166 Frank Carney 



ties wells had to be drilled about 2000 feet, to reach the Berea.^^ 

 The Berea has been drilled in widely distant parts of the state, 

 and whenever penetrated it shows at least a trace of oil and gas, 

 but has produced in commercial quantities only in the following 

 counties : Lorain, Medina, Trumbull, Columbiana, Stark, Jefferson, 

 Harrison, Belmont, Guernsey, Monroe, Noble, Vinton, Perry, 

 Athens, Morgan and Washington. 



The Logan group of the Mississippian, in Monroe and Wash- 

 ington counties, produces oil. These were oil centers of con- 

 siderable importance in earlier days. The three horizons of the 

 Logan that gave oil have been named by drillers in descending 

 order: Keener sand. Big Injun sand, and Squaw sand. At only a 

 few points outside of these two counties, does the Logan yield 

 oil or gas in commercial value. 



Pennsylvanian. Several sandstone horizons in the ' ' Coal Meas- 

 ures" contain some oil and gas; each has a designation, usually a 

 name associated with the locality where it was first found to be oil- 

 bearing. The wide distribution of Pennsylvanian rocks through- 

 out the state has led to much testing, but the successful wells are 

 confined mostly to Noble, Morgan and Washington counties. 



Occurrence in rock. An interesting fact in connection with 

 these natural resources is their occurrence in such a variety of 

 rocks. Both oil and gas have been found in limestone, in shale, 

 and in sandstone, even sandstone that is conglomerate in structure. 

 It is usually held that only in the porous zones of these rocks do 

 we find oil and gas. Generally, only dolomitic limestone is gas- 

 bearing; this phase of limestone is much coarser in texture, due 

 to its crystalline structure, than is the purer calcium carbonate. 

 The shale horizons are usually fissile and much broken by joints; 

 while sandstone is always more or less porous. So far as the eye 

 can detect, most of these rocks do not appear to be very porous, 

 but, when examined under the glass, one is surprised at what a 

 fraction of a given area the openings make. Sometimes a surface 

 one foot square will show four square inches of combined inter- 

 stitial spaces. 



It has been found that oil and gas are not homogeneously dis- 

 tributed in any of these formations, but are usually localized in 

 pools or reservoirs. Much has been written on the '^ anticlinal 



i» Geological Sirr>wy of Ohio, Bulletin 1, (1903), p. 185, and p. 201. 



