Microbial Hydrogen From Depleted Oil Wells: Scaling, Prices & Challenges

August 14, 2025

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Somebody requested me not too long ago a couple of Houston-based startup known as Gold H2. That was sufficient to ship me down the rabbit gap. After a number of hours of studying, checking some chemistry, and doing a number of back-of-the-envelope calculations, I had sufficient materials that it was value pulling collectively in a single place. This isn’t the Australian firm with the identical title that’s drilling for naturally occurring hydrogen. This can be a non-public spin-out from Cemvita Manufacturing unit that’s attempting to make hydrogen underground in depleted oilfields by feeding the precise microbes and letting them do their work.

Gold H2 calls its method Black 2 Gold. The method includes injecting vitamins and hydrogen-producing microbes into outdated oil wells, letting the reservoir sit for a interval, after which producing fuel again by means of the identical properly. The microbes are supposed to break down residual hydrocarbons within the reservoir into hydrogen and different gases. The corporate says this avoids the necessity for brand spanking new drilling and makes use of current oilfield infrastructure. In idea, it’s much like microbially enhanced oil restoration, however as a substitute of attempting to get extra oil out, the intention is to get hydrogen.

Microbially enhanced oil restoration is a set of methods that use microorganisms to enhance the movement of oil from a reservoir. The microbes will be injected into the reservoir or stimulated in place with vitamins, they usually act in a number of methods. Some species produce gases reminiscent of carbon dioxide or methane that assist push oil towards the wellbore. Others create biosurfactants that cut back the floor stress between oil and water, permitting trapped oil droplets to movement extra simply. Sure microbes can change the viscosity of crude oil by breaking down heavier hydrocarbons. These strategies have been examined in varied oilfields because the Nineteen Eighties, usually with combined outcomes as a result of microbial exercise is determined by reservoir temperature, salinity, pH, and nutrient availability.

In apply, microbially enhanced oil restoration has remained a distinct segment device utilized in particular reservoirs the place standard secondary restoration strategies have been exhausted or are uneconomic. That serves as a crimson flag for guarantees of utilizing comparable applied sciences to extract hydrogen as a substitute of oil.

Solely a fraction of depleted oil wells are more likely to have the mixture of circumstances wanted for microbial hydrogen manufacturing. Many elderly reservoirs are both too sizzling or too chilly for the goal microbes, or have salinity ranges within the formation water that exceed microbial tolerance. Others have low residual oil saturation after many years of manufacturing or waterflooding, leaving little feedstock for conversion. Sulfate contamination from earlier water injection applications can be frequent and might result in hydrogen loss by means of undesirable chemical pathways. When these elements are mixed, the pool of viable candidates in all probability narrows to a minority of depleted wells, with essentially the most promising present in reservoirs that also maintain reasonable residual oil, have formation water of reasonable salinity, sit in the precise temperature vary, and haven’t been closely altered by incompatible injection fluids.

In 2025, Gold H2 ran a subject trial in California’s San Joaquin Basin. They reported that the produced fuel stream contained about 400,000 ppm hydrogen, which is 40% by quantity. The remaining was not damaged out intimately, however seemingly included methane, carbon dioxide, nitrogen, and presumably hint hydrogen sulfide, a really nasty fuel that needs to be fastidiously managed. There was no disclosure of the overall fuel movement fee, absolutely the quantity of hydrogen produced, or whether or not any of it was purified and saved. With out that info, it’s tough to evaluate how shut they’re to their said goal of manufacturing hydrogen for below $0.50 per kilogram.

Hydrogen content material in fuel streams is usually reported in quantity %. For gases on the identical temperature and strain, quantity % is identical as mole fraction. That’s helpful for pipeline and combustion issues, however it may be deceptive when pondering when it comes to mass. Hydrogen could be very gentle. A mixture that’s 40% hydrogen and 60% methane by quantity works out to solely about 7.7% hydrogen by mass. If the opposite 60% have been carbon dioxide, the mass fraction of hydrogen would drop to about 3.6%.

As a result of Gold H2 didn’t launch any movement charges, I bracketed some cheap values based mostly on what’s frequent for end-of-life wells. In america, a marginal fuel properly, usually known as a stripper properly, produces 90 thousand cubic toes per day or much less. Many produce far much less. I used three circumstances: 50 thousand cubic toes per day, 200 thousand, and 1,000 thousand. For a mid-case of 200 thousand cubic toes per day complete fuel and 40% hydrogen by quantity, that works out to about 204 kg of hydrogen per day. At 300 working days per yr that’s roughly 61 tons of hydrogen per yr.

For depleted oil wells producing microbial hydrogen, 50 and 200 Mcf/d are wise central circumstances. A fee of 1,000 Mcf/d is feasible in an unusually favorable properly however shouldn’t be the idea for planning. These wells will not be high-pressure fuel reservoirs. They’ve already misplaced most of their drive vitality and infrequently have excessive water saturation, with oil-wet rock limiting fuel motion. The huff-and-puff cycle additional reduces common output as a result of manufacturing solely occurs between injection and soak durations. Even when the properly briefly flows within the excessive lots of of Mcf/d throughout manufacturing, the cycle common will probably be decrease.

Many repurposed oil wells with fuel output find yourself at or beneath the U.S. stripper threshold of 90 Mcf/d, which makes 50 Mcf/d an affordable low case. A fee of 200 Mcf/d would point out a properly with respectable permeability, a brief elevate to floor, low backpressure, and a productive microbial response. Reaching 1,000 Mcf/d would take unusually good rock, a high-quality completion, quick flowlines, little water blockage, and robust transient drawdown, making it extra appropriate for a stress-test state of affairs than a base case.

As with my evaluation of the potential of white hydrogen, i.e. naturally occurring hydrogen that’s mined, extraction and purification is barely half of the fee problem, with compressing or liquefaction and use being expensive as properly. That’s why I articulated the worth proposition for any truly recoverable white hydrogen reserves being for industrial feedstocks utilized in crops shut sufficient to the hydrogen extraction website to permit quick pipelines at most. We use 85% of hydrogen on the level we make it in the present day due to that, and there’s no purpose to imagine that’s going to vary. Hydrogen isn’t a helpful vitality provider and it’s not a helpful transportation gas, so we’ll proceed to make it or doubtlessly extract it at level of use and switch it into one thing helpful like ammonia or use it to hydrotreat biofuels.

To place the potential volumes into market context, ammonia crops in Louisiana, Oklahoma and Texas produce about 7.7 million tons of ammonia per yr. Making that ammonia requires about 1.37 million tons of hydrogen yearly. At 61 tons of hydrogen per properly per yr, it could take round 224 wells to fulfill 1% of that regional demand. Assembly 10% would require over 2,200 wells. These figures are earlier than any separation losses, they usually assume regular output, which is unlikely for a huff-and-puff course of that alternates injection, soaking and manufacturing.

Purification is unavoidable if the purpose is to produce hydrogen for gas cells or ammonia synthesis. Stress swing adsorption and membrane techniques have prices that rise because the inlet focus falls. An 80% hydrogen inlet would possibly add about $0.30/kg to the fee. At 40% hydrogen, separation would possibly add $0.60/kg. At 20% hydrogen it could possibly be $1.20/kg. If Gold H2 is beginning at 40% by quantity, purification alone may push their complete manufacturing value over the $0.50/kg goal they’ve said. That’s earlier than contemplating capital restoration, working bills for injection and dealing with, and any financing prices.

The composition of the opposite 60% of the fuel issues for economics and local weather influence. Whether it is largely methane, there’s potential worth in promoting it or utilizing it to energy operations. In fact, that’s perpetuation of fossil fuels, which isn’t precisely a really useful exercise. Whether it is vented or leaks, the local weather influence could possibly be important. Whether it is largely carbon dioxide, there’s little market worth and it’ll nonetheless have to be managed. Each circumstances make purification extra difficult. An truly sustainable apply can be to pump both fuel again below floor in a special properly, including to the fee case.

Gold H2’s idea has some strengths. It goals to reuse current oil and fuel wells, which reduces the capital value in comparison with constructing new infrastructure. It makes use of organic processes that work at reservoir circumstances moderately than energy-intensive floor gear. The primary questions are about scale, stability and economics. With out understanding how a lot hydrogen a properly can produce over months or years, and what it prices to get that hydrogen to market on the required purity, it’s laborious to guage whether or not it’s a useless finish, is a distinct segment resolution for a number of reservoirs or a pathway to important volumes. My math suggests the primary possibility.

As a reminder, whereas I’m a broad spectrum nerd who has spent numerous time working to grasp domains most haven’t, I’m not a subsurface oil and fuel engineer and do make errors. It’s doable that my studying of the information is improper, however I’m snug I’ve sufficient proper with my evaluation to think about Gold H2 to be deeply unlikely to ever be economically viable as a producer of hydrogen.

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