How Are Hydrate Plug Formations Prevented

The five studies of hydrate formation given in Section 8.1 are of two types. The first three case studies show thermodynamic (time-independent) methods to prevent plug formation. However, the second type provides a closer, mechanistic look at the physical kinetics (time-dependent) hydrate formation and agglomeration. A goal of this section is to show how these two methods provide two different methods of plug prevention. 

Avoidance of the hydrate formation thermodynamic conditions of temperature, pressure, or inhibitor concentration, makes it impossible for plugs to form. The calculations of thermodynamic conditions can be made with acceptable accuracy. Using the methods presented in Chapters 4 and 5 along with the CD program CSMGem provided with this book, the temperature, pressure, and inhibitor concentrations can be calculated respectively, to within 2°F, 10% in pressure and 3% of inhibitor concentration. Since the discovery of hydrate flowline plugs in 1934, such thermodynamic methods have served to provide the major method of flow assurance. 

However, as mankind has exhausted the most accessible hydrocarbon supplies, more severe conditions (e.g., higher pressures, lower temperatures, and higher acid gas contents) caused thermodynamic prevention means to be less acceptable economically. The following two case studies illustrate the fact that thermodynamic inhibition is becoming very expensive. 

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