Laboratory Investigation of Hydraulic Fracture Networks in Formations with Continuous Orthogonal Fractures
In recent years,water fracturing attracted the attention of petroleum engineers again with the continuous development of unconventional reservoirs(tight gas,shale gas,coalbed methane etc.).After years of research,people have realized that water fracturing treatments can create complex fractures which increase the “stimulated reservoir volume in naturally fractured formations,or hydraulic fracture networks.However,the mechanism of hydraulic fracture network to be created is not well understood.Laboratory experiments are proposed to study the evolution of fracture networks in naturally fractured formation with specimens containing two groups of orthogonal cemented fractures.The influence of dominating factors was studied and analyzed,with emphasis on natural fracture density and injection rate.In laboratory,we concluded that hydraulic fracture networks are formed by the interactive process between reopening and connecting of the natural fractures through water fracturing in the specimens,indicated by the frequent pressure fluctuations.In contrast to previous researches of ellipse of stimulated reservoir area,assuming unvaried fracture heights,our work shows that the spacial envelope of the fracture network is an approximate ellipsoid with the major axis deviating from the orientation of maximum horizontal stress.From the pressure curve,it is suggested that great natural fracture density and high injection rate tend to raise the treatment pressure.And the injection rate can obviously change the fluid pressure profiles along with natural fractures.Besides,the pressure profiles could reflect different characteristics of extending behaviors.When the rate is small(0.10 ml/s),hydraulic fractures extend steadily,indicated by slow rise of treatment pressures; when the rate is increased to 0.16 ml/s,hydraulic fractures becomes unstable,indicated by repeated fluctuations of treatment pressures; and when the rate is increased further,hydraulic fracture extensions become stable again,with pressure fluctuation reduced in amplitude but raised in frequency.
Hydraulic Fracture Network Injection Rate Natural Fracture Density Naturally Fractured Formation Simulation Experiment
Tiegang Fan Guangqing Zhang
College of Mechanical and Transportation Engineering,China University of Petroleum,Beijing,China College of Petroleum Engineering,China University of Petroleum,Beijing,China
国际会议
桂林
英文
1-16
2013-07-16（万方平台首次上网日期，不代表论文的发表时间）