Diatomite (diatomaceous earth) Monterey Formation at a diatomite quarry just south of Lompoc

The Monterey Formation is an extensive

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

oil-rich

geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...

sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...

formation in California, with outcrops of the formation in parts of the

California Coast Ranges The Coast Ranges of California span from Del Norte or Humboldt County, California, south to Santa Barbara County. The other three coastal California mountain ranges are the Transverse Ranges, Peninsular Ranges and the Klamath Mountains. P ...

Peninsular Ranges The Peninsular Ranges (also called the Lower California province) are a group of mountain ranges that stretch from Southern California to the southern tip of the Baja California peninsula; they are part of the North American Coast Ranges, which ...

, and on some of California's off-shore islands. The type locality is near the city of

Monterey, California Monterey (; es, Monterrey; Ohlone: ) is a city located in Monterey County on the southern edge of Monterey Bay on the U.S. state of California's Central Coast. Founded on June 3, 1770, it functioned as the capital of Alta California under bo ...

. The Monterey Formation is the major source-rock for 37 to 38 billion barrels of oil in conventional traps such as sandstones. This is most of California's known oil resources. The Monterey has been extensively investigated and mapped for petroleum potential, and is of major importance for understanding the complex geological history of California. Its rocks are mostly highly

siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

strata that vary greatly in composition,

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

, and tectono-stratigraphic history. The US Energy Information Administration (EIA) estimated in 2014 that the 1,750 square mile Monterey Formation could, as an unconventional resource, yield about 600 million barrels of oil, from

tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in unconventional petroleum-bearing formations of low permeability, often shale or tight sandstone. Economic production from ...

contained in the formation, down sharply from their 2011 estimate of a potential 15.4 billion barrels.Drilling California: A Reality Check on the Monterey Shale
J. David Hughes, Post Carbon Institute, 2013. An independent review by the

California Council on Science and Technology The California Council on Science and Technology (CCST) is an independent, not-for-profit 501(c)(3) organization designed to offer expert advice to the California state government and to recommend solutions to science and technology-related polic ...

found both of these estimates to be "highly uncertain." Despite intense industry efforts, there has been little success to date (2013) in producing Monterey-hosted tight oil/shale oil, except in places where it is already naturally fractured, and it may be many years, if ever, before the Monterey becomes a significant producer of shale oil. The Monterey Formation strata vary. Its lower Miocene members show indications of weak coastal

upwelling Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutr ...

, with

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

assemblages and

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

-siliceous rocks formed from

diatom A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

s and

coccolithophorid Coccolithophores, or coccolithophorids, are single celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the kingd ...

s. Its middle and upper Miocene upwelling-rich assemblages, and its unique highly siliceous rocks from diatom-rich plankton, became

diatomite Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 μm to le ...

s, porcelainites, and banded

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

Shale oil resources and exploitation

The Monterey formation has long been recognized as the primary source of the oil produced from other formations in Southern California; the Monterey itself has been very productive where it is naturally fractured. Since 2011, the possibility that hydraulic fracturing might make the Monterey Shale productive over large areas has gained widespread public attention. According to the US

Energy Information Administration The U.S. Energy Information Administration (EIA) is a principal agency of the U.S. Federal Statistical System responsible for collecting, analyzing, and disseminating energy information to promote sound policymaking, efficient markets, and publ ...

(EIA) in 2011, the Monterey Shale Formation contained more than half of the United States's total estimated technically recoverable shale oil (

contained in

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

, as distinct from

oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitute ...

) resource, about . In 2012, the EIA revised its recoverable volume downward, to . As of 2013 advances in

hydraulic fracturing Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "frack ...

commonly called "fracking," and the high price of oil resulted in spirited bidding by oil companies for leases.

Occidental Petroleum Occidental Petroleum Corporation (often abbreviated Oxy in reference to its ticker symbol and logo) is an American company engaged in hydrocarbon exploration in the United States, and the Middle East as well as petrochemical manufacturing in the ...

and

Venoco Venoco, Inc. was a company engaged in hydrocarbon exploration. It primarily operated in the Monterey Formation in California. In 2017, the company filed bankruptcy and was liquidated. History The company was founded in September 1992 by Timothy M ...

were reported to have been major players. The deposit lies below the surface. A widely cited March 2013 study released by the University of Southern California (USC) estimated that if extensive resource play development of the Monterey through hydraulic fracturing were successful, it could generate as many as 2.8 million jobs and as much as $24.6 billion in state and local taxes. However, observers have pointed out that as of 2012, however large its theoretical potential, no one as yet has succeeded in making the Monterey Shale widely economic through hydraulic fracturing; to date it has been economic only in those limited locations already naturally fractured. Richard Behl, a geology professor who heads the "Monterey And Related Sediments" (MARS) consortium at

California State University Long Beach California State University, Long Beach (CSULB) is a public research university in Long Beach, California. The 322-acre campus is the second largest of the 23-school California State University system (CSU) and one of the largest universities i ...

, said that "The IAnumbers probably were overblown, but it was a simple method and had an essence of truth." Compared to other

shale oil Shale oil is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil ca ...

plays, the Monterey formation is much thicker and more laterally extensive, but also much more geologically complex and deformed. See the linked photos from a field trip to Monterey outcrops at

Vandenberg Air Force Base Vandenberg may refer to: * Vandenberg (surname), including a list of people with the name * USS General Harry Taylor (AP-145), USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in K ...

. "To say California geology is complex is an understatement. ... The Monterey play is no slam-dunk." In 2013, Bakken shale-oil pioneer

Harold Hamm Harold Glenn Hamm (born December 11, 1945) is an American entrepreneur in the oil and gas business. He is known for extracting shale oil resources. , Hamm's net worth is estimated to be billion, making him the 63rd wealthiest person in the wor ...

said the Monterey "might have a lot of potential, but there are reasons why it’s not being produced."Monterey/Santos: Operators struggle with cracking code

World Oil This is a list of countries by oil production (i.e., petroleum production), as compiled from the U.S. Energy Information Administration database for calendar year 2021, tabulating all countries on a comparable best-estimate basis. Compared wi ...

, Nov. 2013 (Google title to bypass paywall) J. David Hughes, a Canadian geoscientist and Fellow of

Post Carbon Institute Post Carbon Institute (PCI) is a think tank which provides information and analysis on climate change, energy scarcity, and other issues related to sustainability and long term community resilience. Its Fellows specialize in various fields relate ...

, published a report in December 2013 analyzing the assumptions behind the EIA's forecast of Monterey tight oil production and the USC's forecast of resulting job and tax revenue growth. He found the EIA report's assumptions on prospective well productivity to be "extremely optimistic," and the total estimate of 15.4 billion barrels of recoverable oil "highly overstated." He also found the USC study's assumption that development of the Monterey shale could increase California oil production as much as seven-fold to be "unfounded," and the economic projections regarding jobs and tax revenue to be "extremely suspect."

Source rock

The Monterey Formation is considered the source of 84% of the oil in known fields of the San Joaquin Basin, a total of 12.2 billion barrels of oil. Of this, 112 million barrels of oil in known fields is produced from the Monterey itself. The Monterey formation is the source for such giant oilfields as the

Kern River The Kern River, previously Rio de San Felipe, later La Porciuncula, is an Endangered, Wild and Scenic river in the U.S. state of California, approximately long. It drains an area of the southern Sierra Nevada mountains northeast of Bakersfiel ...

Elk Hills The Elk Hills are a low mountain range in the Transverse Ranges, in western Kern County, California. They are near and east of the Elkhorn Hills in San Luis Obispo County, California San Luis Obispo County (), officially the County of San ...

Midway-Sunset Oil Field The Midway-Sunset Oil Field is a large oil field in Kern County, San Joaquin Valley, California in the United States. It is the largest known oilfield in California and the third largest in the United States. The field was discovered in 1894, ...

,Monterey Shale Continues to Tempt and Tease
AAPG Explorer, February 2013 and probable source for the overlying

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and

South Belridge Oil Field The South Belridge Oil Field is a large oil field in northwestern Kern County, San Joaquin Valley, California, about forty miles west of Bakersfield. Discovered in 1911, and having a cumulative production of over of oil at the end of 2008, i ...

History

Monterey Formation oil was discovered at the

Orcutt Oil Field The Orcutt Oil Field is a large oil field in the Solomon Hills south of Orcutt, in Santa Barbara County, California. Discovered in 1901 by William Warren Orcutt, it was the first giant field (over in ultimate recovery) to be found in Santa Barba ...

in the Santa Maria Basin of Santa Barbara County in 1901. This was quickly followed by other Monterey discoveries nearby, including the

Cat Canyon Oil Field The Cat Canyon Oil Field is a large oil field in the Solomon Hills of central Santa Barbara County, California, about 10 miles southeast of Santa Maria, California, Santa Maria. It is the largest oil field in Santa Barbara County, and as of 2010 ...

and Lompoc Oil Field. Each of these early Monterey discoveries depended on natural fractures in the Monterey. The Monterey Formation is one of the reservoirs in the

Elk Hills Oil Field The Elk Hills Oil Field (formerly the Naval Petroleum Reserve No. 1) is a large oil field in western Kern County, in the Elk Hills of the San Joaquin Valley, California in the United States, about west of Bakersfield. Discovered in 1911, and ...

of Kern County. Major Monterey production was also discovered in offshore oil fields, such as the South Ellwood Oil Field in the Santa Barbara Channel, and the Point Arguello Field in the Santa Maria Basin.Mero, W.E., Thurston, S.P., and Kropschot, R.E., 1992, The Point Arguello Field, In Giant Oil and Gas Fields of the Decade, 1978–1988, AAPG Memoir 54, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, The North Shafter and Rose oil fields of Kern County, which produce primarily from the Monterey Formation, were discovered in 1983, but attempts to produce the oil have not been highly economic. Some horizontal wells were drilled in the Rose field in the early 2000s, with 2,500-foot lateral lengths and single-stage open-hole fracs; the results were said to be improvements over vertical wells. Carbon dioxide injection has been tested in the Monterey shale, with mixed results. "The main problem was that the carbon dioxide didn't increase production as much as hoped. ... That could be because the rock formation is so jumbled up, it's hard to find the right spot in which to inject the carbon dioxide."Oil Firms Seek to Unlock Big California Field
Wall Street Journal, Sept. 22, 2013 Oil companies such as

are using acidizing to stimulate production in Monterey wells, and other companies are experimenting with proprietary mixes of

hydrochloric Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the digestiv ...

and

hydrofluoric acid Hydrofluoric acid is a Solution (chemistry), solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly Corrosive substance, corrosive. It is used to make most fluorine-containing compounds; examples include th ...

s. "There's a lot of discussion around the Monterey Shale that it doesn't require fracking, that acidizing will be enough to open up the rock," said Chris Faulkner, chief executive officer of Breitling Oil and Gas.

Opposition and regulation

The Monterey Formation underlies the southern half of the

San Joaquin Valley The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven c ...

, a prime agricultural region. The possibility of environmental damage has caused some farmers in Kern County to press for close regulation of hydraulic fracturing. Opponents say that hydraulic fracturing poses risks in the seismically active region. The California legislature passed a bill regulating fracking in September 2013. Some environmentalists criticised the bill as being too lax. Some environmentalists promised not to rest until fracking is banned completely. Oil industry representatives criticized the bill as too restrictive. The measure was supported by state Sen. Fran Pavley, author of a fracking bill defeated the previous year. The bill, which Governor

Jerry Brown Edmund Gerald Brown Jr. (born April 7, 1938) is an American lawyer, author, and politician who served as the 34th and 39th governor of California from 1975 to 1983 and 2011 to 2019. A member of the Democratic Party, he was elected Secretary of S ...

promised to sign, provided for disclosure of chemical used, pre-testing of nearby water wells, and a study on environmental and safety issues to be completed by January 2015.California lawmakers approve fracking bill
NBC Bay Area, 12 Sept. 2013. Given the very limited success with fracking the Monterey to date, some find the controversy "much ado about little." In

Santa Barbara County Santa Barbara County, California, officially the County of Santa Barbara, is located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria. Santa Barba ...

, Santa Maria Energy LLC (SME) has proposed a total of 136 wells in the Monterey formation that would use cyclic steam injection to produce

. In 2013, the county planning commission declined its staff's recommendation to approve the project, calling for more study on concerns raised by environmentalists about greenhouse-gas emissions. The County Board of Supervisors approved the proposed project on November 18, 2013 and SME was cited as a model operator and applicant during the proceedings.

References

External links

UCMP.Berkeley.edu: The Monterey Formation of California
— ''from the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham and ...