The overall logic for the Liquid Loading Monitor (Liquid Loading sub-tab) is as follows:
- Obtain the gas properties for the well (or scenario) from the Properties editor.
- Use a Harmony Reservoir™ model's forecast. (Forecasts from analytical or numerical models are used since they have both rate and sandface pressure.)
- For each timestep in the forecast:
- Obtain the sandface pressure, sandface temperature, and wellbore flow path diameter.
- Use the sandface pressure and temperature, along with gas properties, to determine the gas compressibility factor (Z) and gas density.
- Calculate the liquid loading rate 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
- Indicate the timestep where the actual gas rate is less than the liquid loading gas rate
Note: As with other Harmony Optimize™ tools, liquid loading calculation details can be configured in the Wellbore editor. This includes the liquid loading equation (Turner, Coleman, or custom), the liquid used to calculate against (water or condensate), and the location of the wellbore flow path diameter (either at EOT or datum). The default equation is Turner with water, and the default location for the flow path diameter is at EOT.
As can be seen from the logic steps above, 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, model forecasts usually default to monthly timesteps. For example, if the Monitor displays that liquid loading occurs on “March 8th, 2024”, it is likely that the previous timestep was February 8th (and therefore the liquid loading threshold could have been passed on February 9th). Consider this tool to be a simple diagnostic, while other Optimize tools use more detailed information.