Hewitt Oil Field 217 
Upper Mississippian age, or from the Simpson formation of Ordovician 
age. 
No doubt much of the oil, and possibly most of it originated in the 
Pennsylvanian shales and limestones and the Caney shale of Mississip- 
pian age where present. These shales are dark and appear organic 
which, with the presence of limestone, indicates plenty of organic life 
at the time of deposition for the formation of a considerable quantity 
of oil and gas. 
The Simpson formation may have been a very important source 
of oil in the Hewitt and Healdton fields. This formation is known 
to carry oil in the Healdton field as there are two wells producing oil 
from sands of Simpson age at a depth of about 2,700 to 2,775 feet. 
The Simpson formation has much asphalt and other evidences of oil at 
its outcrop in the Arbuckle Mountains. This formation seems to have 
carried oil in great quantities and may have given up large amounts 
to the overlying Pennsylvanian sands thru faults, fissures and uncon- 
formable contact with the Pennsylvanian sands. 
The regional movements which occurred in Pre-Pennsylvanian times 
before the deposition of the Pennsylvanian caused very extensive folding 
and faulting. These movements were followed by erosion over a long 
period which exposed the earlier rocks along the crests of the anticlines. 
The Pennsylvanian was then deposited upon these eroded upturned edges 
of older rocks and no doubt in direct contact with the Simpson and other 
oil forming formations. This made conditions ideal for the migration 
of oil from the older eroded beds into the overlying Pennsylvanian reser- 
voirs from which the oil is now produced. This migration took place 
across the unconformity from the older oil bearing formations and also 
thru the faults which no doubt existed. 
Oil Sands. 
In addition to the main Hewitt sand which has produced most of 
the oil to date there are other oil and gas bearing sands. These sands 
will be discussed in order from the top down. 
Shallow Gas Sand.—The shallow gas sand has produced considera- 
ble gas from wells drilled to it. This shallow sand is found on top of 
the structure at depths varying from 250 to 400 feet and les about 1,000 
to 1,050 feet above the Hewitt sand. These shallow wells produce from 
100,000 to 3,000,000 cubic feet of gas per day. This gas was of con- 
siderable importance on account of the shortage of gas in the field and 
was used for operating purposes. Many of the gas wells in this shallow 
gas sand were short-lived and soon became exhausted. The sand varies 
considerably in thickness but has an average thickness of about 20 
feet. Further down on the flanks of the structure this sand either pro- 
duced water or was cut off entirely by the unconformity between the 
Permian and Pennsylvanian. 
The 600 to 700 Foot Gas Sand.—A second shallow gas sand has 
been found 600 to 700 feet, which has produced some good gas wells. 
The wells which produce gas from this sand have an initial production 
from 3,000,000 to 10,000,000 cubie feet of gas per day. For the most 
part the wells in which this gas is encountered are bradenheaded and 
