Oil is still being formed today through the same geological and biological processes that created the petroleum reserves we drill into, but the rate is so slow that it is essentially irrelevant on a human timescale. The fossil fuels we burn for transportation are consumed at roughly 100,000 times their natural rate of formation.1Applied Sciences. Emissions from Combustion of Second-Generation Biodiesel Produced from Seeds of Date Palm Fruit (Phoenix dactylifera L.) So while the planet’s oil-making machinery has never switched off, it runs on a clock measured in millions of years, and we are draining the tank in centuries.
How Oil Forms in the First Place
Most conventional petroleum starts with dead marine organisms, mainly microscopic algae and plankton, that settle on the seafloor and get buried under layers of sediment. If that organic material is shielded from oxygen long enough, it avoids being fully decomposed by microbes. How long the material sits exposed to oxygen turns out to be a critical factor: researchers have found that the concentration of the carbon compounds most useful for generating oil can be two orders of magnitude higher in coastal sediments with short oxygen-exposure times compared to deep-sea sediments that sit in oxygenated water for ages.2PubMed. Organic carbon composition of marine sediments: effect of oxygen exposure on oil generation potential In other words, the faster organic-rich mud gets sealed away from oxygen, the better its chances of eventually producing oil.
Once buried, the organic material slowly transforms into a waxy substance called kerogen as pressure and temperature rise. Over millions of years, continued burial pushes that kerogen into what geologists call the “oil window,” a range of temperatures and depths where heat cracks the kerogen molecules into liquid hydrocarbons. In many basins, this happens when temperatures reach roughly 100 to 150°C and depths sit between about 1,300 and 2,600 meters, though the exact numbers shift depending on the local geology.3Organic Geochemistry. Primary migration theory of petroleum and its application to petroleum exploration Push the temperature higher still and the oil cracks further into natural gas; experiments show that crude oil typically starts cracking between 165 and 190°C and is completely broken down into gas by around 230 to 240°C.4ScienceDirect / Natural Gas Industry B. Control effects of temperature and thermal evolution history of deep and ultra-deep layers on hydrocarbon phase state and hydrocarbon generation history
This entire sequence, from plankton dying on the surface to oil collecting in a reservoir rock, takes on the order of tens of millions of years for conventional petroleum. Organic-rich sediments being deposited in today’s oceans and lakes are, right now, starting that same journey. Sediment is piling up, kerogen precursors are forming, and given enough geological time, some of those deposits will cook into oil. The process is continuous; it just operates on a timescale that makes it invisible to us.
Places Where Oil Is Being Made Right Now
The deep-time process is not the only one. In certain geologically active spots, petroleum-like substances are being generated on timescales of hundreds to thousands of years rather than millions. The best-documented example is the Guaymas Basin in the Gulf of California, where a mid-ocean ridge is actively spreading beneath a thick blanket of organic-rich sediment. Superheated water from hydrothermal vents essentially pressure-cooks the sediment, converting geologically immature organic matter into petroleum products far faster than normal burial would.5Elsevier ScienceDirect. Petroleum generation, an easy and widespread process in hydrothermal systems: an overview
The Guaymas Basin is not unique. Researchers have documented the same hydrothermal petroleum-generation process at the Escanaba Trough off northern California, the Bransfield Strait near Antarctica, and the Atlantis II Deep in the Red Sea, and it likely occurs at other sedimented rift systems around the world.5Elsevier ScienceDirect. Petroleum generation, an easy and widespread process in hydrothermal systems: an overview In some cases, the transformation is practically instantaneous: when living microorganisms or fresh organic debris get pulled into turbulent hydrothermal vent waters, they undergo a flash version of hydrous pyrolysis and produce petroleum-like compounds on the spot. This is not a laboratory curiosity. It is happening continuously at these sites, providing a kind of real-time demonstration of how heat and organic matter combine to make hydrocarbons.
Natural Oil Seeps as Ongoing Evidence
One of the most tangible signs that the Earth continues to generate and release hydrocarbons is the existence of natural oil seeps on the seafloor. These are places where oil migrates upward through faults and fractures and escapes into the ocean, sometimes forming visible slicks on the surface. They are common in the Gulf of Mexico, where satellite imagery shows that natural seeps can produce oil slicks longer than 20 kilometers that persist for up to 48 hours under the right wind and current conditions.6Remote Sensing of Environment. Hindcast modeling of oil slick persistence from natural seeps
These seeps are not exclusively a warm-water phenomenon. An Arctic seep off the coast of Svalbard, Norway, was tracked using satellite radar images from 2014 to 2021 and found to be persistently releasing oil at an estimated rate of roughly 4 to 23 barrels per day, depending on the size of the slick observed. Uranium-thorium dating of carbonate cements at the site showed the seep has been active for about 18,500 years, since shortly after the peak of the last ice age.7Science of The Total Environment. An Arctic natural oil seep investigated from space to the seafloor The oil leaking from these seeps was generated deep underground over geologic time, and the fact that seepage persists for millennia tells us that the subsurface petroleum system feeding it has not run dry.
Natural seeps also play interesting ecological roles. Certain marine organisms have evolved to thrive around them, and the slow, steady release of hydrocarbons can influence local chemistry and microbiology. For the question of whether oil is “still being formed,” seeps are a reminder that petroleum generation, migration, and release to the surface is an ongoing geological cycle, not a single event locked in the distant past.
Methane Is Being Produced Even Faster
While liquid petroleum takes extreme time and conditions to form, methane, the main component of natural gas, is being generated by two distinct processes happening right now. The first is biological: microorganisms called methanogens live in low-temperature environments like swamps, rice paddies, landfills, ocean sediments, and the guts of ruminant animals, and they produce methane as a metabolic byproduct. This biogenic methane forms at temperatures below about 50°C.8PubMed. Gas formation. Formation temperatures of thermogenic and biogenic methane
The second is the same thermal cracking that produces oil. When organic matter or existing oil is buried deep enough that temperatures climb above roughly 157°C, methane is generated thermogenically.8PubMed. Gas formation. Formation temperatures of thermogenic and biogenic methane In practice, many gas reservoirs contain a mix of both. Research on the Antrim Shale in Michigan found that roughly half the methane in the system was thermogenic, a larger proportion than previously thought, with the rest produced by subsurface microbial communities.9Geochimica et Cosmochimica Acta. Distinguishing and understanding thermogenic and biogenic sources of methane using multiply substituted isotopologues Distinguishing the two is important because biogenic gas is being made continuously at low temperatures, meaning it replenishes on a much shorter timescale than thermogenic gas or conventional oil.
Researchers have developed techniques based on the clustering of heavy isotopes within methane molecules to tell the two sources apart. In systems where biogenic methane generation is slow, the gas tends toward chemical equilibrium with its environment; where it forms rapidly, it carries a distinctive isotopic signature that is out of equilibrium.9Geochimica et Cosmochimica Acta. Distinguishing and understanding thermogenic and biogenic sources of methane using multiply substituted isotopologues This matters because ongoing biogenic methane production is not a trivial footnote. Wetlands alone emit hundreds of millions of tons of methane per year, making microbial gas generation one of the most prolific hydrocarbon-forming processes on the planet in terms of volume produced per year.
Microbes That Eat Oil Underground
While some microbes produce hydrocarbons, others destroy them. Deep beneath the surface, in conditions that seem inhospitable to life, anaerobic bacteria are slowly breaking down oil in many of the world’s reservoirs. A study that examined 77 degraded oil samples from marine and land-based sources around the world, including Canada’s massive tar sands, found metabolic byproducts consistent with anaerobic hydrocarbon degradation in a large fraction of those samples.10PubMed. Anaerobic hydrocarbon biodegradation in deep subsurface oil reservoirs This biodegradation is widespread and can substantially alter the composition of oil over time, turning lighter crude into the heavy, viscous oil found in places like Alberta.
This sets up a tension that is easy to overlook. Oil is simultaneously being formed in some parts of the subsurface and consumed by microbes in others. The net effect depends on local conditions: temperature, nutrient availability, the types of organisms present, and how quickly fluids move through the rock. In cooler, shallower reservoirs where microbial life can thrive, biodegradation can strip out the most useful hydrocarbon fractions and leave behind heavy residues. In deeper, hotter zones, microbial activity drops off and thermal processes dominate. The subsurface petroleum cycle is not a simple conveyor belt from organic matter to oil well. It is a dynamic system with creation and destruction happening in parallel.
Why None of This Helps With Energy Supply
It might seem encouraging that the planet’s oil-making machinery is still running. But the mismatch in rates is staggering. Humanity currently burns through fossil fuels at a pace roughly 100,000 times faster than they form naturally.1Applied Sciences. Emissions from Combustion of Second-Generation Biodiesel Produced from Seeds of Date Palm Fruit (Phoenix dactylifera L.) Even the relatively rapid hydrothermal systems in places like the Guaymas Basin produce quantities that are trivial compared to global demand. The world consumes around 100 million barrels of oil per day. A vigorous natural seep might release a few dozen barrels per day. Every active seep on the planet combined would not fill a single supertanker.
There is also a timescale problem beyond just rate. The oil being generated today in conventional basins will not be accessible for tens of millions of years. It has to be buried, heated, cracked, expelled from the source rock, and trapped in a reservoir before anyone could extract it. The oil we pump today was generated from organisms that lived during the Jurassic, Cretaceous, or other ancient periods, and it has been sitting underground ever since. Thinking of petroleum as a “renewable” resource because formation continues is like thinking of a bank account as self-replenishing because someone deposits a penny every century while withdrawals run at thousands of dollars per minute.
Can We Speed Up the Process Artificially?
Researchers have been working on exactly this question, and the answer is a qualified yes. A technology called hydrothermal liquefaction essentially mimics what happens naturally at hydrothermal vents: organic feedstock is subjected to high temperatures and pressures in the presence of water, producing a crude-oil-like substance called biocrude. Recent work has explored using forestry biomass, including both hardwood and softwood, as feedstock for this process, with ongoing efforts to optimize yields through co-solvents and process tweaks.11Sustainable Energy & Fuels. Advancing hydrothermal liquefaction of Canadian forestry biomass for sustainable biocrude production: co-solvent integration, co-liquefaction, and process optimization The biocrude that comes out is not identical to conventional petroleum, but it can be refined into transportation fuels.
Microalgae are another avenue. Some algae species contain lipid content exceeding 70 percent, and their oil yields can be up to 200 times greater than those of the best-performing vegetable oil crops. To put this in concrete terms, microalgae can produce over 12 kilograms of biodiesel per square meter per year, compared to less than 0.1 kilograms for rapeseed oil and about 0.5 kilograms for palm oil.12Elsevier / ScienceDirect. Algae biodiesel as a alternative green fuel: A futuristic scope The appeal is obvious: algae grow fast, do not compete with food crops for arable land, and absorb carbon dioxide as they grow. The challenge has always been cost. Growing, harvesting, and processing algae at scale has so far remained more expensive than simply pumping oil from the ground, though that gap has been narrowing.
Both of these approaches essentially compress the geological timescale of oil formation into hours or days. They take modern biological material and apply heat and pressure, or extract lipids directly, to produce fuels that would otherwise take millions of years to appear naturally. Whether they count as “making oil” depends on your definition, but the chemistry is fundamentally similar to what the Earth does on its own.
Oil in Ultra-Deep Formations
One counterintuitive finding from recent research is that liquid oil can survive at depths and temperatures that were long thought to destroy it. In strata buried between about 7,500 and 9,600 meters, liquid hydrocarbons have been found existing at temperatures exceeding 300°C when the rock’s thermal maturity indicator reaches levels geologists once considered well past the oil-destruction threshold.4ScienceDirect / Natural Gas Industry B. Control effects of temperature and thermal evolution history of deep and ultra-deep layers on hydrocarbon phase state and hydrocarbon generation history The key variable is time. Under conditions of short heating duration, oil can remain stable at temperatures well above what it could survive if exposed for millions of years. Liquid hydrocarbons disappear completely only at maximum depths of around 8,000 meters and formation temperatures above 200°C under prolonged heating, while gas reservoirs can persist down to 10,000 to 12,000 meters.
This has practical implications for exploration. It means that deeply buried basins in places like western China, the Persian Gulf, and portions of the Gulf of Mexico may hold oil at depths that older geological models would have written off. It also means that ongoing thermal processes at great depth are continuing to transform hydrocarbons right now, generating gas from oil and breaking complex molecules into simpler ones. The deep subsurface is not static; it is an active chemical reactor.
Microplastics as Future Source Material
Here is a thought experiment that has started to attract genuine scientific attention. Around 10 million tons of plastic waste enter the oceans every year, and that figure is expected to increase tenfold by 2025. Of that total, an estimated 16 percent consists of microplastics, either manufactured at that size or broken down from larger pieces. Sea-surface accumulations account for less than 1 percent of the known marine plastics budget; the rest is likely on the seafloor.13Environmental Science & Technology. Transport and Burial of Microplastics in Deep-Marine Sediments by Turbidity Currents
Most conventional plastics are themselves derived from petroleum, which means their molecular backbone is hydrocarbon. As microplastics accumulate in deep-marine sediments, they become part of the organic carbon pool being buried. Given enough time, pressure, and heat, those buried plastics could theoretically undergo the same diagenetic and thermal processes that convert natural organic matter into kerogen and eventually into petroleum. Nobody is suggesting this would produce commercially useful oil on any timeline relevant to humans. But it raises a strange circularity: we extract ancient hydrocarbons, turn them into plastic, dump the plastic into the ocean, and the ocean begins burying it in conditions that could, in tens of millions of years, reconvert it into something like the hydrocarbons we started with. Whether that irony counts as “oil still being formed” is a question as much philosophical as geological, but the chemistry does not care about the origin of the carbon.