The Late Pennsylvanian Palo Pinto Limestone (lower Canyon Series) of western Runnels County, Texas, generally is found between the depths of 3,800 and 4,200 ft. The two porosity zones in the Palo Pinto which are productive are in the uppermost 50 ft of the formation.

The second, or lower, zone is by far the better producer of the two zones. The Palo Pinto can produce only on structure, but the best producing fields are those in which stratigraphic pinchouts are associated with low-relief structures. Several of the presently active fields produce 30-60 percent water with the oil. Production histories now show that these fields have much higher primary recovery rates than originally was believed, a fact which indicates that this produced water is not all connate, and that water drive is an important feature of the reservoirs. Calcite-lined vuggy porosity commonly makes it very difficult to detect shows in drilling samples from the second porosity zone. Therefore, where porosity is indicated to be present in this zone, a drill-stem test is recommende . In many wells, 2½-in tubing (in contrast to the 2-in tubing normally employed in this area) and 2¼-in pumps are required to move sufficient fluid to obtain the oil allowables. However, indicated recovery rates in excess of 200 bbls/acre-ft more than justify the higher production costs which result.