相控线阵声源在套管井中的应用

Application of linear phased array transmitter in cased boreholes

在常规的单极子套管井测井中,由于过套管测量,即使在I、II界面均胶结好的状况下,测量的地层波信息也比较弱。利用相控线阵声源的声束偏转和能量聚焦技术,可大大提高声源的辐射强度和信噪比。采用FEM有限元软件建立了套管井和相控声源的二维模型,计算了点声源和相控线阵声源在套管井中的声压波形。计算结果发现当控制相控线阵阵元间延迟时间使其辐射主声束偏转角满足地层纵波发生临界折射时,可以明显增强地层波幅度,即使在I界面或II界面胶结不好时也可观测到地层波,因此利用相控线阵声源的强穿透性可以帮助我们在套管井胶结不好的情况下探测地层。

The measured formation wave is weak even if the interfaces between Ⅰ and Ⅱ are properly cemented in a cased borehole. Excitation intensity of the source can be strengthened and signal-to-noise ratio be improved by using a linear phased array transmitter whose directivity is controllable and the radiation lobe can be regulated. A model of cased borehole and a linear phase array were built and waveforms of acoustic logging in cased boreholes simulated with the finite element method. The results show that formation waves are clearly enhanced when the steered radiation angle of the linear phase array satisfies the generation condition of the refracted compression wave. The formation information can be detected even under poor bonding conditions. Therefore the technique of linear phase array is useful in the new generation of acoustic welllogging in the cased boreholes.