Q: When should I use the “Calculate Free Gas Separation” option?

If you use this calculation option built into PC-PUMP (in multiphase flow) it will do one of two things. If the pump (or tail joint) intake is located below the perforations, it will assume 100% separation efficiency—all the free gas at the perforations is assumed to go up. If the intake is located above the perforations, it will estimate a separation efficiency. This calculation assumes that the pump intake is centralized and that the well is near vertical where the intake is located—if these conditions are true, the calculation should be reasonably accurate. Times when you might not want to use the calculation option include:
a ) The intake is located below the perforations but there is high velocity and/or high viscosity, which could drag free gas down to the intake. In this case, the separation will be less than 100%.
b) The intake is not centralized. If the intake is pushed against the wall of the tubing, the separation efficiency may be improved.
c ) The intake is not in a vertical portion of the well. If the intake rests on the low side of the well, the efficiency should be improved, but if it is pushed against the high side, it could be worsened. If it is centralized, the efficiency may be increased or decreased, depending on the amount of free gas and the angle of the well.
d) A gas separation device is used. If working properly, a gas separator should increase the separation efficiency, but the amount of increase will depend on several factors.
In any of these cases, you will need to estimate a value for gas separation and enter it manually.

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