gas_rate_radial
Calculate gas production rates for vertical wells using real gas pseudopressure formulation to account for pressure-dependent properties in radial flow systems.
Instructions
Calculate gas production rate for radial flow (vertical well).
INFLOW PERFORMANCE TOOL - Computes gas production rate for vertical wells with radial flow geometry using real gas pseudopressure formulation. This accounts for pressure-dependent gas properties (Z-factor, viscosity) which are significant for gas systems. More accurate than simplified Darcy's law for gas.
Parameters:
pi (float, required): Initial/reservoir pressure in psia. Must be > 0. Example: 5000.0.
sg (float, required): Gas specific gravity (air=1). Valid: 0.55-3.0. Typical: 0.6-1.2. Example: 0.7.
degf (float, required): Reservoir temperature in °F. Valid: -460 to 1000. Example: 180.0.
psd (float or list, required): Sandface/draining pressure(s) in psia. Must be > 0 and < pi. Can be scalar or array. Example: 2000.0 or [1000, 2000, 3000].
h (float, required): Net pay thickness in feet. Must be > 0. Typical: 10-200 ft. Example: 50.0.
k (float, required): Permeability in millidarcies (mD). Must be > 0. Typical: 1-1000 mD. Example: 100.0.
s (float, optional, default=0.0): Skin factor (dimensionless). Negative = stimulation, positive = damage. Typical: -5 to +20. Example: 0.0 for undamaged well.
re (float, required): Drainage radius in feet. Must be > rw. Typical: 500-5000 ft. Example: 1000.0.
rw (float, required): Wellbore radius in feet. Must be > 0. Typical: 0.25-0.5 ft. Example: 0.5.
h2s (float, optional, default=0.0): H2S mole fraction (0-1). Typical: 0-0.05. Example: 0.0.
co2 (float, optional, default=0.0): CO2 mole fraction (0-1). Typical: 0-0.20. Example: 0.0.
n2 (float, optional, default=0.0): N2 mole fraction (0-1). Typical: 0-0.10. Example: 0.0.
Pseudopressure Method: Uses real gas pseudopressure (m(p)) which linearizes the gas diffusivity equation: m(p) = 2∫(p/(μZ))dp from pb to p
This accounts for:
Z-factor variation with pressure
Gas viscosity variation with pressure
Non-linear pressure behavior
Flow Formula: qg = (kh × (m(pi) - m(pwf))) / (1422 × T × (ln(re/rw) + S))
Where PVT properties are integrated over pressure range.
Returns: Dictionary with:
value (float or list): Gas rate in MSCF/day (matches input psd shape)
method (str): "Pseudopressure radial flow"
units (str): "MSCF/day"
inputs (dict): Echo of input parameters
Common Mistakes:
Using separator temperature instead of reservoir temperature
Pressure in barg/psig instead of psia (must be absolute)
Not accounting for non-hydrocarbon fractions (H2S, CO2, N2)
Using wrong drainage radius (re) - should be well spacing/2
Confusing net pay (h) with gross thickness
Not accounting for skin factor (s)
Example Usage:
{
"pi": 5000.0,
"sg": 0.7,
"degf": 180.0,
"psd": [2000, 3000, 4000],
"h": 50.0,
"k": 100.0,
"s": 0.0,
"re": 1000.0,
"rw": 0.5,
"h2s": 0.0,
"co2": 0.0,
"n2": 0.0
}Result: Gas rate decreases as sandface pressure increases (typical IPR curve).
Note: This tool uses pseudopressure method which is more accurate than simplified Darcy's law for gas. Always account for non-hydrocarbon components (H2S, CO2, N2) as they affect Z-factor and flow calculations significantly.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| request | Yes |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||