Neqsim E300 Fluid Io

E300 Fluid I/O

Use this skill to move fluids between Eclipse 300 (E300) compositional EOS files and NeqSim, and to add water to a fluid or E300 file using the public PVTsim water parameterization.

The skill has two layers:

• A pure-Python layer that parses, edits, and writes the E300 keyword format without requiring NeqSim. It is used to inspect files, add water, and produce E300 files that NeqSim can read back.
• A NeqSim bridge that wraps neqsim.thermo.util.readwrite.EclipseFluidReadWrite to load E300 files into rigorous NeqSim SystemInterface fluids, add water, and write fluids back to E300.

When to Use

• When a task provides an E300 file and needs a NeqSim fluid for simulation.
• When a NeqSim fluid must be exported to an E300 file for PVTsim or Eclipse.
• When water must be added to a dry fluid using the public PVTsim water parameters (reproducing a PVTsim *_water.e300 file).
• When an existing E300 file must be copied with water appended as the last component with a binary interaction parameter of 0.5 against all components.
• When a task must document or verify the E300 keyword layout.

Inputs

• e300_path: path to an Eclipse E300 file.
• add_water: whether to append a water component (H2O).
• water_kij: water binary interaction parameter (PVTsim default 0.5).
• reservoir_temp_c: reservoir temperature written to the RTEMP keyword.
• neqsim_fluid: a NeqSim SystemInterface fluid (for export).

Outputs

• neqsim_fluid: a NeqSim fluid created from an E300 file.
• e300_file: a written E300 file (with or without water).
• e300_string: E300 keyword text for a NeqSim fluid.
• E300Fluid: a pure-Python object with component names, EOS parameters, the binary interaction matrix, and the overall composition.

Engineering Method

E300 file format

An E300 file is a keyword text file. Each keyword introduces a value block that is terminated by a /. Lines starting with -- are comments. The keywords this skill reads and writes are:

The BIC block lists, for component r (1-based, r = 1..n-1), the r interaction values against components 0..r-1. The skill reconstructs the full symmetric matrix with a zero diagonal.

Adding water

Water is appended as the last component with the public PVTsim Peng-Robinson water calibration. These constants match a PVTsim *_water.e300 file:

NeqSim's EclipseFluidReadWrite.addWaterToFluid applies the same volume shift (0.084004), parachor (10.0), and binary interaction parameter (0.5) and enables the multiphase check, so the pure-Python path and the NeqSim path agree.

Python Usage Pattern

Pure-Python: add water to an E300 file

from e300_fluid_io import add_water_to_e300_file, read_e300_file

# Read an E300 file (no NeqSim required)
fluid = read_e300_file("osebergfluid.e300")
print(fluid.names, fluid.ncomps)

# Add water and write a PVTsim-style *_water.e300 file
add_water_to_e300_file("osebergfluid.e300", "osebergfluid_water.e300")

NeqSim bridge: E300 to fluid, fluid to E300

from e300_fluid_io import (
    read_e300_to_neqsim,
    neqsim_add_water,
    write_neqsim_to_e300,
    neqsim_to_e300_string,
)

# Read an E300 file into a rigorous NeqSim fluid
fluid = read_e300_to_neqsim("osebergfluid.e300")
fluid.setMixingRule("classic")

# Or read and add water in one call (PVTsim water parameters)
wet = read_e300_to_neqsim("osebergfluid.e300", add_water=True, water_kij=0.5)

# Add water to an existing NeqSim fluid
neqsim_add_water(fluid, water_kij=0.5)

# Write a NeqSim fluid back to an E300 file
write_neqsim_to_e300(fluid, "exported.e300", reservoir_temp_c=110.0)

# Or render the E300 text directly
text = neqsim_to_e300_string(fluid, reservoir_temp_c=110.0)

The bridge functions raise a clear RuntimeError when the optional neqsim Python package is not installed. The pure-Python functions always work.

Validation Checklist

• E300Fluid.validate() returns an empty list (vectors match component count, BIC is square).
• Overall composition ZI sums to the expected basis before simulation.
• Water appears once as the last component after adding water.
• Water volume shift is 0.084004 and parachor is 10.0.
• Water binary interaction parameter is 0.5 (or the chosen water_kij) against all components.
• An E300 file written by this skill reloads in NeqSim without error.
• setMixingRule("classic") is called before NeqSim property calculations.

Common Mistakes

Per-component EOS tuning survives the export: TCRIT, PCRIT, ACF, SSHIFT and BIC are all written and read back, so regressed critical-property multipliers, volume shifts and binary interaction parameters transfer.

Limitations

• The pure-Python writer emits one value per line and one BIC row per line. This is valid E300 that NeqSim reads back, but it is not byte-identical to a PVTsim Nova export.
• The skill does not characterize plus fractions, regress binary interaction parameters, or tune the equation of state.
• Water is added with the public PVTsim calibration only; project-specific water models require qualified data and review.
• The skill does not validate laboratory data or replace PVT specialist judgement.

Related NeqSim Functionality

This skill wraps validated, rigorous NeqSim Java functionality that a qualified engineer should use for design-grade work:

• neqsim.thermo.util.readwrite.EclipseFluidReadWrite#read(String) — read an E300 file into a NeqSim fluid.
• neqsim.thermo.util.readwrite.EclipseFluidReadWrite#read(String, boolean, double) — read an E300 file and add water.
• neqsim.thermo.util.readwrite.EclipseFluidReadWrite#addWaterToFluid(SystemInterface, double) — add water with the PVTsim water parameters.
• neqsim.thermo.util.readwrite.EclipseFluidReadWrite#write(SystemInterface, String, double) — write a NeqSim fluid to an E300 file.
• neqsim.thermo.util.readwrite.EclipseFluidReadWrite#toE300String(SystemInterface, double) — render a NeqSim fluid as E300 text.

In Python these classes are reachable through the neqsim package (from neqsim import jneqsim).

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md
• Eclipse 300 / PVTsim Nova compositional EOS keyword documentation (vendor manuals).