Coupled Geomechanical-Fluid Flow Simulation of CO2 Sequestration: Optimizing Injection Strategies to Preserve Caprock Integrity
本研究提出了一个集成的耦合油藏-地质力学建模框架，用于优化天然裂缝性枯竭油藏（含底部盐水层）中的CO₂注入参数。核心目标是确定最优注入速率、井位和射孔深度，在最大化CO₂封存容量的同时，通过Barton-Bandis裂缝本构模型的机理应用确保盖层完整性，防止天然裂缝再激活和意外泄漏通道的形成。
研究使用CMG软件建立了基于Burgan油田参数的三维合成油藏模型。采用迭代耦合方法连接组分多相流模拟与地质力学分析：Barton-Bandis模型根据注入过程中有效应力变化，在每个时间步动态更新裂缝开度和渗透率。这种应力依赖性耦合能够实时评估CO₂注入期间的裂缝行为演化和流动通道动态。
研究量化了三种CO₂封存机制：构造封存、残余封存和溶解封存。通过CMOST优化工具运行120次模拟，系统评估多种注入速率情景，确定最大化总CO₂封存量且零泄漏风险的最优设计。
结果表明：经优化的注入策略可实现80-90%的CO₂封存效率，同时保持盖层所有裂缝的有效正应力稳定，确保零再激活风险。该研究为天然裂缝性地层中的CO₂封存提供了实用工程指导，支持全球净零排放目标。
CMG软件应用详情
| 应用模块 | 具体功能 | 技术细节 |
|---|---|---|
| 建模平台 | 三维合成油藏模型构建 | 基于Burgan油田地质架构和物性参数建立模型 |
| 流动模拟 | 组分多相流模拟 | 模拟CO₂-水-油多相流动及传质过程 |
| 地质力学耦合 | Barton-Bandis裂缝模型 | 动态更新裂缝开度和渗透率，实现应力-流动耦合 |
| CMOST优化 | 注入参数优化 | 运行120次模拟，优化注入速率、井位和射孔深度 |
| 封存机制分析 | 三种捕获机制量化 | 评估构造、残余和溶解封存贡献 |
核心结论
- 技术有效性：集成耦合框架能有效评估注入引起的渗透率变化，识别保持地质封存安全性的操作窗口（Safe Operational Envelopes）
- 封存效率：经过仔细优化的注入策略可实现80-90%的CO₂封存效率，显著高于常规设计
- 盖层完整性：优化方案能维持盖层裂缝的有效正应力稳定，实现零再激活风险（无泄漏）
- 工程价值：通过显式关联操作参数与地质力学裂缝行为，为CO₂封存项目提供了可操作的工程设计准则
- 方法论创新：迭代耦合方案（流动-地质力学）结合Barton-Bandis模型，可实时捕捉裂缝动态演化
Abstract
This study presents an integrated coupled reservoir-geomechanical modeling framework to optimize CO2 injection parameters in naturally fractured depleted reservoirs with underlying saline aquifers. The primary objective is to identify optimal injection rates, well locations, and perforation depths that maximize CO2 storage capacity while ensuring caprock integrity through mechanistic application of the Barton-Bandis fracture constitutive model, thereby preventing natural fracture reactivation and unintended leakage pathways.
A three-dimensional synthetic reservoir model, developed using Computer Modelling Group (CMG) software, incorporates architecture and petrophysical parameters inspired by Burgan Field. This depleted hydrocarbon reservoir is sealed by a naturally fractured caprock and underlain by a saline aquifer storage target. The modeling approach employs iterative coupling between compositional multiphase flow simulation and geomechanical analysis, where the Barton-Bandis model dynamically updates fracture aperture and permeability at each timestep based on effective stress changes during injection. This stress-dependent coupling enables real-time assessment of fracture behavior evolution and flow pathway dynamics during CO2 injection operations. The model quantifies three CO2 trapping mechanisms: structural, residual, and solubility trapping. Multiple injection rates scenarios are systematically evaluated to determine the optimal design maximizing total CO2 trapped while eliminating leakage risk. Optimization is conducted using CMOST (CMG Optimization and Uncertainty Estimation) through 120 simulation runs.
The integrated framework offers a robust systematic tool for evaluating injection-induced permeability changes and identifying safe operational envelopes preserving geological containment. Results demonstrate that carefully optimized injection strategies can achieve 80–90% CO2 trapping efficiency while maintaining stable effective normal stress on all caprock fractures, ensuring zero reactivation risk. This work advances CO2 storage optimization by explicitly linking operational parameters with geomechanical fracture behavior through fully coupled modeling, providing practical engineering guidelines for CO2 injection in naturally fractured geological formations and supporting global net-zero emission targets.
