Downhole Gas Separator Performance in Sucker Rod Pumping System

Date

2005-12

Authors

Guzman, Manuel

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Abstract

Volumetric efficiency of a sucker rod pump has been a major concern for artificial lift designers for a long time. One way to reduce the amount of gas entering into the pump is to use downhole gas separators. The main purpose of these devices is to facilitate agglomeration of gas bubbles so that they migrate upwards and can be released through the casing annulus. Design and selection of downhole gas separators is usually done using heuristics. The objective of this research is to offer the oil industry novel software for the design and selection of gravity type downhole gas separators to improve the pump performance. Separator performance relations are based on laboratory data of 10 different gas separators for continuous flow (such as developed by the progressing cavity pumps). This data was used to generate correlations between the gas flowing through the separator, thesuperficial gas velocity in the annulus and the superficial liquid velocity inside theseparator. These relations were then applied to model the performance of the separator when operating in conjunction with a sucker rod pump. This model used actual plunger velocity data from different types of surface units to calculate the liquid fraction inside the pump for each combination of separator design and annular gas velocity. In addition, we developed a motorized butterfly valve to reproduce the intermittent flow observed in sucker rod pumps. Experimental results show that the downhole gas separation efficiency depends on the port area and the annular area inside the separator. When ports area is smaller than the annular area, the first controls the flow regime inside the separator. Results confirm that the downhole gas separator efficiency depends on the ratio between the plunger diameter and the downhole gas separator annular area. Additionally, visual observation confirms that the best way to maximize the gas separation is to set the intake below the perforations, if possible.

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