Experimental Investigation of Acoustic Sand Detector Performance in Multiphase Flows

Acoustic Sand Detectors (ASDs) are widely used, in oil and gas industries, to detect sand transport in pipelines by triggering warnings or alarms. For ASDs to be highly effective for providing an alarm, it is crucial to determine the threshold sand rate (TSR), which is the minimum sand rate at which detectors can no longer distinguish between background noise from the real flow conditions and the noise generated by sand impacting the pipe walls. This study experimentally investigates a wide range of multiphase operating conditions using ASDs in a large-scale flow loop facility to assess their effectiveness in detecting very fine sand particles in multiphase flows. A series of experiments were conducted in a vertically oriented 101.6 mm (4 in) diameter pipeline, exploring various combinations of superficial velocities, ranging from 5 m/s to 30 m/s for gas and 0.1 m/s for liquid, using sand particles with different mean diameters of 25 μm, 75 μm, and 300 μm. These results were compared to those obtained from previous experiments conducted for the same flow conditions in the horizontal orientation. Additionally, a flow visualization study utilizing an acrylic elbow test section provided deeper insights into the flow behavior under churn, slug, and annular flow conditions. This analysis helped assess the impact of flow on the elbow section and evaluate changes in flow behavior across different flow regimes in both vertical and horizontal orientations. In the 101.6 mm ID test loop, it was observed that the acoustic sensors were ineffective in detecting sand noise when 25 μm sand was present in several flow conditions due to the high background noise generated by multiphase flow impacting the walls. As the sand particle size increased, the TSR values decreased. When analyzing the effect of flow regime, it was observed that flows with high gas velocities exhibited a lower TSR compared to conditions with lower gas velocities. Specifically, in annular flow regimes, at higher gas velocities, the TSR was lower than those in churn flow conditions. The highest TSR was recorded under the higher liquid velocity and dispersed bubble flow conditions as the liquid provides a cushion reducing particles impact momentum. These findings highlight the influence of both flow regimes on the effectiveness of acoustic sand detection in multiphase flow. The findings of this study provide valuable insights for operators on the effectiveness of acoustic monitors in distinguishing sand impact noise from background flow noise in multiphase flow. Additionally, the results highlight the performance of acoustic sensors under various flow conditions. This understanding enhances the operators’ confidence in optimizing oil and gas production rates, particularly in wells prone to sand production.