San Miguelito Oil Field facts for kids
The San Miguelito Oil Field is a large area in the hills near Ventura, California, where oil is found deep underground. It's located in southern California, close to the coast. This oil field is nestled between the bigger Ventura Oil Field to its east and the Rincon Oil Field to its north, which even extends into the ocean.
Oil was first discovered here in 1931. While it once held about 125 million barrels of oil, around 7 million barrels are still left. This makes it the 44th largest oil field in California. As of early 2009, 61 oil wells were actively pumping oil here. All these operations are managed by Vintage Production California LLC, which is part of Occidental Petroleum.
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Where is the San Miguelito Oil Field?
This oil field is one of several that follow the east-west direction of the Transverse Ranges mountains. To the west, you'll find the Rincon Oil Field and the Dos Cuadras Offshore Oil Field in the ocean. To the east is the much larger Ventura Oil Field.
The San Miguelito field covers about 940 acres (or 1.5 square miles) on the surface. This area is along the coast between Ventura and Carpinteria, California, a stretch often called "the Rincon." The hills here rise steeply from the ocean. U.S. Highway 101 runs along this narrow strip between the beach and the hills.
You might spot a group of houses by the ocean at Solimar Beach. One of the field's oil pumps can be seen from the highway, right at sea level, near the Solimar Beach exit. Most of the other oil wells and equipment, like storage tanks, are hidden from public roads.
What is the land like?
The hills are covered mostly by chaparral and coastal sage scrub plants. The land is very steep, and the dirt roads that lead to the oil wells wind back and forth many times. Some parts of the hills are bare because of landslides, as this area is very prone to them.
The weather here is like the Mediterranean climate. This means cool, rainy winters and mild, dry summers. Morning clouds from the coast help keep things cool. The elevation in the oil field ranges from sea level up to over 1,200 feet (366 meters) on the highest hilltops. Any water that runs off the oil field flows west and southwest into the Pacific Ocean through small streams that only flow during the rainy season.
How does the San Miguelito Oil Field work?
The San Miguelito oil field holds oil in a special underground rock formation. This formation is part of the western end of the Ventura Anticline. An anticline is like an upside-down U-shape in rock layers. To the north, a fault (a crack in the Earth's crust) called the Grubb Thrust Fault has pushed another rock fold on top of the Ventura Anticline.
The oil is found in layers of sand from the Pliocene and Miocene periods, which are millions of years old. These layers are named numerically, like 1st Grubb, 2nd Grubb, all the way down to 5th Grubb. There's also a "Grubb D" zone for even deeper layers. These layers are found on both sides of the fault but are shifted by about 4,000 feet (1,219 meters) vertically.
This is a very deep oil reservoir. The shallowest oil-producing layer is about 6,800 feet (2,073 meters) below the surface. The deepest layers are over 14,000 feet (4,267 meters) deep! The California Department of Conservation groups these layers into three main areas: Grubb 1-3, Grubb 4-5, and Grubb D (Deep).
The oil found here is considered medium-grade. Its quality is measured by something called API gravity. The oil in the first four Grubb zones has an API gravity of 31, while the 5th Grubb zone has an API gravity of 25.
History of Oil Production
The nearby Ventura Oil Field was discovered in 1919. However, it wasn't until 1931 that people started looking for oil at the western end of the Ventura Anticline. Here, they had to drill very deep to find oil.
The first successful well in the San Miguelito field was drilled by Continental Oil Co. It was called "Grubb No. 1." This well reached 7,623 feet (2,323 meters) deep. It was drilled from a ridge about half a mile from the ocean and 800 feet (244 meters) above sea level. This well produced over 600 barrels of oil per day, and soon, more wells were drilled to develop the field.
In 1944, the 2nd Grubb Zone was found, and in 1950, the 3rd Grubb. The San Miguelito field produced the most oil in 1951, reaching 4.5 million barrels that year. More oil zones were discovered later, with the 4th Grubb starting production in 1970 and the 5th Grubb in 1979. By 1983, the deepest well was already pumping oil from 14,752 feet (4,496 meters) underground.
How do they get more oil out?
To help push more oil out of the ground, several "waterflooding" projects have been used since 1955. This involves injecting water into the oil reservoir to increase the pressure. Most of this water injection has happened in the Grubb 1-3 zones. As of 2009, only one waterflood well was active in Grubb 4-5, while 31 were active in Grubb 1-3.
In 1993, a company called Vintage Petroleum bought both the San Miguelito and the nearby Rincon Oil Field from other companies like Mobil and Conoco. To make things more efficient, Vintage combined the operations of these two fields. In 2006, Occidental Petroleum bought Vintage, but they kept the Vintage name. Vintage still operates the Rincon and San Miguelito fields today.
Images for kids
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The San Miguelito Oil Field in Ventura County, California. Other oil fields are shown in dark gray.
