In mining operations, well temperature is an indispensable measurement parameter. Accurate downhole temperature measurement plays a key role in geological and gas well monitoring, especially in heavy-oil thermal recovery processes where downhole temperature changes must be monitored.
In traditional well temperature measurement, infrared thermometers, thermal imaging cameras, temperature sensor arrays and other equipment are used. However, the harsh downhole environment greatly affects the test equipment, easily causing measurement errors, and there are many deficiencies in temperature field measurement. The distributed fiber optic temperature sensing system has the advantages of many measurement points, high accuracy, light weight and tolerance to the harsh downhole environment, and can obtain the temperature field information of the entire area covered by the fiber. At present, distributed fiber optic temperature sensing systems have completed the measurement of downhole temperature fields and other technical parameters, and have broad application prospects in temperature field measurement in heavy-oil thermal recovery.
Technical principle: the distributed fiber optic temperature measurement system (DTS) is based on Raman scattering in optical fiber. The light pulse generated by the laser source interacts with the fiber molecules, producing scattering. The scattered light varies — such as Rayleigh scattering, Brillouin scattering and Raman scattering — among which Raman scattering is closely related to the thermal vibration of fiber molecules and therefore sensitive to temperature, making it usable for temperature measurement. In the fiber, the scattered signal is continuous. By using high-speed signal acquisition technology to measure the time interval between the incident light and the Raman scattered light, the position where the Raman scattered light is generated can be determined. Since Raman scattered light is sensitive to temperature, the corresponding temperature distribution along the fiber can be measured.
Advantages and features: the optical fiber itself is the sensor, transmitting signals and sensing temperature at the same time. The system is easy to install — just lay the cable along the top. Distributed continuous measurement: one fiber measures thousands of temperature points.
