Experimental investigation of the effect of pipe inclination on the hydrodynamic behaviour of slug flow using electrical capacitance tomography

Abstract

Two-phase gas–liquid slug flow in inclined pipes is important in oil/gas transportation. Due to the fact that slug flow can change characteristics from one well to another, it is important to investigate the response of the characteristics of a two-phase slug flow as a result of a change in the pipe inclination angle. This paper therefore presents an investigation of the effect of pipe inclination on the hydrodynamics of slug flow in a 67-mm internal diameter inclinable pipe. The slug flow regime was generated using air–silicone oil mixture over a range of gas ( ) and liquid ( ) superficial velocities. The 3D structures are particularly difficult to visualise using conventional optical techniques because even if the pipe wall is transparent near-wall bubbles would mask the flow deep inside the pipe. Therefore, more sophisticated methods are required. An advanced wire mesh sensors (WMS) was used and the two-phase mixtures employed was air–silicone oil. In addition, Electrical Capacitance Tomography (ECT) was used to determine: the velocities of the Taylor bubbles and liquid slugs, the slug frequencies, the lengths of Taylor bubbles and the liquid slugs, the void fractions in the Taylor bubbles and liquid slugs. A differential pressure transducer was used to measure the pressure drops along the length of the pipe. It was found that the flow pattern is affected by the pipe inclination angle. The results from the WMS revealed that unlike what is commonly assumed when modelling pipe flow, the flow is not symmetric, with a lot of distortion, which turned out to be high. In addition, the hydrodynamics of slug flow were found to be highly affected by the pipe inclination.