The Wilshire Ellenburger field is in west-central Upton County, Texas. The field, in the Midland basin part of the Permian basin, was discovered in April, 1951, with the completion of the Sinclair Oil and Gas Company's McElroy No. 1 in the Ellenburger at total depth of 12,438 feet.

The proved Ellenburger producing area is 1,600 acres and is 2½ miles in length and 1½ miles in width, with a productive anticlinal closure of 577 feet. On January 1, 1955, 12,278,824 barrels of 54° gravity oil had been produced from the Ellenburger.

The discovery well was located by a combination of reflection-seismograph and subsurface data. Oil is produced from fractured, vuggy Ellenburger dolomite of Lower Ordovician age. A secondary pay in the Pennsylvanian Strawn section is not produced at present. The Wilshire Ellenburger field structurally is a subsidiary fold parallel with the Central Basin platform zone of deformation.