pyResToolbox MCP Server

Instructions

{
    "sg": 0.7,
    "degf": 180.0,
    "p": [1000, 2000, 3000, 4000],
    "h2s": 0.0,
    "co2": 0.05,
    "n2": 0.01,
    "zmethod": "DAK"
}

Implementation Reference

• src/pyrestoolbox_mcp/tools/gas_tools.py:406-500 (handler)

  The core handler function for the 'gas_density' tool. It takes a GasDensityRequest, computes density using pyrestoolbox.gas.gas_den with specified Z-factor method, handles array inputs, and returns structured response with value, method, units, and inputs.

  def gas_density(request: GasDensityRequest) -> dict:
      """Calculate gas density (ρg) at reservoir conditions.
  
      **CRITICAL GAS PVT PROPERTY** - Computes gas density from real gas equation of state.
      Essential for gradient calculations, well pressure analysis, and material balance.
      Gas density increases significantly with pressure due to compressibility.
  
      **Parameters:**
      - **sg** (float, required): Gas specific gravity (air=1.0). Valid: 0.55-3.0.
        Typical: 0.6-1.2. Example: 0.7.
      - **degf** (float, required): Reservoir temperature in °F. Valid: -460 to 1000.
        Typical: 100-400°F. Example: 180.0.
      - **p** (float or list, required): Pressure(s) in psia. Must be > 0.
        Can be scalar or array. Example: 3500.0 or [1000, 2000, 3000, 4000].
      - **h2s** (float, optional, default=0.0): H2S mole fraction (0-1).
        Typical: 0-0.05. Example: 0.02.
      - **co2** (float, optional, default=0.0): CO2 mole fraction (0-1).
        Typical: 0-0.20. Example: 0.05.
      - **n2** (float, optional, default=0.0): N2 mole fraction (0-1).
        Typical: 0-0.10. Example: 0.01.
      - **zmethod** (str, optional, default="DAK"): Z-factor method for density calculation.
        Options: "DAK", "HY", "WYW", "BUR". DAK recommended.
  
      **Density Formula:**
      ρg = (P × MW) / (Z × R × T)
  
      Where:
      - P = pressure (psia)
      - MW = molecular weight = sg × 28.97 lb/lbmol
      - Z = gas compressibility factor
      - R = gas constant = 10.732 psia·ft³/(lbmol·°R)
      - T = temperature (°R = °F + 460)
  
      **Density Behavior:**
      - Increases with pressure (gas compresses)
      - Decreases with temperature (gas expands)
      - Typical range: 5-20 lb/cuft at reservoir conditions
      - At standard conditions: ~0.05-0.1 lb/cuft
  
      **Returns:**
      Dictionary with:
      - **value** (float or list): Density in lb/cuft (matches input p shape)
      - **method** (str): Z-factor method used
      - **units** (str): "lb/cuft"
      - **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
      - Using ideal gas law (Z=1) instead of real gas (Z<1)
      - Temperature in Celsius instead of Fahrenheit
  
      **Example Usage:**
      ```python
      {
          "sg": 0.7,
          "degf": 180.0,
          "p": [1000, 2000, 3000, 4000],
          "h2s": 0.0,
          "co2": 0.05,
          "n2": 0.01,
          "zmethod": "DAK"
      }
      ```
      Result: Density increases from ~8 lb/cuft at 1000 psia to ~18 lb/cuft at 4000 psia.
  
      **Note:** Gas density is much lower than oil density (typically 5-20 lb/cuft
      vs 40-60 lb/cuft). Always use reservoir conditions. Account for all non-hydrocarbon
      components - they significantly affect molecular weight and density.
      """
      method_enum = getattr(z_method, request.zmethod)
  
      den = gas.gas_den(
          sg=request.sg,
          degf=request.degf,
          p=request.p,
          h2s=request.h2s,
          co2=request.co2,
          n2=request.n2,
          zmethod=method_enum,
      )
  
      # Convert numpy array to list for JSON serialization
      if isinstance(den, np.ndarray):
          value = den.tolist()
      else:
          value = float(den)
  
      return {
          "value": value,
          "method": request.zmethod,
          "units": "lb/cuft",
          "inputs": request.model_dump(),
      }

• src/pyrestoolbox_mcp/models/gas_models.py:141-177 (schema)

  Pydantic schema (BaseModel) defining input parameters and validation for the gas_density tool, including sg, degf, p (scalar or list), h2s, co2, n2, zmethod with field validators for positive pressure.

  class GasDensityRequest(BaseModel):
      """Request model for gas density calculation."""
  
      sg: float = Field(
          ..., ge=0.5, le=2.0, description="Gas specific gravity (air=1, dimensionless)"
      )
      degf: float = Field(
          ..., gt=-460, lt=1000, description="Temperature (degrees Fahrenheit)"
      )
      p: Union[float, List[float]] = Field(
          ..., description="Pressure (psia) - scalar or array"
      )
      h2s: float = Field(
          0.0, ge=0.0, le=1.0, description="H2S mole fraction (dimensionless)"
      )
      co2: float = Field(
          0.0, ge=0.0, le=1.0, description="CO2 mole fraction (dimensionless)"
      )
      n2: float = Field(
          0.0, ge=0.0, le=1.0, description="N2 mole fraction (dimensionless)"
      )
      zmethod: Literal["DAK", "HY", "WYW", "BUR"] = Field(
          "DAK", description="Z-factor calculation method"
      )
  
      @field_validator("p")
      @classmethod
      def validate_pressure(cls, v):
          """Validate pressure values."""
          if isinstance(v, list):
              if not all(p > 0 for p in v):
                  raise ValueError("All pressure values must be positive")
          else:
              if v <= 0:
                  raise ValueError("Pressure must be positive")
          return v

• src/pyrestoolbox_mcp/server.py:25-25 (registration)

  Call to register_gas_tools(mcp) which defines and registers all gas tools including gas_density via @mcp.tool() decorators within the function.

  register_gas_tools(mcp)

• src/pyrestoolbox_mcp/tools/gas_tools.py:26-26 (registration)

  The register_gas_tools function where the gas_density tool is defined with @mcp.tool() decorator for registration.

  def register_gas_tools(mcp: FastMCP) -> None: