Numerical analysis of the effect of natural microcracks on the supercritical CO2 fracturing crack network of shale rock based on bonded particle models |
| |
| Authors: | Peihuo Peng Yang Ju Yongliang Wang Shaoqin Wang Feng Gao |
| |
| Affiliation: | 1. School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing, China;2. School of Sciences, Beijing University of Civil Engineering and Architecture, Beijing, China;3. State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining & Technology, Xuzhou, China;4. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing, China |
| |
| Abstract: | The problem of predicting the geometric structure of induced fractures is highly complex and significant in the fracturing stimulation of rock reservoirs. In the traditional continuous fracturing models, the mechanical properties of reservoir rock are input as macroscopic quantities. These models neglect the microcracks and discontinuous characteristics of rock, which are important factors influencing the geometric structure of the induced fractures. In this paper, we simulate supercritical CO2 fracturing based on the bonded particle model to investigate the effect of original natural microcracks on the induced‐fracture network distribution. The microcracks are simulated explicitly as broken bonds that form and coalesce into macroscopic fractures in the supercritical CO2 fracturing process. A calculation method for the distribution uniformity index (DUI) is proposed. The influence of the total number and DUI of initial microcracks on the mechanical properties of the rock sample is studied. The DUI of the induced fractures of supercritical CO2 fracturing and hydraulic fracturing for different DUIs of initial microcracks are compared, holding other conditions constant. The sensitivity of the DUI of the induced fractures to that of initial natural microcracks under different horizontal stress ratios is also probed. The numerical results indicate that the distribution of induced fractures of supercritical CO2 fracturing is more uniform than that of common hydraulic fracturing when the horizontal stress ratio is small. |
| |
| Keywords: | bonded particle model (BPM) distribution uniformity index (DUI) mechanical properties natural microcracks supercritical CO2 fracturing |
|
|
