Electrical submersible pumps could be installed in four different production environments where the criteria for the design changes as fluid properties and well conditions change. In this article, four basic design types of ESP’s will be presented.
The basic designs will change accordingly and will mainly depend on:
Downhole flow rate can be calculated from surface flow rate (stock tank barrels) using the following equation. It is assumed that no gas is dissolved in the water phase and the water formation volume factor is equal to one.
Downhole flow rate = [(Oil rate)sc × Bo] + [(Free GOR) × (Oil rate)sc × Gas FVF] + (Water rate)sc
Free GOR = Producing GOR – Solution GOR, therefore:
Where:
If CO2 is present, the calculation of downhole flow rate becomes more complex for many reasons:
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:
In this article “ Total Dynamic Head Calculation ”, the concept of the dynamic head is further detailed. As discussed in the previous article titled: “Total Dynamic Head (TDH)”, TDH is the sum of three basic components:
To properly select the pump, well performance must be estimated. Fundamentally, well performance estimates define what additional energy (i.e., volumetric flow rate and differential pressure or head) must be supplied by the pump to deliver a desired stock tank flow rate (API RP11 S4).
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
