低渗透油田注入井井底滤饼对注入能力的影响

通过岩心流动实验和理论计算,并结合实际生产情况,研究了注入井井底滤饼对注入压力和注水量的影响。结果表明,"等效渗透率"理论适用于计算井底滤饼对不同储层的伤害程度。实验测得120 m L 5%、150 m L30%硅藻土形成滤饼的厚度分别为0.35、2.51 cm,滤饼渗透率分别为4.2×10-3、0.3×10-3μm2。滤饼渗透率为0.3×10-3μm2时,滤饼对低渗透储层的渗透性影响较小,对中高渗和高渗储层的伤害非常严重,储层渗透率越大伤害率越高;当储层渗透率为50×10-3、100×10-3μm2时,储层渗透率伤害率分别为29.0%、45.3%。滤饼渗透率为4.2×10-3μm2时,滤饼对不同储层的渗透性几乎没有影响。低渗透储层井底滤饼的形成会引起注水压力的升高;但注水井的注水量随滤饼厚度的增加变化较小。

Influence of Bottom-Hole Filter Cake on Injection Capacity of Water Injection Wells in Low Permeability Oilfield

The influence of bottom-hole filter cake on injection pressure and water injection in water injection wells was studied through the core flow experiments and theoretical calculation methods combining with actual production situation. The results showed that "the equivalent permeability" theory was applicable to calculate the formation damage degree of filter cake in different reservoir. The thickness of filter cake formed by 5% (120 mL) and 30% (150 mL) diatomite had reached to 0.35 and 2.51 cm, and the permeability of filter cake was 4.2×10^-3 and 0.3×10^-3 mm2. The filter cake had a smaller effect on the permeability of low permeability reservoir and a serious effect on the permeability of mid-high permeability and high permeability reservoir when the permeability of filter cake was 0.3×10^-3 mm2. Damage rate increased with increasing reservoir permeability. When the permeability of reservoir was 50×10^-3 and 100×10^-3 mm2, the damage rate of reservoir permeability was 29.0% and 45.3%. The filter cake had little effect on the permeability of different reservoir when cake permeability was 4.2×10^-3 mm2. The downhole filter cake of low permeability reservoir could result in the increase of water injection pressure. However, the water injection quantity of water injection well changed a little with increasing filter cake thickness.