(1. State Key Laboratory of Coal Mine Disaster Dynamics and Control，Chongqing University，Chongqing 400044，China；2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China)
Abstract：To investigate the propagation characteristics and spatial distributions of hydraulic fractures of tight sandstone，the large real traixial physical model experiment system has been selected to conduct hydraulic fracture tests on the outcrop tight sandstone samples drilled from Xujiahe Group，Jiannan Area. Based on the tests results，the mechanism of crack extension and initiation is exposed and bedding plane with the fracture morphologies has been analyzed. Also，the effects of types and delivery capacity of fracture fluid and differential parameters of in-situ stress on the fracture morphology have been discussed. The results indicate that hydraulic fractures of tight sandstone are easy to extend along one direction and present single-wing style，so they are less likely to form crossover crack network. As to tight sandstone，the rock properties play important roles in controlling initiation and extension mode of fractures. In summary，there are four kinds of hydraulic fracture initiation modes and six kinds of extension mode. And，pumping pressure-time curves can be divided into four types：the 1th curve type is correspinding to single-wing，planar crack；the others are belonged to network crack. The fracture pressure has a linear relation with delivery capacity，and it is irrelevant to differential parameters of in-situ stress. Its worth mentioning that leak-off effect should not be considered unless distilled water is employed as fracture fluid.
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2016, Vol. 35 
