Prediction and application of lower annular pressure of hanger of ultra-deep horizontal well

During multi-packer segmented transformation of ultra-deep horizontal wells, temperature drop of shaft will cause drop of lower annular pressure of packer of tail tube hanger, which is easy to cause failure of packer of tail tube hanger, packer for lower segmented transformation as well as tubing string. In regard of the structure of horizontal well in typical segmented transformation, the analysis of affecting factors and potential consequences of change of lower annular pressure of packer of tail tube hanger during segmented transformation is developed, and full consideration is taken into for the influence on lower annular pressure of packer of tail tube hanger by annular volume change caused by ballooning effect of tubing string, annular fluid volume change caused by change of shaft pressure and temperature and volume change of tubing string caused by change of shaft temperature to establish a prediction model for change of lower annular pressure of packer of tail tube hanger. An ultra-deep horizontal well of Tarim Oilfield is taken for example to develop prediction for lower annular pressure of packer of tail tube hanger during segmented transformation, and mechanical analysis is developed for packers and tubing strings under transformation on this basis. The analysis results show that, during segmented transformation of ultra-deep horizontal wells, sharp drop of shaft temperature field will greatly lower relative setting conditions of lower annular pressure of packer of tail tube hanger, thus to bring about high risk of failure to tubing strings and packers under transformation. Therefore, it is necessary to take into full consideration of such factors in design of tubing string during segmented transformation of ultra-deep horizontal well.