Large scale experimental simulation and analysis of interlayer stress difference effect on hydraulic fracture extension

Horizontal geostress difference between reservoir and caprock is the main controlling factor for hydraulic fracturing height growth. A large scale full 3D hydraulic fracturing experiment system was used to simulate the geostress conditions of reservoir and caprock; simulation experiment was conducted to vertical growth of hydraulic fracturing for Chang-6 sandstone in Changqing Oilfield, and full 3D real-time acoustic monitoring was accomplished to internal fracture growth in large-size rock samples. A discussion was made regarding the effect interlayer stress difference, job parameters (flow rate, viscosity) and job pressure on vertical growth of fractures by comparing the results of acoustic monitoring and actual fracture geometry. The results show that fracture height is evidently controlled by interlayer stress difference; meanwhile, the job parameters will also affect the vertical growth of fractures, and fracturing with high-viscosity fluid is favorable for extension of fracture height; for homogeneous tight sandstone samples, real-time acoustic monitoring technique can effectively monitor the fracture growth conditions. This paper provides an experimental approach for the study on fracture height extension mechanism and also provides a reference for field micro-seismic monitoring.