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Numerical analysis of the effect of natural microcracks on the supercritical CO 2 fracturing crack network of shale rock based on bonded particle models
Author(s) -
Peng Peihuo,
Ju Yang,
Wang Yongliang,
Wang Shaoqin,
Gao Feng
Publication year - 2017
Publication title -
international journal for numerical and analytical methods in geomechanics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.419
H-Index - 91
eISSN - 1096-9853
pISSN - 0363-9061
DOI - 10.1002/nag.2712
Subject(s) - supercritical fluid , hydraulic fracturing , fracture (geology) , oil shale , geotechnical engineering , materials science , geology , mechanics , thermodynamics , paleontology , physics
Summary 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 CO 2 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 CO 2 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 CO 2 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 CO 2 fracturing is more uniform than that of common hydraulic fracturing when the horizontal stress ratio is small.