Since the late 19th century, the Los Angeles Basin has produced an estimated 9 billion barrels of oil—roughly the equivalent of 14 months of current national consumption.
The USGS evaluation spans a broad geographic area, including the Los Angeles coastal plain, East Los Angeles, and the northern reaches of the Santa Monica Mountains. It also extends into the Angeles National Forest, the foothills of the Sierra Nevada, and much of Orange County. Within this region, four distinct assessment units were analyzed based on their geological features and production trends: one targeting conventional oil reservoirs, two examining shale oil formations, and one focused on shale gas potential.
Although large-scale production in the basin is no longer viable, the findings may inform federal and state land-use decisions, legacy infrastructure management, and discussions around decommissioning and site remediation. In areas with existing infrastructure, targeted redevelopment or enhanced recovery could be considered, but would likely face environmental and regulatory scrutiny given California’s climate and air quality mandates. These insights can also help guide policy discussions around regional energy reliability and how conventional resources may be phased out over time.
The USGS’s approach to oil and gas resource evaluation has significantly changed over the past few decades. Since the 1990s, the agency has integrated assessments of unconventional resources, responding to technological advancements such as horizontal drilling and hydraulic fracturing.
While these technologies have extended extraction potential in mature basins, they have also raised environmental and public health concerns—particularly in urban and ecologically sensitive areas like Southern California. Including them in assessments helps ensure that resource data reflects current extraction capabilities, even as the broader energy sector shifts toward decarbonization and renewable development.
