274 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1916. 



been found in waterless synclines. The reservoir rocks are prin- 

 cipally sandstones and coarse sediments. The oil from this field 

 is of the best quality in the world, yielding a high percentage of 

 the lighter oils such as gasoline and kerosene, and is utilized entirely 

 for refining. It is of paraffin base and varies in gravity from 25° 

 to 50° Beaume (0.9032 to 0.7778 sp. gr.), the heavier grades coming 

 only from the southern end of the field. The price of the " Penn- 

 sylvania grade" oil is always high, ranging up to $2.50 per barrel. 

 The average daily production of the wells is low, being 0.2 to 0.4 

 barrels in 1911. This field is almost completely developed except the 

 portions in Kentucky and Tennessee, and even here recent pros- 

 pecting has resulted negatively in a majority of cases. 



Limu-Indiana. fdd. — The Lima-Indiana field covers a considerable 

 portion of northwestern Ohio and eastern Indiana. The oil is 

 derived from the Ordovician, Silurian, and Carboniferous, largely 

 from the Trenton limestone, the reservoir rock being porous dolo- 

 mitic lenses or beds or sandstones. Favorable structures, such as 

 half domes, terraces, etc., on the flanks of the Cincinnati uplift, 

 usually harbor the commercial deposits. The oil is of paraffin base, 

 varies in gravity from 30° to 35° Beaume (0.8750 to 0.8484 sp. gi\), 

 carries a little sulphur, and is utilized entirely for refining purposes. 

 The average initial daily production of the wells up to 1911 was 15.5 

 barrels; the average daily production per well was 0.7 barrel for 

 that year. This field also is practically outlined, although new pools 

 are even yet being occasionally discovered. 



Illinois -field — The Illinois field occupies a strip of territory along 

 the La Salle anticline in the southeastern part of the State. It also 

 extends a short distance into Indiana. The oil is derived largely 

 from the Pennsylvanian and a little from the upper Mississippian 

 (both Carboniferous), and occurs principally in well-defined sand- 

 stone horizons along the crest of the asymmetric La Salle anticline. 

 Impregnation is governed locally by the lithology. A little of the 

 oil comes from limestone. The oil is of paraffin base, although 

 locally carrying some asphalt, ranges in gravity from 28° to 39° 

 Beaume (0.8860 to 0.8284 sp. gr.), and is used principally for re- 

 fining purposes. The average initial daily production up to 1911 

 was 63 barrels; the average daily production of the individual wells 

 for the same year was 4.2 barrels. With the exception of some 

 possible territory in the western part of the State the Illinois pro- 

 ductive area is well defined at the present time. 



Mid-Continent field. — The Mid-Continent field comprises the pools 

 in Oklahoma, southeastern Kansas, and northern Texas. The oil 

 is secured from the sandstones of the Pennsylvania (Carbonifer- 

 ous) formations in domes, half domes or terraces, and local anti- 

 clines on the flanks of the great Ozark uplift The oil is of paraffin 



