As oil and gas resources are increasingly utilized,exploration and development activities are reaching greater depths,resulting in rising downhole pressure and temperature.Electrical sensors no longer offer clear advantages over traditional temperature sensors.The advancement of temperature and pressure sensors in oil and gas wells is crucial not only for production and development purposes,but also for cost reduction.This paper proposes a temperature and pressure sensor that utilizes fiber Bragg grating.The sensor is designed to withstand the harsh conditions of underground oil and gas environments and can operate for extended periods of time in high-temperature and highpressure conditions.The focus of this paper is on the design of temperature and pressure sensors for oil and gas wells.The main research contents are as follows:(1)This paper provides a comprehensive overview of the current research on fiber Bragg grating temperature and pressure sensors.It presents a summary of the packaging structures commonly used for these sensors,explains the sensing principle of fiber Bragg grating sensors,and analyzes the design concepts of underground sensors for oil and gas applications.The subterranean environment of oil and gas extraction is characterized by extreme conditions,such as high temperatures,high pressures,corrosive surroundings,and electromagnetic interference generated by various instruments.(2)The design scheme of fiber Bragg grating temperature and pressure sensor suitable for oil and gas underground environment is presented.The sensor uses high temperature and corrosion resistant femtosecond pulse laser written fiber Bragg grating as the basic sensing element,uses stainless steel material as the packaging material of the sensor,and uses low temperature glass solder to fix the fiber Bragg grating.The design method can work at the temperature of 200℃.(3)A temperature and pressure sensor has been designed based on a combination of a diaphragm and lever structure.This sensor has the characteristics of a small volume and a large range.The sensor utilizes a diaphragm structure and an eccentric lever structure.The diaphragm serves as the direct bearing element,and the displacement resulting from deformation is amplified by the lever structure.It has been found that the sensor’s sensitivity can be increased by placing the force transfer rod in the eccentric position of the diaphragm within the asymmetric partial structure.The diameter of the structure is 20 mm.The sensor has a pressure range of 0-40 MPa,a pressure sensitivity of 29.8 pm/MPa,a linearity of 0.9999,and a repeatability of0.01%.The sensor has a temperature measuring range of 50-200℃ and a sensitivity of 32.7pm/℃.The sensor has high linearity,repeatability and stability.(4)This paper investigates a temperature and pressure sensor that utilizes a diaphragm and beam structure in combination.The device exhibits features such as compact size,extensive coverage,convenient packaging,and quasi-distributed measurement capabilities.The theoretical displacement of the structure exhibits a 4.9-fold increase compared to the diaphragm deformation.The structure’s effective diameter measures 20 millimeters.The sensor’s range spans from 0 to 40 MPa,with a measurement range of 0-40 MPa,a sensitivity of 24.1 pm/MPa,a linearity of 0.9997,and a repeatability of 0.38%.The temperature range is 25-200℃,while the sensitivity of the system is measured at 31.2 pm/℃.The theoretical specifications of the enhanced pressure sensor include a range of 0-100 MPa and a sensitivity of 12.7 pm/MPa.Notably,the temperature measurement range and sensitivity remain unaltered.The temperature and pressure sensor presented in this paper is appropriate for monitoring temperature and pressure. |
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