electrical submersible pumping unit

Introduction

The electrical submergible pump invented and developed by Reda over 70 years ago, now plays a vital role in helping meet the world's energy needs.

Over one-fourth of all oil produced by artificial lift in the free world is produced with submergible pumps. Such units are capable of lifting 200 to 20,000 bpd at depth of 1,000 to more than 10,000 ft; they are suitable for both onshore and offshore application and can handle widely different well conditions such as high viscosity fluids, gassy and/or high temperature wells.

History of ESP

The electrical submersible pumping unit (ESP) was invented by the Russian–born A.Arutyunoff whose pumps were first manufactured by the REDA Company,

ARUTYUNOFF was born in Tiflis, Russia, in 1893.

In 1911, at the age of 18, he organized the Russian Electrical Dynamo of Arutunoff company in Ekaterinoslav, Russia, and invented the first electric motor that would operate in water and operate a drill.

In 1916, Arutunoff redesigned a centrifugal pump to be coupled to his submergible electric motor for dewatering mines and ships. In 1919, he and his brother, Suren, immigrated to Berlin.

Acronym, REDA, obtained financing and further developed the submergible electric motor and pump.

In 1923, he immigrated to U.S. where he went to Michigan and California trying to interest backers in the project. He went to Bartlesville (Oklahoma) in 1928 and there he established REDA Pump Company in 1930.

Why and when we use the ESP

Submersible pumps are used in oil wells. By decreasing the pressure at the bottom of the well (by lowering bottom hole flowing pressure, or increasing drawdown), when the reservoir  pressure cant lift the fluids inside the tubing , significantly more oil can be produced from the well compared to natural production. This makes Electric Submersible Pumping (ESP) a form of "artificial lift" (as opposed to natural flow) along with Gas Lift, sucker rode pump. New varieties of ESP can include a water/oil separator which permits the water to be re injected into the reservoir without the need to lift it to the surface.

We can summaries the cases where we use ESP as following:-

	Typical Range		maximum
Operating Depth	1,000' - 10,000' TVD		15,000' TVD
Operating Volume	200 - 20,000 BPD		30,000 BPD
Operating Temperature	100° - 275° F		400° F
Wellbore  Deviation	10°		90°
Corrosion Handling		Good
Gas Handling		Poor to Fair
Solids Handling		Poor to Fair
Fluid Gravity		>10° API
Servicing		Workover
Prime Mover Type		Electric Motor
Offshore Application		Excellent
System Efficiency		35% - 60%

System components:-

v The surface equipment

1.     Electrical power supply

2.     Electrical transformer

3.     Switchboard (motor controller )

4.     The junction box

5.     Wellhead

§  Electrical power supply

Ø For an efficient operation, it is necessary to have a dependable uniform power supply. The two basic supplies are:-

1.    Lease generation equipment.

2.    Local power company

§  Electrical transformer:-

The propose of the transformer is to provide correct surface voltage to proper motor operation by changing electric power from a high voltage to low

§  Switchboard

The primary purpose of the switchboard is to control the pump motor and provide overload and under load protection.

§  The Junction Box

A junction box is located between the wellhead and switchboard for safety reasons :

Ø Functions of junction box:-

1).To connect the surface cable from the switchboard to the power cable from the Well.

2).Provides a vent to the atmosphere for any Gas that might migrate through the Power cable.

3).To change the motor rotation.

§  Wellhead:-

The wellhead is designed to support the weight of the subsurface equipment and is used to maintain surface annular control of the well.

v Subsurface equipment :-

1.    The electric Motor.

2.    Seal Section (Protector).

3.    Intake or Gas separator.

4.    The centrifugal pump.

5.    Electric cable.

1.   The electric Motor

The motor is the driving force which turns the pump. The electrical motors used in submersible pump operations are two poles, three phases, squirrel cage induction type. These motors run at relatively constant speed of (3450 rpm) on frequency (60HZ) and (2850) on (50 HZ).

The nonconductive oil in the motor housing lubricates the motor bearings and transfers heat generated in the motor to the motor housing. Heat from the motor housing is carried out away by the well fluids.

2.   SEAL SECTION (PROTECTOR)

Ø Connects the pump housing to the motor housing by connecting the drive shaft of the motor to the pump shaft.

Ø Prevents the entry of well fluid into the motor.

Ø Provides the area necessary for the expansion of the units oil due to heat generated when the motor starts.

3.   Intake or Gas Separator

The pump intake is used to allow fluid enter the pump, when the gas liquid ratio (GLR) is less than 10%.

If (GLR) grater than 10% it is may also have a gas separator which is a bolt-on section between the protector and the pump where the gas separator is an aid in preventing gas lock .

4.   The centrifugal pump

Submergible pumps are multi-staged centrifugal pumps. Each stage consists of a rotating impeller and a stationary diffuser.

 The type and size of stage used determines the volume of fluid to be produced. The number of stages determines the total head generated and the horsepower required.

 

Impeller

Each "stage" consists of

Rotating an impeller and stationary diffuser.

 

5.   Electric cable

Power is supplied to the electric motor by an electric cable.

Available in either round or flat styles, these insulated cables may be installed in well temperatures in excess of 300° F.

          

Cable styles

Round cable is used from pump discharge head to junction box.

Flat Cable is used from pothead of the motor to the pump discharge head.

v Miscellaneous Equipment Installed with ESP:-

Ø Check Valve.

Ø Bleeder Valve.

Ø Centralizer.

Ø Y-Tool.     

Data required for pump selection:-

§  Mechanical Data:-

Ø Casing size and weight.

Ø Tubing size, weight.

Ø Well depth.

Ø Perforations depth.

§  Fluid data :-

Ø Oil API gravity, viscosity.

Ø Water specific gravity.

Ø Gas specific gravity.

Ø Reservoir FVF, bubble point pressure.

§  Production Data:-

Ø Current and desired production rate.

Ø oil-production rate.

Ø Water production rate.

Ø GOR-free gas and solution gas.

Ø Static BHP and fluid level.

Ø Producing BHP and stabilized fluid level.

Ø BHT.

Ø System backpressure from flow lines, separator, and wellhead choke.

§  Surface electrical system Data:-

1.    Available primary voltage.

2.    Electrical power restrictions.

§  Possible problems:-

Ø Sand production.

Ø Corrosion.

Ø Emulsion.

Ø High well temperature.

Ø Gassy well.