Experimental Investigation of Pressure-Drop/Flow-Rate Relationship for Small-Aperture Holes for High-Viscosity Fluids

Abstract

Summary This paper studies the effect of viscosity and fines-particle loading on the pressure drop across a 4-mm orifice in a specific geometry built to mimic a representative well completion. It also provides experimental data in the range of operating conditions (high aspect ratio, low Reynolds number) that were not covered by any previous studies. The past experiments concentrated on studying the orifices with high aspect ratio (>1) and high Reynolds number (>1,000) or with a combination of low aspect ratio and low Reynolds number. In previous research conducted within the petroleum industry, most of these orifices were validated experimentally for viscosities up to 200 cp only for such completions. The current study focused on a wider viscosity variation (1 to 3,000 cp) with lower flow rates (0.5 to 30 m3/d). Even though fines are an integral part of the flow stream passing through the orifice for a sand reservoir, none of these studies further considered the effect of small particles on the orifice performance. The pressure drop was measured across the orifice and through the entire pipe assembly. The measured data were nondimensionalized by use of the Euler number and plotted against the Reynolds number for all rates and viscosities. The data were also compared and validated against commercially available computational-fluid-dynamics (CFD) software. The effect of sand-particle loading was also studied, and its effect on apparent viscosity increase was measured in the laboratory. The pressure-drop/flow-rate relationship and flow coefficient disclosed in this paper can be used to design effective completions for intermediate- to high-viscosity-oil applications and will be able to predict the completion pressure drop more accurately.