Numerical simulation of fracture propagation in high-energy gas fracturing of shale reservoir

Abstract

High-energy gas fracturing technology can create radial-shaped fractures through instantaneous high-pressure energy and represents a specialized production enhancement technique aimed at improving oil and gas well productivity. To analyze the fracture propagation mechanism using this technology, this study introduces a stress dependent numerical simulation strategy based on finite element method and discrete fracture network (FEM-DFN). A comparison of simulation results with physical experiments validated the accuracy of the model. The fracture propagation law of High-energy gas fracturing is studied from geological and engineering factors respectively. The results indicate that variations in natural fracture length and orientation significantly influence the propagation direction and morphology of high-energy gas fractures but have minimal impact on reservoir damage. When the angle between the natural fracture and the direction of the maximum principal stress increases, the inhibitory effect on fracture propagation and the activation of natural fractures become more pronounced. For in-situ stress differences ranging from 0 to 20 MPa, high-energy gas fracturing can overcome localized stress concentrations near the wellbore to generate multiple fractures. With the increase of in-situ stress difference, reservoir damage decreases, and the inhibitory effect of High-energy gas fracturing on fractures becomes more pronounced, promoting fracture propagation in the direction of maximum principal stress. For the horizontal section of the horizontal well, the smaller cluster spacing will lead to the intersection of fractures along the wellbore direction, and the number of fractures perpendicular to the horizontal direction will decrease. Smaller cluster spacing and longer explosion section lengths increase the likelihood of downhole accidents; therefore, field construction should design a reasonable explosion section length and cluster spacing to achieve optimal fracturing effects. This research provides theoretical guidance and a scientific foundation for designing schemes in High-energy gas fracturing technology for horizontal wells in shale gas reservoirs.