基于渗流场-化学场-应力场耦合模型的酸蚀碳酸盐岩反应流数值模拟

Carbonate reservoir is widely distributed in the world with huge resources. Acidizing is an essential stimulation technique to increase and maintain the production of development well in carbonate reservoir. The reactive transport of injected acid in the formation is coupled phenomena that involve the fluid flow, rock deformation and the chemical reaction between acid and rock. However, the influence of geo-mechanics on the reactive transport is not considered in the current Darcy scale reactive flow models. In this study, numerical simulations and physical experiments are combined to study the dynamic dissolution process of reactive flow under the confining pressure. Firstly, the acidizing experiments are performed by injecting acid into core samples under the confining pressure to study the stress effect on dissolution patterns. Then, the coupled Hydraulic-Chemical-Mechanical model is developed, and an efficient decoupling algorithm is presented to simulate the reactive flow under the influence of stress. The mathematic model is validated against experimental data and compared with results obtained by full coupling numerical method. Additionally, based on the embedded discrete fracture model, the presented model is extended to simulate the coupled reactive flow and rock deformation in fractured carbonate reservoir. In particular, an effective numerical algorithm is presented to address the discontinuous displacements within elements that intersect with fractures. Finally, a complete framework for simulating the reactive flow under the formation stress is formed, which provides theoretical and technological support for optimizing reservoir acidizing stimulation.

碳酸盐岩油藏在世界范围内分布广泛且产量巨大。酸化是碳酸盐岩油藏建产、增产、稳产的重要措施。酸液在地层中的流动包含复杂的多场作用，涉及流体渗流、岩体介质变形、以及酸与岩石的化学反应，但当前达西尺度的反应流模型中未考虑应力场对溶蚀动态的影响。本课题拟采用实验与数值模拟相结合的方法，研究地应力条件下酸岩反应的溶蚀动态。首先在添加围压的条件下进行岩心酸化实验，研究应力对溶蚀模式的影响；然后建立酸蚀碳酸盐岩渗流场-化学场-应力场耦合模型，并给出有效的解耦算法进行数值求解，通过与岩心酸化实验及全耦合求解结果对比，验证数学模型及解耦算法的正确性；对于裂缝性碳酸盐岩，基于嵌入式离散裂缝模型将建立的模型进行拓展，并给出有效算法处理裂缝两侧位移不连续问题，最终形成一套适用于真实地层应力条件下模拟碳酸盐岩酸化反应流的数值模拟方法，为优化油藏酸化施工方案提供理论与技术基础支撑。

碳酸盐岩油藏在世界范围内分布广泛且产量巨大。酸化是碳酸盐岩油藏建产、增产、稳产的重要措施。酸液在地层中的流动包含复杂的多场作用，涉及流体渗流、岩体介质变形、以及酸与岩石的化学反应，但当前达西尺度的反应流模型中未考虑应力场对溶蚀动态的影响。本课题对地应力条件下酸岩反应的溶蚀动态进行研究，取得了以下原创成果：（1）在添加围压的条件下进行岩心酸化实验，总结出了渗透率、孔隙度随有效应力的变化公式；（2）建立了酸蚀碳酸盐岩渗流场-化学场-应力场耦合模型，并给出了有效的解耦算法进行数值求解；（3）基于嵌入式离散裂缝模型，同时考虑地应力的影响，建立了适用于裂缝性碳酸盐岩储层的反应流模型，并给出了有效算法处理裂缝两侧位移不连续问题；（4）考虑温度影响，建立了渗流场-温度场-化学场耦合的反应流数值模拟方法。最终形成了一套适用于真实油藏条件的碳酸盐岩酸化反应流的数值模拟方法，为优化油藏酸化施工方案提供了理论与技术基础支撑。相关成果在Chemical Engineering Science、International Journal of Thermal Sciences、Oil & Gas Science and Technology等期刊发表SCI论文8篇，申请国家发明专利2项。