海上油田回注污水对储层堵塞机理研究

Study on reservoir plugging mechanism caused by wastewater reinjection in offshore oilfiled

海上油田注水开发过程中常出现注水井欠注问题,主要原因是回注的污水中固体悬浮物和含油量严重超标,造成地层堵塞,使得注入压力升高。通过岩心流动物理模拟研究了回注水中固体悬浮物和乳化油对储层的堵塞规律。结果表明:回注水中悬浮物含量越大,岩心渗透率伤害程度越高,悬浮物含量80 mg/L时,渗透率伤害率超过50%。悬浮物含量相同时,悬浮颗粒对储层的伤害程度取决于颗粒粒径与储层孔喉大小匹配程度,颗粒粒径小于且越接近孔喉直径的1/3时对岩心的伤害程度越高。回注水中乳化油对岩心伤害程度不亚于固体悬浮物,回注水中含油量越大,岩心渗透率伤害程度也越高,含油量50 mg/L时,渗透率伤害率可达50%。且岩心渗透率越低,伤害程度越大。

The problem of insufficient injection often occurs in water injection development in offshore oilfields,which is due to the fact that suspended solids and oil content in the reinjected wastewater are seriously beyond standard.As a result,the formation is plugged and the injection pressure is increased.The plugging mechanism of suspended solids and emulsified oil content in the reinjected water was studied by core simulation experiments.The results indicate that the damage degree of core permeability increases with suspended solid content,and the damage rate exceeds 50%when the suspended solid content is 80 mg/L.When the suspended solid content is the same,the damage degree of suspended particles to the reservoir depends on the matching degree between the particle size and the pore throat size of the reservoir.When the particle size is less than and closer to 1/3 of the pore throat diameter,the damage to the core is higher.Emulsified oil in the reinjected water is not less harmful to the core than suspended solids.The damage degree of core permeability increase with oil content in the reinjected water,and when the oil content is 50 mg/L,the damage rate can reach 50%.And the lower the core permeability,the greater the damage.