Edison Oil Field
Encyclopedia
The Edison Oil Field is a large oil field
Oil field
An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

 in Kern County, California
Kern County, California
Spreading across the southern end of the California Central Valley, Kern County is the fifth-largest county by population in California. Its economy is heavily linked to agriculture and to petroleum extraction, and there is a strong aviation and space presence. Politically, it has generally...

, in the United States, in the southeastern part of the San Joaquin Valley
San Joaquin Valley
The San Joaquin Valley is the area of the Central Valley of California that lies south of the Sacramento – San Joaquin River Delta in Stockton...

 and adjacent foothills east-southeast of Bakersfield
Bakersfield, California
Bakersfield is a city near the southern end of the San Joaquin Valley in Kern County, California. It is roughly equidistant between Fresno and Los Angeles, to the north and south respectively....

. The field has a total productive area of over 8000 acres (32.4 km²), most of which is intermingled with agricultural land uses; oil pumps and storage tanks are surrounded with row crops and orchards in much of the field's extent. Discovered in 1928, and with a cumulative production of 149 Moilbbl of oil as of 2008, and having over 6 million in reserve, it is ranked 38th among California's oil fields by total ultimate recovery. p. 63. It is a mature field in decline, and is run entirely by small independent operators. As of 2008, there were 40 different oil companies active on the field, one of the most in the state for a single field. 914 wells remained active on the field, averaging only two barrels of oil per well per day from the dwindling reservoirs.

Setting

The field lies in the flat bottomlands of the lower San Joaquin Valley, east-southeast of Bakersfield just outside of the outlying residential areas. A small portion of the field – the Racetrack Hill area – extends into the lower foothills of the Sierra Nevada. The active portion of the field is approximately nine miles long north to south by six miles across, with the most productive portions to the east and northeast. California State Route 58
California State Route 58
State Route 58 is an east-west highway across the California Coast Ranges, the southern San Joaquin Valley, the Tehachapi Mountains, which border the southern Sierra Nevada, and the Mojave Desert. It runs between its western terminus near Santa Margarita and its eastern terminus at Barstow...

 crosses the field east to west, and California State Route 184, the Weed Patch Highway, runs north to south through the western part of the oil field.

Terrain in the vicinity of the oil field varies from almost table-flat, in the valley bottomlands, to rolling hills in the northeast, with elevations ranging from approximately 500 to 900 feet (274.3 m) above sea level throughout the productive region. The land rises with a slight gradient to the east and northeast, in the direction of the foothills of the southernmost Sierra Nevada Mountains. Climate is typical of the southern San Joaquin Valley, and is arid. Temperatures in the summer routinely exceed 100 degrees Fahrenheit on cloudless days. Rain falls mainly in the winter months, and averages 5 to 6 inches annually. Freezes occur occasionally during the winter, and the winter months are also subject to frequent dense tule fog
Tule fog
Tule fog is a thick ground fog that settles in the San Joaquin Valley and Sacramento Valley areas of California's Great Central Valley. Tule fog forms during the late fall and winter after the first significant rainfall. The official time frame for tule fog to form is from November 1 to March 31...

s, limiting visibility to near zero. Drainage from the field in generally into the irrigation canal system, but because of the flat surface gradient most rainfall soaks directly into the ground. The air quality in the vicinity of the field, as recorded in the town of Arvin two miles (3 km) to the west, is among the worst in the United States.

Geology

The Edison field, like the other fields in the bottomlands of the San Joaquin Valley, consists of a series of oil pools embedded in various types of traps within a thick section of Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

 sediments lying on top of ancient metamorphic basement rocks of Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 age. These basement rocks, which in the vicinity of the Edison field are primarily green schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...

 containing calcite seams, slope from northeast to southwest with a depth of 2000 feet (609.6 m) in the northeast part of the field to 8000 feet (2,438.4 m) in the southwest, a distance of about five miles (8 km). The basement complex has a weathered surface, from long exposure to the elements tens of millions of years ago, prior to its subsiding into the sea and being covered with the sediments that now contain oil. In places the overlying sedimentary layers buttress against steeper portions of the basement schist, which when fractured may itself be an oil reservoir for hydrocarbons seeping upward from those buttressing units.

The overlying sedimentary layers are a mix of Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

, Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

, and 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...

 continental deposits and Miocene
Miocene
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...

 marine deposits. Oil pools exist both as lenticular accumulations within the units, trapped by stratigraphy, and as pools in structural traps along fault lines. The overall dip of the units within the field is to the southwest.

Quality and characteristics of oil varies widely throughout the field, as would be expected given the widely dispersed nature of the reservoirs both in depth and lateral extent. Near the surface, some of the oil is heavy, with 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...

 around 13, requiring steam injection in order to be efficiently produced. Some of the deeper pools contain light oil with gravity over 40.

The deepest well on the field was drilled by J. Ainslie Bell, reaching the Oligocene-age Vedder Formation at a total depth of 7,458 feet.

History, production, and operations

The Edison field was one of the last fields discovered in California during the boom period of the early 20th century. Unlike other fields alongside the Central Valley which either advertise their existence with tar seeps or with anticlinal hills which serve as a surface expression for the underlying oil-bearing structures, the Edison field is completely hidden underneath the valley floor. The discovery well for the Edison field was drilled by General Petroleum Corporation in July 1928; it produced 65 barrels (10.3 m³) of oil per day, an acceptable flow but no gusher; nevertheless it was sufficient to establish that an oil field lay below the flat farmland of the valley southeast of Bakersfield. Early well drilling in the area was almost always of a "wildcat" nature, with numerous failures, as finding oil-bearing units in the hidden structure was mostly guesswork, until enough borehole logs were available to begin to build a subsurface lithologic model.

During the 1920s the price of oil dropped gradually with new discoveries, including giant fields in the Los Angeles Basin, the Central Valley, and Texas; and with the Great Depression, and the 1930 discovery of the enormous East Texas field
East Texas oil field
The East Texas Oil Field is a large oil and gas field in east Texas. Covering and parts of five counties, and having 30,340 historic and active oil wells, it is the largest oil field in the United States outside of Alaska, both in extent and in total volume of oil recovered since its discovery in...

, the price of oil dropped as low as ten cents a barrel. Drilling during this period was greatly reduced, as the cost to open a new well was unlikely to be recouped unless an exceptional reservoir could be tapped, and few drillers were willing to take this risk, particularly in a field where success was so spotty. After the single well that opened the field's Main Area in 1932, no further wells were put in to the Edison field until 1934, during which seven new wells became active, and in 1935 that number had risen to 46.

Over the next several decades, new reservoirs were discovered and put into production. In 1935, Shell Oil Company successfully completed their first well in the West Area of the field, which would prove to be one of the most productive areas. Also in 1935, the small 50 acres (202,343 m²) Northeast Edison field was discovered by Woodward Oil Company. The Racetrack Hill Area came online in 1944, the Jeppi Area in 1948, and in 1950 Richfield Oil Corporation, ancestor of ARCO
ARCO
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...

 and BP
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...

, found oil in the Edison Groves Area. The field reached its peak production in 1953, a time when oil was flowing from all of these areas: in that year over 6.6 Moilbbl were produced.

In the early 1960s, in an effort to restore declining production several enhanced recovery methods were employed. The first waterflooding operation began in 1963 in the Portals-Fairfax area, and in 1964 both waterflooding and cyclic steam were in use in several areas of the field, with the steam recovery being used on the heavy oil reservoirs such as Racetrack Hill, where a steam system is still in place.

The major oil companies, and companies that are ancestors of today's major oil companies gradually left the field in the decades following 1950. J. Paul Getty
J. Paul Getty
Jean Paul Getty was an American industrialist. He founded the Getty Oil Company, and in 1957 Fortune magazine named him the richest living American, whilst the 1966 Guinness Book of Records named him as the world's richest private citizen, worth an estimated $1,200 million. At his death, he was...

, Standard Oil of California, Richfield Oil Corporation, Shell and Mobil all once had holdings on the Edison field. Smaller independents absorbed these holdings, and in 2009 there were 40 separate operators on the field. Some of the largest of these at the end of 2008 where Vaquero Energy, with 352 wells; Naftex Operating Company, with 163, and Sequoia Exploration, Inc. with 93.

At the end of 2008, 914 wells remained active on the field, with a field-wide average water cut of 92%. In spite of the declining reserves, some independent operators continue to explore for oil. For example, in 2011 Tri-Valley Corp expanded its operations on the Claflin Lease in the Racetrack Hill area, with intent to drill 22 new wells.
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