TY  - EJOU
AU  - Qian, Manqing 
AU  - Chen, Xiyu 
AU  - Li, Yongming 

TI  - Numerical Investigation of Stress and Toughness Contrast Effects on the Vertical Propagation of Fluid-Driven Fractures in Shale Reservoirs
T2  - Fluid Dynamics \& Materials Processing

PY  - 2025
VL  - 21
IS  - 6
SN  - 1555-2578

AB  - Shale reservoirs are characterized by numerous geological discontinuities, such as bedding planes, and exhibit pronounced heterogeneity across rock layers separated by these planes. Bedding planes often possess distinct mechanical properties compared to the surrounding rock matrix, particularly in terms of damage and fracture behavior. Consequently, vertical propagation of hydraulic fractures is influenced by both bedding planes and the heterogeneity. In this study, a numerical investigation into the height growth of hydraulic fractures was conducted using the finite element method, incorporating zero-thickness cohesive elements. The analysis explored the effects of bedding planes, toughness contrasts between layers, and variations in <i>in-situ</i> stress across different strata. The results reveal that hydraulic fractures are more likely to propagate along bedding planes instead of traversing them and extending vertically into barrier layers when (1) bedding strength is low, (2) stress contrast between layers is high, and (3) toughness contrast is significant. Furthermore, for a given bedding strength, increased stress contrast or higher toughness contrast between layers elevate hydraulic fracture extension pressure. When a substantial stress difference exists between layers (<i>L</i><sub>c</sub> = 0.4), hydraulic fractures preferentially propagate along bedding planes. Conversely, as bedding strength increases, the propagation distance along bedding planes decreases, accompanied by an amplified horizontal compressive stress field. Notably, when the stress difference is sufficiently small (<i>SD</i> < −0.2), a phenomenon termed “stress rolling” emerges, wherein hydraulic fractures deviate from vertical growth and instead extend along a near-horizontal trajectory.
KW  - Fluid-driven fracture; hydraulic fracturing; fracture height growth; cohesive element; bedding planes

DO  - 10.32604/fdmp.2025.061652