The Sam Fordyce oil and gas field is located in southwest Hidalgo and southeast Starr counties, Texas.

Magnetometer work in 1929 first indicated structure in the area; however, the first well drilled on the anomaly in 1932 was completed as a dry hole.

The discovery well of the field, which was drilled in September, 1932, by King-Woods Oil Company, was completed from a sand in the basal Frio formation of middle

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Oligocene age. Subsequent development has proved the accumulation of oil and gas in other sands of the same formation.

The reservoir is a faulted anticline whose major axis trends northwest-southeast along regional strike. Closure against a major fault on the updip side of the structure accounts for the oil and gas accumulation. The fault has a maximum throw of 880 feet on top of the Sam Fordyce sand, and 260 feet of producing closure.

Geologically the Sam Fordyce structure is an outstanding example of differential sedimentation during the time of fault movement. A gradual downwarping movement Northeast into the Rio Grande Embayment is responsible for thicker sediments which are found on the downthrown side of the major fault.

The productive area of the field embraces 2,000 acres, of which 900 acres are within the oil productive zone of the Sam Fordyce sand, 260 acres in the Wheeler sand, and 215 acres in the Barlow sand.

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