Downhole Gas Separation in a High-GLR CO2 Application

Abstract

Electric Submersible Pumps (ESPs) are severely affected by free gas entering into the pump, which can cause significant degradation in pump performance. Gas locking (i.e., a gas bubble blocking the fluid from passing through the impeller) results in frequent shutdowns and restarts, thereby increasing the risk of premature failure. The result is unstable production due to ESP shutdowns caused by underload or high motor temperature. Historically, the industry has used shrouds, reverse flow gas separators, dynamic gas separators, and more recently, multiphase pumps to handle the gas. Such multiphase gas handling technology adds cost and requires additional power. Recently Oxy Permian EOR installed a multiphase encapsulated production solution to separate the gas from the liquid in the wellbore. As produced fluids pass the pump at high velocity, the heavier liquid falls back into the shroud in a low-velocity area between the tubing and the top of the shroud, allowing the gas to continue to the surface. This system has proven to separate the gas from the liquid effectively, stabilizing operations within a certain operating window. In this paper, we share field examples showing the results achieved and how uptime improved over the last year. Twenty-four (24) systems have been installed in the Permian Basin with a 99% reduction in the number of shutdowns. All have had improved operational performance, with an average 30% improvement in drawdown and a 16% increase in total fluid production. These particular fields are constantly being injected with CO2, which presents even more challenging conditions for ESPs than merely solution gas. As the CO2 enters the wellbore, the liquid stream composition changes, as does the gas/liquid ratio (GLR), making it difficult to draw down and function consistently over time. Many different systems have been tried with varying degrees of success. This system has proved to be successful in attaining our objectives of higher drawdown, stable operations, and fewer failures.