The Early Years – Accidents and Seeps
Oil or gas production in Illinois began in 1853 when marsh or drift gas was produced from two wells drilled near Champaign. This gas came from rotting vegetation buried in the glacial deposits. At the time, people knew little about where gas or oil came from, or how to search for it.
In the early 1860s, several holes drilled in Clark County produced enough oil for the name “Oilfield” to be given to a small town there, even though commercial-scale production in the area did not begin until 40 years later. The search for oil and gas began in earnest there in 1866 when the Clark County Petroleum and Mining Company established its headquarters at Marshall. Natural gas seeps near Oilfield led the company’s owners to believe that commercial quantities of oil and gas were there. However, because well casing technology did not yet exist, water from drilled-through upper layers of earth flowed into the wells and prevented most of the oil in deeper layers from seeping out of the rocks.
Farther to the west near Litchfield, holes drilled in the late 1860s to search for coal leaked oil and water into the workings of a mine, and for several years people skimmed oil off the water and sold the oil. By the early 1880s, natural gas had been discovered in the area and was being piped to Litchfield for domestic use. Continued drilling in the area eventually established oil production, and in 1889 wells produced 1,460 barrels. By 1902, when production ceased, the wells had produced only 6,576 barrels of oil. (The barrel equals 42 U.S. gallons and is a standard unit of volume measurement in the petroleum industry.)
Technologies Improve — Anticlines Become Targets
By the turn of the century, new well casing technologies solved the problem of water flowing into oil wells. Producers also now recognized that oil and gas collected at anticlines, or the crests of upwarps in the rock layers. From 1904 to 1910, numerous shallow oil and gas reservoirs were discovered in the many anticlines in a large structure now known as the LaSalle Anticlinorium, which lies beneath eastern Illinois. With these discoveries, Illinois leaped to third among states as its annual petroleum production rose from 181,000 barrels in 1905 to 33 million barrels by 1910.
Seismic Exploration – Sounding the Depths Brings an Oil Boom
In the late 1930s, a new technology called seismic exploration allowed geologists to find hidden anticlines — structures too deeply buried or too subtle to be found otherwise. Still used today, this technique uses sensitive microphones called “geophones” to record sound waves from ground-level dynamite blasts as they “echo” off the tops of the successive rock layers below. The echo data are then used to form a picture of the rock layers below. With seismic exploration, hundreds of new anticlines and other types of oil traps were found and drilled in many areas of southern Illinois. In 1940, the state’s total oil production rose to 147.6 million barrels, the largest in the state’s history. Some of the largest oil fields—in area and volume of oil produced—were discovered in this period. These include the Clay City Field, which covers parts of Clay, Richland, and Jasper Counties, the Salem Field in Marion County, and the Louden Field in Fayette County. Although intensive exploration with the seismic technique continued during World War II, production declined after the 1940 peak as the size and number of new fields found each year fell. All the large and easily found targets had already been drilled, and even with the new technologies, the new fields being discovered did not hold enough new oil to replace the production from increasingly depleted old fields.
Oil Production in Illinois
Illinois has about 650 oil fields, primarily in the southern half of the state. You can recognize an oil field by the presence of “rocking” oil pump jacks and clusters of large storage tanks. Deep beneath this equipment — typically about ½ mile deep — lie one or more layers of porous rock called “reservoirs” that contain the “black gold.” Oil flows from the reservoir into the 4- to 8-inch-pipe in the oil well.
Drilling for oil has always been a risky financial venture because fewer than half of the holes drilled in Illinois actually strike enough oil to repay the drilling costs. Unsuccessful wells, called “dry holes,” are filled with cement and plugged to protect the groundwater.
Illinois’ drilling boom was in the 1940s and 1950s when the state was one of the nation’s leading producers. In 1996, Illinois produced over 15 million barrels (630 million gallons) of oil; about 500 new wells were drilled, mostly to continue the development of known fields. In 1998, the average daily oil production from an Illinois well was only 1 to 2 barrels (42 to 84 gallons); but with 30,000 active wells, that adds up!