压裂充填方式对疏松砂岩储层油水运移的影响

Influence of frac-packing methods on oil-water migration in unconsolidated sandstone reservoirs

压裂充填是目前解决疏松砂岩稠油油藏产能低、易出砂问题的有效技术手段,但注水过程中压裂充填方式对储层油水运移的影响规律尚不明确。基于储层油水两相流动基本原理,建立了注采井纵向非均质储层油水两相流动数值模拟模型,分析了注采过程中不进行压裂充填以及不同压裂充填方式条件下含水率、产油量和采出程度随开发时间的变化规律。结果表明,不进行压裂充填时注入水更容易沿高渗储层运移,从而影响低渗储层的波及效果,导致高低渗储层采出程度不平衡,总采出程度较低;进行压裂充填后,提高低渗储层裂缝的渗透率与适当封堵高渗层能够最大程度改善低渗储层的动用状态,提高油藏最终采收率,获得较好的调剖、增产效果。本文研究成果可对疏松砂岩稠油油藏压裂设计提供借鉴。

Frac-packing is an effective technical means to solve the problems of low productivity and sand production of unconsolidated sandstone heavy oil reservoirs.However,the influence of frac-packing methods on oil and water migration in reservoirs during water injection has not been clearly understood.Based on the basic principle of oilwater two-phase flow,a numerical simulation model of oil-water two-phase flow for injection-production wells in longitudinal heterogeneous reservoirs was established,and the changing laws of water cut,oil production and the degree of recovery over time in the process of injection and production were analyzed for the case without frac-packing and case with different frac-packing methods.The results show that the injected water is more likely to migrate along the high-permeability reservoir when no frac-packing is conducted.In such a case,the sweeping effect in low-permeability reservoirs will be compromised,resulting in an unbalanced degree of recovery in high/low permeability reservoirs and the low total recovery degree.After frac-packing,the fractures permeability of low-permeability reservoir is improved and the high-permeable layer is properly blocked,which can improve the utilization state of low-permeability reservoirs to the most extent,enhance the ultimate recovery factor of reservoirs,and achieve ideal profile control and stimulation effects.The study results in this paper can provide references for the fracturing design of unconsolidated sandstone heavy oil reservoirs.