Theoretical Study on Critical Liquid-Carrying Capacity of Gas Wells in Fuling Shale Gas Field

The most common type of well in the Fuling shale gas field is the long horizontal section well. Once the energy attenuates, it is difficult to discharge the accumulated liquid. So, it is particularly important to determine the time of accumulation. Through indoor experiments, it was observed that droplets in the gas core flowing under critical conditions and the liquid film adhering to the tube wall cannot be ignored. It was also discovered that the liquid phase on the tube wall can form fluctuations due to the shear effect of the gas phase. Based on the observed distribution of gas–liquid phases in experiments, a critical liquid-carrying velocity calculation method considering the coexistence of droplets and liquid films, as well as the frictional resistance coefficient at the gas–liquid interface under wave morphology, was established. Integrating production data from 106 wells at home and abroad, as well as testing data from the Fuling example well, the new model was validated. The results showed that the new model can accurately diagnose fluid accumulation in different gas fields, with an accuracy rate of 86.8%, and it can provide an accurate diagnosis for fluid accumulation in gas wells in different water-producing gas fields.