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The Kettleman North Dome Oil Field in Central California. Other oil fields are shown in gray.

The Kettleman North Dome Oil Field is a large oil and gas field in Kings and Fresno Counties, California. Discovered in 1928, it is fifteenth largest field in the state by total ultimate oil recovery, and of the top twenty oil fields it is the closest to exhaustion, with less than one-half of one percent of its total original oil remaining in place.^[1] Only forty wells remain in production in this once rich field.

[edit] Setting

The Kettleman North Dome occupies the northernmost portion of the Kettleman Hills, a northwest-southeast trending line of hills about 30 miles long which parallels the San Andreas Fault to the west. The range consists of two elongate "domes", the North Dome and Middle Dome; a portion of the Middle Dome is sometimes called the "South Dome," although the North and Middle Dome are the most topographically distinct. Both the North and Middle Domes overlie oil fields.^[2]

The Kettleman Hills is named, and misspelled, after Dave Kettelman, a pioneer sheep and cattle rancher who grazed his animals there in the 1860s.^[3] The hills, which rise to an elevation of approximately 1,200 feet, divide the San Joaquin Valley on the east from the much smaller Kettleman Plain to the west. They are discontinuous, as indicated by their name ("hills" rather than "ridge"). The predominant vegetation in the hills themselves is grassland, with surrounding areas containing grassland, low scrub, orchards, and agricultural fields. The climate is arid, with 6 to 12 inches of precipitation per year on the average, all falling as rain. Summers are hot, with daily highs regularly exceeding 100 degrees Fahrenheit in the summer months, and winters are cool with occasional freezes.^[4]

Interstate 5 parallels the range of hills to the northeast, and SR 33 to the southwest. State Route 41, which runs from Paso Robles to Kettleman City to Fresno, crosses the hills at the southern extremity of the North Dome, and SR 269, which connects the town of Avenal to Interstate 5, crosses the hills in the middle of the North Dome.

North Dome itself is one of the longest of the California oil fields; only Midway-Sunset is longer. Its long axis, northwest to southeast, is approximately 14 miles, and it is almost three miles across at its widest point.^[5]

[edit] Geology

The oil field is one of a long line of similar long, narrow, anticlinal fields paralleling the San Andreas Fault, where tectonic forces squeezed the rock formations into anticlinal structures, trapping large quantities of petroleum. To the northwest is the large Coalinga Oil Field; to the southeast are the Lost Hills Oil Field, Cymric, McKittrick, North Belridge, South Belridge, Elk Hills, Buena Vista, and finally the largest of all, the enormous Midway-Sunset field in the southwestern corner of the San Joaquin Valley. The total productive area of the Kettleman Hills North Dome is 13,700 acres.^[6]

Within the Kettleman Hills, oil is found in the large structural trap represented by the anticline. The large McLure Formation, of upper Miocene age, forms an impermeable cap beneath which enormous quantities of oil have pooled over millions of years, principally in the Temblor Formation, which is of Middle and Lower Miocene age. Within the Temblor Formation, five different zones are identified in cross section, with a total thickness of petroleum-bearing rock approaching 2,000 feet. Underneath the Temblor is yet another series of impermeable and permeable strata, like layers on a cake: the Vaqueros Sandstone and Kreyenhagen Formation are impermeable units beneath the Temblor, and underneath them yet another large pool of oil is found in the Upper McAdams Formation, of Eocene age, at a depth of around 10,000 feet. This formation was not discovered until 1940. A few other smaller oil pools were discovered later, such as one in the Kreyenhagen in 1957, and the Whepley, a small additional pool at great depth in the Temblor Formation discovered in 1976. While the Kreyenhagen is normally an impermeable shale body, where it is highly fractured it is a productive unit in its own right, as oil then collects in the fractures.^[7]

Removal of oil from the large Kettleman Hills fields, mainly the North Dome, has been suggested as a cause of the 1985 M6.1 earthquake, since the total deformation caused by the quake was exactly that necessary to compensate for the oil removed historically, i.e. by filling the vacated space. The same mechanism has been suggested the the 1983 Coalinga earthquake and the 1987 Whittier Narrows earthquake, both of which occurred near the centers of mature oil fields.^[8]

[edit] History, production, and operations

The presence of a large oil field was long suspected in the Kettleman Hills region, since it is an anticlinal structure like so many of the nearby San Joaquin Valley oil fields; however, early test wells found nothing, since early drilling methods lacked the ability to drill the 7,000 feet necessary to tap the huge reservoirs. Before 1910, drillers made nine separate unsuccessful attempts to reach oil.

Finally a persistent attempt paid off. In 1927, the Milham Company drilled its Elliott No. 1 well: after 19 months of labor, in October 1928, at a depth of 7,108 feet, they hit oil and a terrific blowout ensued, which took three years to bring under control at this one well. Elliott No. 1 and other wells in the huge Temblor pool produced 3,670 barrels a day during that period; the initial measured pressure was 3,540 psi.^[9] The town of Avenal, originally named Milham City after the oil company, quickly grew near the field, the latest in a series of oil boom towns in the Central Valley.

Unrestricted production of oil at the Kettleman Hills fields, mainly North Dome, was controversial during the 1930s. Other states, such as Oklahoma, Texas, and Kansas, restricted production of oil through agreements with each other, in order to keep the price from falling too far; however, in California no such regulation existed.^[10] Production from Kettleman peaked in 1936, with over 29 million barrels pumped during that year, making it one of the most productive fields in the United States.^[11] In 2006, the latest year for which data was available, production was a mere 128,000 barrels, even with the modern technologies available.^[12]

Unlike many of the other major California oil fields, enhanced recovery have been used minimally at Kettleman Hills. Water flooding was used in both the Temblor and Vaqueros pools, between 1965 and 1977, but many of the methods (steam flooding, fire flooding, gas injection, and so forth) used at other fields, such as Midway-Sunset, Kern River, Cymric, or San Ardo, have proved impractical, both because of the relatively light API gravity of the oil as well as the depth of the reservoirs.

[edit] References

[edit] Notes

Category:Fresno County, California Category:Kings County, California Category:Geology of California Category:Oil fields of the United States Category:Energy resource facilities in California