Submergible pumping systems are used for raising fluids, such as petroleum, through a wellbore drilled into the earth. The production fluids enter the wellbore via perforations formed in a well casing adjacent a production formation. Fluids, e.g. petroleum, contained in the formation collect in the wellbore and may be raised by the submergible pumping system to a collection point in another zone or above the surface of the earth.
Commonly, the produced fluid is a mixture of liquid and gas components. The gas component distributed through the fluid can reduce the efficiency of the submergible pump, and potentially can damage or reduce the life of the pump. Gas separators have been used to separate the gas component from the fluid prior to its entering the submergible pump of the submergible pumping system. Thus, the gas component can be routed around the pump and vented to the surface through, for example, the annulus formed between the wellbore casing and the tubing utilized to carry the produced fluid. Once the gas is separated, the liquid component may be pumped through, for instance, the production tubing or coiled tubing used to deploy the submergible pumping system.
A conventional gas separator uses an inducer to induce the produced fluid into a circular flow pattern as it moves through the hollow interior of the gas separator. Specifically, the inducer draws fluid from the wellbore into the gas separator where it is circulated along an interior wall of the gas separator as it moves upwardly into a separation chamber. A vortex generator, such as a propeller or a cylinder, is disposed in the separation chamber and is used to promote the circulation of fluid and the creation of a vortex. The centrifugal force created by the circulation causes the heavier liquid component to move to a radially outward position, while the lighter gas component remains in a more centralized radial position. Appropriate outlet channels are used to vent the gas component and to direct the liquid component to the submergible pump.
Generally, the gas separator is connected between a submergible electric motor and the submergible pump. A drive shaft connects the submergible electric motor with the submergible pump and provides power thereto. The drive shaft extends through the hollow interior of the gas separator, and often is used to rotate the inducer. Typically, the drive shaft is composed of individual sections in each system component. For example, the gas separator may include a self-contained section of the drive shaft designed to matingly engage a section of the drive shaft disposed in the submergible pump.
The gas separator also may include a propeller or rotating cylinder mounted to the shaft above the inducer. This propeller or rotating cylinder helps create a vortex within the gas separator to facilitate separation.
A problem with conventional gas separators, however, is that the separation chamber is not long enough to allow sufficient separation of the gas and liquid as the fluid circulates through the chamber. On the other hand, the separation chamber is not readily lengthened because the drive shaft cannot be allowed to extend unsupported through a lengthened chamber. In the latter situation, vibrations develop in the shaft that can damage the gas separator or reduce its effective life.
It would be advantageous to have multiple, consecutive separation chambers to facilitate a greater separation of the gas and liquid components, while supporting the drive shaft to reduce or eliminate detrimental vibration.