Estudo experimental do escoamento trifásico sólido-líquido-gás em golfadas em dutos horizontais

Abstract

The formation and agglomeration of solid precipitations along the oil and gas production lines represents one of the hardest challenges in the flow assurance area. Among the precipitations that can be formed along the line, are hydrates, whose fast agglomeration process is critical, causing the flow reduction, the pressure drop increase and eventually pipelines obstruction. In order to prevent these problems, one of the alternatives is the usage of anti-agglomerants, which allow the hydrates to flow as solid particles dispersed in the liquid phase. Despite the method is widely used in the industry, not much is known about how the presence of dispersed hydrates affects the slug flow dynamics. In order to study this influence, in the present work an experimental study was carried out on the three-phase solid-liquidgas slug flow. Polymeric particles, with density (937 kg/m3) similar to hydrates, were used to simulate the behavior of these solid precipitations in the flow. Four different particle diameters (100 µm, 200 µm, 300 µm and 400 µm) and three volumetric concentrations (1%, 2.5% and 5%) were studied. The fluids used were water and air at room temperature and atmospheric pressure at the pipe outlet. The slug flow parameters, such as elongated bubble velocity, bubble and slug lengths and frequency, were monitored using non-intrusive resistive sensors specially designed for the flow with particles. For qualitative analysis, images were obtained using a high-speed camera, and through them, it is possible to notice that the particles distribution along the unit cell is highly dependent on the liquid flow rate. When the liquid flow rate is high, the particles are distributed homogeneously, and they mainly affect the interfacial tension of the flow. On the other hand, when the liquid flow is low, the particles tend to accumulate in the slug region, causing the flow to behave more viscously. These two effects explain the results obtained in the quantitative analysis: for flows with higher apparent viscosity, there is an increase of the elongated bubble velocity, and for flows dominated by the increase of interfacial tension, the elongated bubble velocity tends to decrease. Both effects tend to decrease the lengths of bubbles and slugs, however for some points they increase, because the particles affect the slug formation process. The frequency is a result of variations in the bubble velocity and lengths. Finally, it is possible to notice that particles do not affect the pressure drop in a significant way.