Study On The Preferred Method Of Casing In Salt Layer Of Tahe Oilfield

Due to the casing sleeve risk in casing273.1mm pipe in salt formation in the X block of the Tahe oil field, multiple reaming operations for salt formation are required, severely reducing the drilling efficiency. In the meantime, the206mm casing also triggered damage in this formation before. Research results show that the main reason for salt formation damage is the rheological effects. Therefore, for the choice of salt formation, it is necessary to accurately calculate the load at different time during the oil well life period. In this thesis, the viscoelastic theory, based on the field drilling and logging data, combining elasticity and viscoelasticity method, is used to analyze the wall displacement reducing rule and the rheological load distribution. The fourth strength theory is used to analyze the casing of TP155V and TP140V wear safety, and the results are further applied to the choice of the salt formation casing in the Tahe oil field. The main research contents and conclusions in this thesis as shown as following:(1) Based on the viscoelastic theory and the measured data of well diameter, the calculation method for the salt formation viscoelastic rock mechanics parameters is proposed. This method is applied to analyze the well wall displacement reducing pattern. Research shows that improving the drilling mud density up to1.70g/cm3can effectively reduce the well wall displacement speed.(2) Proposed the salt formation and casing mechanical model based onthe Kelvin viscoelastic model, and acquired the analytic solution for the salt formation casing. Research results show that increasing the cemented ring thickness can reduce the casing load, but the effect of the cemented ring with the thickness increasing gradually decreases. When the cemented ring thickness is relatively small, the casing load will be larger than the situation without cemented ring.(3) Proposed the casing strength evaluation method based on the fourth strength theory. Analysis shows that without cemented ring, the TP155V casing is8%safer than the TP140V casing; when the cemented ring thickness is10mm, the two casing nearly have the same safety in salt formation. Therefore, compared to TP140V, TP155V casing is more suitable for the Tahe oil field formation.