| Abstract: According to daqing oilfield chao103-73well,zhao66-40, South1-11-P023wells,la153well’s completion and geological data base profiles, reservoir characteristics, thestring combination of fracture, drilling out and gas lift jobs are designed.Based on the wellhead equipment components of workover treatment under pressure, theelastic bending and inelastic bending critical load are derived. The calculation method ofcritical load for unsupported and the maximum downward force are established in this paper.It will provide a theoretical basis for choosing workover operations scientifically. Based onthe above calculation method, the critical bending loads of S-9SnubCo press workingmachine with three columns is calculated. It was obtained that with the same course, themaximum bending load was the31/″2column, followed by the27/″8column, the minimumwas the23/″8column. In the same well depth and control conditions, the critical bending loadis reduced with wellhead pressure increased. With the well depth increased, the string hangingweight increased, but the downward force was decreasing before the neutral point and theallowable course was also increasing. The operation pipe strings in bore hole was selected asresearch object. Considering different wellbore parameters, the mechanical model wereestablished about picking up, landing and operating conditions. The work string was scatteredinto a number of beam elements and gap element was adopted to simulate the random contactstate for string and the casing wall. A finite element analysis method was established in thispaper. With calculation for chao103-73Wells, zhao66-40well, South1-11-P023wells,153wells, the strength datas about axial force, axial stress, equivalent stress and safety factorswere obtained. The combination of column design can meet the job requirements. Therefor,the analysis methods established in this paper can provide a theoretical basis for the theoperation of workover treatment under pressure. |
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