Horizontal Injectors Rejuvenate Mature Miscible Flood—South Swan Hills Field

Abstract

Summary The South Swan Hills pool, located in northwest Alberta, Canada, is a carbonate reef with an original oil in place (OOIP) of approximately 850 million bbl. Waterflooding began in 1963, and a staged hydrocarbon miscible flood covering most of the field began in 1973. Solvent injection in the main miscible flood was terminated in 1989, and chase gas injection ceased in 1998. In 1994, however, solvent injection was reinitiated into a single pattern in the reef margin area of the field using a horizontal injector and reduced well spacing. The reef margin is an area of thick, stacked pay that experienced high gravity override during the original miscible flood. The horizontal injector was placed at the base of the reef margin to minimize the effects of gravity override and to maximize sweep efficiency. Four patterns have been developed to date. The two earliest patterns have now completed solvent injection and are on chase waterflood. Both patterns are projected to recover almost 1 million bbl of incremental oil per pattern (more than 10% of pattern OOIP) from areas that were part of the original miscible-flood project. This paper covers the development of the original miscible flood, the redevelopment of the reef margin area using horizontal miscible injectors, and the performance of the four patterns implemented to date. The geological and performance factors that made this redevelopment successful, and their impact on field production, are discussed. Finally, plans for future development of this mature field are presented.