South Cuyama Oil Field
Encyclopedia
The South Cuyama Oil Field is a large oil and gas field in the Cuyama Valley
and the adjacent northern foothills of the Sierra Madre Mountains
in northeastern Santa Barbara County, California
. Discovered in 1949, and with a cumulative production of around 225 Moilbbl of oil, it ranks 27th in size in the state, but is believed to retain only approximately two percent of its original oil (approximately 4.6 Moilbbl), according to the official estimates of the California Department of Oil, Gas, and Geothermal Resources (DOGGR). Of the top forty onshore oil fields in California, it is the most recent to be discovered, but by the end of 2008 only 87 wells remained in production. p. 63
in the portion of the Cuyama Valley that slopes gently into the northern foothills of the Sierra Madre Mountains. Parts of the field are on hilly terrain, and some is within the Los Padres National Forest
. The field can be reached from California State Route 166
via Aliso Canyon Road on the northwest, and Perkins Road on the northeast; Perkins Road joins 166 at the town of New Cuyama. While these roads run roughly north-south, Foothill Road crosses through the field from east to west, eventually reaching Santa Barbara Canyon Road on the east and State Route 33
. Elevations on the field range from approximately 2,200 to 3,000 feet (670 to 910 meters). The productive area of the field is approximately 4 miles (6.4 km) long by two across, with the long axis running northwest to southeast; the total productive area as reported by DOGGR is 2650 acres (10.7 km²).
The climate is semi-arid, with occasional marine influence, as the Cuyama Valley is open to the sea, although through a narrow gap. Summers are hot with temperatures commonly exceeding 100 °F (37.8 °C); winters are cool, with the mean freeze-free period being about 250 days. Average annual rainfall is about 12 inches, almost all of it falling in the winter in the form of rain, although occasional snowfall has occurred. All streams are dry in the summer, and even the Cuyama River dries up by the late summer in most years. The area is prone to brushfires in the summer and fall; indeed a fire in 1994 caused a loss of $76,000 to the operators, and in July 2006 an accident on the oil field involving a metal plate crossing power lines started the Perkins Fire, which burned 15000 acres (60.7 km²) on the north side of the Sierra Madre Mountains.
Native vegetation in the vicinity of the field ranges from grassland
to chaparral
to oak woodland. Drainage is to the north, towards the Cuyama River
, along Bitter Creek, Branch Canyon Wash, and several ephemeral drainages.
-age Dibblee Sand and the Colgrove Sand, porous units in the Vaqueros Formation underneath the largely impermeable Monterey Formation
. The sedimentary Cuyama Basin is cut by many small faults, and the oil exists in a series of stratigraphic traps, where it is in most cases blocked in its upward motion by impermeable blocks of Monterey, often offset by faults. The average depth of oil in the field is about 4200 feet (1,280.2 m) below ground surface, and the thickness of the oil-bearing units rarely exceeds 200 feet (61 m); in the separate southeastern area of the field, where the Colgrove sand is 5840 feet (1,780 m) below ground surface, the oil bearing rock is only 50 feet (15.2 m) thick. The source rock
for the South Cuyama oil is most likely the Soda Lake Shale member of the Vaqueros Formation.
Overlying the faulted and broken Miocene rocks, which include the Monterey, Branch Canyon, and Santa Margarita Formations, and separated by an unconformity
, is about 2,000 to 2500 feet (762 m) of the Pliocene
Morales Formation. None of these upper rocks are oil-bearing, although gas has been produced from the Santa Margarita Formation.
Oil from the South Cuyama Field is of generally medium to high API gravity
, ranging from 28 to 36 API, so it flows easily. A small pool in the Dibblee Sand in the now-abandoned Southeast Area of the field had oil of even higher gravity and lower viscosity; a well drilled there in 1975 was abandoned in 1978 after producing 42000 barrels (6,677.5 m³).
), drilled the first well in the area to hit oil, on the advice of Thomas Dibblee
, in May 1949. Richfield named the oil-bearing unit, the Dibblee Sand, in his honor. This single well initially produced 525 oilbbl/d, a large find for a region previously written off as being without petroleum potential. The discovery of oil here and in the nearby Russell Ranch Oil Field
transformed the Cuyama Valley from an almost uninhabited region with a few cattle ranches into a mini-boom area; ARCO built the town of New Cuyama in the years after the oil discovery to house the oil workers and provide associated services.
ARCO was only the first of several companies to work the New Cuyama Field. In 1990, they sold off their interest in the field to Stream Energy. The next company to operate the field was Hallador Petroleum, which continued operations until 2005, at which time it sold its interest to E&B Natural Resources Management Corporation, the current operator, which also runs the Russell Ranch field four miles (6 km) to the northwest.
Peak production for the field was in 1951, shortly after discovery, during which over 14 Moilbbl of oil were pumped from the Dibblee and Colgrove pools. Production has declined steadily since, with around 820000 barrels (130,369.6 m³) pumped in 1977, 500,000 in 1987, 390,000 in 1997, and 270,000 in 2007. At the end of 2008, there were only 87 oil wells still in production. p. 88.
Some enhanced recovery
projects have been undertaken on the field. Since the oil in the South Cuyama Field is not heavy, steam injection
has not been necessary to reduce viscosity and improve flow; however, both gas injection and waterflooding have been used, both in the Colgrove and Dibblee formations. The field operators used waterflooding between 1956 and 1973 in the Colgrove, with some success, and both gas injection and waterflooding have been used in the Dibblee Formation commencing in 1964 and 1955, respectively. As of 2008, E&B Resources still uses waterflooding to assist in flow of oil to pumping wells; other wells are designated for water disposal. At the end of 2008, the average water cut – the percentage of liquid pumped from oil wells that was water – was running at 98.4 percent, indicating a field very close to the end of its useful life. Wells on the field were producing an average of 7.9 barrels of oil per day, and the operators have been reinjecting the enormous quantities of water produced with the oil back into the formation through approximately 50 water disposal and water flood wells scattered throughout the field.
E&B also maintains a gas processing plant, known as Gas Plant 10, on the eastern side of the oil field; all natural gas production from the oil wells goes there. The purpose of the gas plant is to strip out hydrogen sulfide, nitrogen, carbon dioxide, water, and natural gas liquids (NGLs) from the gas, making it acceptable for commercial use. After processing at the plant it is sent on for sale, reinjected into the field to enhance recovery, or used as fuel for oilfield operations. NGLs are sent to a tank farm where they are mixed with the oil. Santa Barbara County gave the plant its first permit to operate in 1988.
Cuyama Valley
The Cuyama Valley is a valley along the Cuyama River in central California, in northern Santa Barbara, southern San Luis Obispo, southwestern Kern, and northwestern Ventura counties. It is a sparsely inhabited area containing two significant towns – Cuyama and New Cuyama – and is largely used for...
and the adjacent northern foothills of the Sierra Madre Mountains
Sierra Madre Mountains (California)
The Sierra Madre Mountains are a mountain range in northern Santa Barbara County, California, USA. They are a portion of the Inner South Coast Ranges, representing the southernmost part, which are themselves part of the Pacific Coast Ranges of western North America. The Sierra Madre Mountains...
in northeastern Santa Barbara County, California
Santa Barbara County, California
Santa Barbara County is a county located in the southern portion of the U.S. state of California, on the Pacific coast. As of 2010 the county had a population of 423,895. The county seat is Santa Barbara and the largest city is Santa Maria.-History:...
. Discovered in 1949, and with a cumulative production of around 225 Moilbbl of oil, it ranks 27th in size in the state, but is believed to retain only approximately two percent of its original oil (approximately 4.6 Moilbbl), according to the official estimates of the California Department of Oil, Gas, and Geothermal Resources (DOGGR). Of the top forty onshore oil fields in California, it is the most recent to be discovered, but by the end of 2008 only 87 wells remained in production. p. 63
Setting
The oil field is south of the town of New CuyamaNew Cuyama, California
New Cuyama is a census-designated place in the Cuyama Valley, in Santa Barbara County, California, in the United States. It was named after the Chumash Indian word for "clams", most likely due to the millions of petrified prehistoric clamshell fossils that are found in the surrounding areas...
in the portion of the Cuyama Valley that slopes gently into the northern foothills of the Sierra Madre Mountains. Parts of the field are on hilly terrain, and some is within the Los Padres National Forest
Los Padres National Forest
Los Padres National Forest is a forest located in southern and central California, which includes most of the mountainous land along the California coast from Ventura to Monterey, extending inland...
. The field can be reached from California State Route 166
California State Route 166
State Route 166 is a state highway in the U.S. state of California. It connects the Central Coast to the southern San Joaquin Valley....
via Aliso Canyon Road on the northwest, and Perkins Road on the northeast; Perkins Road joins 166 at the town of New Cuyama. While these roads run roughly north-south, Foothill Road crosses through the field from east to west, eventually reaching Santa Barbara Canyon Road on the east and State Route 33
California State Route 33
State Route 33 is a north–south state highway in the U.S. state of California. SR 33 replaced part of U.S. Route 399 in 1964 during the "great renumbering" of routes. In the unincorporated sections of Kern County it is known as the West Side Highway...
. Elevations on the field range from approximately 2,200 to 3,000 feet (670 to 910 meters). The productive area of the field is approximately 4 miles (6.4 km) long by two across, with the long axis running northwest to southeast; the total productive area as reported by DOGGR is 2650 acres (10.7 km²).
The climate is semi-arid, with occasional marine influence, as the Cuyama Valley is open to the sea, although through a narrow gap. Summers are hot with temperatures commonly exceeding 100 °F (37.8 °C); winters are cool, with the mean freeze-free period being about 250 days. Average annual rainfall is about 12 inches, almost all of it falling in the winter in the form of rain, although occasional snowfall has occurred. All streams are dry in the summer, and even the Cuyama River dries up by the late summer in most years. The area is prone to brushfires in the summer and fall; indeed a fire in 1994 caused a loss of $76,000 to the operators, and in July 2006 an accident on the oil field involving a metal plate crossing power lines started the Perkins Fire, which burned 15000 acres (60.7 km²) on the north side of the Sierra Madre Mountains.
Native vegetation in the vicinity of the field ranges from grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
to chaparral
Chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...
to oak woodland. Drainage is to the north, towards the Cuyama River
Cuyama River
The Cuyama River is a river in southern San Luis Obispo County, northern Santa Barbara County, and northern Ventura County, in the U.S. state of California. It joins the Sisquoc River forming the Santa Maria River...
, along Bitter Creek, Branch Canyon Wash, and several ephemeral drainages.
Geology
Oil in the South Cuyama Basin comes from two primary pools, the MioceneMiocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
-age Dibblee Sand and the Colgrove Sand, porous units in the Vaqueros Formation underneath the largely impermeable Monterey Formation
Monterey Formation
The Monterey Formation is an extensive Miocene oil-rich geological sedimentary formation in California, with massive outcroppings of the formation in areas of the California Coast Ranges, Peninsular Ranges, and on some of California's off-shore islands...
. The sedimentary Cuyama Basin is cut by many small faults, and the oil exists in a series of stratigraphic traps, where it is in most cases blocked in its upward motion by impermeable blocks of Monterey, often offset by faults. The average depth of oil in the field is about 4200 feet (1,280.2 m) below ground surface, and the thickness of the oil-bearing units rarely exceeds 200 feet (61 m); in the separate southeastern area of the field, where the Colgrove sand is 5840 feet (1,780 m) below ground surface, the oil bearing rock is only 50 feet (15.2 m) thick. The source rock
Source rock
In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
for the South Cuyama oil is most likely the Soda Lake Shale member of the Vaqueros Formation.
Overlying the faulted and broken Miocene rocks, which include the Monterey, Branch Canyon, and Santa Margarita Formations, and separated by an unconformity
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
, is about 2,000 to 2500 feet (762 m) of the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
Morales Formation. None of these upper rocks are oil-bearing, although gas has been produced from the Santa Margarita Formation.
Oil from the South Cuyama Field is of generally medium to high API gravity
API gravity
The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water. If its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks...
, ranging from 28 to 36 API, so it flows easily. A small pool in the Dibblee Sand in the now-abandoned Southeast Area of the field had oil of even higher gravity and lower viscosity; a well drilled there in 1975 was abandoned in 1978 after producing 42000 barrels (6,677.5 m³).
History, production and operations
Richfield Oil Co., later part of Atlantic Richfield Company (ARCOARCO
Atlantic Richfield Company is an oil company with operations in the United States as well as in Indonesia, the North Sea, and the South China Sea. It has more than 1,300 gas stations in the western part of the United States. ARCO was originally formed by the merger of East Coast-based Atlantic...
), drilled the first well in the area to hit oil, on the advice of Thomas Dibblee
Thomas Dibblee
Thomas Wilson Dibblee, Jr. was an American geologist best known for his extensive geological mapping...
, in May 1949. Richfield named the oil-bearing unit, the Dibblee Sand, in his honor. This single well initially produced 525 oilbbl/d, a large find for a region previously written off as being without petroleum potential. The discovery of oil here and in the nearby Russell Ranch Oil Field
Russell Ranch Oil Field
The Russell Ranch Oil Field is an oil and gas field in the Cuyama Valley of northern Santa Barbara and southern San Luis Obispo Counties, California, in the United States...
transformed the Cuyama Valley from an almost uninhabited region with a few cattle ranches into a mini-boom area; ARCO built the town of New Cuyama in the years after the oil discovery to house the oil workers and provide associated services.
ARCO was only the first of several companies to work the New Cuyama Field. In 1990, they sold off their interest in the field to Stream Energy. The next company to operate the field was Hallador Petroleum, which continued operations until 2005, at which time it sold its interest to E&B Natural Resources Management Corporation, the current operator, which also runs the Russell Ranch field four miles (6 km) to the northwest.
Peak production for the field was in 1951, shortly after discovery, during which over 14 Moilbbl of oil were pumped from the Dibblee and Colgrove pools. Production has declined steadily since, with around 820000 barrels (130,369.6 m³) pumped in 1977, 500,000 in 1987, 390,000 in 1997, and 270,000 in 2007. At the end of 2008, there were only 87 oil wells still in production. p. 88.
Some enhanced recovery
Enhanced oil recovery
Enhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field...
projects have been undertaken on the field. Since the oil in the South Cuyama Field is not heavy, steam injection
Steam injection (oil industry)
Steam injection is an increasingly common method of extracting heavy oil. It is considered an enhanced oil recovery method and is the main type of thermal stimulation of oil reservoirs. There are several different forms of the technology, with the two main ones being Cyclic Steam Stimulation and...
has not been necessary to reduce viscosity and improve flow; however, both gas injection and waterflooding have been used, both in the Colgrove and Dibblee formations. The field operators used waterflooding between 1956 and 1973 in the Colgrove, with some success, and both gas injection and waterflooding have been used in the Dibblee Formation commencing in 1964 and 1955, respectively. As of 2008, E&B Resources still uses waterflooding to assist in flow of oil to pumping wells; other wells are designated for water disposal. At the end of 2008, the average water cut – the percentage of liquid pumped from oil wells that was water – was running at 98.4 percent, indicating a field very close to the end of its useful life. Wells on the field were producing an average of 7.9 barrels of oil per day, and the operators have been reinjecting the enormous quantities of water produced with the oil back into the formation through approximately 50 water disposal and water flood wells scattered throughout the field.
E&B also maintains a gas processing plant, known as Gas Plant 10, on the eastern side of the oil field; all natural gas production from the oil wells goes there. The purpose of the gas plant is to strip out hydrogen sulfide, nitrogen, carbon dioxide, water, and natural gas liquids (NGLs) from the gas, making it acceptable for commercial use. After processing at the plant it is sent on for sale, reinjected into the field to enhance recovery, or used as fuel for oilfield operations. NGLs are sent to a tank farm where they are mixed with the oil. Santa Barbara County gave the plant its first permit to operate in 1988.