Single and multiphase flow through restrictions

The negative impact of the use of chokes (or any type of restriction) in the flow line or the production tubing in a gas lifted well is illustrated at the beginning of the chapter with the help of pressure–depth diagrams and inflow–outflow curves. However, despite this negative impact, several operational conditions for which it is necessary to use chokes to restrict the liquid and gas flow rates are also described. The equation that describes the gas flow rate for compressible flow through restrictions is developed from the energy balance equation. The general Thornhill–Craver equation is presented and its use is illustrated in an example problem. The iterations that are required to find the gas injection pressure upstream of a restriction, from the downstream pressure and the gas flow rate, is illustrated with the use of gas flow rate diagrams. One equation that can be used to model the liquid flow through a restriction is presented and illustrated in an example problem. Finally, an updated list of correlations and mechanistic models that can be used to model multiphase flows through chokes is described.