Simulation and optimization of fracture pattern in temporary plugging fracturing of horizontal shale gas wells

Abstract

Horizontal well-staged fracturing is a key technology for efficient shale gas production. However, stress shadows between clusters make it difficult to synchronize the initiation and expansion of hydraulic fractures in multi-cluster fracturing. Mine practice has shown that the use of temporary plugging fracturing can promote the balanced expansion of the multi-fractures. This study establishes a numerical model for fracture-opening temporary plugging fracturing based on the three-dimensional discrete lattice method. Then, the impacts of perforation cluster spacing, stress difference, temporary plugging timing, amount of temporary plugging balls (TPBs), and temporary plugging times on the expansion pattern of multi-fractures were simulated. Additionally, the effectiveness of temporary plugging was further verified by laboratory experiments and mine site experiments. The result shows that, decreasing the cluster spacing can significantly increase the extension range of hydraulic fractures, but the uneven propagation of fractures is severe. Meanwhile, the fracture volume differentiation coefficient gradually increased with the increase of the stress difference. When the temporary plugging timing is 2/3 of the overall fracturing duration, the fracture clusters expand evenly and the fracture volume differentiation coefficient reaches the minimum value. Moreover, as the quantity of TPBs increases, the fracture volume differentiation coefficient first decreases and then increases. Finally, to increase the effectiveness of temporary plugging fracturing, the times of temporary plugging should be minimized. The results of this research can help optimize temporary plugging fracturing in shale gas reservoirs.