Waterflood Performance in a High Viscosity Oil Reservoir

Abstract

Abstract The Howard "ABC"-Rowland 950-ft sand water flood, operated by Continental Oil Co., is located 10 miles north of Nocona in Montague Co., Tex. Pilot operations commenced in Nov., 1958, and subsequent expansions continued through Dec., 1960.Despite the high reservoir oil viscosity of 48 cp, ultimate secondary recovery from the project is projected at 480,600 bbl, or 300 bbl/acre-ft of floodable area. Secondary oil recovery will be approximately 21.5 per cent of the oil in place, as compared to a primary recovery of 10.8 per cent. Ultimate water requirements are projected at 6.28 million bbl, equivalent to 2.2 pore volumes. Actual performance of the flood will exceed theoretical performance as predicted from core data. Introduction Continental's N. J. Howard "ABC" and J. W. Rowland leases produce in an area locally called the North Nocona field, which is shown in the General Location Map, Fig. 1. Both leases are assigned on the Railroad Commission proration schedule to the Montague Co. Regular Field. Oil production in the general area is from sands of the Cisco and Canyon series that occur between the depths of approximately 800 and 1,600 ft. Between July, 1925, and Dec., 1960, 94 wells were drilled on the Howard "ABC" lease and 118 wells on the Rowland lease. Individual zone development is essentially on 2 1/2-acre spacing. Water flooding on the subject leases began during Sept., 1951, with a pilot of the 800-ft sand. This test was unsuccessful due to the presence of an underlying water section. A successful water flood of the 1,400-ft sand commenced during Sept., 1955, and is still in progress. Initial injection into the 950-ft sand was in Nov., 1958. This report covers performance of water flooding the 950-ft zone underlying Continental's Howard "ABC" and Row- land leases. Geology and Reservoir Characteristics The N. J. Howard "ABC" and J. W. Rowland leases are situated on the northwest trending Rowland anticline, a portion of the regional Muenster Arch. Surface outcrops are Cretaceous in age and underlain by the Cisco and Canyon series of Pennsylvanian age. Present interpretation locates the 800, 950 and 1,000-ft producing intervals in the Cisco sand series, while the 1,150, 1,200, 1,400 and 1,600-ft intervals are located in the Canyon series. Structure and porosity development are the principal controls for accumulation of oil in these sands.A log cross section through a portion of the 950-ft zone is shown in Fig. 2. Figs. 3 and 4 present a structure map and net pay isopach map for the 950-ft sand underlying the subject leases and surrounding area. Wells shown on the cross section are indicated by a connected line on the maps. Two oil-water contacts exist, and they have been established at 146-ft subsea in the eastern portion of the reservoir and 112-ft subsea in the western portion. A lack of porosity development, which defines productive limits to the north and south, precludes connection of the two water-saturated sections. The primary producing mechanism of the 950-ft sand was solution-gas expansion. There was no evidence of natural water encroachment during primary production. JPT P. 1281^