Development of 3‐D Curved Fracture Swarms in Shale Rock Driven by Rapid Fluid Pressure Buildup: Insights From Numerical Modeling

• Published in: Geophysical research letters 2021-04, Vol.48 (8), p.n/a
• Main Authors: Li, Sanbai, Zhang, Dongxiao
• Format: Article
• Language: English
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL092638

Despite the variety of studies that have investigated the development of fracture networks during kerogen maturation in organic‐rich shale, the fracture interaction modes and generation mechanisms in three‐dimensions are not yet fully understood. In this study, we introduce a novel numerical approach to model the evolution of fracture swarms with three‐dimensional nonplanar geometries. This model enables precise simulation of the propagation, interplay, and coalescence of the fracture swarms with variable apertures and geometries via solving fluid flow, fracture growth, and stress interference. Our results suggest five basic fracture interaction modes between neighboring fractures. The evolving fracture swarms exhibit simultaneous, alternant, and differential growth characteristics at different development phases. We also elucidate the mechanical mechanisms that determine the evolution of three‐dimensional curved fracture swarms. This work yields an improved understanding of fluid‐driven fracture swarms' development in organic‐rich shale due to rapid fluid generation. Plain Language Summary Rapid pressure increase due to fluid generation or fluid injection in pores of rock may promote the extension of multiple fractures, which is a common issue involved in natural geological processes and geo‐resources development. However, how the grown fractures interact with each other in three‐dimensions and why these fractures tend to develop into curved, interconnected geometries remain poorly understood. Here, we introduce a novel computer algorithm to accurately simulate the growing process of three‐dimensional fracture arrays with evolving fracture apertures and geometries. It is found that there are five basic fracture interaction modes that support the fracture arrays to form complex geometry and topology in three‐dimensions during fluid generation in shale rock. Through modeling, we also demonstrate how the stress in shale rock governs the growth of fracture arrays. This study results in a better understanding of fracture generation and oil/gas transport in unobservable subsurface rock. Key Points Development of three‐dimensional nonplanar fracture swarms due to kerogen maturation in organic‐rich shale is numerically simulated Five basic fracture interaction modes are proposed to understand the patterns of geomechanically grown fracture swarms in three‐dimensions Mechanical mechanisms that determine the simultaneous, alternant, and differential growth of curved