The Effect of Slug Frequency on Corrosion in High Pressure, Inclined Pipelines

Abstract The effect of inclination on flow regimes and individual flow characteristics has been studied and the subsequent effect on corrosion has also been examined. Experiments were carried out in high pressure. 10 cm diameter, inclinable flow loops using brine, one oil with water cuts of 100, 80, and 60%, using carbon dioxide gas at pressures up to 1.13 MPa and temperatures up to 90 C. When the pipe is inclined upwards, the stratified flow regime virtually disappears and slug flow dominates the flow regime map. In the film region between slugs, water layers at the bottom of the pipe were still found. Oil/water mixtures flow above the water layer. The slug frequency and Froude number change with increase in inclination. The slug frequency is higher for the inclined flows than horizontal flows at the same conditions. Further, near to the change of inclination, the slug frequency is almost double that found at distances 10-15 m along the inclined pipe. The Froude numbers of these slugs are similar to those found in horizontal flows. However, values as high as 17 have been recorded. These were not noted in horizontal flows and are very turbulent slugs with regions of severe wall shear forces at the slug front. The corrosion rate increased substantially as the slug frequency was increased to about 80 slugs per minute. Above this, there was little change in the corrosion rate. At a fixed slug frequency, the corrosion rates have been found to increase with an increase in Froude number, carbon dioxide partial pressure, and temperature.