相控圆弧阵声波辐射器在井旁地层中产生的声场特征

Characteristics of acoustic field generated by acoustic phased arc array transmitter in the borehole formation

常规的单极子声波测井仪器无法对井旁地层的方位性质进行评价,多极子声波测井仪器有一定的方位测量能力,方位分辨率较低且反演地层性质时存在多解性。设计了一种具有方位辐射特性的声波测井相控圆弧阵声波辐射器,采用三维有限差分法对其在井旁地层中产生的声场进行了数值模拟。对模拟声场的方位特征进行的分析表明:相控圆弧阵声波辐射器产生的声波能量基本向某一周向角范围的井壁入射,进入地层的声波在一定周向角范围内传播。随着轴向源距的不断增大,相控圆弧阵声波辐射器在井旁地层中产生的声束周向角宽度逐渐变大。这种相控圆弧阵声波辐射器可用于方位反射声波测井新技术中,能评价井旁地层声学性质沿井周方向的变化,有助于复杂油气藏的识别和评价。

The conventional acoustic logging tools with monopole source cannot be used to evaluate the azimuth properties in the borehole formation. The multi-pole acoustic logging tools have a certain limited ability/or the azimuth measurement, such as low resolution of azimuth measurement and multi-solution in the inversion of formation information. An acoustic phased arc array transmitter with azimuth radiation was designed. The acoustic field generated by the acoustic phased arc array transmitter in the borehole formation was simulated using the 31） finite difference method. The analysis on the numerical simulation results of the azimuth characteristics of the acoustic field generated by the transmitter showed that the aeoustic energy generated by the phased arc array transmitter could radiate onto the sidewall of oil well in a certain azimuth range. The acoustic energy could be transmitted into the borehole formation propagated in a certain azimuth range, too. The azimuth lobe width of the aeoustic beams became wider as the axial offset increased. The acoustic phased arc array transmitter can be used in azimuth acoustic reflection logging and evaluate the azimuth variation of acoustic properties in the borehole formation and also be useful for complex reservoir recognition and evaluation.