Heavy oil-water flow patterns in a small diameter vertical pipe under high temperature/pressure conditions

Experimental measurements were conducted to investigate the upward oil-water flow patterns in a small diameter vertical pipe (0.01m I.D.) under high temperatures up to 130 degrees C and high pressures up to 20 MPa. The viscosity of the oil sample was 584.24 mPa s and the density was 1.899 g/cm(3) at 30 degrees C. The effects of pressure, temperature, input water fraction (IWF) and mixture velocity on the flow patterns were systematically investigated. The observed flow patterns were plotted on a flow pattern map in which input water fraction was used as the y-axis and the mixture velocity was used as the x-axis. Based on the measurement results, the following flow patterns were observed: water-in-oil dispersed flow (D w/o), water-in-oil bubbly flow (B w/o), water-in-oil slug flow (S w/o), water-in-oil creep flow (CE w/o), churn flow (Churn) and core annual flow (AF). Phase inversion was not observed in this work. With an increase in temperature at a given input water fraction, S w/o, CE w/o and Churn flow with large water drops tended to transform into B w/o and D w/o with smaller water drops, the CE w/o disappears gradually, and the boundaries in the flow pattern maps tend to occur at lower input water fraction values. The effect of pressure on the flow patterns was found to be opposite to that of temperature. The possible causes leading to the changes in the flow patterns subjected to pressure/temperature variations were provided in terms of changes in density ratio, interfacial tension, and viscosity ratio of oil and water.