Prediction of the flow regime transitions in high pressure, large diameter, inclined multiphase pipelines

In multiphase flows, flow regime determination has many design applications such as boiler tubes and oil and gas pipelines. This study focuses on the oil production from older wells in which brine and carbon dioxide gas are commonly present in the pipelines. Often these oil, water, and gas mixtures create a highly corrosive environment for typical carbon steel pipelines. Since the highest corrosion rate occurs in slug flow, the ability to predict this flow regime becomes of great importance.; The transitions from stratified to slug and from slug to annular flow are not well understood. Further, little data is available for flows in large diameter, multiphase pipes which include the effects of pressure and inclination.; For this purpose, oil/water/gas tests were conducted in a 9.72-cm diameter, 18-m long pipe at inclinations of 0, {dollar}pm{dollar}2, and {dollar}{lcub}pm{rcub}5spcirc{dollar} and pressures of 0.27, 0.45, and 0.79 MPa. The ratio of the translational velocity to the superficial mixture velocity was found to be about 2.0 for plug flow, 1.2 for slug flow, and 0.5-1.2 for pseudo-slug flow. The film Froude number in slug flow was found to increase with increasing gas flow rate to a value of about 18. The value then dropped as pseudo-slug flow was achieved. It again increased with gas flow rate until it reached a value of about 16, then annular flow ensued.; The slug frequency was found to increase with increasing superficial gas velocity at high liquid flow rates while decreasing with increasing superficial gas velocity at lower liquid flow rates. The frequency also increased with inclination.; The flow pattern data matched the transitions predicted by the mechanistic models developed. In upflow, stratified flow was not found to occur for the conditions studied but was prominent in downflow. The stratified to slug flow transition occurred at higher liquid flow rates at higher pressures and in larger diameter pipes. Annular flow was found to occur at lower superficial gas velocities at higher pressures and smaller diameters. Inclination was not found to have a large effect on the annular transition.