A Python library for reading and writing LAS files, a standard text format for borehole and oil-well measurement logs. It handles well information, depth-based curves, units, and curve data.

Use it to inspect well headers and curves, convert logs to tables or spreadsheets, create LAS files, and modify existing logs.

It avoids parsing LAS files by hand and makes their measurements available for analysis in Python.

lasio — Skill for Claude Code and Codex by SteadfastAsArt

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 SteadfastAsArt/geoscience-skills --skill lasio

Clone the repo

git clone --depth 1 https://github.com/SteadfastAsArt/geoscience-skills

Made for: Claude Code, Codex.

Its marketplace also offers this one on its own, as the plugin lasio — /plugin install lasio after adding the marketplace above.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/steadfastasart/geoscience-skills/lasio/github.svg)](https://agentmods.dev/skills/steadfastasart/geoscience-skills/lasio)

Your own site

<a href="https://agentmods.dev/skills/steadfastasart/geoscience-skills/lasio"><img src="https://agentmods.dev/badge/skills/steadfastasart/geoscience-skills/lasio/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/steadfastasart/geoscience-skills/lasio"><img src="https://agentmods.dev/badge/skills/steadfastasart/geoscience-skills/lasio.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 117 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,356 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.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00117	$0.01356
Opus 5	$0.00059	$0.00678
Sonnet 5	$0.00023	$0.00271
Haiku 4.5	$0.00012	$0.00136

Measured 9d ago against content hash 4e4eaa7a7b40, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

lasio 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 9d ago.

The scan reads SKILL.md. This mod also ships 3 executable files (scripts/las_to_csv.py, scripts/merge_curves.py, scripts/validate_las.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

lasio/SKILL.md · 172 lines

How it starts

The opening of the file, as written. The whole thing — 172 lines — stays where its author put it; the contents beside it link to each section on GitHub.

lasio - LAS Well Log Files

Quick Reference

import lasio

# Read
las = lasio.read("well.las")

# Access data
df = las.df()                    # DataFrame (depth as index)
gr = las['GR']                   # Single curve as numpy array
depth = las['DEPT']

# Well info
well_name = las.well['WELL'].value
uwi = las.well['UWI'].value

# Write
las.write('output.las')

Key Classes

Class	Purpose
`LASFile`	Main container - holds headers, curves, data
`CurveItem`	Single curve with mnemonic, unit, data array
`HeaderItem`	Header entry (mnemonic, unit, value, descr)

Essential Operations

Read and Inspect

las = lasio.read("well.las")
print(las.curves.keys())         # Available curves
print(las.well)                  # Well section headers
print(las.version)               # LAS version info

Access Curve Data

# As numpy arrays
gr = las['GR']
depth = las['DEPT']

# With metadata
curve = las.curves['GR']
print(curve.unit, curve.descr)   # 'GAPI', 'Gamma Ray'

Create New LAS

import numpy as np

las = lasio.LASFile()
las.well['WELL'] = lasio.HeaderItem('WELL', value='Test-1')
las.well['UWI'] = lasio.HeaderItem('UWI', value='12345678901234')

depth = np.arange(1000, 2000, 0.5)
las.append_curve('DEPT', depth, unit='M', descr='Depth')
las.append_curve('GR', gr_data, unit='GAPI', descr='Gamma Ray')
las.write('output.las')

Modify Existing

las = lasio.read("well.las")
las.append_curve('GR_NORM', las['GR'] / 150, unit='V/V')
del las.curves['BAD_CURVE']
las.well['WELL'].value = 'New Name'
las.write('modified.las')

Handle Problematic Files

# Ignore header errors
las = lasio.read("messy.las", ignore_header_errors=True)

# Check null value
null_val = las.well['NULL'].value  # Usually -999.25

Null Value Handling

LAS files use a specific null value (typically -999.25). Always check and handle:

import numpy as np
null_val = float(las.well['NULL'].value)
df = las.df().replace(null_val, np.nan)

Read the full file on GitHub · 172 lines

Files

What ships with it

6 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

9d ago First seen · 172 lines · 117 tokens per session scan A 4e4eaa7a7b40

Subscribe to this mod's changes

lasio is a skill published in the GitHub repository SteadfastAsArt/geoscience-skills (57 stars, last pushed 5mo ago), licensed MIT. It adds 117 tokens to every session and 1,356 once invoked, about $0.0006 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.

Borehole CWLS Claude Code Data I/O LAS Lasio Petrophysics Scientific Well Logs Wireline ai-agents geophysics geoscience

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