The Slip Velocity of Gases Rising Through Liquid Columns

This paper presents the results of a study of the slip velocity of gasesrising through liquids in vertical tubes, inclined tubes, and vertical annuli.The data were obtained in gas-liquid systems which included combinations ofair, propane and natural gas (over 97 percent methane) with water, lubricatingoils, and crude oils. The 214 data points obtained in this study along with 11data points reported in the literature are incorporated in an empiricalcorrelation which relates the mean slip velocity of gases flowing throughliquids with the parameters gas rate, tube size, ratio of liquid viscosity toliquid density, gas density, liquid density, and the angle of the tube from thevertical. The average numerical deviation of the measured slip velocity data fromvalues obtained from the correlation is 9.2 per cent. The average algebraicdeviation between measured and predicted data is 0.31 per cent, an indicationthat the correlation is a satisfactory representation of the data. The correlation presented in this paper will be useful primarily in thedesign of subsurface gas-oil separation equipment for increasing the efficiencyof oil-well pumping installations, but may perhaps be extended to othersituations of gases rising through liquid columns. Introduction The production of oil by pumping is often complicated by the presence offree and dissolved gas in the oil at bottomhole conditions. This gas can bedrawn into the pump barrel and result in "vapor locking" the pump, thusreducing the efficiency of the pumping operation. Large amounts of free gas maybe excluded from the pump by the use of a gas-anchor, which is designed toallow the separation of free gas from the oil before it is drawn into the pump.The design of a suitable gas-anchor depends on a knowledge of the differencebetween the velocity of the free gas and that of the oil as the oil travelsdown toward the pump intake. This rate of gas rise through the oil is termed"slip velocity. T.P. 3394