A new wellbore fluid load diagnosing model based on the energy conservation law

Liquid load in the borehole would affect the rate stability of gas well adversely. However, the existing liquid load detection techniques are somewhat limited by practical application. For the purpose of clarifying the liquid-carrying mechanism of two-phase flow in the wellbore with a higher liquid rate, it is necessary to accurately diagnose the presence of liquid loading in the wellbore and reasonably formulate the production measures of the gas well. On the basis of previous studies, this paper established a new model for diagnosing the liquid-carrying conditions of gas–liquid two-phase vertical pipe flow according to the law of energy conservation. Then, by comparing with field practice statistics and indoor experimental data, the accuracy of the new model was verified. Finally, the new model was applied to analyze the liquid-carrying condition of one certain liquid-producing gas well. And the following research results were obtained. First, when the liquid production rate is lower, the critical liquid-carrying gas rate calculated by the new model is much lower than the calculation result of the Turner model. Second, with the increase of the liquid production rate, the critical liquid-carrying gas rate calculated by the new model increases gradually. And the higher the pressure is, the more obvious the increase of the critical liquid-carrying gas rate is. Third, from the perspective of flow pattern, the gas–liquid two-phase vertical pipe flow can be divided into 5 kinds, including bubble flow, slug flow, transition flow, wavy flow and annular mist flow. When the two-phase flow is transition flow, wavy flow or annular mist flow, there is no liquid loading in the wellbore. In conclusion, the calculation result of the new model is basically accordant with field practice statistics and indoor experimental data, and its diagnostic conclusion conforms to the actual situations. Obviously, this model is of universality and provides a theoretical support for the diagnosis of liquid-carrying condition and the prevention of fluid loading in liquid-producing gas wells.