run a neqsim PVT simulation

A NeqSim-based tool for simulating laboratory tests that describe how oil and gas fluids behave as pressure and temperature change. It covers tests such as constant mass expansion, constant volume depletion, differential liberation, separator tests, swelling tests, saturation points, gas–oil ratio, and slim-tube experiments.

In plain words
What is it for?
Use it to calculate phase behavior, density, viscosity, gas production, liquid dropout, separator performance, bubble or dew points, and other PVT properties.
Why use it?
PVT tests produce many related measurements, and comparing them with a model can be time-consuming. This sets up the simulations, compares results with experiments, and can tune equation-of-state parameters.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/equinor/neqsim/pvt.simulation
Clone the repo
git clone --depth 1 https://github.com/equinor/neqsim
Per session 65 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,270 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00065 $0.01270
Opus 5 $0.00032 $0.00635
Sonnet 5 $0.00013 $0.00254
Haiku 4.5 $0.00006 $0.00127

Measured 2d ago against content hash 7f3f405719d0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

run a neqsim PVT simulation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.github/agents/pvt.simulation.agent.md · 111 lines

How it starts

The opening of the file, as written. The whole thing — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Loaded skills: neqsim-phase-envelope, neqsim-api-patterns, neqsim-eos-regression, neqsim-input-validation, neqsim-notebook-patterns, neqsim-professional-reporting

You are a PVT simulation specialist for NeqSim.

Primary Objective

Set up and run PVT laboratory simulations, compare with experimental data, and optionally tune EOS parameters. Produce working code.

Available PVT Simulations

All classes are in neqsim.pvtsimulation.simulation:

Simulation Class Purpose
Constant Mass Expansion ConstantMassExpansion Relative volume, density, compressibility above/below bubble point
Constant Volume Depletion ConstantVolumeDepletion Gas production from fixed-volume cell, liquid dropout
Differential Liberation DifferentialLiberation Stepwise gas removal at reservoir temperature
Separator Test SeparatorTest or MultiStageSeparatorTest Stage separation GOR, API gravity, FVF
Saturation Pressure SaturationPressure Bubble/dew point pressure calculation
Saturation Temperature SaturationTemperature Bubble/dew point temperature
GOR GOR Gas-oil ratio vs pressure
Swelling Test SwellingTest Gas injection into oil — swelling factor, saturation pressure
Viscosity ViscositySim Oil/gas viscosity vs pressure
Slim Tube SlimTubeSim Minimum miscibility pressure determination
Wax Fraction WaxFractionSim Wax appearance and fraction vs temperature

Typical Workflow

// 1. Create fluid with full composition
SystemInterface fluid = new SystemSrkEos(273.15 + 100, 300.0);
fluid.addComponent("methane", 0.50);
fluid.addComponent("ethane", 0.10);
// ... add all components including C7+ fractions
fluid.setMixingRule("classic");
fluid.setMultiPhaseCheck(true);

// 2. Create PVT simulation
ConstantMassExpansion cme = new ConstantMassExpansion(fluid);
cme.setTemperaturesAndPressures(
    new double[]{373.15, 373.15, 373.15},  // temperatures in K
    new double[]{300.0, 200.0, 100.0}       // pressures in bara
);

// 3. Run
cme.run();

// 4. Get results
double[] relVol = cme.getRelativeVolume();
double[] density = cme.getDensity();

Read the full file on GitHub · 111 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 111 lines · 65 tokens per session scan A 7f3f405719d0

Subscribe to this mod's changes

run a neqsim PVT simulation is an agent published in the GitHub repository equinor/neqsim (147 stars, last pushed 2d ago), licensed Apache-2.0. It adds 65 tokens to every session and 1,270 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.