776 Subsurface Geologic Methods 



production and may enable the working of inferior reservoirs at a profit; 

 in some instances, a successive reworking of a field is made possible. In 

 this respect, secondary-recovery operations resemble the mining of ores, 

 where an improvement in production methods or an increase in price will 

 permit profitable recovery of lean or more difficult deposits. 



Secondary-recovery operations, although yielding only a small part 

 of the oil production of the United States, nevertheless are an important 

 factor in the business of oil production in several states. To a large 

 extent they are confined to the older fields, where their use has maintained 

 the production of oil far beyond the time when the natural decline of the 

 wells would have enforced abandonment. Therefore, the application of 

 secondary methods may be regarded as a true conservation measure, re- 

 sulting in an increased recovery of oil that otherwise • could not be ob- 

 tained profitably and in many cases in the preservation of natural-gas. 

 reserves which might be dissipated. 



History of Secondary-Recovery Operations in the United States 



The use of compressed air or air-gas mixtures, gas, steam, water, 

 and other suitable fluids to increase the recovery of oil is about as old 

 as the art of removing oil from the earth. Shortly after oil was discovered 

 in Venango County, Pennsylvania, patents were issued covering mechanical 

 devices and techniques designed to stimulate the extraction of oil from 

 underground reservoirs. Many of these patents were based on inventions 

 involving the creation of a vacuum in producing wells or the injection of 

 fluids into the reservoir by means of input wells equipped especially for 

 this purpose. 



The first recorded use of vacuum was in the Triumph pool, Pennsyl- 

 vania, in 1869. It has been well-established that an attempt to apply a 

 combination of vacuum and gas repressuring was made in Clarion County, 

 Pennsylvania, in 1895. This project was unsuccessful on account of the 

 tightness of the producing formation. However, shortly thereafter, com- 

 bined vacuum and repressuring were employed successfully in Venango 

 County, Pennsylvania. 



The first known intentional injection of gas into oil-bearing rocks to 

 increase production was accomplished by James D. Dinsmoor on the Ben- 

 ton farm, Venango County, Pennsylvania, in 1890. In this operation gas 

 from a lower formation was introduced into the Third Venango oil sand 

 at a pressure of about 100 pounds per square inch. The production of oil 

 was more than doubled. Subsequently, repressuring operations, which 

 were sometimes combined with application of vacuum, were carried on by 

 Dinsmoor in the vicinity of St. Marys, West Virginia, and in other parts 

 of Venango County. 



In 1911 I. L. Dunn commenced the historic air- and gas-repressuring 



