The Block 31 Field in east-central Crane County, Texas holds a singular place in petroleum history: discovered in November 1945 with the University A No. 1 on University Lands, it became the site of the world’s pioneering high-pressure miscible gas injection project when Atlantic Refining began injecting in June 1949. Producing light, 40-plus-gravity oil from the Devonian Thirtyone chert, Block 31 blew past 100 million barrels decades ago — recovery far beyond what primary depletion could have delivered. For mineral owners, it is the original proof that engineered floods multiply a reservoir’s royalty life.
Source: Texas Railroad Commission production filings, aggregated across RRC field designations 09358450, 09358900, 09358540, 09358910. Reported volumes lag the calendar by several months.
Atlantic Refining completed the University A No. 1 discovery in November 1945, opening deep Devonian pay beneath University Lands acreage in east-central Crane County. The reservoir’s light, volatile oil and strong solution gas made it an ideal candidate for an idea Atlantic’s engineers were developing: rather than simply maintain pressure, inject gas at pressures high enough to become miscible with the oil and sweep it almost completely from the rock it contacted.
Injection began in June 1949 — the first application of high-pressure miscible gas displacement anywhere — initially using produced gas from the Devonian and Ellenburger, injected at the crest of the structure. The project worked spectacularly, and Block 31 became a landmark studied worldwide; by the early 1960s, papers were documenting recovery approaching 80 percent of the oil primary methods would have taken far longer to produce. Operations later shifted to injecting flue gas and inert gas, stretching the miscible program across decades.
A Texas historical marker commemorates the field’s first 100 million barrels, a milestone reached under Atlantic and its successor ARCO. The unitized Devonian field passed through the consolidations that folded ARCO’s Permian legacy into larger portfolios, and in recent years Block 31 has been listed among Occidental’s conventional Permian assets. Seventy-five years after the first miscible injection, the field remains a working monument to enhanced recovery.
Block 31 produces from the Devonian Thirtyone Formation — a deep chert and carbonate reservoir renowned in the Permian Basin for light oil and strong deliverability — at depths far below the shallow Grayburg fields that made Crane County famous. The Thirtyone’s porous chert intervals hold volatile, high-gravity crude ideally suited to miscible displacement: at high pressure, injected gas dissolves into this oil and strips it from the rock with recovery efficiencies unattainable by waterflooding heavier crudes. The rock and fluid pairing is precisely why the world’s first miscible flood happened here.
Block 31 is where miscible flooding began. Atlantic’s June 1949 high-pressure gas injection predated commercial CO2 flooding by more than two decades, and the field went on to inject well over 100 billion cubic feet of gas — later including flue gas and inert gas generated on site — while recovering a far higher fraction of its oil in place than primary depletion allowed. The lesson for royalty owners is foundational: engineered recovery transformed a good Devonian field into a multi-generation producer, and the same economics keep mature miscible projects running long past ordinary field lifetimes.
A mineral or royalty interest at Block 31 sits atop one of the most technically distinguished reservoirs in Texas — deep, light-oil pay with a 75-year enhanced-recovery pedigree and unitized operations built for the long term. Valuing such an interest requires understanding miscible-flood behavior, not just counting wells or extrapolating a recent check. Owners with inherited fractions here often hold more durable income than they realize. We buy minerals and royalties in Crane County and provide free written offers.
County-level well data, production charts, and selling guides for the counties this field spans:
Yes. The field has produced since 1945, surpassed 100 million barrels decades ago, and its unitized Devonian reservoir has operated under miscible gas injection in various forms since 1949.
Atlantic Refining discovered the field and pioneered its miscible flood; the asset passed through successor ARCO and subsequent consolidations, and in recent years has been listed among Occidental’s conventional Permian holdings.
Materially, yes. Miscible injection sustains rates and extends field life well beyond primary decline, so a valuation should model that long, supported tail. We provide free written offers that price the flood’s longevity rather than a snapshot.