砾岩油藏聚合物驱的注入方式优化

Optimization on Injection Mode of Polymer Flooding in Conglomerate Reservoir

砾岩储层具有典型的复模态孔隙结构特征,非均质性强,易形成不同级别优势通道,采用单一段塞、笼统的注入方式很难达到扩大波及体积效果。本文采用三管并联岩心驱替实验首先考察了与现场聚合物用量相近的条件下采用单一恒黏、梯次降黏、梯次增黏的注入方式的驱油效果,在获得最佳注入方式的基础上,开展了不同轮次和不同注入速率下的三管并联岩心驱替实验。研究结果表明,梯次降黏注入方式的驱油效果最好,在水驱的基础上可提高采收率13.61%,比单一恒黏注入方式进一步提高采收率2.31%。在相同条件下,采收率增幅与注入轮次的多少相关不大,在合理注入速率(1.5 mL/min)下可进一步提高采收率。在采收率相近的情况下,与单一恒黏注入方式相比,梯次降黏注入方式可节约50%的聚合物用量。现场试验结果表明,采用梯次降黏注入方式可有效提高聚合物驱对砾岩油藏的增油控水效果。

Conglomerate reservoir has typical complex mode pore structure,strong heterogeneity and is easy to form dominant channels of different grades;hence,it is difficult to achieve the effect of expanding sweep volume by single slug and general injection method.Three-pipe parallel core displacement experiments with different injection modes,including single constant viscosity,step-by-step viscosity reduction and step-by-step viscosity increase,was carried out and the enhanced oil recovery(EOR)were investigated under the same polymer dosage.In the best injection mode,three-pipe parallel core displacement experiments were carried out at different injection cycles and injection rates.The experimental results showed that,the EOR could be increased by 13.61%by using step-by-step viscosity reduction injection mode,which was 2.31%higher than that by single constant viscosity injection mode.Under the same conditions,the EOR was not related to the number of injection cycles.At the reasonable injection rate of 1.5 mL/min,the EOR could be further increased.When EOR was similar,the polymer dosage by step-by-step viscosity reduction mode was 50%lower than that by single constant viscosity injection mode.The results of the step-by-step viscosity reduction in the filed indicated the oil production was increased and the water cut was decreased obviously.