Oilfield Terminology & Definitions.
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OilfieldTerms is a free online reference for anyone who works in, studies, or works alongside the oil and gas industry. Our goal is simple: every oilfield term, defined clearly — no paywalls, no registration, no fluff.

Whether you call it oil and gas terminology, oilfield lingo, or just “what does that mean?”, we’ve built the resource we always wished existed when learning the industry.

Who This Glossary Is For

The oil and gas industry spans an enormous range of disciplines — and the vocabulary spans just as wide. OilfieldTerms is written for:

  • Engineers & Geologists: drilling terminology, reservoir concepts, formation evaluation, and completions
  • Landmen & Attorneys: lease clause definitions, royalty structures, pooling, and unitization
  • New Hires & Students: plain-English introductions to industry concepts without the jargon overload
  • International Professionals: English vocabulary for oil and gas used in global operations
  • Investors & Analysts: upstream, midstream, and downstream terminology, reserves classifications, and financial vocabulary
  • Curious Readers: anyone who wants to understand what the people on the rig, in the field office, or in the boardroom are actually talking about

What We Cover

The glossary includes thousands of terms across every segment of the industry:

  • Drilling & Well Operations: from spud to total depth, including mud engineering, directional drilling, and pressure control
  • Well Completion & Production: perforating, hydraulic fracturing, artificial lift, and surface equipment
  • Reservoir & Geology: formation types, petrophysics, seismic interpretation, and reserve estimation
  • Lease & Legal: habendum clause, Pugh clause, depth clause, royalty, working interest, and lease terms
  • Oilfield Slang & Lingo: the unofficial vocabulary every roughneck, toolpusher, and hands-on worker uses daily
  • Upstream, Midstream & Downstream: E&P, gathering, processing, refining, and marketing terminology
  • Acronyms & Abbreviations: decoded in full with context so you always know what BOP, API, TD, and WI actually mean
  • Oil & Gas Accounting: revenue decks, AFEs, LOEs, working interests, and the financial language of the patch

Why OilfieldTerms.com?

There are other oil and gas glossaries out there — some behind paywalls, some buried in textbooks, some hopelessly out of date. We built OilfieldTerms.com because we believed there should be one free, searchable, comprehensive place to look anything up.

We’re not affiliated with any oil company, operator, service company, or industry organization. We have no financial interest in what we define. We just want the definitions to be accurate, clear, and accessible to everyone.

Always Free. Always Open.

OilfieldTerms.com has always been free and always will be. No subscription. No download. No account required. Just search for a term or browse the glossary A–Z and find what you’re looking for.

If you spot an error, know a term we’re missing, or want to get in touch, visit our Contact page.