neqsim: Skill for Claude Code

.github/skills/neqsim-ccs-hydrogen/SKILL.md

neqsim-ccs-hydrogen is a skill for Claude Code, Codex from equinor/neqsim. It costs 85 tokens per session (4,050 once invoked), scanned A, original, Apache-2.0.

A guide to modeling carbon capture, transport, and storage systems and hydrogen systems with NeqSim.

In plain words
What is it for?
It helps model CO2 pipelines and storage, injection wells, dehydration, impurity effects, hydrogen blending, electrolysis, blue hydrogen, and hydrogen pipelines.
Why use it?
It gives developers and engineers domain patterns for handling phase behavior, impurities, transport conditions, and relevant industry standards.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

This is equinor/neqsim's own configuration. It tells Claude Code and Codex how to work on neqsim itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything neqsim configures →

Reuse

Borrowing it

Nothing to install: this file belongs to equinor/neqsim. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/equinor/neqsim/master/.github/skills/neqsim-ccs-hydrogen/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/equinor/neqsim

Made for: Claude Code, Codex.

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README.md
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Per session 85 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,050 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 5.1 $0.00085 $0.04050
Opus 5 $0.00043 $0.02025
Sonnet 5 $0.00017 $0.00810
Haiku 4.5 $0.00009 $0.00405

Measured 11d ago against content hash 73f723229c4e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

neqsim-ccs-hydrogen 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 11d 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/skills/neqsim-ccs-hydrogen/SKILL.md · 381 lines

How it starts

The opening of the file, as written. The whole thing — 381 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CCS and Hydrogen Systems with NeqSim

Guide for modeling carbon capture and storage (CCS) value chains and hydrogen systems, including CO2 transport, injection wells, impurity effects, and H2 blending.

When to Use This Skill

  • CO2 pipeline design and phase behavior
  • CO2 injection well analysis and safety
  • Impurity effects on CO2 phase envelope (H2, N2, O2, H2S, CH4)
  • Dense phase CO2 transport conditions
  • CO2 dehydration requirements
  • Hydrogen blending with natural gas
  • Water electrolysis and green hydrogen
  • Blue hydrogen (SMR/ATR + CCS)
  • Hydrogen pipeline transport

Applicable Standards

Domain Standards Key Requirements
CO2 pipeline DNV-RP-F104, ISO 27913, DNV-ST-F101 Project composition/phase envelope, transport hydraulics, structural design, fracture/materials/corrosion and lifecycle evidence
CO2 storage ISO 27914, EU CCS Directive Storage site characterization
CO2 transport ISO 27913 Composition specs, phase management
CO2 quality ISO 27916 CO2 stream specification
Hydrogen pipeline ASME B31.12 H2 piping and pipelines
Hydrogen quality ISO 14687 (fuel cell), EN 16726 (grid) Purity requirements

1. CO2 Phase Behavior

CO2 Critical Point and Phase Envelope

The pure-CO2 critical point is useful for model verification, but it is not a transport acceptance boundary for an impure project stream. Calculate and validate the phase envelope for the actual bounded composition and operating path.

// Pure CO2 phase behavior
SystemInterface co2 = new SystemSrkEos(273.15 + 25, 80.0);
co2.addComponent("CO2", 1.0);
co2.setMixingRule("classic");

ThermodynamicOperations ops = new ThermodynamicOperations(co2);
ops.calcPTphaseEnvelope();
// Inspect the calculated phase state; do not infer F104 acceptance from pure-CO2 P/T alone.

Impurity Effects on CO2 Phase Envelope

Impurities widen the phase envelope and raise the cricondenbar, creating risk of two-phase flow in pipelines designed for dense phase operation.

Read the full file on GitHub · 381 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. 11d ago First seen · 381 lines · 85 tokens per session scan A 73f723229c4e

Subscribe to this mod's changes

neqsim-ccs-hydrogen is a skill published in the GitHub repository equinor/neqsim (151 stars, last pushed today), licensed Apache-2.0. It adds 85 tokens to every session and 4,050 once invoked, about $0.0004 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.

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