These later wells generally have poorer production history and reduced pressures, indicating partial depletion. By July 1999, there were a total of 47 producing wells, many of which were multiple-zone completions, making performance determination of individual zones difficult. Arapaho Field, Custer County, Oklahoma , produces primarily from upper Morrow and lower Morrow Primrose sands in the deep part of the Anadarko Basin. Two upper Morrow units have been identified, although there may be several independent reservoirs. Because there is no downdip water leg in any of the upper Morrow reservoirs in this field, the drive mechanism is pressure depletion.
Trapping is stratigraphic.
The second major producing zone in the field is the Primrose sandstone. Upper and lower Primrose units are recognized in the field. The lower unit consists of a number of isolated, stratigraphically-controlled reservoirs. The lower unit has been developed on 320 to 160-acre spacing because of reservoir heterogeneity. The field also produces from a younger Pennsylvanian unit, the Skinner sandstone.