胜坨油田高温高盐油藏强化聚合物驱油体系的性能评价

Performance Evaluation of Reinforced Polymer Flooding Oil System for High Temperature and High Salinity Reservoir in Shengtuo Oilfield

李 彬

LI Bin

胜坨油田地层温度大于80℃、地层水矿化度大于20000 mg/L、地层水钙镁离子大于500 mg/L，非均质性强。根据该油藏特点，室内研制了强化聚合物驱油体系，在超高分疏水缔合型聚丙烯酰胺中加入聚合物强化剂。结果表明，强化剂加量由0增至2500 mg/L，驱油体系的表观黏度由7.8增至42.9 mPa·s，黏性模量由120增至315 mPa，弹性模量由0增至106 mPa。在模拟胜坨油田条件下，强化聚合物驱油体系（超高分缔合聚合物、强化剂质量比4:1）老化60 d的黏度保留率为85.5%，好于改性聚丙烯酰胺（GXPAM）（66.2%），热稳定性良好。在非均质岩心中注入强化聚合物驱油体系（2500 mg/L），高渗模型产液百分比由98.5％逐渐降低，最低值为32.7%；低渗模型产液百分比由1.5%逐渐增大，最大值为67.3%；后续水驱1.0 PV时，高渗模型产液百分比为58.5%，低渗模型的为41.5%，岩心非均质性得到明显改善。岩心渗透率级差分别为1:5和1:3时，强化聚合物驱油体系的采收率增幅为26.0%和10.9%，GXPAM的为14.8%和7.1%。强化聚合物驱油体系的驱油效果明显优于GXPAM，并且在高渗透率级差下的驱油效果较好。

In Shengtuo oilfield, the formation temperature was more than 80℃, the salinity of formation water was above 20000 mg/L, the concentration of calcium and magnesium ions was more than 500 mg/L, and the heterogeneity of reservoir was strong. According to the reservoir characteristics of Shengtuo oilfield, reinforced polymer flooding oil system was developed by adding polymer enhancer to ultra-high molecular weight hydrophobic associating polyacrylamide. The results showed that when the dosage of enhancer increased from 0 to 2500 mg/L, the apparent viscosity of oil displacement system increased from 7.8 to 42.9 mPa·s, the viscous modulus increased from 120 to 315 mPa, and the modulus of elasticity increased from 0 to 106 mPa. In the simulation of Shengtuo oilfield conditions, when the mass ratio of ultra-high molecular weight associative polymer and enhancer was equal to four, the viscosity retention rate of reinforced polymer flooding system was 85.5% after 60 days, which was better than that of modified polyacrylamide (GXPAM) (66.2%). The reinforced polymer displacement system had well thermal stability. When the reinforced polymer flooding oil system (2500 mg/L) was injected in heterogeneous core, the liquid production percentage of hypertonic model decreased from 98.5% gradually with 32.7% minimum value, and that of low permeable model increased from 1.5% step by step with 67.3% maximum value. When the sequent water (1 PV) was injected, the liquid production percentage of hypertonic model was 58.5%, and that of low permeable model was 41.5%. The core heterogeneity was improved obviously. When the core permeability ratio was 1:5 and 1:3, the enhanced recovery rate of reinforced polymer flooding oil system increased by 26.0% and 10.9%, however that of GXPAM increased by 14.8% and 7.1%, respectively. Oil recovery efficiency of reinforced polymer flooding oil system was better than that of GXPAM, and the flooding effect was better in high permeability ratio.