2016 套管井中泄漏弯曲型Lamb波声场的模拟与分析_陈雪莲.pdfVIP

35 1 Vol.35, No.1 2016 2 Technical Acoustics Feb., 2016 Lamb (()266555) Lamb (Lamb ) 33°Lamb Lamb Lamb Lamb Lamb Lamb P631.51P631.81 A 1000-3630(2016)-01-0038-06 DOI 10.16300/ki.1000-3630.2016.01.009 Simulation and analysis of leaky flexural-Lamb wavefield in a cased wellbore CHEN Xue-lian, LI Jian-sai, TANG Xiao-ming, LI Sheng-qing, SU Yuan-da (School of Geosciences Technology, China University of Petroleum, Qingdao 266555, Shandong, China) Abstract: The lowest order antisymmetric mode of leaky Lamb waves (hereinafter referred to as Lamb flexural mode) has been used for cement evaluation because it is sensitive to the acoustic parameters of media behind the casing (espe- cially the low-impedance and slow cement). With the real-axis numerical integration method and a multi-layered media model, this paper simulates the full waveforms launched and received by directional transmitting and receiving trans- ducers of finite sizes as well as the leaky flexural-Lamb wave field in a cased wellbore. The results suggest that the Lamb flexural mode is mainly excited in casing, when the angle of incidence approximately equals 33 degree. Simulated time snapshots present that the Lamb flexural mode propagates inside the steel casing while leaking bulk waves, whose ve- locities are lower than the flexural mode’s velocity, in the upper water layer and inside the water or cement annulus below the casing. For the slow cement, whose compressional velocity and shear velocity are both lower than that of flexural mode, existing beh