Design and Evaluation of the Shiells Canyon Field Steam-Distillation Drive Pilot Project

This paper describes a steam-distillation drive pilot project being conducted in the Shiells Canyon Field to determine the effectiveness of steamflooding a light-oil reservoir. Overall oil recovery for the project has been good, with a reduction in oil saturation from a preflood value of 45% to less than 5% in the steam-swept zone. Introduction Thermal recovery techniques normally are applied to heavy-oil or tar-sand reservoirs in an effort to reduce viscosity and mobilize oil; however, steamflooding also can be an effective recovery technique for light-oil reservoirs. In this application, steam distillation of crude oil in the steam zone becomes an important recovery mechanism. In addition, the solvent generated in the steam zone will condense ahead of the steam front and enhance other recovery mechanisms. The application of this process to light-oil reservoirs commonly is referred to as the "steam-distillation drive process" because of the large amount of solvent generated by steam distillation in the steam zone. However, crude oil of original gravity is produced during the major portion of the flood life, and produced during the major portion of the flood life, and solvent production occurs only during the time just before steam breakthrough in the producing wells.Steam distillation has been recognized in the literature as a major recovery mechanism during steamflooding of light- and heavy-oil reservoirs. Farouq Ali estimated that 10% of the heavy oil recovered by steamflooding can be attributed to steam distillation and that as much as 60% of the light-oil recovery with steamflooding can be attributed to the same mechanism. Wu and Brown showed that up to 65% of some light oils could be recovered by steam distillation. In a field test of the steam-distillation drive process in a light-oil (0.910 g/cm3 or 24 degrees API) reservoir, Volek and Pryor reported residual oil saturations in the steam-swept zone of less than 8%. Encouraged by the potential of the steam-distillation drive process, a pilot project was initiated on March 3, 1973, in Zone 203 of the Shiells Canyon Field, Ventura County, CA. The Shiells Canyon Field was selected for application of this process because of the volatile (0.855 g/cm3 or 34 degrees API) nature and low viscosity (0.006 Pa s or 6 cp) of the crude oil. In addition, the 35 degree dip of the formation is ideal for an expanding steam-vapor/gas-cap recovery mechanism. Here, experimental laboratory work used for designing the process is presented with the design and evaluation of the field pilot. Process Process The steam-distillation drive process has been characterized in the literature as four fluid regions progressing radially from the injection well. Oil saturation progressing radially from the injection well. Oil saturation and displacement mechanisms are characteristically different in each zone (Fig. 1). In the formation fluid bank, saturation approaches the initial oil saturation. In the cold-condensate zone, displacement is representative of a waterflood; however, oil saturation in this zone is greater than the initial oil saturation because of the amount of oil displaced from the hot-condensate and steam zones. In the hot-condensate zone, waterflood recovery improves because of thermal swelling, viscosity reduction, and solvent extraction. JPT P. 546