Air-Injection EOR in Highly Water-Saturated Light-Oil Reservoir

摘要

Since 1950s In-Situ Combustion (ISC) has been applied tornmainly heavy-oil reservoirs. In recent years, High Pressure AirrnInjection (HPAI) which is a displacement process categorizedrnas ISC, is applied to light-oil reservoirs. And it has proven tornbe a valuable Enhanced Oil Recovery (EOR).rnReduction of oil viscosity is very important for ISC process. Inrncontrast, it is not so essential for HPAI because originalrnviscosity of light-oil is not as high as that of heavy oil. HPAIrnis considered as flue gas injection, since a flue gas sweep isrnone of the most important recovery factors of HPAI. Howeverrna flue gas sweep recovery factor is not effective for highlyrnwater saturated light-oil reservoirs, while thermal effectsrnbecome an important recovery mechanism.rnThis paper discribed the feasibility study of HPAI for wateredrnout light-oil reservoirs, oil recovery mechanism and severalrnsimulation studies to establish maximum oil recovery factor.rnFor the feasibility study, Combustion Tube tests (CT tests) andrnsimulation studies were conducted. The oil recovery wasrnobserved in the CT test with crushed core which was floodedrnout by water. This result suggests that HPAI can be applied tornhighly water saturated light-oil reservoir. The results ofrnsimulation studies also indicate its feasibility. They also madernclear that distillation process that was one of thermal effects ofrnHPAI was a main recovery factor for a HPAI in this case.rnIn order to maximize the oil recovery, controlling a channelingrnof injected air is important because early breakthrough of thernair reduces oil production period significantly. The results ofrnour studies show that not only a design of well completion butrnalso an adjustment of air injection rate enable to increasernvertical sweep efficiency and that line drive injection isrneffective to increase areal sweep efficiency.