The McDonald, Venice, McCurdy, and Moon Run oil fields form a producing area 15 miles long by 1-4 miles in width, located in southwest Allegheny and north Washington counties, Pennsylvania. Regionally the area is in the western part of the Appalachian foreland, and approximately 5 miles west of the axis of the Pittsburgh-Huntington synclinorium.

Development in the area took place largely during the period 1890-1900. The McDonald field, one of the largest and most prolific in the Appalachian basin, was discovered in 1891. Two wells in the field each had an initial production variously estimated at 14,000-17,000 barrels per day. In late 1891, McDonald was producing 1,800,000 barrels per month. Cumulative production of all the fields to the middle of 1909 totalled 42,135,000 barrels.

The Wildwood anticline and Mt. Nebo syncline, northeast-southwest trending structures, pass through the fields. Approximately perpendicular to these two structures, and limiting them on the south, is the Cross Creek syncline. Minor structural features are common. Regional dip is south and southeast into the Nineveh and Cross Creek synclines.

Oil is produced principally from Conewango sands of Upper Devonian age--One Hundred foot, Fifty foot, Lower Nineveh, Gordon Stray, Gordon, Fourth and Fifth sands--the last three producing most of the oil.

The fields are typical of the stratigraphic-trap type, oil accumulation in the various pools being

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controlled by the lenticular and lithologic character of the sands. Some structural control is indicated. Gas is found in the structurally higher parts of the sands.

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