pyResToolbox MCP Server

Calculate solution gas-oil ratio (Rs) at specified pressure.

CRITICAL PVT PROPERTY - Computes volume of gas dissolved in oil at given pressure and temperature. Rs increases with pressure up to bubble point, then remains constant (equal to rsb) above bubble point.

Parameters:

• api (float, required): Oil API gravity in degrees. Valid: 0-100. Example: 35.0.

• degf (float, required): Reservoir temperature in °F. Valid: -460 to 1000. Example: 180.0.

• p (float or list, required): Pressure(s) in psia. Must be > 0. Can be scalar or array. Example: 3000.0 or [2000, 3000, 4000].

• sg_g (float, optional, default=0.0): Separator gas specific gravity (air=1). Valid: 0-3. Typical: 0.6-1.2. Example: 0.75.

• pb (float, optional, default=0.0): Bubble point pressure in psia. If 0, will be calculated. Must be ≥ 0. Example: 3500.0.

• rsb (float, optional, default=0.0): Solution GOR at bubble point in scf/stb. If 0 and pb provided, will be calculated. Must be ≥ 0. Example: 800.0.

• method (str, optional, default="VELAR"): Correlation method. Options: "VELAR", "STAN", "VALMC".

Pressure Behavior:

• p < pb: Rs calculated from correlation (increases with pressure)

• p ≥ pb: Rs = rsb (constant, no additional gas dissolves)

Method Selection:

• VELAR (Velarde 1997): Default, good accuracy. Use for most cases.

• STAN (Standing 1947): Classic, widely used. Use for compatibility.

• VALMC (Valko-McCain 2003): Alternative method.

Returns: Dictionary with:

• value (float or list): Rs in scf/stb (matches input p shape)

• method (str): Method used

• units (str): "scf/stb"

• inputs (dict): Echo of input parameters

Common Mistakes:

• Using separator gas gravity instead of separator gas gravity (sg_g parameter)

• Not providing pb when p > pb (will calculate incorrectly)

• Pressure in barg/psig instead of psia (must be absolute)

• Confusing rsb (at bubble point) with separator GOR

Example Usage:

Result: Rs increases from ~400 scf/stb at 2000 psia to 800 scf/stb at 3500 psia, then remains 800 scf/stb at 4000 psia (above bubble point).

Note: Always provide pb and rsb when available for accurate results. If unknown, set pb=0 and rsb=0 to auto-calculate, but accuracy may be reduced.