Numerical Simulation Study on Synergistic Influencing Factors of CO2 Flooding and Geological Storage in Low-Permeability and High-Water-Cut Reservoirs

本研究以大庆油田Y区块为对象，针对其低渗透、高含水特征，采用数值模拟方法系统揭示了CO₂驱油与地质封存协同作用机制。研究建立了表征该区块地质特征的三维组分模型，重点分析了地质因素（埋深、非均质性、物性）与工程参数（注气速度、注气量、井底流压）对驱替与封存过程的控制作用。模拟结果表明，Y区块的低渗透特性有效抑制了气窜，CO₂驱可提高采收率15.65%。随着埋深增加，地层压力与温度升高，驱替与封存效率同步提升。优化注入参数是实现协同效益的关键：最佳注气速度为700–900 m³/d，经济注气量为0.4–0.5 PV，最优井底流压为9–10 MPa。研究证实，对于类似Y区块的高含水低渗透油藏，CO₂驱是一项极具潜力的接替技术，可在提高采收率的同时实现高效碳封存。

🧪 CMG软件应用情况

  • 使用CMG软件的Winprop模块进行流体组分建模与PVT拟合，准确复现了最小混相压力（MMP），实验值17.5 MPa，模拟值18.1 MPa，误差仅3.4%。
  • 使用GEM组分模拟器建立三维地质模型，模拟水驱后转CO₂驱全过程，分析不同参数对采收率与封存效率的影响。
  • 模型采用均质概念模型，网格尺寸为19×19×5，共1805个网格块，模拟了水驱至含水80%后转CO₂驱的全过程。

✅ 结论

  1. Y区块低渗透率（约5.45 mD）天然抑制CO₂气窜，有利于提高驱替效率，采收率增幅达15.65%。
  2. 埋深增加显著提升CO₂驱替与封存效果，是地质因素中最关键的影响参数。
  3. 存在最优的垂向渗透率比值（KV/Kh ≈ 0.3），较薄储层更有利于提高采收率。
  4. 工程参数优化是实现协同效益的核心：
    • 注气速度：700–900 m³/d
    • 注气量：0.4–0.5 PV
    • 井底流压：9–10 MPa
  5. 在Y区块类似油藏中，通过地质与工程参数协同优化，完全可实现“增油+封存”双赢目标。

🏢 作者单位

  • 提高油气采收率教育部重点实验室（东北石油大学）

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Abstract

How to economically and effectively mobilize remaining oil and achieve carbon sequestration after water flooding in low-permeability, high-water-cut reservoirs is an urgent challenge. This study, focusing on Block Y of the Daqing Oilfield, employs numerical simulation to systematically reveal the synergistic influencing mechanisms of CO2 flooding and geological storage. A three-dimensional compositional model characterizing this reservoir was constructed, with a focus on analyzing the controlling effects of key geological (depth, heterogeneity, physical properties) and engineering (gas injection rate, gas injection volume, bottom-hole flowing pressure) parameters on the displacement and storage processes. Simulation results indicate that the low-permeability characteristics of Block Y effectively suppress gas channeling, enabling a CO2 flooding enhanced oil recovery (EOR) increment of 15.65%. Increasing reservoir depth significantly improves both oil recovery and storage efficiency by improving the mobility ratio and enhancing gravity segregation. Parameter optimization is key to achieving synergistic benefits: the optimal gas injection rate is 700–900 m3/d, the economically reasonable gas injection volume is 0.4–0.5 PV, and the optimal bottom-hole flowing pressure is 9–10 MPa. This study confirms that for Block Y and similar high-water-cut, low-permeability reservoirs, CO2 flooding is a highly promising replacement technology; through optimized design, it can simultaneously achieve significant crude oil production increase and efficient CO2 storage.

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