Attic oil recovery by gas injection

摘要

Attic oil recovery, upstructure oil recovery by down structure gas injection, is a feasible and economical process. This research presents experimental and simulation results designed to investigate the attic oil recovery process. Three types of experimental models were used: a micromodel; a prototype sandpack; and a large-scale sandpack. A micromodel glass apparatus was used to visually observe the gas migration process. A prototype sand pack was used to explore the design parameters for a large-scale sandpack. The large-scale apparatus was used to investigate oil recovery mechanisms. In all of the experiments, the core was vertical. The water saturated sandpack was oilflooded to irreducible water saturation. Water was then injected from the bottom port producing oil from the center leaving a high oil saturation in the upper portion of the core. Gas was injected from the center port, and the core was shut-in to soak to allow time for gas migration. Numerical simulations were performed to investigate the effect of soak time, slug size, dip angle and injection scheme. Experimental and simulation results demonstrated that the gas injection process was capable of recovering a substantial quantity of attic oil, and that gas utilization factors were favorable. The results also indicated that the process performance was affected by soak time, slug size, dip angle and injection scheme.