Experimental Measurement of Slippage in Flow through Vertical Pipes

Abstract

In many of the important problems of the petroleum engineer, it is necessaryto know accurately the laws governing the flow of gas and liquid mixtures invertical pipes. Although much work has been done along these lines, nosatisfactory solution to the problem has been found. A good theoreticaldiscussion of the energy balance in a gas-lift has been published by Versluys.One of the most important factors affecting the efficiency of the flow of oiland gas mixtures is slippage, and in most of the experimental work that hasbeen done no provision has been made for the measurement of this quantity. As Versluys pointed out, since there is no method now known to estimate it fromthe data usually taken, slippage must be determined empirically. This paper presents the results of some work carried on to measure slippage inshort experimental gas-lifts. As shown herein, slippage can be easilycalculated in a vertical pipe carrying a mixture of oil and gas if thefractions of the pipe occupied by liquid and gas respectively are known. In this work, the fraction of the pipe occupied by the liquid was measured under awide variety of conditions and the relationship between this fraction and otherquantities, which are easily measured in ordinary work, was determined. It was hoped that the quantitative relationship obtained from this work couldbe used for making accurate calculations in flowing or gas-lift wells, butunfortunately it did not check satisfactorily when applied to actual wells. Apparently flow in long flow pipes is more efficient than in the short onesused for the experimental work. Nevertheless, it is felt that the datathemselves are of interest; that the method of attack may be of value in futurework and that the relationship derived between slip and the relative velocitiesis a contribution toward the solution of the gas-lift problem.