海上油田聚合物驱与加密协同开发模式下微观渗流特征

Micro-scale seepage characteristics in the cooperative development model of polymer flooding and well densification in offshore oilfields

摘要

海上油田SZ36-1油田Ⅰ期大井距聚合物驱试验区提高采收率幅度低于陆上油田的,含水率上升速度快,且连片状剩余油赋存量高。以增加驱替相黏度为核心的聚合物驱开发模式为基础,结合井网调控、提升驱替压力梯度的加密措施,提出聚合物驱与加密协同增效的开发模式。基于Cahn-Hilliard与Navier-Stokes方程,建立静态孔隙尺度聚合物驱数值模型,对水驱后聚合物驱过程进行数值模拟,分析压力梯度与黏度对聚合物驱开发效果的影响。结果表明:提高注入压力梯度和增加水油黏度比可以显著提升波及因数和洗油效率。压力梯度增加1.5倍,采出程度可提高22.2%;黏度比增加1倍,采出程度可提高4.8%。聚合物驱后新增波及区内压力梯度提升,结合化学剂增黏作用,综合动用连片状剩余油,实现聚合物驱与加密协同增效。流度控制作用与压力梯度增加对聚合物运移能力提升具有增效作用,为海上油田聚合物驱方案设计及提高采收率提供指导。

Abstract

The recovery rate in the SZ36-1-I phase offshore oilfield development area is lower than that in onshore fields, with a rapid increase in water cut and high amounts of residual oil in the contiguous regions. Based on increasing the displacement-phase viscosity, a polymer flooding development model is proposed, which incorporates well pattern optimization and measures to enhance the displacement pressure gradient. This approach combines polymer flooding with enhanced well pattern density for a synergistic effect. A numerical model for polymer flooding at the pore scale is established based on the Cahn-Hilliard and Navier-Stokes equations, which simulates the polymer flooding process after water flooding and analyzes the effects of pressure gradient and viscosity on the development outcome. The results indicate that increasing the injection pressure gradient and the water-oil viscosity ratio can significantly enhance the sweep efficiency and oil recovery. When the pressure gradient increases by 1.5 times, the recovery rate can increase by 22.2%. When the viscosity ratio is doubled, the recovery rate can further increase by 4.8%. The increase in pressure gradient in the newly swept region after polymer flooding, combined with the viscosity-enhancing effect of chemical agents, effectively mobilizes the residual oil in the contiguous regions, achieving synergistic effects between polymer flooding and enhanced well pattern density. These findings clarify the enhanced effect of flow control and the increase in pressure gradient on the improvement of polymer migration capabilities, providing guidance for designing polymer flooding plans to further improve the recovery rate in offshore oilfields.

关键词

海上油田 / 孔隙尺度 / 聚合物驱 / 加密开发 / 毛细管数 / 采出程度 / 微观渗流

Key words

offshore oilfields / pore scale / polymer flooding / well densification / capillary number / recovery degree / microscopic seepage

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基金资助

中国海洋石油有限公司“十四五”重大科技项目(KJGG2021-0500)