## Submersible Pump System Overview

The submersible pump system consists of both downhole and surface components. The main surface components are transformers, motor controllers, junction box and wellhead. The main downhole components are the motor, seal, pump and cable. Additional downhole components may be included to the system: data acquisition instrumentation, motor lead extension, cable bands and protectors, gas separator, check and drain valves.

The following video gives a quick equipment overview of the ESP submersible pumping system:

The following figure shows schematic diagram of a submersible pump installation:

## ESP design – Step 6: Optimum Size of Compounds

ESP compounds have different sizes and can be assembled in a variety of combinations. These combinations must be carefully determined to operate the ESP with production requirement, downhole conditions, material strength and temperature limits, etc. to select the optimum size of compounds.

### Pump:

To determine the required number of stages of the pump to produce the anticipated capacity; just divide the Total Dynamic Head (TDH) by the Head developed by Stage.

Refer to the article “ESP design – Step 4: Total Dynamic Head” to review how the TDH is calculated.

The Head developed per stage is deducted from the published performance curve which shows the discharge head developed by the pump. It is an experimental curve given by the manufacturer and obtained with fresh water at 60 F under controlled conditions detailed in API R11 S2. Refer to the articles “Pump Performance Curves – part 01” and “Pump Performance Curves – part 02” for more details.

Once calculated, divide the TDH by the Head developed per stage to get the Total Number of Stages required to produce the anticipated capacity.

Total Stages = TDH / [(Head / stage)]

## ESP design – Step 4: Total Dynamic Head

The step4 of the ESP design consists on determining the total dynamic head required to pump the desired capacity. It is common to simplify the procedure by combining or summarizing the additional energy that the pump must supply into a single term, Total Dynamic Head (TDH). TDH is a summation of the net vertical distance ﬂuid must be lifted from an operating ﬂuid level in the well, the frictional pressure drop in the tubing and the desired wellhead pressure.

TDH = HD + HF + HT

• TDH: total dynamic head in feet (meters) delivered by the pump when pumping the desired volume.
• HD: vertical distance in feet (meters) between the wellhead and the estimated producing fluid level at the expected capacity.
• HF: the head required to overcome friction loss in tubing measured in feet (meters).
• HT: the head required to overcome friction loss in the surface pipe, valves, and fittings, and to overcome elevation changes between wellhead and tank battery.

PS: HT is normally measured in gauge pressure at the wellhead. It can be converted to head, in feet (meters) as follows: HT = (psi / (0.433 psi/ft x sp. gr.)

## Affinity Laws

The affinity laws, also known as “Pump Laws”, for pumps are used to express the relationship between variables involved in pump performance (such as head, flow rate, shaft speed) and power.

According to the affinity laws, the following relationships exist between the actual speed of the centrifugal pump and its most important performance parameters:

• The flow rate of a pump changes directly proportional to its operating speed.
• The head developed by the pump changes proportionally to the square of the speed.
• The brake horsepower required to drive the pump changes proportionally to the cube of the speed.
• The efficiency of the pump does not change with speed changes.

## Pump Performance Curves – part 02

In the previous article “Pump Performance Curves – part 01“, we have discussed how pump performance curves are obtained? How there are plotted? What are the downthrust and the upthrust? and what is the recommended operating range of the pump? In this article, pump performance curve is further detailed and we will answer the following two questions :

• How the shape of the pump performance curve is related to changes in well performance?
• What are the tolerance limits of performance data?

### Shape of the pump performance curve:

The  ability  of  a  pump  to  adapt  to  changes  in  well  performance  depends  on  the characteristic  shape of  the pump performance  curve.