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• In fluence of stress shadow on multi-clusters fracturing was analyzed. • The proppant transport and placement were considered in the model. • Multiple cluster hydraulic fracturing in multiple horizontal wells was simulated. Multiple cluster hydraulic fracturing is widely used in the development of shale reservoir. The morphology of multiple fractures propagating from multiple cluster is complex due to the stress shadow effect. The design and operation of multiple cluster hydraulic fracturing in horizontal wells require adequate knowledge of the effect of different factors, including rock properties, in-situ stresses and fluid properties on the fracture morphology. In this paper, lattice simulation, a new particle based computational method was used to investigate the multiple cluster hydraulic fracturing in shale. The results showed that stress anisotropy and cluster spacing play an important role on geometry of the propagating fracture. The middle hydraulic fracture is restricted to propagate when cluster spacing is decreased. Simultaneous, two-step and sequential fracturing scenarios in a single horizontal well were simulated. The simultaneous and sequential fracturing showed to mainly affect the fracture propagation morphology with little effect on fracture length, while the middle fracture is shorter than its two side fractures in two-step fracturing. In two horizontal models, the simultaneous and sequential fractures showed similar morphology during multiple cluster hydraulic fracturing. In term of stimulated reservoir volume (SRV), zipper fracturing showed the largest SRV during multiple cluster hydraulic fracturing in two horizontal wells. [ABSTRACT FROM AUTHOR]

To understand the fracture behavior for variable density in-plane perforations on a horizontal well, true triaxial hydraulic fracturing experiments were performed with acoustic emission monitoring. The experimental results indicate that the variable density in-plane perforations can not only create transverse fractures but also arrest fracture propagation toward undesirable zones. The in situ stress and treatment parameters play significant roles in the fracture morphology and breakdown pressure. Under a large horizontal principal stress difference, there is a high possibility for simple transverse fracture creation, which results in a lower breakdown pressure. Moreover, the decrease in fracturing fluid viscosity can increase the fracture complexity and increase in pump rate can increase breakdown pressure and induce the complex fracture geomtetry. The acoustic emission (AE) characteristics and cutting fracture morphology demonstrate that not all perforations can be successfully initiated during the fracturing process. Because of the stress interaction from side perforations, fracture initiation and propagation from the middle perforation are strongly suppressed. Although the middle fracture is not fully initiated and propagated, it is still beneficial for the side hydraulic fracture connection and propagation in one plane. Secondary and axial fractures can still be observed, primarily due to the stress interaction between neighboring perforations and misalignment of the perforation tunnel orientation with the principal stress direction. In addition, the creation of complex fractures tends to occur using a high pump rate, which relates to tense fluid distribution competition from each perforation tunnel. Fracture initiation may follow an order but mostly tends to initiate from side perforations. Because of the stress interaction, hydraulic fractures from the side perforation can sometimes deviate from the perforation tunnel direction, twist and kink, and finally, generate nonplanar fractures. A large horizontal principal stress difference is recommended and beneficial for simple, straight and planar fracture creation during hydraulic fracturing stimulation with variable density in-plane completion for the horizontal well. • The application of local in-plane perforations can control the fracture path and complexity. • Tri-axial fracturing experiments were conducted on tight rock samples with local in-plane perforations. • The change in fracturing fluid viscosity and pump rate can alter the fracture path between perforations. • The connectivity of neighboring fractures can lower the breakdown pressure. [ABSTRACT FROM AUTHOR]