宽带相控线阵声源在套管井外地层辐射声场的指向性

Directivity of acoustic fields in the formation excited by the broadband linear phased-array source through casing

套管井中的声传播涉及到波在柱状多层介质中的传播问题。通过数值计算对比了宽带相控线阵声源在套管井外均匀地层中产生的纵横波声场的指向性。结果表明,在任意胶结状况下,均可实现向套管井外地层定向辐射纵横波的技术;与地层中纵波的传播特征不同的是在主瓣偏转角方向横波幅度随着偏转角的增大逐渐增加,且在主瓣辐射方向的横波幅度受套管井胶结状况的影响较纵波小;采用玻璃钢套管代替钢套管,会进一步减弱地层声场受胶结状况的影响,这有利于实现在套管井外地层较大范围内的精确定向辐射声波的技术。

The application of linear phased-array transmitter in a cased borehole relates to wave propagation in cylindrical multilayered medium. Aimed at the engineering requirements of measurement of formation acoustic properties through casing, acoustic fields of near-borehole formation excited by the broadband linear phased- array source（LPAS） in cased boreholes with different bonding conditions were simulated using the real axis integration method. Numerical results show that the main lobe steered angle in the formation can be controlled by adjusting the delay time between the neighboring array elements in both well-bonded or poorly-bonded conditions. It is different from the compressional wave radiation pattern that the shear wave amplitude in the steered direction can be strengthened gradually with the main lobe steered angle increasing and the radiated energy to the formation is affected little by cemented conditions. The application of the glass case with lower acoustic impedance can decrease the influencing extent of the cemented conditions further and improve the technique of the directional radiating acoustic field to the formation at bigger angles.