Numerical study on the propagation mechanism of the water-induced fracture during water injection for low-permeability reservoirs
Yuan JI , Yan PENG , Zhangxin CHEN , Keliu WU , Xiaohan WANG , Peihong LYU
Front. Earth Sci. ›› 2026, Vol. 20 ›› Issue (3) : 553 -570.
Low-permeability reservoirs are globally significant oil and gas resources and their recovery can commonly be enhanced by water injection technology. However, water-induced fracture (WIF) is caused by water-rock interactions during long-term water injection. Their rapid propagation leads to premature water breakthroughs between injection and production wells. Traditional research has often ignored water-rock reactions, leading to an insufficient theoretical foundation for controlling water breakthrough risks. Based on damage mechanics theory, this study established a comprehensive numerical model coupling two-phase flow, water-rock interactions, rock deformation, and fracture propagation. By introducing a rock hydration coefficient (Kw) to quantitatively characterize the effect of hydration on rock mechanical properties, the mechanism of WIF propagation and its controlling factors are systematically revealed. The results demonstrate that: 1) Water-rock interactions exacerbate reservoir heterogeneity, altering geomechanical properties such as Young's modulus and leading to stress redistribution. The stress at the fracture tip can be reduced by up to 18.2%; 2) Water-rock reactions significantly influence WIF propagation. Compared to low hydration states, The propagation rate of WIF increases by 12 times under high hydration conditions (Kw>0.5); 3) In order to avoid rapid WIF propagation, fracture spacing between production and injection wells should exceed 180 m, injection pressure should be 12.5% lower than the minimum horizontal stress, and the viscosity of injection fluid should be increased to over 10 cp. These measures effectively control fracture connectivity risks and avoid water breakthrough.
low-permeability reservoirs / water-induced fracture / two-phase flow / rock hydration / coupled modeling / stress redistribution
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Higher Education Press
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