Wyoming’s 3.5-Mile CO₂ Well Aims to Turn Rock Into a Carbon Bank

Crews in Sweetwater County just punched through 18,437 feet of Wyoming rock—about 3.5 miles straight down—to hit the Madison Limestone, a formation developers say could become one of the country’s biggest vaults for planet-warming carbon dioxide.

It’s the second characterization well for the Sweetwater Carbon Storage Hub, a $54 million public-private project that’s part of Wyoming CarbonSAFE, the long-running effort led by the University of Wyoming’s School of Energy Resources to prove up safe, permanent CO₂ storage in the state. Project officials say the new hole—dubbed J1-15—is now the deepest Class VI carbon-injection well drilled in the US, a regulatory category reserved for geologic sequestration with the most stringent monitoring rules.

For starters, Wyoming’s subsurface is busy. There are very deep legacy oil and gas wells in the Green River Basin, and carbon storage can’t interfere with existing mineral rights. Going deeper lets the team test beneath those zones. Depth also helps the physics: CO₂ becomes denser the deeper you go, which means more storage per cubic foot and thicker rock layers overhead to keep it locked away for the long haul.

Geologically, the area checks a lot of boxes. The Madison has naturally held fluids and gases for tens of millions of years in nearby fields—exactly the kind of long-term sealing behavior storage developers want to mimic. Core pulled from the well even turned up traces from Wyoming’s ancient past—marine fossils and old dune sands—offering a time-capsule look at layers that now could be pressed into climate service.

Backers say the Sweetwater hub could ultimately store more than 350 million metric tons of CO₂ by targeting multiple stacked formations, with the Madison as the headline act. (For scale, a typical passenger car emits ~4.6 tons a year.) The vision: capture CO₂ from nearby emitters—think trona mines and soda-ash processing plants in southwest Wyoming—and pipe it to injection wells for permanent storage thousands of feet below drinking-water aquifers.

The first Sweetwater well hit just over 16,000 feet; this new one deepens the dataset and helps verify years of reservoir modeling. Frontier Infrastructure—a Tailwater Capital portfolio company and the project’s primary private partner—says the results so far “reinforce” the geology and the business case to build scalable, practical carbon solutions for Wyoming’s industries.

Under EPA’s Underground Injection Control program, Class VI wells face rigorous requirements for site characterization, well construction, seismic and pressure monitoring, financial assurance, and long-term stewardship. The goal is straightforward: keep CO₂ put. Most Class VI sites drill around a mile deep; Sweetwater is pushing the envelope to increase storage capacity and sealing confidence.

Of the hub’s $54 million price tag, about $43 million comes from federal funding, with state and private partners covering the rest. The funding is currently obligated through February, according to project officials. With the second deep well done, the team shifts to reservoir testing, detailed modeling, permitting, and injection planning, all under EPA oversight.

The Sweetwater effort is one pillar of Wyoming’s broader “Decarbonizing the West” push championed by Gov. Mark Gordon—an attempt to keep the state’s fossil-fuel economy competitive while tackling emissions. Related CarbonSAFE work is underway at Echo Springs (Carbon County) and Dry Fork Station (Campbell County), and Tallgrass Energy is exploring a separate storage site in Laramie County.

Even with storage potential next door, some operators are picking different decarbonization paths. Tata Chemicals in Green River, for example, says capturing and compressing plant-wide CO₂ is too capital-intensive for its older facility and is instead pursuing small modular nuclear reactors to replace coal-fired steam—an alternate route to shrinking its footprint.

Wyoming just added a record-deep CO₂ well to its climate and energy toolbox. If the reservoir behaves the way early data suggests, the Sweetwater Carbon Storage Hub could turn a slice of the state’s deep geology into a massive, long-term carbon bank—and position Wyoming as a serious player in the emerging CO₂ storage market.

WyoFile and Cowboy State Daily contributed to this report.