Miscible Drive Field Applications in the Parks Field

Abstract

Introduction A review of the field-wide miscible displacement program being utilized in the Parks field unit is presented to assist others in the oil industry in evaluating the application of the miscible displacement process. Geological Description The structure is a long, gently sloping, deep-seated anticline trending north and south. The anticline is traversed, in a northwest-southeast direction, by a major fault which has divided the structure into two segments. This discussion is confined to the larger east segment. No significant oil accumulation was found on the west side of the fault. The productive area on the east side of the fault has an average net pay thickness of 21 ft (see Fig. 1). The Bend section of the Pennsylvanian formation in the Parks area is composed of tan, finely crystalline limestone, interspersed throughout with shale stringers varying from mere shale partings to shale beds several feet in thickness. Porosity of the Bend limestone is described as fossiliferous, with voids having been created as the result of leaching of microfossil shells. Intercrystalline porosity is negligible. Production History and Data The primary producing mechanism was solution gas drive. Cumulative production to Jan. 1, 1958, was 3.5 million bbl of oil, 21,000 MMcf of gas, and 35,000 bbl of water. The bottom-hole pressure declined from an original 4,567 to 1,760 psig in July, 1957, and the produced gas-oil ratio increased from 1,800 to 16,000 cu ft/bbl. Primary production and shrinkage of the reservoir oil has created a present gas saturation of approximately 25 per cent. The average porosity for the net pay is 6 to 8 per cent; the average interstitial water saturation is 30 to 35 per cent; and the average permeability is 3 md. The reservoir oil was undersaturated at the original reservoir pressure, 4,567 psig. The bubble point pressure is 3,508 psig. The original dissolved gas-oil ratio was 1,817 cu ft/bbl, and the initial formation volume factor was 2.014 reservoir bbl/STB. The reservoir temperature is 174°F. The oil gravity is 45°API, and the initial reservoir oil viscosity was 0.22 cp.