Development characteristics of low oil saturation reservoirs

The filtration characteristics of low oil saturation reservoirs are obviously different from that of conventional reservoirs. The development performance and the influence factors for low oil saturation reservoirs were studied using laboratory large model physical modeling and reservoir numerical simulation, to match and establish the empirical formula of water cut variation. In the numerical stimulation process, the effect of threshold pressure on filtration for low permeability reservoirs was considered, which made the results more realistic. There wasn't a period of oil recovery without water for low oil saturation reservoirs; the water cut increased rapidly at the beginning, and dropped slightly before the period of oil production with stable water cut. The higher the initial water saturation, the shorter the production time with stable water cut. Recovery changed greatly with the injection/production pressure gradient when the injection/production pressure gradient was close to the pseudo threshold pressure gradient. Recovery changed little, even no change, with the injection/production pressure gradient when the injection/production pressure gradient was far larger than the pseudo threshold pressure gradient. There was a positive correlation between recovery degree and water injection rate when the injection/production pressure gradient was less than the pseudo threshold pressure gradient. Key words: low oil saturation reservoir, low permeability reservoir, pseudo threshold pressure gradient, filtration