声波测井圆环阵指向性设计

Directivity Design for Acoustic Logging Circlular Array

常规的单极子发射声波没有指向性,能量损失过多,用模态分解的方法设计出合适的阵列加权系数,就可以控制圆环阵的辐射主瓣角宽和旁瓣级,以利于在任意地层中有效激励滑行纵横波和减少能量损失。通过comsol有限元软件对圆环阵声波辐射数值模拟的例子,分析了圆环阵的辐射指向性对声波测井中各种模式波的接收幅度和到达时间的影响。结果表明,只要在圆环阵的各阵元上施加合适延迟时间合适幅度的激励信号,就能根据不同的实际情况设计出各种主声束的宽度和方向。圆环阵的使用可明显地改善声波测井的测量质量,为声波辐射器在石油勘探中的应用提供一定理论依据。

Conventional monopole has no sound directivity, resulting in too much energy loss. The suitable array weighting coefficientit is designed by the method of modal decomposition, which can control the circlular array radiation angle of main lobe width and sidelobe level, and facilitate to excite effectively and reduce the energy loss of p-wave. By the finite element software comsol to circlular array acoustic radiation examples of numerical simulation, the influence of the circlular array radiation directivity on all kinds of mode wave receiving amplitude and arrival time in acoustic logging is analyzed. Results show that the width and direction of all kinds main beam can be designed according to the different actual situation as long as the excitation signal with appropriate delay time and amplitude is applied to each array element of the circlular array. The use of circular array can obviously improve the measuring quality of acoustic logging and provide certain theory basis for the application of acoustic transmitter in oil exploration.