Core Studies of the Second Sand of the Venango Group, from Oil City, Pa.

The oil fields of Western Pennsylvania have reached that stage in theirdevelopment history in which the rejuvenation of depleted properties, by suchmethods as compressed air, water flooding, etc., offers a much more attractiveproposition to capital than the search for new pools in undeveloped territory.In order to apply such methods intelligently, a more detailed knowledge of thecharacter of the oil sands, than has heretofore been deemed necessary, ishighly essential. Such information can be obtained to best advantage with thecore drill. Cores yield data that cannot possibly be obtained otherwise, evenby the most careful study of cuttings taken by the ordinary cable-toolmethod. The Brundred Oil Corp., of Oil City, Pa., the pioneer in the introduction ofcompressed air for the restoration of production on depleted properties inPennsylvania, recently completed a diamond-drill test of the Second Sand of theVenango Group, on one of its properties in Cornplanter township, about a milenorthwest of Oil City. Through the courtesy of H. D. Brown and W. J. Brundred, officials of the company, the cores were made available to the writer for studyin connection with an investigation of the oil and gas sands of the State forthe Pennsylvania Geological Survey. Drilling Equipment A Sullivan-type diamond drill, with double-tube core barrel, and capable oftaking a core 2 1/4 in. in diameter, was used. The wells were first drilledwith cable tools to within 5 or 10 ft. of the top of the sand, as calculatedfrom the logs of nearby wells, using a single string of 5 5/8-in. casing toshut off the water from upper horizons. A string of 4 1/4-in. casing was thenset on the bottom of the hole and the diamond drilling was done through it inorder to prevent excessive vibration of the drill rods. The 5 or 10 ft. ofshale above the sand permitted the starting of a straight hole with the coredrill before the sand was penetrated. Core losses in the sand were practicallynegligible.