Natural gas is not technically a petroleum product, but it is closely related to petroleum. The U.S. Energy Information Administration defines petroleum as “a broadly defined class of liquid hydrocarbon mixtures,” which includes crude oil, condensate, and refined products like gasoline and diesel. Natural gas, being a gas rather than a liquid, falls outside that formal definition. However, natural gas and petroleum share the same geological origins, often come from the same wells, and are deeply intertwined in both chemistry and industry.
Why the Answer Depends on the Definition
The confusion is understandable because “petroleum” gets used in two different ways. In its strict technical sense, petroleum refers to liquid hydrocarbons. The EIA’s glossary specifically limits it to liquids: crude oil, lease condensate, unfinished oils, refined products, and natural gas plant liquids. By this definition, natural gas itself is not a petroleum product.
But in everyday language and across much of the energy industry, “petroleum” is used as a catch-all for all fossil hydrocarbons pulled from underground reservoirs, gas included. The American Petroleum Institute covers both oil and natural gas under its umbrella. Federal regulations list “Petroleum Products and Natural Gas Liquids” as a combined category. The EIA itself notes that petroleum products are “fuels made from crude oil and the hydrocarbons contained in natural gas,” acknowledging that natural gas contributes components to products classified as petroleum. So while natural gas isn’t petroleum in the narrow sense, it’s rarely discussed as something entirely separate from it.
They Come From the Same Source
Natural gas and crude oil form through the same geological process. Hundreds of millions of years ago, microscopic marine organisms (mostly plankton) settled on the ocean floor and were buried under layers of sediment. Over time, heat, pressure, and microbial activity transformed this organic material into a waxy substance called kerogen. As burial continued and temperatures rose, the kerogen broke down further into hydrocarbon chains, a process geologists call catagenesis.
The key variable is temperature. Moderate heat produces longer hydrocarbon chains, which stay liquid at the surface: that’s crude oil. Higher temperatures “crack” the kerogen more completely, producing shorter, lighter molecules. The shortest and lightest of these is methane, the primary component of natural gas, with just one carbon atom per molecule. Compare that to gasoline, which is a mix of molecules with six to eight carbon atoms, or the waxy solids in petroleum that can have dozens. Oil and gas are really just different points on a spectrum of the same chemical transformation.
Associated vs. Non-Associated Gas
Natural gas doesn’t always sit in its own separate reservoir. According to the U.S. Geological Survey, “associated gas” is natural gas produced alongside crude oil, typically separated from the oil at the wellhead. When you drill for oil, gas often comes up with it because the two formed together or migrated into the same rock formations.
“Non-associated gas,” by contrast, comes from wells that produce only gas and no crude oil. These deposits formed under conditions hot enough to convert nearly all the kerogen into small gas molecules rather than liquid oil. The distinction matters because associated gas is so physically intertwined with petroleum that separating the two is an industrial process in itself. Non-associated gas, found on its own, feels more like a distinct resource.
Where Natural Gas and Petroleum Products Overlap
Raw natural gas isn’t pure methane. It comes out of the ground as a mixture that includes ethane (two carbon atoms), propane (three), and butane (four), along with heavier hydrocarbons and impurities. Gas processing plants strip these heavier components out, and once separated, they’re called natural gas liquids, or NGLs.
Here’s where the classification gets interesting: NGLs are generally counted as petroleum products. Propane and butane, sold as fuels for grills and lighters, are liquids under modest pressure and are included in petroleum statistics. Federal emissions regulations list ethane, propane, and butane alongside other petroleum products in the same data tables. So while the raw gas stream isn’t petroleum, several of the products extracted from it are. The methane that remains after processing is the part that stays firmly in the “natural gas” category.
Different Processing, Different Industries
Crude oil goes through refining, a complex process of heating, distilling, and chemically treating liquid hydrocarbons to produce gasoline, diesel, jet fuel, and hundreds of other products. Natural gas goes through processing, a related but distinct set of steps focused on removing impurities (water, carbon dioxide, hydrogen sulfide) and separating out NGLs. The American Geosciences Institute treats “Oil Refining” and “Natural Gas Processing” as parallel but separate operations.
This separation carries through the rest of the supply chain. Crude oil and its refined products move through pipelines, tankers, and tank trucks designed for liquids. Natural gas travels through its own dedicated pipeline network and is measured in cubic feet rather than barrels. The two commodities have different pricing benchmarks, different regulatory frameworks, and often different companies specializing in each. Even though they share geological origins and overlapping chemistry, the energy industry treats them as related but distinct resources.
The Short Version
Natural gas is not a petroleum product by the formal, technical definition, which limits “petroleum” to liquid hydrocarbons. But it forms from the same ancient organic material through the same geological process, frequently comes out of the same wells, and yields liquid byproducts (propane, butane, ethane) that are classified as petroleum products. In the broadest industry sense, oil and natural gas are two faces of the same resource. Whether natural gas “counts” as petroleum depends entirely on how narrowly you draw the line.