Study About Evaluation Method Of Frac-string Tripping Ability In Horizontal Well

Currently,fracturing technology in horizontal well has been widely applied in unconventional petroleum.However,because of complex structures,that frac-string tripping in long horizontal well is essential for fracturing operation.In the article,basic composition and structural features of horizontal well frac-string are introduced,and suitable condition of each kind of frac-string are also pointed out.The bending deformation deflection calculation model of bending section and level section is set up,and method for judging the new contact point is also put forward,analysis results indicate that frac-string between packers is easy to contact with the under side of the borehole and then generate additional friction.Calculation model of fractional resistance for string with packer or not is set up,and friction model of frac-string,soft-string model are compared with the actual frictional resistance through example of a well in Jilin oilfield,results show that friction model of frac-string considering stiffness and packer is more close to the actual frictional resistance.Considering the basic effect in the whole process of fracturing construction,mechanics and axial deformation analysis of frac-string are made.Considering various forces in fracturing construction,the basic formula of strength check is provided.On the basis of analysis of mechanics and friction,the evaluation method of frac-string's tripping ability in horizontal well is established,that is to say,judging criteria and analytical method of tripping ability are presented.And through examples of T825 well,the results show that frac-string can trip in the expected depth.Frac-string's tripping ability is analyzed by established evaluation method,results show that hole curvature and tubing combination are main influence factor of frac-string's tripping ability.The fracturing operation is made through the example of T825 well.Results indicate thatfrac-string's maximum stress point is located in wellhead and packer.Wellhead is dangerous position on account of maximum force with frac-string reaching or leaving the bottom of the well,and packer is dangerous position on account of maximum force with hydraulic setting or injecting fracturing fluid.On the basis of theoretical method,the software which is used to analyze frac-string's tripping ability and make strength check is compiled by means of Visual Basic 2012.It brings an important guidance to safe fracturing construction.