The 1984 Natl. Petroleum Council Estimate of Potential EOR for Miscible Processes

Abstract

Summary In March 1982, the Secretary of Energy requested the Natl. Petroleum Council (NPC) to evaluate the EOR potential of the U.S. The NPC Committee on EOR was formed to fulflll this request. Under this committee, a coordinating subcommittee and four working task groups were selected to perform the study. This paper describes the work of the Miscible Displacement Task Group and reports their findings and conclusions on the potential for EOR by miscible processes in known U.S. reservoirs. In conjunction with the coordinating subcommittee and the other task groups, the Miscible Displacement Task Group helped upgrade the DOE reservoir data base into the most comprehensive data base available to date on U.S. reservoirs. A miscible process and economic screening model prepared under contract for the DOE was analyzed, modified, and calibrated by the Miscible Displacement Task Group for this study. With physical screening parameters, the Miscible Displacement Task Group selected reservoirs susceptible to miscible processes from the data base, and then processed them with the NPC model to estimate tertiary oil recovery. Sensitivity to oil prices and rate of return (ROR) were investigated, and the results were combined with the results from the other process task groups (thermal and chemical) to reach an overall assessment of the EOR potential in the U.S. The potential EOR for miscible flooding is estimated to vary between 2.0×109 and 8.5×109 bbl [0.32×109 and 1.4×109 m3] over the range of prices and technologies considered. Peak rate varies from 200×103 to 980×103 B/D [32×103 to 156×103 m3/d] for the cases investigated. Introduction Field tests and full-scale operations of EOR have increased in recent years. Research in the basic fluid behavior and specific reactions of reservoir fluids to heat, chemicals, and miscible fluids have increased industry knowledge of EOR processes. These activities and the growing importance of increasing potential oil recovery in the U.S. prompted the Secretary of Energy to request the NPC to evaluate the EOR potential from known reservoirs. This paper reports on the methodology used and results developed by the Miscible Displacement Task Group. Miscible floods to date have used CO2, N2, and hydrocarbons as miscible solvents. Commercial hydrocarbon miscible floods have been operated since the 1950's. CO2 miscible flooding on a large scale is relatively recent, and CO2 is expected to be the significant solvent used in the future. There were at least 11 commercial, large-scale CO2 projects under way in Dec. Several additional commercial projects have been started in west Texas. Since then, development of natural sources of CO2 in Colorado, New Mexico, and Mississippi are in progress. All these activities indicate that CO2 miscible flooding will be a significant EOR process. In this study, two levels of technology, designated as implemented and advanced, were considered. The implemented-technology case is based on current project design used in recent field projects. A CO2 slug size equivalent to 40% of the HCPV was assumed, along with a water-alternating-gas (WAG) ratio of 1.5:1. The advanced-technology case assumed that certain improvements in technology would be developed and available for full-scale operations in 1995. For reservoirs with moderate heterogeneity, those with good waterflood sweep efficiency, the volume of CO2 injected was increased. For more highly stratified, heterogeneous reservoirs, it was assumed that "foam" chemicals would be developed to control the flow of CO2 and to improve the sweep efficiency. The estimated potential for miscible EOR from known reservoirs varies between 2.0×109 and 8.5×109 bbl [0.32×109 and 1.4×109 m3] over the range of oil prices considered. The peak rate of EOR production from miscible flooding varies between 200×103 and 980×103 B/D [32×103 and 156×103 m3/d] for the same cases. These ranges cover both the implemented- and advanced-technology cases. Related papers: SPE 13239, SPE 13240, SPE 13241 Related discussions and replies:SPE 18397, SPE 20007, SPE 20009