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The Los Angeles Basin Province and its two assessment units. Base: National Park Service. USGS.
Using a geology-based method, the USGS estimates that 13 million barrels of oil, 22 billion cubic feet of gas and 1 million barrels of natural gas liquids are technically recoverable (mean estimates) from continuous accumulations in the Miocene Monterey Formation of the Los Angeles Basin Province, southern California.
Background
- Continuous accumulations hold oil or gas throughout the rock, in nearly every well that penetrates them, without needing a structural or stratigraphic trap and usually without oil–water or gas–water contacts. They are usually produced with well stimulation such as hydraulic fracturing — the "unconventional" label — though the same methods are used in many conventional fields too.
- The source rock: the Monterey Formation generated the oil in the basin's conventional traps, including the giant Wilmington and Huntington Beach fields.
- Earlier estimates: a mean of 0.98 billion barrels of undiscovered oil (1996) and 3.2 billion barrels of potential additions to reserves in discovered fields (2012).
- This assessment targets oil still in the Monterey at depth, in or near the zone where oil forms, that never migrated up into conventional traps.
Assessment units
Two assessment units (AUs), excluding conventional fields with oil–water contacts, outline where oil generation began as the base of the organic-rich Monterey reached burial depths of about 9,000 to 12,000 feet:
| AU | Defined by |
|---|---|
| Central and Eastern Los Angeles Monterey Continuous Oil | the −12,000-foot structure contour near the base of the Monterey |
| Western Shelf Los Angeles Monterey Continuous Oil | the area west of the Newport–Inglewood fault zone where the Monterey's base is deeper than 9,000 feet |
Oil likely forms at shallower depth in the west (about 9,000 feet) than in the east (about 12,000 feet), because the western organic matter holds more sulfur and generates oil with less heating.
The analog: using the southern San Joaquin Basin, where the Monterey was deposited in a similar setting, the team concluded that some oil may remain in the source rock but success rates (wells producing at least 2,000 barrels) will be low and recoveries small even for successful wells, with tightly spaced wells.
Results
| Assessment unit | Oil (million bbl), mean | Gas (billion ft³), mean | NGL (million bbl), mean |
|---|---|---|---|
| Central and Eastern Los Angeles | 8 (range 2–19) | 15 (3–37) | 1 (0–2) |
| Western Shelf Los Angeles | 5 (1–13) | 7 (2–18) | 0 (0–1) |
| Total | 13 (3–32) | 22 (5–55) | 1 (0–3) |
Ranges are the F95 (95 percent chance of at least this much) to F5 estimates.
These volumes are small compared with possible undiscovered conventional oil or added recovery from producing fields. Extraction would most likely use vertical (not horizontal) wells and acid stimulation; hydraulic fracturing is less likely to succeed.
Sources
Based on Assessment of Undiscovered Continuous Oil and Gas Resources in the Monterey Formation, Los Angeles Basin Province, California, by the Los Angeles Basin Monterey Assessment Team (Marilyn E. Tennyson and others), USGS Fact Sheet 2016–3036, U.S. Geological Survey (DOI), citing Beyer (1996), Gautier and others (2012) and Wright (1991); a work of the United States government in the public domain. The map and results table come from the fact sheet's PDF. More: USGS Energy Resources Program.
Licens: CC0 1.0 (offentligt eje) · Bearbejdet efter pubs.usgs.gov
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