PRODUCTION ENGINEERING - CHOKE PERFORMANCE

Flow Through Chokes (Gas)

INPUT   DATA

Title  

Choke diameter 64ths of inch
Choke flow coefficient  
Gas gravity  
Heat capacity ratio  
Wellhead flowing pressure psia
Wellhead temperature ° F
Outlet flowing pressure psia

     Reset

OUTPUT   VARIABLES   &   GRAPH

Gas flow rate MSCF/d
Critical pressure ratio  
THEORY  &   FORMULAE

Gas Flow Through Chokes

The isentropic flow of ideal gas through a choke is related to the pressure ratio by the following equation {Equation-I} expressed in oilfield units:


        

where:

    qg= flow rate, MSCF/day
    D64= choke diameter (bean size), 64th of inch
    α = flow coefficient of the choke
    γ = heat capacity ratio, [Cp/Cv]
    ρ = gas gravity
    T1 = temperature upstream of choke, ° F
    p1 = pressure upstream of choke, psia
    p2 = pressure downstream of choke, psia

Equation-I applies when the pressure ratio (p2/p1) is equal to or greater than the critital pressure ratio. The critical pressure is given by the following equation {Equation-II}:

        

When the pressure ratio is less than the critical pressure ratio, (p2/p1) should be set equal to (p2/p1)c in Equation-I, since the flow rate is insensitive to the downstream pressure whenever flow is critical.

BIBLIOGRAPHY