抄録
To clarify the effects of the viscosity of the hydraulic fluid and the weak planes of the rocks on the fracture creation, the hydraulic fracturing experiments were conducted on 15 cm-cubic Inada granite and Ogino tuff with the fracturing fluids of water and the super critical carbon dioxide. The borehole was bored in the perpendicular direction of the rift or bedding planes. Two horizontal stresses of 5 and 3 MPa and the vertical stress of 1 MPa were applied to the specimens. The vertical single fracture along the borehole was created in the specimen by the injection of water, while multiple complicated fractures along the rift or bedding planes were tended to be created by the injection of the super critical carbon dioxide. The numbers of the fracture branches obtained for the super critical carbon dioxide were greater than those obtained for the water. These results suggest that both the viscosity of the hydraulic fluid and the weak planes of the rocks significantly influence the formation of hydraulic fractures.
