FEASIBILITY OF FORMATION OF COMPLEX FRACTURES UNDER CRACKS INTERFERENCE IN SHALE RESERVOIR FRACTURING
GUO Jianchun1，YIN Jian1，2，ZHAO Zhihong1
(1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation，Southwest Petroleum University，Chengdu，Sichuan 610500，China；2. CCDC Drilling and Production Engineering Technology Research Institute，CNPC，
Guanghan，Sichuan 618300，China)
Abstract：In order to understand the impact of stress interference caused by the artificial open cracks on the formation of complex fractures of subsequent fracturing，and to guide the optimal design of shale fracturing，a model of stress interference of artificial fractures was established based on the homogeneous and isotropic two-dimensional artificial fracture model. The model considered the displacement discontinuity with the cracks of unequal half-lengths，unequal spacing and arbitrary angles of inclination between cracks and horizontal wellbore to study the feasibility of the formation of complex fractures with different perforations，crack parameters and original principal stress on the basis of geostress conditions. The calculated results indicate that the staged multi-cluster perforation and simultaneous multi-cluster fracture initiation have stronger stress interference for developing complicate fractures than the single-stage perforation and single stage fracture initiation do. The longer length the open cracks，the larger the net pressure and the stronger the interference of fracture induced stress，the greater the possibility of complex fractures formation by the subsequent hydraulic fracturing. The optimal crack spacing between the formal open cracks exists for the formation of complex fractures. Besides，if the difference between the original maximum and minimum horizontal principal stress is too large in shale reservoir，then it?s hard to achieve the geostress condition of complex fracture formation effectively even with the crack interference. So，forming complicate fractures by hydraulic fracturing should not be regarded as the main tool of reservoir stimulation.
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2014, Vol. 33 
