Dynamic Simulation of Nano-Gel Microspheres for Plugging Preferential Flow Channels and Enhancing Oil Recovery in Waterflooded Reservoirs

长期水驱后优势通道（PFC）导致注水突破，剩余油难以动用。本文利用CMG 软件，耦合岩石应力-孔隙度物性时变（CROCKTAB）与水饱和度-渗透率演化（CROCKTABW）两大关键词，建立了 PFC 动态演化模型，并将纳米凝胶微球（NGM）“运移-封堵-再封堵”机理嵌入模拟。结果显示：

  1. 忽略 PFC 会导致采收率高估约 8.7 %；
  2. NGM 通过“桥堵-滤饼”结构使高渗层渗透率降低 33 %（12→8 mD），低渗层渗透率提高 33 %（4.5→6 mD），有效驱替剩余油；
  3. 在鄂尔多斯盆地长 6 致密油藏现场应用：>10 年有效期，采收率提高 0.84 %（7.31 %→8.15 %），投入产出比约 10:1，为同类油藏提供可行技术路线。

CMG 软件应用情况

• 软件：CMG-IMEX + CROCKTAB/CROCKTABW 自定义耦合
• 网格：150×150×2，水平 1 m×1 m，垂向 5 m；一注一采，井距 150 m
• 关键设置：
– CROCKTAB：应力-孔隙度滞后，实现长期水驱渗透率不可逆增长
– CROCKTABW：水饱和度驱动渗透率动态变化，刻画优势通道
– ADSCOMP/ADSTABLE：依据 NGM 吸附量实时修正相渗曲线
• 参数：孔隙度 0.12→0.16，渗透率 8→12 mD；油粘度 2.62 mPa·s；含水 90 % 后转 NGM 驱

结论

  1. 首次在 CMG 平台实现“应力-渗流-化学”全耦合，可量化优势通道演化及其对开发指标的影响。
  2. NGM 封堵机理明确：高渗层“桥堵-滤饼”降低渗透率，低渗层能量补充提高动用程度。
  3. 现场验证：长 6 致密油藏 20 年模拟表明，NGM 驱后>10 年持续增油，经济效益显著。
  4. 所建模型与方法可直接推广至其他高含水、强非均质油藏，为纳米凝胶规模化应用提供理论依据与工程模板。

作者单位： 西安石油大学 

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Abstract

This study addresses the unclear mechanisms by which preferential flow channels (PFCs), formed during long-term waterflooding, affect nano-gel microsphere (NGM) flooding efficiency, utilizing CMG reservoir numerical simulation software. A dynamic evolution model of PFCs was established by coupling CROCKTAB (stress–porosity hysteresis) and CROCKTABW (water saturation-driven permeability evolution), and the deep flooding mechanism of NGMs (based on their gel properties such as swelling, elastic deformation, and adsorption, and characterized by a “plugging-migration-replugging” process) was integrated. The results demonstrate that neglecting PFCs overestimates recovery by 8.7%, while NGMs reduce permeability by 33% (from 12 to 8 mD) in high-conductivity zones via “bridge-plug-filter cake” structures, diverting flow to low-permeability layers (+33% permeability, from 4.5 to 6 mD). Field application in a Chang 6 tight reservoir (permeability variation coefficient 0.82) confirms a >10-year effective period with 0.84% incremental recovery (from 7.31% to 8.15%) and favorable economics (ROI ≈ 10:1), providing a theoretical and engineering framework for gel-based conformance control in analogous reservoirs.

Keywords: 

nano-gel microspheres (NGMs); preferential flow channels (PFCs); plugging mechanism; numerical simulation; enhanced oil recovery (EOR)

 

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