What is a pump
A pump is used to transfer liquid from source to destination or circulate liquid around a system, pumps can be classified in three types according to the method that they use to move the fluids they are direct lift, displacement, and gravity pumps. The operation process of the pump is depended upon many energy sources they are electricity, engines, manual operation, or wind power. The size of the pumps is depended upon its applications, the size of the pump varies from microscopic to large industrial pumps. Mechanical pumps are used widely for pumping water from well and in-car industry for water cooling and fuel injection, and in the energy industry for pumping oil and natural gas.
What is an Electrical pump
The electrical submersible pump is a subsurface centrifugal pump with multistage driven by an electric motor. Electric power is supplied from the transformer through the switch board and then it will be forwarded from the switchboard to the electrical submersible pump motor through a power cable that is attached along with the tubing. The electrical submersible pump is also known as “submergible” because it is mostly used in oil production to lift the oil by artificial methods.
How does an electric pump work
An electric pump needs electrical power for its operation and the required power is supplied from a transformer through a switchboard. The electric submersible pump motor will convert the electric power to mechanical power. In an electric submersible pump, the whole assembly is submerged in the fluid to be the pump, some pumps are submerged fully while others may be submerged or placed in dry areas. The submersible pumps which is used in ESP installations are multistage centrifugal pumps operating in a vertical position. The shaft of the ESP will rotate and the impeller spins and push the fluid towards the surface through a pump intake or a gas separator. Artificial lift data is needed for the inflow production relationship and productivity index which will indicate the magnitude of the potential production from the reservoir. Artificial lift is a mechanism to lift hydrocarbons from the reservoir to the surface because the reservoir pressure is not enough to push the oil up to the surface. Artificial lift is of two types of surface facilities and downhole facilities.
The operational mechanism of radial and mixed flow pump is when produced liquids, after being subjected to great centrifugal forces caused by the high rotational speed of the impeller, lose their kinetic energy in the diffuser where a conversion of kinetic to pressure energy takes place.
Characteristics of electrical submersible pumps
An electric motor rotates at a relatively constant rate, rotates the pump passes the shaft which is connected with the part protector. Power is channeled to the equipment below through the electrical conductor wires affixed to the tubing, fluid enters the pump in operation. The efficiency of the pump will be high when liquids are produced and the high volume of free gas can cause inefficient pump operation, ESP can only deal with the free gas between 10-20 % and more than that it will cause inefficiency in pump performance.
Components of the electrical submersible pump
The motor in an electric submersible pump is a two-pole three-phase squired cage induction type and they run at a speed of 3500 rev/min in 60Hz operation. These motors are filled with highly refined mineral oil that provides dielectric strength. Bearing lubrication, and thermal conductivity. The construction of the motor could be of a single section or several tandems bolted together to get the desired horsepower. Motors are selected on the basis of the maximum OD that can be run in a given casing size.
ESP is a multistage centrifugal type pump, the design of an electrical centrifugal pump the right will set the pump to operate at its optimum flow rate range. The flow rate will be adjusted to the ability of the reservoir. The type of stage used determines the design volume rate of fluid production. The number of stages determines the total design head generated and the required horsepower of the motor.
Protector is also called a seal section or equalizer. Protector is filled with an oil that has high resistance value. The major purpose of the protector is to isolate the motor oil from the well fluid while balancing the bottom-hole pressure and internal pressure. There are certain functions for the protector they are, the protector connects the pump to the motor by connecting the housing and drive shafts, isolates motor oil from well fluid, houses a thrust bearing to absorb pump shaft axial thrust.
Two types of intake are used to allow fluid to enter the pump, these are the standard intake and the gas separator intake. Intake will reduce the amount of gas that goes into a gas pump separator. A gas separator intake is used when the gas-liquid ratio is higher than the pump can handle.
The special submersible cable is used to supply power to the down-hole motor. There are two types of cable they are the flat cable and round cable type. Electric wires are of the three conductors, they serve as a conductor of electric current from the switchboard to the motor. The thickness and composition of the insulation and sheathing determines the conductor’s resistance to current leakage
Switchboard is basically a motor control device, and the voltage level ranges from 600-4900 V on standard switchboards. Switchboard can also be called as a control panel work surface. The switchboards range in complexity from a simple motor starter/disconnect switch to an extremely sophisticated monitoring device. The switchboard can provide protection against down-hole equipment damage. Solid-state switchboard can protect the down-hole unit by sensing the abnormal power service and it will shut down the power service.
ESP system has three different transformer configurations they are 3 single-phase, one three-phase standard transformer and one three-phase autotransformer. Transformers are needed because the primary down voltage does not meet the down-hole motor voltage requirement.
The junction box connects the power cable from the switchboard to the well power cable. The junction box can remove the gas to the atmosphere that may come from the power cable from the well and this will prevent the accumulation of gas in the switch-board.
Pressure sensing instrument
This equipment can provide proper down-hole pressure and temperature data. PSI has two major components they are pressure sensing instrument down-hole unit, and pressure sensing instrument surface-hole unit.
A wellhead is a seating hung tubing in the well, they are used as a limited pressure seal. It provides a pressure-tight pack off around the tubing and the power cable. They can prevent gas migration through the cable
What are the advantages of an electrical pump
- They can be used in oil and water well
- It can be used in deviated wells
- Low lifting cost for high fluid volumes
- They can be used in offshore, urban or other confined locations