In this study, an improved version of the Simplified 3D Displacement Discontinuity Method (S3D DDM) is introduced which can be used to simulate single and multiple fracture problems in a layered formation. The developed model is then used to predict the geometry of hydraulic fractures, and to characterize the stress shadowing effect between fractures with variable heights and vertical offsets. Similar to the original S3D DDM, 3D correction factors are used to calculate the normal and shear displacements along the fracture length. For this improved version, the original 3D correction factors are modified to account for fractures with nonuniform height along the length direction. A stress correction factor is employed to calculate the influence of stress contrast between layers on fracture opening. Static simulation results from the improved model compare favorably with reference analytical solutions for penny-shaped fractures and with fully 3D numerical solutions. While the fully 3D model requires discretization in both lateral and vertical directions, the simplified model requires only a single row of elements in height, resulting in considerably lower computation time and memory utilization without a loss of accuracy.

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