Study On Load Spectrum Of Casing During Fracturing Of Shale Gas

The multistage fracturing technology is one of the key technology for shale gas reservoir,which can break down the shale formation through increase energy artificially,so as to improve the flow conductivity of the formation,transform the shale gas from adsorption state into parse state,implement the low porosity and low permeability shale gas reservoir to production transformation.But the casing deformation often appear in the process of multi-stage fracturing,which influences the fracturing effect of shale gas reservoirs seriously.Casing deformation is a new problem that associated with shale gas development.This problem is not well studied both at home and abroad,the reason of the casing deformation is not clear,therefore,definitude the casing load spectrum during multistage fracturing,find out the main factors influencing casing deformation,is of great significance to development of shale gas in ChinaAfter the investigation of the literature at home and abroad,combining the experimental and numerical simulation,the casing load in the process of multistage fracturing is calculated.First of all,according to analyze the cementing quality of horizontal section of shale gas well,and form the finite element models of different cement ring,combining with the construction parameters and the mechanical parameters of casing-cement ring – formation combination,the casing load is calculated under the different cement ring form.Secondly,according to the temperature conduction equation of fracturing fluid-casing-cement ring-formation,calculated the temperature profile of fracturing fluid and the casing in the process of fracturing,on this basis,use the finite element software to calculate the casing load under the coupling of temperature and pressure,comparing with the result which only considering the casing pressure,verify the necessity of considering thermal stress during multi-stage fracturing process when calculating the casing load.Conduct temperature cycle experiments to the cement,measure the relationship between the elastic modulus and the number of temperature cycles,the influence of the cement elastic modulus to casing load is studied by finite element software.Finally,coupling the quality of well cementation,thermal stress and young’s modulus of cement stone change and other factors,calculated the casing load under multi-factor coupling,comparing the calculated results with the actual,found the main factors that influence the casing load.And Put forward the measures to prevent casing deformation in the process of multi-stage fracturing,which can help the popularization and application of multi-stage fracturing technology.