Department of Petroleum and Geosystems Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
Department of Petroleum Engineering, Texas A&M University, College Station, TX, 77843, USA.
Sci Rep. 2016 Sep 15;6:33445. doi: 10.1038/srep33445.
The recent development of tight oil reservoirs has led to an increase in oil production in the past several years due to the progress in horizontal drilling and hydraulic fracturing. However, the expected oil recovery factor from these reservoirs is still very low. CO2-based enhanced oil recovery is a suitable solution to improve the recovery. One challenge of the estimation of the recovery is to properly model complex hydraulic fracture geometries which are often assumed to be planar due to the limitation of local grid refinement approach. More flexible methods like the use of unstructured grids can significantly increase the computational demand. In this study, we introduce an efficient methodology of the embedded discrete fracture model to explicitly model complex fracture geometries. We build a compositional reservoir model to investigate the effects of complex fracture geometries on performance of CO2 Huff-n-Puff and CO2 continuous injection. The results confirm that the appropriate modelling of the fracture geometry plays a critical role in the estimation of the incremental oil recovery. This study also provides new insights into the understanding of the impacts of CO2 molecular diffusion, reservoir permeability, and natural fractures on the performance of CO2-EOR processes in tight oil reservoirs.
近年来，由于水平井和水力压裂技术的进步，致密油藏的开发使得石油产量有所增加。然而，这些油藏的预期采油率仍然非常低。二氧化碳强化采油是提高采收率的一种合适的解决方案。在评估采收率时，面临的一个挑战是要正确模拟复杂的水力裂缝几何形状，由于局部网格细化方法的限制，这些裂缝通常被假设为平面。更灵活的方法，如使用非结构化网格，可以显著增加计算需求。在这项研究中，我们引入了一种有效的嵌入式离散裂缝模型方法，以明确地模拟复杂的裂缝几何形状。我们构建了一个组合油藏模型，以研究复杂裂缝几何形状对 CO2 吞吐和 CO2 连续注入性能的影响。结果证实，适当的裂缝几何形状建模对增量油采收率的估算起着至关重要的作用。本研究还为理解 CO2 分子扩散、储层渗透率和天然裂缝对致密油藏 CO2-EOR 过程性能的影响提供了新的见解。
