The overall logic for liquid loading is as follows:
- Use a Harmony Reservoir™ model's forecast. (These forecasts are used since they have both rate and sandface pressure.)
- For each time step in the forecast, obtain the sandface pressure and wellbore flow-path diameter.
- Use the sandface pressure and temperature to determine gas density.
- Calculate the liquid loading rate (Turner, Coleman, or custom) from that gas density and the wellbore flow-path diameter
- Compare the liquid loading rate to the actual gas rate from the model's forecast, and then indicate the time at which actual gas rate < liquid loading gas rate.
The math used to calculate the liquid loading threshold in the Liquid Loading Monitor is less precise than other Optimize tools. For example, the Flowing Gradient tool shows liquid loading velocity vs. actual velocity all along the wellbore – even if the wellbore diameter changes with depth. On the other hand, the Liquid Loading Monitor exclusively uses the sandface pressure and temperature to calculate gas properties, and compares that against a single diameter. Furthermore, when using model forecasts, the frequency is limited to the number of calculations done in the forecast. In other words, if the Sputter Monitor declares that liquid loading occurs on “March 8th, 2024”, remember that the previous calculation may have been done on January 2nd (and therefore the liquid loading threshold could have been passed on January 3rd). Consider this tool to be a simple diagnostic, while other Optimize tools use more detailed information.