Abstract: Shale gas reservoirs have low porosity and low permeability characteristics. One of the best ways to produce gas from shale gas reservoir efficiently is using hydraulic fracturing to create complicated fracture networks. Displacement discontinuity method is employed to set up a mathematical model of two-dimensional induced stress field distribution based on the assumption that the formation is homogeneous and elastic. Through the horizontal stress difference coefficient, fracture spacing has been researched. The results show that the horizontal stress difference coefficient is affected by fracture net pressure, fracture length and in-situ stress field etc. The greater the net stress is, the longer the fracture length is, the smaller the difference coefficient of horizontal stress is. With the increase of fracture spacing, the horizontal stress difference coefficient firstly decreases and then increases. Therefore, there is a best fracture spacing for subsequent fracture to form complicated fracture network. The fracture spacing of consecutive multi-stage hydraulic fracturing should not be too large and subsequent fracture spacing should be suitably reduced. When the fracture spacing of alternate multi-stage hydraulic fracturing is optimal, the horizontal stress difference coefficient between the first two fractures is the minimum, and it provides the most advantages for the third fracture to form more complex fracture networks in the altered stress region.

Key words: shale gas, network fracturing, fracture spacing, displacement discontinuity, induced stress