Secondary Recovery of Petroleum 777 



operations in the Chesterhill field of southeastern Ohio, which have been 

 described so ably by Lewis. ^ Only a few years later, in 1917, repressuring 

 operations were started in the Midcontinent region (Nowata County, 

 Oklahoma), and subsequently the injection of air ^nd gas has been em- 

 ployed to varying extent in practically all of the important oil-producing 

 regions of the United States. 



Until about 1935, water-flooding operations were far more restricted 

 geographically in the United States than air- and gas-repressuring pro- 

 jects. However, as a source of crude- oil supply water flooding has been 

 of great importance in certain of the Eastern states, where a greater part 

 of the production of oil is derived from the application of this method. 

 It is reasonably certain that intentional water flooding was initiated in 

 the Bradford field, McKean County, Pennsylvania, and Cattaraugus Coun- 

 ty, New York. Effects of increased production from this source were 

 first noted in 1907, although it is believed that floods were being operated 

 secretly prior to that time. Because of the clandestine nature of most of the 

 early water-flooding operations in northern Pennsylvania, little detailed 

 information has been preserved on the»results that were obtained, such as 

 is available on the early air- and gas-injection operations in Pennsylvania. 

 West Virginia, and Ohio. 



Unsystematic water floods were commenced in Nowata County, Ok- 

 lahoma, in 1931, which were followed, in 1934, by a systematic operation 

 developed similarly to the methods employed in the Bradford field. The 

 latter project established the effectiveness of water flooding in the Bartles- 

 ville sand, and in succeeding years it has been followed by ever-expanding 

 secondary-recovery activity in the Midcontinent and Southwestern regions. 



Mining for petroleum is the most ancient known production method. 

 The early mining operations consisted of the enlargement at the surface 

 of natural seepages, and of shallow pits or short drifts into the outcrop of 

 oil-bearing sands, from which the accumulated oil could be removed by 

 bailing. More recently, actual underground mining for petroleum has 

 been practiced in France, Germany, and Japan, in fields where primary 

 production has declined to a low level. 



There have been several attempts to mine petroleum in the United 

 States, the most recent of which are projects in Miami County, Kansas, 

 at Richards, Missouri, and at Rocky Grove, Venango County, Pennsyl- 

 vania. These operations differ from the European mines in that no drifts 

 or cross cuts have been dug into the oil-bearing formation, but rather the 

 sand has been penetrated by a series of horizontal holes drilled in a cart- 

 wheel pattern back away from the central shaft' None of these recent 

 operations in the United States has been economically successful, but the 

 Pennsylvania mine did provide a great deal of valuable scientific and 

 technical information. 



^ Lewis, J. 0., Methods for Increasing the Recovery from Oil Sands: U. S. Bur. Mines Bull. 148. 

 Oct. 1917. 



