Impact of Gas Composition and Injection Rate on Hydrate Formation Pressure in Gas Lifting

In oil production wells, which reservoir is under water injection process or when perforated area of well is near to oil water contact of reservoir, water is also produced as a by product. Light hydrocarbon components when are produced together with water fractions, at low temperature conditions, form hydrates within well or in surface production facilities and cause plugging problems. When gas lifting process is used in such a production well, separator gas or an inert gas from an exterior resource is injected into well and it changes composition of producing fluid within well bore. This, in turn changes hydrate formation pressure of producing oil. In this work, several cases of producing fluids with different injection gas compositions and rates were simulated with PVTsim software for prediction of hydrate formation pressures. The results show that when we inject separator gas into well, since it consists mainly of light hydrocarbons, hydrate formation pressure decreases. This decrease can be up to 3000 psia in 80° Fahrenheit with 1 Mscf/STB injection rate. But when we inject an inert gas into well, water fraction decreases rapidly and hydrate formation pressure increases. This increase can become 3500 psia in 80° Fahrenheit with 1 Mscf/STB injection rate.

کلیدواژه ها:

Gas lifting ، Hydrate formation ، Hydrate PT curve ، Injection rate ، Minimum inhibitor