Mechanics Mechanism of Re-fracturing Propagation and Reorientation in Low Permeability Reservoirs

Hydraulic fracturing is an important EOR technology of low permeability reservoirs which occupy a considerable proportion in China's oil reserves. If hydraulic fracturing fails, re-fracturing will be used in most oil-water wells. However, there are often a large number of inclusions in low-permeability reservoirs. Due to the complexity of the re-fracturing mechanism in low permeability reservoirs, the theoretical researches are far behind the field practices. Theoretical and experimental studies on the mechanical mechanism of re-fracturing are significant for the development of inclusion reservoirs. Ground stress distribution is one of the major factors which affect fracture propagation after re-fracturing. In this paper line inclusion is seen as a thin bar, and the basic solution of elastic mechanics for line inclusion in infinite plane is used to solve the stress field. Stress field around artificial fracture which is influenced by single line inclusion is deduced. The interference problem of single line inclusion and artificial fracture under internal pressure is reduced to a set of Cauchy singular integral equations. In addition, a validation test with a large size (500mmx500mmx500mm) true tri-axial test equipment is carried out. The results show that, the inclusions reduce rock intensity, and induce reservoir to generate more complex fractures.