The Bradford oil field is of peculiar interest for several reasons. It is located about equidistant between the place where oil was first discovered in America and the famous Drake well. Its 85,000 acres of continuously productive territory from the Bradford sand, its 25,000 producing wells, and its fifty-five years of productive history make it one of the most outstanding oil fields of the world. It has received much publicity because of the successful use of water-flooding for increasing oil recovery within the past twenty years. The field was opened in 1871, and the peak of production was reached in 1881, when 23,000,000 barrels of oil were produced. The present production is about 3,700,000 barrels per year.

The stratigraphic column of the Bradford oil field is limited to the Paleozoic. The principal oil-producing horizons are in the lower part of the Chemung formation of Upper Devonian age. The reservoir rocks are very fine-grained and tightly cemented sandstones. The most important sand, the Bradford, has an average thickness of 40 feet and an average porosity of approximately 15 per cent.

Two anticlines, plunging southward, and converging northward into the Knapp Creek dome, with a closure of approximately 250 feet, have been the dominating factor influencing oil accumulation in the Bradford sand. This structure was also a primary influence in the accumulation of oil and gas in the minor productive sands, although the irregular depositional character of these minor sands has been an important contributing factor in limiting production.

Bradford oil has an average gravity of 45.5° A.P.I. and is widely known for its high-grade lubricating fractions. Gas wells were rare in the original development of the field. On the Knapp Creek dome and at intervals along the crest of the anticlines, the upper part of the Bradford sand was a gas "pay." The original rock pressure was presumably subnormal, but data on this are indefinite. The Bradford sand thins out on the east edges of the pool. Elsewhere edge water is present. Encroachment has been so very slight that from existing operating records it is impossible to establish any definite rate.