Dual sensing coils used for RFEC testing of joint casings in oil wells

Abstract

In the detecting of joint casings in oil wells based on remote field eddy current (RFEC) testing, the two penetrations of RFEC on casings (near the transmitter and near the sensing coils) enhance the complicacy of detecting joint casings. The proposed method in this paper is an efficient way to overcome this problem by removing the signal caused by wall’s proximity to the transmitter from the testing signal. In the method, the secondary peaks caused by the transmitter passing over defects need to be removed from the testing signal by employing dual sensing coils firstly. Then the iterations of the testing signals from the dual sensing coils are deduced for the further application of the Wiener deconvolution filter to identify the signal that is used to indicate anomalies. Thirdly, the acquisition of the signal caused by normal wall’s proximity to the transmitter is obtained according to the indicator signal. Lastly, after the both removal of secondary peaks and the signal caused by normal wall’s proximity to the transmitter from the testing signal, the remaining signal can be used to monitor the present joint casings in a well adaptively. The method proposed in this paper is validated via a logging tool, the Kesuo #1 well and ANSYS simulation.