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.
Natural gas seeps near Oilfield led the company's owners to believe that commercial quantities of oil and gas were there.
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.
After the hole is drilled, a metal pipe slightly smaller than the hole size (called a ‘well casing') is run into the hole.
The casing is perforated in the reservoir rock to allow the oil –water mixture to flow into the well bore.
The oil-water mixture is pumped to the surface through a production pipe located inside the well casing pipe.
A Typical Oil Well in Illinois At the well head is the rocking pump jack (at the left). A water oil mixture is recovered from the reservoir rock The mixture is pumped to the separator tank (center), and the oil then flows by gravity to one of the two storage tanks (right). The water flows to the other storage tank where it is collected and may be pumped back underground through an injection or disposal well.