ABSTRACT
Steam distillation of reservoir oil occurs in the steam flooding process. The steam distillation phenomenon has been established and extensively studied in the laboratory, but has not been well understood in the field. The present work describes a compositional analysis of remaining oil with depth from a mature field steamflood, and supportive numerical simulation. Inclusion of the steam distillation mechanism in the analysis of the steamflood process is a potential emerging strategy for more enlightened reservoir operation and management.
Heavy stock tank oil characterization by a pseudo carbon number molar distribution and conventional analyses have been used to monitor changes in residual oil in a 70 ft mature steamflood zone in the Kern River Field, California, U.S.A. In order to obtain residual oil distributions, analysis methods were developed where the effect of the extraction solvent on oil composition determination was minimized, and assessments of the non-analyzable portion of the oil were made. The results of analyses of residual oil samples extracted from field core establish the effects of steam distillation and solvent formation in a mature steamflood.
The compositional effects on residual oil observed in the field have been supported by simulation. Numerical simulation of the cored zone was carried out using volatile pseudo components. The results showed the distribution of hydrocarbon components at various depths and grid blocks, and corroborated the laboratory work. Although this was applied to the Kern River Field, the approach has wider application to other steamfloods. The compositional effects will be even more important for lighter oil reservoirs, such as the Duri Field Steamflood.
