Abstract
In double fracturing, in contrast to the case with hydraulic fracturing where a peak pressure appears at the point of fracture initiation, the fracture length increases with a further increases in the loading pressure beyond the point of fracture initiation. Angular distribution of tangential stress around borehole boundary then changes with the fracture length and tangential stress at the points distant from the primary fracture approaches the tensile strength there and secondary fracture initiation occurs. The double fracturing system called S-100 has already been developed by the authors, being based on the above fact. This paper describes outline of the system and demonstrates applicability of the stress determination procedure employed in the system. For the demonstration, precise elastic analyses by a Boundary Element Method, the coupled Fictitious Stress and Displacement Discontinuity Methods, were carried out for crack models in consideration of stress intensity factor at crack tip.
