The Design of the FBG Sensor System for Strain Monitoring Specific to the Key Stratum in Casing Annulus

Abstract

Due to the tube is suffering deformation and damage by a series of factors, such as external force, chemical corrosion etc. The production of oil and the oil wells' service life is directly affected. As the number of casing damage is increasing year by year, the casing damage especially the casing inspection of key layer has become the focus of oilfield development process. The height of critical layer is usually about 5m, so the author puts forward that it's much more accurate to use the distributed FBG sensor as the short distance measurement method to guarantee the precision, and coupled with the traditional temperature compensation method of FBG strain monitoring. With a special installation process and the application of 40-Caliper logging tool to get the FBG' s azimuth, we get real-time strain data in the process of installing casing pipe. This paper analyzes the variation of value of the casing strain in each installation stage, the theoretical calculation results are basically the same with the data got by XMAC logging method. This proves the reliability of the distributed casing deformation monitoring system which is specifically used for the key layer of casing annulus.