The Healdton field, in western Carter County, Oklahoma, is largely confined to the northeast half of T4S, R3W, but extends into adjacent townships. The townsite of Healdton lies within the field's limits. Oil production is principally from the Hoxbar Group (Missourian) of Pennsylvanian age and the Arbuckle Group (Canadian) of Ordovician age.

Production was first established in 1913 with subsequent field development resulting in oil production from four shallow Pennsylvanian sandstone bodies--the Healdton sandstones. All of them can be recognized over most of the field with some local discontinuities. Approximately 2,600 wells had been drilled by 1955, covering a production area of more than 7,100 acres.

Several of the earlier development wells were drilled into the pre-Pennsylvanian section where minor amounts of Ordovician oil was found.

In 1960, the discovery of a commercial reservoir within the Arbuckle brought renewed importance to this already prolific field. The new production is from three dolomite zones--Wade, Bray, and Brown. These zones are restricted to the upper 1,600 ft of a 5,000-ft carbonate section. The Brown zone, the lowermost, has proved to be the only zone of significance. It is crystalline dolomite, approximately 600 ft thick, with good intercrystalline porosity and excellent permeability caused by a highly developed fracture system. The Arbuckle produces from 43 wells within an area of 1,800 acres.

Entrapment of hydrocarbons is attributed to a northwest-southeast structural trend which originated in Early Pennsylvanian time and was again activated during Late Pennsylvanian. The Healdton area was subjected to intense uplift and faulting in Morrowan time by the Wichita orogeny. Associated high-angle faulting with displacement of 10,000 ft placed Pennsylvanian shales and sandstones in juxtaposition with Ordovician carbonates. These younger sediments are believed to be the source and means of migration for most, if not all, Arbuckle oil in the Healdton structure. Following an extensive period of erosion, Hoxbar sandstones and shales were laid down over truncated pre-Pennsylvanian rocks, and later folded by the Arbuckle orogeny.

Owing to the magnitude of forces affecting pre-Pennsylvanian strata, the Arbuckle producing structure has closure in excess of 1,500 ft whereas the overlying Pennsylvanian closure is approximately 600 ft.

Hoxbar sandstones, from an average depth of 1,000 ft, have yielded about 250 million bbl of oil, and secondary recovery methods are now being employed. The Arbuckle produces from an average depth of 3,900 ft and had a cumulative in excess of 3 million bbl to January 1968.