Numerical study on the multi-stage blasting in horizontal well to enhance the permeability of deep reservoir

Blasting fracturing technique has developed into a most promising option replacing the hydraulic fracturing for enhancing the permeability of deep formation in the resource exploitation. At present, blasting-enhanced permeability mostly focus on the blasting-inducing fractures in vertical well. Thus, this paper emphatically studies the issues associated with the multi-stage blasting in horizontal well. In this work, a numerical rectangular-solid model consisting of 64000 elements has a size of 100 x 10 x 8 m (L x W x H) is established based on the finite-difference method to simulate a uranium resource reservoir in the Xinjiang Autonomous Regions, China. A horizontal well with the diameter of 20 cm and the length of 100.0 m is located at the center of this model. The shock wave resulted from the explosive detonation is simulated as a time-varying pressure applied to the wall of the well borehole. Four modes of the multi-stage blasting are investigated with the consideration of different in-situ stress conditions. The results show that multi-stage blasting has great effect on the rock damage and blasting-enhanced permeability, while the in-situ stress condition can not be an ignored factor in this affection. For relatively large compressive in-situ stress, 1-stage blasting is a recommended mode for improving the permeability of rock reservoir. However, for relatively small in-situ stress, the permeability of rock reservoir increase first and then decrease along with the increasing of subsections of multi-stage blasting. There must be an optimal mode of multi-stage to improving the permeability of rock reservoir.