Finite Element Analysis (FEA) for Water-Foam Fracturing of Granite Rock

In addition to the foam data that were obtained from literature and that were collected from the current study, simulation data was also generated from finite element analysis (FEA) conducted in this study using COMSOL Multiphysics software. The FEA models were built to simulate the experiments conducted at Oak Ridge National Laboratory (ORNL) on cement and granite samples. In these FEA models, temperature was kept at ambient while the pressure profile resembled the loading conditions during the ORNL experiments, where pressure was either monotonically increased or applied cyclically.

The cement material was used as a model material and was used to study Von Mises stress and tensile stress distribution for different bore hole length geometry using a parametric sweep with water as fracturing fluid using solid-fluid interaction module.

For the granite material, FEA models were developed for stress analysis of cylindrical samples with water or foam fluids. The solid mechanics module in COMSOL was implemented to solve for Von Mises stress and tensile stress. The fluid-structure interaction module was implemented to solve for water-foam interaction on granite cylinder with addition of fluid-loading on structure, i.e., large deformation in solid mechanics with no impact on fluid deformation. Foam was considered as a pseudo single-phase compressible fluid for which material properties were calculated from water and gas (nitrogen) phases. The density of foam is calculated as a function of the densities of water and nitrogen, while viscosity is a function of temperature. Four types of FEA analyses were modelled:
1. Monotonic injection with water
2. Monotonic injection with foam
3. Cyclic injection with water
4. Cyclic injection with foam
All the COMSOL files are converted to a zip file which is save in .mph.

此外，本研究不仅收集了来自文献的泡沫数据以及当前研究中的数据，还利用 COMSOL Multiphysics 软件，通过有限元分析（FEA）生成了模拟数据。所构建的 FEA 模型旨在模拟橡树岭国家实验室（ORNL）对水泥和花岗岩样品进行的实验。在这些 FEA 模型中，温度保持为环境温度，而压力分布则与 ORNL 实验中的加载条件相似，压力要么单调增加，要么周期性施加。以水泥材料作为模型材料，并利用水作为裂解流体，通过参数扫描研究不同钻孔长度几何形状下的冯·米塞斯应力及拉伸应力分布。对于花岗岩材料，开发了 FEA 模型以分析圆柱形样品在水和泡沫流体中的应力。COMSOL 中的固体力学模块被用于求解冯·米塞斯应力和拉伸应力。流体-结构相互作用模块被用于求解花岗岩圆柱体中的水-泡沫相互作用，即在结构上添加流体加载，即固体力学中的大变形，对流体变形无影响。泡沫被视为伪单相可压缩流体，其材料属性由水和气体（氮气）相计算得出。泡沫的密度是水密度和氮气密度的函数，而粘度是温度的函数。共模拟了四种类型的 FEA 分析：1. 单调注水；2. 单调注泡沫；3. 周期注水；4. 周期注泡沫。所有 COMSOL 文件均转换为 zip 文件，并保存为 .mph 格式。