Calculation model on hydraulic fracturing time in gas vertical well based on PKN analysis
WANG Zhirong
GUO Zhiwei
HE Ping
CHEN Lingxia
Abstract：Hydraulic fracture is one of the most effective methods to improve productivity of low permeability coal seam vertical well.In order to explore the time effect of interaction between gas and rock,and to explore the fracturing time evolution rule in gas containing soft coal seam,according to the stress characteristics of ver-tical wells,a model of initiation fracture pressure was set up on the base of elastic mechanics theory.Consider-ing the influence of damage to the coal/rock body,the model of extension stress was established by taking dam-age factor into account.Combination of the nonlinear dropping pressure law of net pressure in crack extension, extension pressure calculation model and the classic PKN model,a new model of crack extension was estab-lished,which reflects the functional relationship between fracture time t and fracture radius L.The results of case study in Jiaozuo mines show that,when the fracture time is 40~60 min,the corresponding fracture radius can reach to 88.04~108.75 m.The theoretical value was consistent with the field monitoring data,which pre-liminarily proved the validity of the model.The conclusions provide a solid theoretical basis for the actual con-struction control and groundwater environment protection in mining area.
Keywords：gas vertical wellgas-containing soft coalextension pressurefracture extending modelfracturing time
Publication Date：2018-07-02
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：7( 24-30 )