Numerical Investigation of Multiple Non-Planar 3D Fracture Propagation and Proppant Transport in Horizontal Wells
Authors: Peng Yang , Shicheng Zhang , Yushi Zou , Xinfang Ma , Xiaohuan Zhang , Li Liu , Wenchao Wang 
Published: August 2024

ABSTRACT:
Multi-stage and multi-cluster fracturing techniques are beneficial to enhance the flow capacity of unconventional oil and gas reservoirs to promote economic productivity. However, in-situ stress heterogeneity and the geomechanical interactions of densely spaced fractures could result in fracture curving, intersection, and uneven growth, which poses challenges to the fracturing optimization and sustainable development of reservoirs. In this work, a coupled fracturing model considering both non-planar 3D fracture propagation and proppant transport is established based on the displacement discontinuity method (DDM) and Eulerian-Eulerian framework (E-E), which considers perforation erosion, dynamic flow rate distributions in wellbore, fracturing fluid leak-off, stress interactions, proppant settling, and proppant bridging. The numerical results show that most hydraulic fractures propagate as Perkins-Kern-Nordgren (PKN)-like geometries due to the limitation of stress barrier layers, and the growth of interior fractures is stunted under the influence of compressive stress field induced by outer fractures, while the outer fractures deviate from the direction of maximum horizontal stress to avoid strong stress shadowing. Large horizontal stress differences are beneficial to mitigate stress interference, suppress out-of-plane deflection of fracture path, and reduce the risk of fracture communication and coalescence. Besides, in-situ stress heterogeneity increases the possibility of fracture curving and intersection. Specifically, when the minimum horizontal stress is not parallel to the wellbore axis, hydraulic fracture growth will deflect because the fracture preferentially propagates in the direction of the maximum principal stress. The evolution areas of in-situ stress caused by parent-well production or infill well fracturing may attract or hinder hydraulic fracture growth, resulting in asymmetric fracture geometries and proppant distribution.

1. INTRODUCTION
Horizontal wells combined with hydraulic fracturing is an indispensable technique for the sustainable development of unconventional oil and gas reservoirs (Zou et al., 2023). In the process of oil and gas development, the fluid production or injection of parent wells will induce significant three-dimensional stress reorientation and redistribution in reservoirs, which directly governs the fracture growth in the new well (Kumar and Ghassemi, 2021; Pei et al., 2022). For example, hydraulic fracturing field tests (HFTS) supported by advanced measurements have shown that the fractures of child wells will preferentially propagate towards the pressure depletion zones caused by parent-well production and then trigger fracturing hits, resulting in compromised stimulated volume of child wells and reduced production of parent-wells (Tan et al., 2021; Ugueto et al., 2021). Therefore, the heterogeneous distribution of the in-situ stress field has an important effect on fracture propagation.