neqsim-electrolyte-systems

neqsim-electrolyte-systems is a skill for Claude Code, Codex from equinor/neqsim. It costs 90 tokens per session (3,931 once invoked), scanned A, original, Apache-2.0.

A NeqSim guide for simulating water-based systems containing dissolved salts and ions, such as produced water, seawater, or brine. It covers electrolyte thermodynamic models and salt components.

In plain words
What is it for?
Use it for produced-water and seawater models, scale-risk studies, CO2 or H2S solubility in brines, and MEG or DEG injection and hydrate-inhibitor calculations.
Why use it?
It helps choose and configure suitable models when ordinary gas-and-liquid calculations do not represent salt chemistry, scale formation, or gas solubility in water accurately.

Skill for Claude CodeCodex

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

Good fit Use it for produced-water and seawater models, scale-risk studies, CO2 or H2S solubility in brines, and MEG or DEG injection and hydrate-inhibitor calculations.

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Install with agentmods
npx agentmods add skills/equinor/neqsim/neqsim-electrolyte-systems
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.

Any agent
npx skills add equinor/neqsim --skill neqsim-electrolyte-systems
Clone the repo
git clone --depth 1 https://github.com/equinor/neqsim

Made for: Claude Code, Codex.

Wrote this? Show the measurements

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README.md
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Per session 90 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,931 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 $0.00090 $0.03931
Opus 5 $0.00045 $0.01965
Sonnet 5 $0.00018 $0.00786
Haiku 4.5 $0.00009 $0.00393

Measured today against content hash 643d7ecab47a, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

neqsim-electrolyte-systems 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 today.

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-electrolyte-systems/SKILL.md · 331 lines

How it starts

The opening of the file, as written. The whole thing — 331 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Electrolyte Systems Guide

Guide for modeling electrolyte/brine systems in NeqSim.

When to Use Electrolyte Models

  • Produced water with dissolved salts (NaCl, CaCl2, BaCl4)
  • Scale prediction (CaCO3, BaSO4, CaSO4)
  • CO2/H2S solubility in brines
  • MEG injection rate calculations
  • Hydrate inhibitor dosing
  • Seawater injection and mixing
  • Desalination process modeling

EOS Selection for Electrolyte Systems

System NeqSim Class Mixing Rule
Water + salt + HC gas SystemElectrolyteCPAstatoil 10
MEG/DEG + water + gas SystemSrkCPAstatoil 10
Pure water + gas SystemSrkCPAstatoil 10
Brine + multiple salts SystemElectrolyteCPAstatoil 10

Basic Electrolyte Setup

import neqsim.thermo.system.SystemElectrolyteCPAstatoil;

// Create electrolyte system
SystemInterface brine = new SystemElectrolyteCPAstatoil(273.15 + 80.0, 200.0);

// Add gas components
brine.addComponent("CO2", 0.05);
brine.addComponent("methane", 0.80);

// Add water
brine.addComponent("water", 0.10);

// Add salt components (as ions)
brine.addComponent("Na+", 0.02);
brine.addComponent("Cl-", 0.02);
brine.addComponent("Ca++", 0.005);
brine.addComponent("SO4--", 0.005);

// Set mixing rule (MUST be numeric for CPA)
brine.setMixingRule(10);
brine.setMultiPhaseCheck(true);

Common Ion Components in NeqSim

Ion NeqSim Name Common Source
Sodium "Na+" NaCl
Chloride "Cl-" NaCl, CaCl2
Calcium "Ca++" CaCl2, CaCO3
Barium "Ba++" BaSO4, BaCl2
Strontium "Sr++" SrSO4
Sulfate "SO4--" Na2SO4, BaSO4
Bicarbonate "HCO3-" NaHCO3
Carbonate "CO3--" CaCO3, Na2CO3
Magnesium "Mg++" MgCl2
Potassium "K+" KCl
Iron(II) "Fe++" FeCl2, FeS

Produced Water Modeling

// Typical produced water composition
SystemInterface prodWater = new SystemElectrolyteCPAstatoil(273.15 + 80.0, 50.0);

// Dissolved gas
prodWater.addComponent("CO2", 0.01);
prodWater.addComponent("H2S", 0.001);
prodWater.addComponent("methane", 0.005);

// Water (dominant)
prodWater.addComponent("water", 0.90);

// Ions (typical North Sea produced water)
prodWater.addComponent("Na+", 0.03);
prodWater.addComponent("Cl-", 0.035);
prodWater.addComponent("Ca++", 0.003);
prodWater.addComponent("Ba++", 0.0001);
prodWater.addComponent("SO4--", 0.001);
prodWater.addComponent("HCO3-", 0.005);

prodWater.setMixingRule(10);
prodWater.setMultiPhaseCheck(true);

// Flash to get gas/liquid split
ThermodynamicOperations ops = new ThermodynamicOperations(prodWater);
ops.TPflash();
prodWater.initProperties();

Read the full file on GitHub · 331 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. today Changed · +7 lines 643d7ecab47a
  2. 3d ago Changed · +3 lines b3ffdbaca9f9
  3. 5d ago Changed · +65 lines 951f9534a229
  4. 9d ago First seen · 256 lines · 90 tokens per session scan A 0dcbe3c84100

Subscribe to this mod's changes

neqsim-electrolyte-systems is a skill published in the GitHub repository equinor/neqsim (151 stars, last pushed today), licensed Apache-2.0. It adds 90 tokens to every session and 3,931 once invoked, about $0.0005 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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