ESP design – Step 5: Pump Type

In order to select the most suitable pump, Refer to the pump selection data table in the manufacturer’s catalog for pump type, range and pump performance curve. Based on expected fluid production rate and casing size, select the pump type which will be operating within the recommended operating range and nearest to the pump’s peak efficiency.

When two or more pump types have similar efficiencies at the desired production rate, the following recommendations should be considered to select the most adaptable pump to the well conditions:

The 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. A pump with a steep characteristic (i.e.  large  change  in  head with  respect  to  flow  rate)  is  less  suited  to  a well with  poorly defined  inflow  performance  (IPR),  especially  if  it  is  intended  to  produce  with  a  fixed drawdown.  For  such pumps,  a  small  loss  in  IPR  translates  to  a  large  fall  in pump  intake pressure and may result in gas locking. Conversely, the head produced by a pump with a flatter characteristic will change less for a given  change  of  flow  rate  and  can  therefore  be  used  over  a wider  variety  of  IPR’s with limited changes in intake pressure.

Refer to the article “Pump Performance Curves – part 02” for more details.

The number of pump stages:

If two pump types have approximately equal efficiency at the desired fluid production rate, select the pump type which requires the greatest number of stages. Such a pump will produce a capacity nearest the desired production rate even if the well productivity is substantially more or less than expected. In the other hand, a greater number of stages means longer pump which couldn’t be recommended in deviated wells with high dogleg severity.

The presence of gas at the pump intake:

If gas is present in the produced fluid, a gas separator / gas handler may be required to achieve efficient operations. Refer to the article “ESP: Intake & Gas Separator” to review the different technologies of gas separator, as well as the article “ESP: Gas handling device” to review the additional benefits of gas handlers. The calculation of the percentage of free gas present at the pump intake was detailed in Step 3 of the 9 Step Design Procedure.

Viscous fluid / Emulsion / Sand production…:

If the produced fluid is quite viscous and/or trends to emulsify, the reservoir trends to produce sand, or any other extraordinary circumstances, some corrections to the pump design may be necessary to ensure a more efficient operation. In such case, contact the manufacturer for recommendations.

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