Sand Detection Using Acoustic Sand Monitors for Liquid-Dominated Multiphase Flow Production

Summary Solid particle erosion in the oil and natural gas industry can be damaging to pipe fittings and equipment, which can lead to maintenance or, in the worst case, a production shutdown. In both cases, this represents a huge economic loss for industry. Acoustic sand monitoring is one of the most widely used practices to provide an alarm and/or estimate the amount of sand entrained in the flow. In addition to being commercially available, they can be easily clamped to the outside of a pipe wall, measuring the acoustic energy generated by sand grain impacts on the inner side of a pipe wall. In this work, a broad range of multiphase operating conditions has been experimentally investigated with acoustic sand monitors in large-scale flow loop facilities to determine the effectiveness of sand monitoring in liquid-dominated multiphase flow. The main objective is to use acoustic sand monitors to determine the threshold sand rate (TSR). This is the minimum sand rate necessary to achieve monitor output higher than the background noise (BN) level. Acoustic monitors were placed upstream and downstream of standard (r/D = 1.5) elbows while varying superficial gas and liquid velocities, sand sizes (25 μm, 75 μm, 150 μm, 300 μm, and 600 μm), and pipe diameters (2 in. and 3 in.) in the vertical orientation. The experimental conditions were selected to cover slug-churn, dispersed-bubble flow, and liquid-sand flow conditions. These results are compared with the previously obtained test results on 50.8-mm (2-in.) internal diameter (ID) test loops. In the 50.8-mm (2-in.) loop, threshold limits were observed for dispersed-bubble flow regimes and liquid-sand as compared with gas-dominated flow conditions. While TSR is the highest in dispersed-bubble flow regimes, the present data were compared with previous results obtained for annular, slug, and stratified flow patterns (FPs) in vertical flow. It was observed that the annular flow regime has the lowest TSR values, showing an increase in TSR when the liquid rate increased. The results from this work can help operators understand how acoustic monitors can detect and distinguish sand impact noise from the background flow noise in liquid-dominated multiphase flow in production facilities. In this way, greater assurance is provided to operators for optimizing oil and gas production rates, especially in wells that tend to produce solids.