Influences on unstable hydraulic fractures: propagation of adjacent multiple perforations and bedded interfaces in multilayered reservoir via FE-DE model

Abstract

PurposeSimultaneous hydrofracturing of multiple perforation clusters in vertical wells has been applied in the stimulation of hydrocarbon resources reservoirs. This technology is significantly impeded due to the challenges in its application to the multilayered reservoirs that comprise multiple interlayers. One of the challenges is the accurate understanding and characterization of propagation and deflection of the multiple hydraulic fractures between reservoirs and embedded interlayers.Design/methodology/approachNumerical models of the tight multilayered reservoirs containing multiple interlayers were established to study hydrofracturing of multiple perforation clusters and its influencing factors on unstable propagation and deflection of hydraulic fractures. Brittle and plastic multilayered reservoirs fully considering the influences of different in situ stress ratio and physical attributes for reservoir and interlayer strata on propagations of hydraulic fractures were investigated. The combined finite element–discrete element method and mesh refinement strategy were adopted to guarantee the accuracy of stress solutions and reliability of fracture path in computation.FindingsResults show that the shear stress fields between adjacent multiple hydraulic fractures are superposed to cause fractures deflection. Stress shadows induce the shielding effects of hydraulic fractures and inhibit fractures growth to emerge unstable propagation behaviors, and a main single fracture and several minor fractures develop. As the in situ stress ratio increases, hydraulic fractures more easily deflect toward the direction of maximum in situ stress, and stress shadow and mutual interaction effects between them are intensified. Compared to brittle reservoir, plastic-enhanced reservoir may limit fracture growth and cannot form long fracture length; nevertheless, plastic properties of reservoir are prone to induce more microseismic events with larger magnitude.Originality/valueThe obtained fracturing behaviors and mechanisms based on engineering-scale multilayered reservoir may provide effective schemes for controlling and estimating the unstable propagation of multiple hydraulic fractures.

Numerical Simulation Study on the Effect of Preinjected CO2 on the Hydraulic Fracturing Behavior of Shale Oil Reservoirs

“…This model aims to elucidate the fracturing behaviors of shale formations after CO 2 soaking. By incorporating a model that accounts for the seepage of fracturing fluid, the effects of fluid–structure interaction, and the adaptive local remeshing strategies at crack tips, it is possible to analyze the stimulated reservoir volume of shale oil with heightened precision. − …”

Deflection of Hydraulic Fractures and Shear Stress Disturbance Considering Thermal Effects: A Numerical Case Study

“…By using numerical methods (such as the finite element method, displacement discontinuity method and boundary element method) and models, the interaction between the fracture network and stress shadow effect were quantitatively analyzed, and the mechanisms of fracture initiation, propagation and disturbance were investigated [27][28][29][30]. Besides, some high-performance mesh optimization models were developed and applied recently [31]. In this study, a field-scale 3D numerical model of multistage hydrofracturing of a horizontal well is developed for the numerical case study of fracture deflection and shear stress disturbance considering thermal effects, and the typical perforation cluster spacing is set to study the influences of cluster spacing on fracture deflection and stress shadows.…”

Spatial Deflection of Parallel Hydraulic Fractures and Induced Shear Stress Disturbance Under Different Perforation Cluster Spacing Considering Thermal Effects

“…By using numerical methods (such as finite element method, displacement discontinuity method and boundary element method) and models, the interaction of fracture network and stress shadow effect are quantitatively analysed, and the mechanisms of fracture initiation, propagation, and disturbance are investigated (Kresse et al, 2013;Paluszny et al, 2013;Taghichian et al, 2014;Kumar and Ghassemi, 2016). Besides, some high-performance mesh optimization models have been developed and applied (Wang et al, 2021).…”