A study of oil-water flows in large diameter horizontal pipelines.

摘要

This study involves an experimental and theoretical investigation of oil-water flows. Oil with a viscosity of 3 cP and a density of 820 kg/m 3 and ASTM substitute seawater were used. The oil-water flow characteristics including pressure gradient, water holdup, phase distribution, velocity profile, phase inversion, mixture viscosity and droplet size in a 10 cm I. D. and 40 m long acrylic pipeline were studied. Input water fractions between 0 to 100% are examined at mixture velocities ranging from 0.4 m/s to 3.0 m/s. The temperature is maintained at 25°C and the system pressure is kept at 0.136 MPa. The effect of surfactant on oil-water flows is also examined.; The results show that the pressure gradient does not change much with the increasing in input water cut until 20%. It then increases and peaks around the phase inversion point, and gradually decreases to the pure water's value at 100% input water. Water holdup and phase distribution are strongly affected by input water cut, and mixture velocity. Above 2.0 m/s, the composition of oil-water mixture across the cross section of the pipe is no longer conspicuous. Velocity profiles show that the mixed layer moves approximately 1.2 times of the input mixture velocity. Phase inversion point is determined at around 45% input water. Minimum droplet size is observed at low mixture velocities.; The pressure gradient is affected at high surfactant concentrations, especially at high velocities. With the surfactant, homogenous flow can be obtained at lower mixture velocities especially for the water cut of 40% and higher. Surfactant does not affect the velocity distribution significantly for the flow conditions investigated. The phase inversion point is lowed to be around 40% when 10 ppm surfactant is added.; A correlation for oil-water mixture apparent viscosity was developed. The three-phase segregated flow model was completed and a four-phase segregated flow model was developed to estimate the flow characteristics in pipeline. Agreement with experimental data is good. A multi-layer model is also proposed and constructed for predicting the water dropout/onset of corrosion, and it can be applied to any complex geometry.