The Wilmington field lies beneath the ports, refineries, and neighborhoods of Long Beach and Wilmington — the third-largest oil field in the United States by cumulative production, with roughly three billion barrels recovered since its 1932 discovery. It is famous twice over: first for the dramatic ground subsidence its early production caused, and second for the engineering answer — one of history’s great waterfloods and the four camouflaged THUMS drilling islands in Long Beach harbor. Royalty and mineral interests here sit atop a field managed as much for the city above it as for the oil below.
Ranger Petroleum completed the discovery well in 1932, and development accelerated after the deeper zones were recognized in 1936. The field quickly became one of the nation’s most prolific, feeding wartime demand from thousands of wells drilled across Wilmington, Terminal Island, and Long Beach. Crucially, much of the oil lay under city- and state-owned tidelands, setting up decades of public involvement in its management.
Heavy withdrawal collapsed the weak reservoir sands, and by the 1950s parts of Terminal Island had subsided nearly 30 feet, flooding docks and buckling infrastructure. The response — mandated repressuring under the state Subsidence Act — turned Wilmington into one of the largest waterflood operations ever undertaken. Injection arrested the sinking and, as a byproduct, dramatically increased oil recovery.
In 1965 the eastern extension was unitized as the Long Beach Unit, developed by THUMS — a consortium named for Texaco, Humble, Union, Mobil, and Shell — from four landscaped artificial islands built in the harbor. Occidental acquired the THUMS contractor role in 2000, and California Resources Corporation carried it forward after its 2014 spin-off, operating the unit today in partnership with the City of Long Beach and the State of California.
Wilmington is a broad, faulted anticline in the Los Angeles Basin, plunging southeast beneath San Pedro Bay. Production comes from stacked Miocene and Pliocene turbidite sands — the Tar, Ranger, Upper Terminal, Lower Terminal, Union Pacific, Ford, and deeper zones — between roughly 2,000 and 10,000 feet. The sands are thick, porous, and poorly consolidated, which made them both prolific and prone to compaction when pressure dropped. Normal faults divide the field into blocks that operators manage as separate waterflood units.
Waterflooding defines Wilmington. Injection began at scale in the late 1950s to stop subsidence that had sunk parts of Terminal Island below sea level, and it continues today: water replaces the volume of every barrel withdrawn, maintaining pressure and sweeping oil to producers. For royalty owners this is a double assurance — recovery is higher than primary depletion would have allowed, and the operator is legally bound to maintain the pressure balance that protects the city above. The Long Beach Unit operates under a unique state-city-contractor framework, with proceeds shared among public entities and private interest holders.
Wilmington interests are urban oil assets: long-producing, waterflood-supported, and administered through unitization structures that can make ownership paperwork more complex than in rural fields. Values turn on which unit and tract you own, your decimal, and the trajectory of an operation whose future is shaped by Long Beach civic decisions and state policy as much as geology. We are comfortable with tract participations, unit interests, and inherited fractions that other buyers find tedious. We buy minerals and royalties in Los Angeles County and provide free written offers.
County-level well data, production charts, and selling guides for the counties this field spans:
The four artificial islands in Long Beach harbor are drilling sites for the Long Beach Unit, built in 1965 and disguised with towers and landscaping. If your interest participates in the Long Beach Unit, the wells drilled from those islands are among the wells generating your payments.
Much of the field was unitized so waterflooding could be managed field-wide — individual tracts receive an allocated share of unit production rather than payments from specific wells. Your tract participation factor, listed in unit documents, is the key number for valuing the interest.
Yes. Fractional urban interests are common here after several generations of inheritance, and we purchase them regularly. Send a check stub or unit statement and we will verify the interest and provide a free written offer, regardless of the size of the decimal.