FREEBURG – Ameren Illinois literally had to go underground to do some “cosmetic surgery” to several of its natural gas storage fields, but the results are reshaping these 60-year-old-plus facilities.
The company is utilizing horizontal drilling in its shallow depleted reservoirs in Tilden, Freeburg, Eden and Centralia – an approach that’s proving to be both technically innovative and economically transformative.
The concept of horizontal drilling first surfaced at Ameren Illinois around 2016. While a few other storage operators had experimented with it, Ameren Illinois faced a challenge: aging infrastructure across multiple farmer’s fields, including Tilden and Freeburg, with dozens of legacy wells and miles of vintage pipeline nearing the end of their useful life.
Tilden had 51 wells and Freeburg had 81 wells – most which were installed in the 1960s and could not be modernized to comply with evolving Federal Regulations. These wells were scattered across many acres of farmland and, in the case of Tilden, some in residential backyards. Replacing each vertical well individually was cost-prohibitive and operationally complex. Horizontal drilling offered an alternative: drill six to seven wells from a single pad, extending laterally up to half a mile, and eliminate the need for extensive surface infrastructure.
“We are going from 81 wells scattered throughout cornfields to three pads with six wells each – our footprint at Freeburg dropped from 4,600 acres to about 10 acres,” said Tim Eggers, Director of Storage Fields for Ameren Illinois. “It’s a tremendous plus in reducing our footprint and for derisking our operation.
“Most important is that our three-year, $40 million investment will allow the Freeburg Natural Gas Storage Field to provide the region with reliable, price-hedged gas supply for generations to come,” Eggers added.
These are the shallowest horizontal wells successfully drilled in the U.S., requiring a 300-foot vertical drill and then turning 90 degrees followed by a 2,500-foot horizontal turn. Thanks to lessons learned while drilling the first pad last year, the company’s engineering and drilling teams completed the second pad in just 55 of the scheduled 75 days. The final pad is planned for 2026, pending regulatory approval.
Engineering Against the Odds
Most people when they think of reservoirs, they envision those containing oil, sitting 10,000 feet deep, whereas Ameren Illinois’ storage fields are shallow – Tilden at 850 feet and Freeburg at just 350 feet. This posed a significant technical hurdle. Without the weight of a long string of heavy drill pipe to provide force to make the curve to drill horizontally, engineers had to rely heavily on motor-driven force to guide the drill bit. Many in the industry doubted it could be done.
But Ameren Illinois proved the doubters wrong. A successful test well at Tilden in 2019 kicked off a multi-year transformation. By 2021, Tilden’s 51 wells had been replaced with just nine horizontal wells. Freeburg’s 81 wells are being replaced with 18 horizontal wells between 2024 and 2026, along with reducing 16 miles of aging pipeline to just two miles of new steel pipeline.
“Most people didn’t think it was possible,” said Eggers. “You’re dealing with a 7-inch diameter steel pipe and making a ninety degree turn only 350 below the surface into sandstone seam that is only 20′ thick. That is really challenging.”
Safety, Efficiency, and Environmental Wins
Retired pipelines are purged, foamed, and plugged, remaining safely in place. This eliminates the need for annual pigging, corrosion monitoring, and other maintenance across 26 miles of small-diameter pipe. The shift also dramatically reduces third-party damage risk – no more wells in backyards or crop fields, and fewer chances of farm equipment strikes or children playing near exposed wellheads.
The operational footprint has shrunk dramatically. Freeburg’s 4,600-acre spread is now concentrated into just 10 acres across three protected well pads. Maintenance is streamlined, crop damage is minimized, and landowner compensation is no longer a recurring concern.
Leadership Buy-In and Financial Impact
Ameren’s leadership embraced the horizontal drilling initiative with enthusiasm. Engineers admired the technical ingenuity, while accountants appreciated the bottom-line impact: projected savings of $600,000 annually in operations and maintenance.
“These are just good projects where you’re investing dollars, you’re decreasing your risk, you’re decreasing your ongoing operating costs,” said Brad Kloeppel, senior director of Gas Operations for Ameren Illinois.
“Ameren’s senior leadership has been very supportive of these projects,” Kloeppel added. “The engineers love it because it’s really cool engineering. The accountants love it because you’re telling them, we’re going to save a half a million dollars in O&M on an ongoing basis.”
Performance and Capacity Gains
While the geology of the fields remains unchanged, horizontal wells offer greater contact with the reservoir, enabling higher withdrawal and injection rates. This boosts daily and hourly throughput, enhancing flexibility and responsiveness to demand –especially valuable in peak periods or future growth scenarios.
Ameren’s depleted reservoir fields allow for rapid cycling: inject one day, withdraw the next, or sustain withdrawal over multiple days. Horizontal drilling enhances this flexibility, enabling the utility to “exercise” the fields more effectively.
Looking Ahead
Ameren Illinois’ horizontal drilling initiative is more than a compliance strategy – it’s a blueprint for modernizing natural gas storage. By reducing risk, cutting costs, and improving performance, the company is setting a new standard for the industry.
As the program expands, Ameren Illinois continues to demonstrate that innovation, when paired with vision and leadership, can redefine what’s possible – even 350 feet below the surface.
