Historic Oil Field
The Seminole San Andres Unit (SSAU) surrounding Seminole, Texas is one of the largest and most productive CO2 floods in the Permian Basin — a 1936-vintage San Andres field that today still reports nearly seven million barrels of oil a year from a single unit designation. It is the anchor asset of Gaines County’s oil economy and a defining example of what disciplined, decades-long EOR investment does for a royalty base.
Source: Texas Railroad Commission production filings, aggregated across RRC field designations 82225142. Reported volumes lag the calendar by several months.
The Seminole field was discovered in 1936 as the San Andres play proved up across the Northwest Shelf. Development and waterflooding through mid-century followed the standard giant-carbonate arc: strong initial development, unitization to enable pressure maintenance, and a long waterflood plateau.
CO2 injection began in the early 1980s under Amerada Hess, which operated the unit for decades and built it into one of the industry’s reference CO2 WAG projects, complete with an associated gas plant recovering CO2 and natural gas liquids from the produced stream. Occidental Petroleum acquired Hess’s Permian EOR position, including Seminole, in 2017, folding the unit into the largest CO2 flood portfolio in the basin.
The unit’s longevity is the story: ninety years after discovery, SSAU’s annual production still exceeds what many newly drilled shale programs deliver, and it does so with a shallow decline that shale cannot match.
SSAU produces from the San Andres dolomite at roughly 5,200 feet on the Northwest Shelf. The reservoir’s thickness and continuity across the unit made it exceptional CO2 flood rock, and its response — documented in decades of SPE literature — helped establish design standards for WAG cycling, pattern spacing, and conformance control across the entire San Andres trend.
Seminole’s water-alternating-gas CO2 flood has run for more than four decades, recovering a third-life of oil after primary production and waterflooding each ran their course. The associated processing infrastructure recycles produced CO2 back into the flood, so the project operates as a closed loop that both sustains production and permanently retains most of the CO2 brought in. For royalty owners the flood has meant one of the steadiest large royalty streams in Texas.
A Seminole San Andres Unit royalty is a long-duration asset: shallow decline, an operator with unmatched CO2 infrastructure, and ninety years of production history under the forecast. That profile deserves a valuation built on the flood’s actual performance — not a shale-style decline assumption that would badly misprice it. We buy Gaines County and SSAU-area minerals and royalties directly and will show you the unit-level data behind our written offer.
County-level well data, production charts, and selling guides for the counties this field spans:
Occidental Petroleum has operated the unit since acquiring Amerada Hess’s Permian EOR assets in 2017. Hess ran the CO2 flood for the preceding three-plus decades.
The Seminole (San Andres) field designation still reports close to seven million barrels of oil a year to the Texas Railroad Commission — extraordinary output for a field discovered in 1936, and a direct result of the long-running CO2 flood.
Decline profile. Shale wells produce most of their value in the first few years; a mature CO2 flood like SSAU produces a comparatively flat stream for decades. That changes both the risk and the fair price of the royalty — which is why flood interests should be valued on flood data.