The Rose Hill oil field is the only oil field in Virginia, the only oil field in the folded and faulted rocks of the Appalachian Valley of the eastern United States, and the only oil field in the United States in which oil is produced from rocks that have been overridden for several miles by an overthrust block of large size. In April, 1947, the field had 15 wells of which 14 were in a small fenster formed by erosion of all the overthrust rocks down to the underlying stationary block, and the other well was located in a similar fenster 4 miles distant. The field was at that time being rapidly enlarged, however, and many favorable areas had not been tested.
Almost all of the oil produced comes from the Trenton limestone at depths of 1,000–1,500 feet. The wells range in productive capacity from 3 barrels a day to approximately 80 barrels a day, of high-gravity, high-volatile, paraffine-base oil. Very little gas is associated with the oil, and almost no water has been found in the Trenton to date.
The producing zones are in the stationary block, whose rocks have been somewhat folded but not faulted or strongly deformed during the overthrusting. The larger producing wells are in an area where the Trenton is almost flat-lying but several producing wells have been drilled in areas where the rocks of the stationary block dip as much as 25º. Although spaced only a few hundred yards apart, the wells produce from different stratigraphic zones in the Trenton in which the oil is believed to be disseminated along fractures, formed during the folding and faulting of the region and probably somewhat enlarged by later solution.
At the time this paper was written the field was very active and numerous new wells were being started or projected to test the rocks of the stationary block in other fensters, and also in areas where the stationary block is concealed by the overthrust block. By the time the paper is printed the known productive area will probably be considerably enlarged toward the east and perhaps also toward the north, and new oil fields may have been found in areas along the Powell Valley anticline where the oil-bearing rocks of the stationary block are not exposed at the surface as they are in the Rose Hill fenster area.
Figures & Tables
Structure of Typical American Oil Fields: A Symposium of the Relation of Oil Accumulation to Structure
Modern petroleum geology in the United States had its beginning in the first decade of the 20th Century when the U.S. Geological Survey began mapping the structure of the rocks in and near old fields in order to discover the various types of structural conditions under which oil and gas are trapped. Structural geology has evolved as a branch of the broader science far more rapidly than have methods of mapping the attitude of rocks at the surface. This volume, published in the late 1920s, was designed to afford authoritative and modern descriptions of the structure of typical oil fields in the United States. Each of the 39 fields contained here is described by an author who is intimately familiar with the available data. The relationship of structure at the surface and at depth for different terranes is clearly set forth wherever the strata are not parallel. The volume concludes with a summary paper on the role of geologic structure in the accumulation of petroleum. Fields include: Florence, Colorado; Stephens, Arkansas; Kevin-Sunburst, Montana; Bradford Pennsylvania; and Salt Creek, Wyoming.