Application of the fiber-optic distributed temperature sensing for monitoring the liquid level of producing oil wells

In the process of petroleum exploitation, liquid level is a significant parameter to determine reasonable production of oil wells. In this paper a novel optical fiber based method is presented to monitor working liquid level of oil well which contains foam section. This method utilizes the principle of heat transfer variation in different medium and Raman optical scattering. A distributed temperature sensor composed of optical fiber and heating cable is proposed and can be placed in the casing-tubing annulus. According to the sudden variations of measured temperature, the interface of gas-foam, foam-liquid can be identified accurately.