I recently had a question from a user that is as follows:
"When I am running RODSTAR and I change the option as to whether I have a pumped off condition or a gas interference condition there is no change in the predictive surface or downhole card. Why is that? "
The answer follows:
The results of RODSTAR if you select Fluid Pound vs. Gas Interference will be the same if the fluid level is at the pump in both cases. Since the pressure of the gas entering the pump depends on fluid level, this pressure will be the same if the fluid level is at the pump, so basically fluid pound and gas interference would be the same as far as the pressure of the gas entering the pump. However, if you select to simulate gas interference with fluid over the pump vs Fluid Pound (for which the program sets the fluid level at the pump) then the results will be different. Please keep in mind that when designing a new system, it is best to design it for full pump with fluid level at the pump to ensure that your system can handle this worst case condition. Then, you can make another run to see what would happen if you have fluid pound of gas interference.