Studies of Multiphase Flow in High Pressure Horizontal and +5 Degree Inclined Pipelines

ABSTRACf In the process of oil production from older wells, brine and carbon dioxide gas are commonly present in the pipelines. Often these oil, water. and gas mixtures create a highly corrosive slug flow environment for typical carbon steel pipelines. The first step in understanding the enhanced corrosion is to characterize the nature of the flow. For this purpose, an 18-m long, 9.7- cm diameter. inclinable 316 stainless steel pipeline has been commissioned for the study of multiphase flow and its subsequent effects upon corrosion. Three component oil/water/gas mixtures with water cuts of 80 and 100% have been examined. At a temperature of 40 DC, flow patterns and slug characteristics were determined at inclinations of zero and five degrees, superficial liquid velocities of 0.1 to 1.5 mls. superficial gas velocities of 1.0 to 11 mls and system pressures of 0.27. 0.45, 0.79, and 1.13 MPa. A non-visual method, using measurement of differential pressure, was established to measure slug frequencies and determine flow patterns. At an inclination of plus five degrees. the frequency of slugs was greater at the entrance to the test loop than further downstream at the test section. Additionally, the slug flow regime occurred at a lower superficial liquid velocity than in horizontal flow. No slugs were present in the downhill return for the matrix studied. The pressure drop increased with increasing gas and liquid flow rates. while decreasing slightly with an increase in pressure. The flow regime transitions for plug flow. slug flow, annular. and stratified flow were identified. Pressure had no apparent effect upon the plug flow/slug flow transition. However, as the pressure was increased, the slug flow regime became dominated by pseudo-slug flow. Slug frequency was observed to increase with increasing superficial gas and liquid velocities while varying little with pressure.