An experimental and theoretical investigation of the mechanisms of downhole gravity (shroud type) separation under slugging conditions has been conducted. Based on the observations, a new mechanistic model for downhole separation failure has been proposed.

A new facility has been designed and built to represent a section of a gravity-driven inverted shroud type separator at the primary separation region. This study focuses on how the Taylor bubble (large bubble) interacts with the primary separation region. High-speed video recordings were used to analyze the interaction in detail.

The results show that the Taylor bubble starts to be ingested into the inverted shroud when a critical liquid flow rate is reached. This critical flow rate separates the regions of the ‘high efficiency’ and ‘disrupted efficiency.’ A gas ingestion criterion model has been proposed based on a simplified slug flow model in vertical wellbore conditions. The model has been evaluated with data from the large-scale downhole separator facility with favorable results.

We present the results of the first experiments to investigate the main mechanisms of gas-liquid separation in a gravity-driven inverted shroud type separator under slugging conditions. Identifying the mechanisms is the first step in developing mathematical models for downhole separation design and troubleshooting. The results could be applied to a horizontal well configuration where electrical submersible pumps are deployed in larger GOR environments.

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