This test is very useful when expecting a Gas fluid column well into annular space. The DP/Casing survey is a special form to calculate liquid levels in which a foam depressurize test was conducted along with the liquid level.
The purpose of this foam depressurize test is to determine the percent of gas in the fluid column.
Once this has been determined, then it calculates a more accurate estimate of the gas-free liquid above the pump and subsequently a more accurate estimate of the producing bottom hole flowing pressure.
Upon determining the PBHP, the maximum producing rate (Qmax) and potential oil gain (P.O.G.) are calculated at a suitable pressure drop using Vogel’s Inflow Performance Relationship.