Study on the Optimization of Displacement in Hydraulic Fracturing of Shale Gas Reservoir

Two matters is often encountered in shale gas reservoir when hydraulic fracturing: (1) unlocking of naturally fractures leads to the increasing of leak-off; (2) the producing of multi-fractures induces friction resistance to bring. So tit is important to optimize the size of displacement. Generally speaking, several question should be considered :(1) There is always a turning point of optimum capacity in a well to be fractured;(2) The size of leak-off, displacement must satisfy leak-off brought by natural fractures;(3) The size of single fracture width; (4) Fracture height; (5) pipe string resistance; (6)The turning trace of fracture; (7) The joining up of fractures; (8) The relation between displacement and excessive fluid loss. All the factors should be considered to optimize displacement. The examples of its application are given.