Q: I’m running a multiphase case with an IPR, and as I try calculations with higher flow rates, the fluid level goes up (i.e. towards surface) when I expect it to go down. Why?

A: This can happen in some cases with very gassy wells. As the pressure at the perforations decreases (as happens when the flow rate is increased with an IPR) more gas comes out of this solution. Some or all of this gas goes up the casing annulus (depending on the free gas separation value, and on whether the pump intake is above or below the perforations). This gas serves to decrease the overall density of the fluid in the casing. The fluid level is determined by calculating what depth of fluid is necessary for there to be the required pressure at the perforations. The pressure at the perforations is determined from the IPR, but is also the sum of the casing head pressure, the hydrostatic pressure due to the gas column (normally very small) and the hydrostatic pressure due to the liquid column. The hydrostatic pressure due to the liquid column depends on the fluid level and the fluid density. In some cases, as the density decreases, the fluid level must be higher in the well (i.e. at a lower mKB or ftKB value) to achieve the required pressure at the perforations. In some extreme cases, it will not be possible to calculate a fluid level. In these cases, you will either get Error 813 or Error 8002 (both these error messages are shown above). Interestingly, in many of these cases, you will see that at higher flow rates a valid result can once again be obtained.

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