Abstract: The blowout stoppage of horizontal gas wells is a common problem in the middle and late stages of the development of constant-volume gas reservoirs, and it is necessary to identify the causes of the stoppage and take measures to restore production in a timely manner. To this end, the theoretical equation of critical liquid-carrying in horizontal wells was combined with the binomial deliverability equation of horizontal wells and the calculation equation of bottomhole flowing pressure to establish three criteria for blowout stoppage: critical liquid-carrying flow rate, critical lifting differential pressure, and critical formation pressure, analyze the influences of factors such as wellhead pressure and tubing inner diameter on the criteria, and study the roles of the three criteria in identifying the causes of blowout stoppage in gas wells, and then create a method to identify the causes of blowout stoppage of gas wells in a quick manner. The study shows that: The critical liquid-carrying flow rate has an increasing multiplicative power function with the wellhead pressure and tubing inner diameter, the higher the wellhead pressure and the larger the tubing inner diameter, the larger the critical liquid-carrying flow rate is, when the actual gas volume of the well is lower than the critical liquid-carrying flow rate, it can be determined that the wellbore has begun to accumulate fluids; the critical lifting differential pressure has nothing to do with the tubing inner diameter, and only rises linearly with the wellhead pressure, when the actual lifting differential pressure is lower than the critical lifting differential pressure, it is necessary to consider the problem of insufficient fluid power of the well; the tubing inner diameter only increases with the wellhead pressure; the critical lifting differential pressure has no effect on the wellhead pressure, so it is necessary to consider the problem of insufficient fluid lifting power of the gas well; when the tubing inner diameter remains unchanged, the critical formation pressure rises linearly with the wellhead pressure, and in the case of a large consumption of formation pressure, the critical formation pressure is easy to exceed the actual formation pressure of the gas well, i.e., the gas well will be triggered to stop blowout due to the insufficient driving energy. The application example proves that the method can effectively identify the reasons for the blowout stoppage of horizontal gas wells and provide theoretical basis for the technological measures. The establishment of this method is of great significance for the high-efficiency development of the low-pressure stage of constant-volume gas reservoirs.

Key words: constant-volume gas reservoir, horizontal well, blowout stoppage, critical liquid-carrying flow rate, critical lifting differential pressure, critical formation pressure