Observing the effects of transition zone properties on fracture vertical propagation behavior for coal measure strata

摘要: Abstract The transition zone is a typical interface with enough thickness and high heterogeneity between the sandstone coal has great effect on fracture propagation in measure strata. In study, true tri-axial experiments were conducted combination of sandstone, limestone outcrops. cementing strength was mainly studied. Three types hydraulic initiation positions used to simulate three fracturing situations field. results showed that vertical extension could be concluded: easy cross or slip low turned inside strength; tended branch blocked by thick zone. horizontal flow through face cleats natural activation contributed more developed network. characters pumping curve pressure “increasing – fluctuation dropping”, “fluctuation than pressure” indicated crossing. agreed previous numerical simulation helped optimize design layered