Abstract
Acoustic waves enter a rock formation from a borehole and are reflected or scattered upon encountering a geologic structure. Consequently, we obtain the structure location represented by the azimuth and distance from the borehole using the acoustic reflection or scattering. Downhole acoustic measurements with the azimuthal resolution are realized using an azimuthal acoustic receiver sonde composed of several arcuate phased array receivers. Eight sensors distributed evenly across the arcuate phased array receiver can record acoustic waves independently; this allows us to adopt the beamforming method. We use a supporting logging tool to conduct the downhole test in two adjacent fluid-filled boreholes, for validating the evaluation of the geologic structure using scattered P-waves. The test results show the multi-azimuth images of the target borehole and the azimuthal variation in scattering amplitudes. Thus, we obtain the precise location of the target borehole. Furthermore, the measured values of the target borehole are consistent with the actual values, indicating that we can accurately evaluate a near-borehole geologic structure with scattered P-waves.
Highlights
Geologic structures are usually associated with the generation, migration, and accumulation of hydrocarbons in a rock formation
We introduced a method to locate a near-borehole geologic structure with the azimuthal acoustic data and verified the performance of the downhole measurements
As the P-wave wavelength in the rock formation and the diameter of the target borehole were of equal magnitude, the acoustic waves from the target borehole were dominated by the scattered P-waves
Summary
Geologic structures are usually associated with the generation, migration, and accumulation of hydrocarbons in a rock formation. The developed azimuthal acoustic well logging can receive the azimuthal P-waves from different directions along the borehole circumference, which helps us obtain the azimuthal variation in an acoustic field by beamforming method (Haldorsen et al 2006, 2010; Maia et al 2006; Qiao et al 2011; Wu et al 2012; Che et al 2014a, b, 2016, 2017; Yang et al 2019a, b). The beamforming method can help us effectively enhance the acoustic reflections in a borehole environment (Yang et al 2019c). In the validation with field results, we directionally enhance the scattered P-waves by utilizing the beamforming method and obtaining a precise location and clear scattering image of the target borehole
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