低渗油藏CO_2驱气水段塞比优化

Optimization of Gas-water Slug Ratio in CO2 Flooding of Low Permeability Reservoirs

根据吉林油田某区块的油藏条件,运用数值模拟方法,研究不同注入方式下的驱油效果。数模结果显示,与水驱和连续注气方式相比,气水交替驱能大幅提高原油采收率。在气水交替驱过程中,在一定井底控制压力下,最佳气水段塞比是变化的,它与渗透率、注气速度和井底压力等因素有关。最佳气水段塞比对渗透率的变化比较敏感,注气速度其次,井底控制压力再次。随着渗透率的增加,最佳气水段塞比逐渐减小,而采收率也逐渐减小。渗透率在一定范围内,渗透率越低,气水交替驱的效果越好。这也从理论上证明,与中高渗透油藏相比,气水交替驱更适合低渗透油藏。它为油田CO2驱油技术提供了理论基础。

According to the reservoir conditions of a certain block in Jilin Oilfield,the displacement efficiency in different displacement modes was studied with numerical simulation.The result of numerical simulation shows that compared with continuous CO2 flooding and water flooding,gas-alternating-water flooding could significantly enhance oil recovery.In the alternating displacement process,under certain bottom hole pressure,the optimal gas-water slug ratio is variable,it was related with permeability,the gas injection rate and the bottom hole pressure and other factors.The best slug ratio is more sensitive to the permeability changes,followed by gas injection rate and the bottom hole pressure.As the permeability increases,the best slug ratio gradually decreases,while the recovery also gradually reduces.Within a certain range,the lower the permeability is,the better the gas-alternating-water flooding would be.It is proved theoretically that compared with the high-permeability reservoirs,gas-alternating-water flooding is more suitable for low permeability reservoirs.The result provides a theoretical basis for field implementation of CO2 flooding.