Semi-Analytical Model for Carbon Dioxide Injection Wells Considering Dynamic Induced Fracture Network: Multi-temporal Case Studies in C Oilfield, China
Authors: Guo Wenting , Ning Zhengfu , Zhan Jie , Zhang Yuanxin , Wang Zhipeng , Rustam Sagirov , Vadim Derevyanko 
Published: November 2023

Abstract
Carbon dioxide injection will induce fracture network. Carbon dioxide will reach a supercritical state under tight reservoir temperatures and pressures. During prolonged carbon dioxide injection, fracture network will extend directionally or even connect to production wells causing gas breakthroughs. Numerical simulations demonstrate that the induced fracture network will affect carbon dioxide utilization and reduce carbon dioxide storage efficiency. Therefore, the identification and efficient utilization of dynamic induced fracture network is necessary. Carbon dioxide injection will induce fracture network. Carbon dioxide will reach a supercritical state under tight reservoir temperatures and pressures. During prolonged carbon dioxide injection, fracture network will extend directionally or even connect to production wells causing gas breakthroughs. Numerical simulations demonstrate that the induced fracture network will affect carbon dioxide utilization and reduce carbon dioxide storage efficiency. Therefore, the identification and efficient utilization of dynamic induced fracture network is necessary. Results demonstrate that tri-radial flow with micro-stepped characteristic, fracture storage with V-shape characteristic, and dynamic fracture network flow with peak-shape characteristic regimes are shown in type curve. Innovation parameters—fracture inter-porosity flow coefficient (ω), dynamic fracture network conductivity (Fdf), and dynamic fracture network radius (rdf) are introduced the DIFN model. Numerical simulations verified the accuracy of the DIFN model. Multi-temporal field cases from the same well are matched by the DIFN model. The physical processes of dynamic induced fracture network expansion are characterized. It is worth noting that the innovative parameters can be used to calculate carbon dioxide fracture storage volume. By coupling the injection parameters, the carbon dioxide physical properties parameters, and the fracture storage volume we will obtain the tight reservoir carbon dioxide storage volume to monitor carbon dioxide storage efficiency in real time. In conclusion, different from the conventional view the supercritical carbon dioxide induced dynamic fracture network will form a circular zone in the near-well area. The dynamic induced fracture network will extend in the maximum principal stress direction to form an elliptical area. The identification of dynamic induced fracture network characteristics helps guide researchers to set reasonable injection parameters and assess carbon dioxide storage efficiency. The supercritical carbon dioxide induced dynamic fracture network is identified and its physical processes can be described by matching multi-temporal field cases using the DIFN model. The innovative flow regimes demonstrate the directional extension and closure of the fracture network preventing them from being identified as incorrect data. Innovative parameters are used to characterize the induced dynamic fracture network and to calculate the carbon dioxide storage volume and storage efficiency.