Research On Detection And Positioning Technology Of Armoured Cable Outside Casing

As digital transformation progresses,dynamic parameters of oil and gas production are captured by installing permanent sensors downhole.The optical fiber sensor is directly placed outside the casing,which can obtain the original information of the outer casing layer in real time and permanently,providing an important basis for monitoring the state of oil and gas exploitation,analyzing the distribution of remaining oil and timely adjusting the production plan.For oil and gas Wells with optical cables laid outside the casing,the optical cables outside the casing should be accurately detected and positioned before perforating in order to ensure that the optical cables will not be damaged during perforation and avoid optical fiber perforation.To avoid the problem of optical fiber perforation,This paper mainly studies the circuit design,development and experiment of the detection and positioning system of outer armored cable.Firstly,the detection method of cable outside casing based on TEM is studied.Based on the analysis of the structure characteristics and cable layout,the transient electromagnetic downhole detection technology is applied to the detection of cable outside the cable.Considering the requirement of circumferential resolution in optical cable detection,a detection method based on transient electromagnetic ring array is proposed,which can achieve accurate location acquisition and identification of optical cable outside the casing.On this basis,the detection and positioning system of sleeve armored optical cable based on transient electromagnetic array is studied,the excitation circuit of transient electromagnetic array and array acquisition circuit is designed,and a multi-channel array acquisition circuit structure based on chrysanthemum chain is proposed.The system can realize the rapid and high precision acquisition of 32 sensor arrays,and the design operating temperature is 175℃.It can ensure normal operation in high temperature and high-pressure gas well.After obtaining the data of the receiving array,the data is adjusted and processed to improve the signal-to-noise ratio,and the optical cable path is identified and imaged according to the changes of the processed data.Finally,indoor and field experiments were carried out to compare and analyze the detection effect of the casing,collar,optical cable and other components respectively.Combined with the attitude positioning of the detection instrument,the position deviation of the optical cable was verified.The experimental results show that the detection and positioning system of armored fiber optic cable outside casing can effectively identify the fiber optic cable outside casing,and realize the positioning of the fiber optic cable through the ring array,which can provide an important basis for avoiding fiber optic perforation in oil and gas Wells.