ABSTRACT: Waterflood Characteristics of the Brushy Canyon Formation: Red Tank Field, Lea County, NM
K. M. GREEN, S. M. FRAILEY, and G. B. ASQUITH
The U.S. Dept. of Energy estimates that 5 billion bbls of oil will remain in existing slope basin clastic reservoirs of the Permian Basin unless new and innovative recovery methods are implemented. This clearly highlights the need for operators to take a more comprehensive look into secondary recovery methods such as waterflooding. In this study, the author used a variety of tools to characterize this reservoir and to predict its response to water injection. Scanning electron microscopy, X-ray diffraction, and thin section analyses were used to determine the bulk and clay mineralogy of the reservoir. Core analysis helped to determine Archie log parameters and net pay cutoffs needed in determining reserves from volumetrics. Analytical waterflood models recommended in SPE Monograph 3 were used to predict the reservoirs response to water injection. Using a porosity-permeability transform a minimum core porosity cutoff for a minimum economic permeability of 1.0 md was 11 percent. Formation resistivity factor measurements indicate a cementation exponent of 1.41 and a coefficient of 1.28. A saturation exponent of 1.80 was obtained using a modified Maute method. From the relative permeability curves it was noted that permeability to oil was insignificant at saturations above 50 percent. This value was used as the saturation cutoff in the net pay criteria. Using the Archie equation with the above parameters and cutoffs, along with a volume of clay cutoff less than 15 percent, the total reserves in the area studied were 9.07 MMstb. Waterflood calculation indicate a mobility ratio of 0.33 and permeability variance of 0.3. Fractional flow calculations predict piston-like displacement. Predicted injection rates are low, and should continually reduce throughout the life of the waterflood due to a low average permeability and low water mobility. Using the Dykstra-Parsons and modified Craig-Geffen-Morse methods the predicted waterflood reserves were 276.7 and 123.7 Mstb of oil per 40 acre five-spot pattern.
AAPG Search and Discovery Article #90947©1997 AAPG Southwest Section Meeting, San Angelo, Texas