Flow Assurance and Artificial Lift

Flow assurance is a set of activities describing the prediction, prevention, mitigation, and remediation of organic and inorganic deposits and other phenomena that reduce the capacity or hinder the flow of a production system. This concern is most relevant at the commencement of a deep-water exploration, because it is an environment where low temperatures and high pressures present greater risks for the flow. Every kind of oil is subject to flow assurance problems due to their chemical composition and to environmental and flow conditions. Therefore, they may occur in light and heavy oils, condensate or natural gas.

The most common risks include wax deposits; hydrate formation; asphaltene flocculation; emulsion formation; the corrosion of materials used in the process; and salt encrustation, as well as severe flow intermittency, which can lead to a partial loss of production, or even the complete interruption of the well, due to a complete obstruction of the production lines.

The main flow assurance activities are: the injection of chemical products; the elaboration of preventive measures, especially in situations involving production interruption and activation; pipeline pigging and other procedures.

Artificial lifts are necessary when the pressure level of a reservoir is insufficient to guarantee the flow of production from a well to the surface. The main artificial lift methods are the continuous gas lift, the mechanical pump, and the centrifugal submersible pump.

Gas lift is the artificial lift method that is most commonly used in deep-water production in Brazil, it consists of natural gas injection through a valve in the production string. The mixture of  gas and fluids from the reservoir results in the reduction of their density and decreases the pressure necessary to elevate the production to the surface.

The mechanical pump, in turn, is one of the most widespread methods in the world, but its application is restricted to onshore operations. In this method, a chamber is installed at the bottom of a well consisting of a piston and a pair of valves. The piston is moved by an axis connected to a motor in the surface (rocking horse), which allows the valves to open and close, and, consequently, the fluids to enter its interior. The ascending movement provides sufficient energy for the fluids to reach the surface.

Unlike the mechanical pump, in the centrifugal submersible pump, the artificial lift method expected for the Atlanta field, the system’s motor is also located inside the well, separated from the pumps only by a protective seal. A cable is necessary to conduct electricity from the surface to this motor, which transforms it into mechanical energy, turning the axis of the system. This same axis moves the impellers of the pump, which transmit kinetic energy to the fluids through its rotation; between each impeller there is a static element, the diffuser, which carries the production to the impeller above, transforming the kinetic energy into potential energy. This gain in potential energy represents a sufficient increase in pressure to elevate fluids to the surface. 

Last updated on 2015-07-01T09:16:21

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