Effects Of Liquid Holdup On Hydrocarbon Production In Tapered Tubing String Using Niger Delta Fluid Properties

Abstract

Effects of liquid holdup on hydrocarbon production in tapered tubing string using Niger Delta fluid properties was undertaken in this work. Oil reservoir fluids flow to the surface as a multicomponent fluid in pipes during production. Multiphase flow occurs due to the density of different phases involved in reservoir fluid and each fluid phase flow at different velocity. In this study, analytically developed equations and existing fluid correlations were used for determination of pressure drop in the tubing using MATLAB program, which can allow the use of any chosen tubing internal diameter (tapered or uniform) and reservoir fluid properties. Liquid holdup was determined in different tubing diameter configurations; uniform internal diameter tubing (2.875 inch and 3.5 inch) and tapered internal diameter tubing (2.875 - 3.5 inch) and its effects on pressure drop were obtained. The pressure drop obtained with tubing diameters of 2.875 inch, 3.5 inch and tapered tubing 2.875 − 3.5 inch increased as liquid flow rate increased from 1000 bopd to 4000 bopd. Effect of oil flow rate on pressure drop was evaluated for both tapered and uniform internal vertical tubing diameter. The pressure drops obtained were also used to determine pump power requirement for both uniform and tapered internal tubing diameters for comparison. Hagedorn and Brown correlation was used to develop real-time proxy equations for pressure drop determination at optimum liquid flow rates using different uniform internal diameter tubing. Results obtained indicated that liquid holdup is minimally reduced in tapered internal diameter tubing, resulting in lower pressure drop than in uniform internal diameter tubing string. Also liquid holdup and liquid flow rate affect pressure drop in tapered internal diameter tubing in the same manner as they affect the uniform internal tubing diameter. The graphs obtained showed that as liquid holdup increases, pressure drop also increases. Liquid flow rate increases as pressure drop increases. Tapered tubing, tapered at an optimum angle of 7o showed least liquid holdup hence, least pressure drop. Typically, the pump power capacity to lift the reservoir fluid in uniform internal diameter tubing of 2.875 inch and 3.5 inch is more compared to that of tapered (2.875 inch to 3.5 inch) tubing string at flow rates between 1000 and 4000 bopd respectively. The real-time proxy equations developed from the Hagedorn and Brown correlation can be used in the field for optimum tubing size selection.

Keywords: Liquid, holdup, tapered, tubing, two-phase, gas-oil, flow, production and pumppower.