Acid Gas Injection (AGI) Well Calculator

CO₂/H₂S Phase, Density, & Injection Pressure for UIC Class II Disposal

Size an acid gas injection well for CO₂/H₂S/CH₄ streams from amine units. Classifies fluid phase (gas, dense-phase, or liquid), computes injection density, BHP at perfs, surface tubing pressure, and frac-gradient limit. Includes NACE MR0175 sour-service flags for tubing material.

Acid Gas Composition

mol %
mol %
mol %
mol %
Saturate water from amine regenerator overhead
MMSCFD

Well & Reservoir

ft
psig
°F
°F
After compression aftercooler
in
ft

Inflow & Limits

mD
ft
psi/ft

Key Approach

Mixture critical point (Kay's rule):

Tpc = Σ yi·Tc,i | Ppc = Σ yi·Pc,i

Pure-component criticals (for reference):

SpeciesTc (°F)Pc (psia)MW
CO₂881,07144.01
H₂S2131,30634.08
CH₄−11666716.04
H₂O7053,20018.02

Phase classification:

Gas: Tr > 1, Pr < 1 | Dense-phase: Tr > 1, Pr > 1 | Liquid: Tr < 1, Pr > 1

Hydrostatic head (compressible):

PBHP = PWH · exp(MW·g·depth / Z·R·T) (Cullender-Smith iterative)