3-D FEM Azimuth Forward Modeling of Hydraulic Fractures Based on Electromagnetic Theory

Accurate monitoring of hydraulic fracturing fracture morphology is of great significance to the follow-up exploration and development work. Electromagnetic monitoring of fractures can effectively identify the effective propped volume (EPV) of fracturing fractures, making up for the disadvantages of other monitoring methods. This letter introduces a modeling method and a physical model based on very-low-frequency (VLF) electromagnetic scattering theory for monitoring the development of asymmetric fracturing fractures. The 3-D finite-element method (FEM) of equivalent fracturing fracture on transition boundary condition (TBC) surface is used to realize the fast forward modeling of 3-D space receiving response in large formations. A sector-shaped receiver is designed and the relationship between electromagnetic receiving signals and orientation parameters of asymmetric fracturing fractures, such as direction of fracture development and tilt angle, is discussed. By analyzing 3-D signals obtained from the rotating receiver sector, the spatial state of multiple asymmetric fracturing fractures can be determined. The problem of how to identify the 3-D direction of crack growth with electromagnetic monitoring method is solved, which provides a theoretical reference for the development and inversion of detection instruments.