Optimal spacing of sequential and simultaneous fracturing in horizontal well

• The simulation of fracture network produced by sequential and simultaneous fracturing is presented.
• Optimal spacing for sequential and simultaneous fracturing can be calculated by our model.
• In-situ stress contrast plays a significant role on complex hydraulic fracturing network.

Sequential and simultaneous fracturing are two main fracturing methods for creating multiple hydraulic fractures in horizontal wells. The fracture spacing of these two fracturing scenarios is critical for creating fracture network to improve unconventional gas or oil reservoirs production. In this paper, a fully coupled (flow and mechanics) hydraulic fracture propagation model based on extended finite element method (XFEM) is established to account for the sequential and simultaneous propagation of nonplanar fractures. By mapping the distribution of in-situ stress contrast during fracturing process, we calculate the fracture network area that is the extent of low in-situ stress contrast zones. The fracture spacing that satisfies the requirement of preventing sand plug as well as creating large field of fracture network is optimal. Sensitivity studies have been conducted for optimal spacing. It is shown that optimal spacing will decrease with in-situ stress contrast, and is not sensitive to varying Young's modulus of the rock matrix. The method presented in this paper can be used in horizontal well design to estimate reasonable fracture spacing.