相控圆弧阵声源在TI地层井孔中产生的声场

Acoustic wave field in fluid-filled borehole surrounded by TI formations produced by a phased arc array source

研究了相控圆弧阵声源在各向异性地层井孔中产生的声场的特征,重点分析了该声源对于地层横波各向异性的方位敏感性,旨在探索一种新的地层声学各向异性测量方法。结果显示:相控圆弧阵声源在地层中可激发多种方位阶数的声场,主要成分为单极子波场和偶极子波场;在HTI地层竖直井中,方位角不同的圆弧阵声源激发的波动的速度不同,相控圆弧阵声源对于地层横波速度的方位各向异性的敏感性主要是它所激发的弯曲波的贡献。相比于传统的正交偶极子声波测井而言,采用相控圆弧阵声源可以评价井附近地层的周向非均质性,可以提高井周测量覆盖次数,提高反演结果的可靠性。另外,相控圆弧阵声源兼具备多极子声源的功能,优化的相位控制方式可以实现方位各向异性的最佳测量。

We study acoustic wave field in a fluid-filled borehole associated with a TI formation produced by a phased arc array source, and analyze the sensitivity of this source to azimuthal anisotropy of formation shear waves in order to develop a new anisotropy evaluation method. Results show that this source is able to generate acoustic field of multi- azimuthal order, and the primary acoustic modes are the monopole modes and dipole modes. In HTI formations, the waves excited by sources with different radiation azimuths propagate with different velocities. The azimuthal sensitivity of phased arc array to formation shear anisotropy is mainly contributed by flexural modes produced by this source. Compared to a traditional cross-dipole source, the phased arc array transmitter can be used to evaluate formation heterogeneity and increase the measurement number around the borehole decreasing uncertainty of inverted results. Additionally, this source has the function of multipole sources. Therefore, it is possible to obtain the most reliable anisotropy measurements by using optimized phased control strategy with this source.