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The multi-stages in-fracture temporary plugging and diverting fracturing technology (ITPDF) is significant for the stimulation of unconventional oil and gas reservoirs. However, the propagation pattern of hydraulic fracture and the pressure response law after temporary plugging still lacks some understanding affected by many factors. Hence, to deeply understand the fracture diverting propagation mechanism and pressure response law after in-fracture temporary plugging, the study developed first a numerical model of cohesive zone considering in-fracture temporary plugging, seepage and fracture propagation based on the effective viscosity characterization method and the USDFLD (user defined field) subroutine. In addition, the accuracy of the numerical model is verified by comparing with laboratory results. The effect of different parameters such as temporary plugging body permeability, temporary plugging body length, temporary plugging location, temporary plugging times, and stress difference on the temporary plugging and diverting behavior of hydraulic fractures and natural fractures are deeply investigated. The fracture diverting pattern, fracture initiation sequence, and pressure response mechanism are clarified for different in-fracture plugging conditions. The results show that the physical properties of the temporary plugging body are vital to the effectiveness of the in-fracture temporary plugging fracturing. The lower the permeability of the temporary plugging body, the longer the length of the temporary plugging body, and the closer the position of the temporary plugging body, the easier it is to activate the natural fractures. In addition, when there are many natural fractures, the more times of temporary plugging, the more range and number of natural fractures are activated. This study can provide a new method to further understand the fracture behavior after in-fracture temporary plugging fracturing. [ABSTRACT FROM AUTHOR]

In deep underground geotechnical engineering, water–rock interaction emerges as a critical factor influencing the stability of engineering rock masses. This study delves into the macroscopic nonlinear mechanical behavior and fracture characteristics of natural water-bearing and saturated sandstone samples under various true triaxial stress states. The objective is to systematically elucidate the impact of actual three-dimensional stress conditions and water content on the mechanical behavior and fracture mechanisms of sandstone formations. The findings reveal significant anisotropic deformation in sandstone under 3D stress, while saturated sandstone exhibits robust plastic deformation capacity. Moreover, changes in the strain ratio coefficient are identified as precursors to rock fracture. The dilatation behavior of sandstone weakens progressively with increasing σ2, indicating reduced expansion in saturated sandstone. To account for the influence of σ2, a novel dilation index is proposed. The true triaxial strength of sandstone demonstrates a close relationship with both σ2 and water content, with strength initially increasing before declining as σ2 rises. In addition, water significantly undermines sandstone strength, although this weakening trend moderates with increasing σ2. Morphological analysis and SEM observations unveil three-dimensional volume fracturing characteristics in rock fractures, primarily characterized by shear accompanied by tensile fractures. Saturated sandstone samples, in contrast, exhibit numerous tensile and intergranular fractures. Overall, this study holds paramount practical significance for the evaluation of rock stability and the design of water-bearing engineering rock masses, encompassing domains, such as geology, water conservancy, and mining. [ABSTRACT FROM AUTHOR]