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The Los Angeles Basin (LA Basin) is located in the southern part of California that is attached to the majority of the Santa Monica Mountains on the north side, the Puente Hills on the east side, and the San Joaquin Hills on the southeast side of the basin. This is displayed in the figure to the right. The LA Basin is California’s most prolific producing basin and known for its oil per unit ratio.
Oil was discovered by Edward Doheny in California in 1892 and soon became one of the top producing states in the country. Offshore exploration and production first occurred in 1896. Oil was first struck near present-day Dodger Stadium. The first drilling well, which was located on the corner of Colton St and Glendale Boulevard, consisted of the sharpened end of a eucalyptus tree. By 1897, five years following the initial discovery, the number of drilling wells in the state of California topped 500. Production continued to boom in California and the state began producing almost a quarter of the world’s oil by the 1930s. With environmental restrictions put in place later in the 20th century, California’s oil production began to decline. While new production isn’t as prominent as production years ago, there are still many reminders of the industry that helped develop the state. Old drilling rigs still exist in extremely populated places, such as Beverly Hills. 
The Los Angeles basin formation consisted of both regressions and transgressions of the west coast shoreline. This tectonic activity along with volcanic activity helped build the Los Angeles basin into what it is today. The Los Angeles Basin is considered one of the smallest petroleum basins in the world. It’s placed between the Palos Verdes fault and the Whittier fault.
Geologic Risks and Uncertainties
Seismic hazards such as surface rupture, liquefaction, ground shaking, and subsidence have great prevalence within the Los Angeles Basin due to the occurrence of earthquakes and faults in the region. The Los Angeles Basin is unable to avoid seismic hazards due to its location in a tectonically and seismically active region, characterized by fault zones and other geologic hazards. 
The Los Angeles Basin is a part of the Central Groundwater Basin, shown on the figure to the right. These basins are made up of layers of aquifers and contribute to California's water supply. Due to groundwater, unstable soils and slopes can cause risk and hazard to the production of oil and gas. When saturated, minerals become corrosive and begin to expand. Under these conditions, an electrical current flow begins to form beneath within the soil. This can cause corrosion to metallic materials, such as tanks, pipelines, and other objects that come in contact with soil. 
The LA basin’s sediment became source rocks when the sediments sat in cool stagnant water in very deep depths, around 1,600 feet deep, during the last marine transgression. The organic material was preserved due to poor circulation within the basin and quick basin filling. During the transgression, the organic material was compacted with great pressure and accumulated great thickness, thus creating source rocks. The other non-organic material compacted as well and created the reservoir rock it has today.
The Miocene era and the Pliocene era, make up the time of oil buildup through migration in the LA Basin. Vertical Migration was a common type of migration for the basin, especially with the Miocene era shales. Vertical migration is when different hydrocarbon systems combine due to the presence of faults.
Seals and Traps
The LA Basin is located near the San Andreas fault (figure to the right), and many more fault zones, which had a major effect on the seals and traps that were found throughout the LA Basin. The convergent strike-slip tectonic movement of the San Andreas fault with other adjacent convergent structures have created oil traps and seals within the LA Basin. These fault traps have created the opportunity for prolific production as one has seen in the past.
The LA Basin has unique structural features compared to other basins. The basin is boxed in by two faults right outside of the basin perimeter. The Whittier fault zone to the northeast and the Newport-Inglewood fault zone to the southwest. On top of those fault zones, the San Andreas fault lies near the basin as well. The basin is also unique in the way that its depth becomes greater as it moves towards the center of the basin. The depression in the center of the basin is about 30,000 feet below sea level.
The Los Angeles Basin contains several reservoir units such as Pico, Fernando, and Repetto formations. These formations are important to the creation of reservoir rocks because of their submarine fluvial sands. These sands come from early to late Pliocene eras to pre-middle, middle and late Miocene eras.
During the early age of California, there weren't immediate plans of extracting petroleum. Although this was the case, in the beginning, oil was eventually discovered in 1892 and was a very prominent industry. Many people may think that Hollywood or real estate helped put California on the map, but the oil and gas industry was the true kick-start of the west coast. As time has progressed, oil production in California has been on a steady decline. As of February 2020, California has at least 35,000 idle wells. Currently, many residents don’t support the exploration and production taking place in their state, and others see the large number of abandoned wells as liabilities. 
Los Angeles has an urban take when it comes to oil and gas production. The basin is located in a nonindustrial area where the population considers oil rigs and pumpjacks an eyesore or dirty. Due to the high number of tourists coming to the area every year and a negative outlook on production, the energy industry needed to come up with a creative way to hide their production machinery. Pumpjacks are located on the outskirts of the city, hidden behind fences, or sometimes, buildings are even built around them in order to hide it from the population’s view. For example, the figure to the right shows a tower that Occidental Petroleum built in 1966 to disguise their drilling site. Most of the time, people don’t even know that there is oil production in Los Angeles because they don’t see the machinery anywhere, and the companies producing use sound muffling technology to reduce the sound created.
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