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Experimentally Investigating Sand Particle Characteristics Under Annular Multiphase Flow Conditions Using a Triaxial Vibration Method


 Sand characterization in annular flows remains challenging for the efficient flow of water-bearing high-production gas wells. In this work, triaxial vibration methods were first developed to quantitatively characterize the sand transport behaviors on pipe walls. First, a series of methods were applied to calculate the time-frequency, noncoherent power, signal-to-noise ratio (SNR), and statistical features to characterize annular flow formation. Second, four sand conveyance patterns were distinguished from the annular flow with different triaxial time-frequency features. Third, the effects of the particle type (sand or glass), median size (150–550 μm), and superficial flow velocity of the gas (14–18 m/s) and liquid (0.0037–0.0114 m/s) on the vibration energy were evaluated. Finally, the established sand quantitative analysis model was verified and compared with existing methods. Corresponding experimental investigation results were used to identify the sand characteristic frequencies with low error rates for sand conveyance patterns of the forward liquid flow (28.2–34.6 kHz on the xyz-axis and 36.2–38.7 kHz on the xz-axis, with an error rate of 3.35%), reverse liquid flow (20.3–22.8 kHz on the xy-axis and 22.8–25.3 kHz on the z-axis, with an error rate of 2.93%), droplet nonwrapped flow in the gas core (40.5–43.5 kHz on the xyz-axis, with an error rate of 4.08%), and droplet wrapped flow in the gas core (46.2–48.7 kHz on the xyz-axis, with an error rate of 2.68%). Therefore, this study effectively complements the current sand characterization method for annular flows and provides a good foundation for the optimization of sand production monitoring in gas wells.