Research On Prediction Model Of Temperature And Pressure Distribution In Wellbore Of High Temperature And High Pressure Gas Well

The development of high temperature and high pressure gas reservoir has not been a long time in China.In order to realize efficient development of gas reservoir,dynamic monitoring of gas reservoir should be done well.Due to the extremely high downhole temperature and pressure,it is difficult to directly test downhole pressure and temperature.Usually,the wellhead test data is adopted and the wellbore temperature and pressure calculation model is used to predict the pressure and temperature distribution of the wellbore.At present,there are some difficulties in the calculation of bottom hole temperature and pressure in high temperature and high pressure gas reservoirs,for example,conventional methods for calculating fluid physical parameters are difficult to be used accurately in high temperature and high pressure gas reservoirs,traditional steady-state temperature and pressure models are difficult to correctly predict wellbore pressure and temperature distribution,and it is difficult to select flow pressure calculation models for multiphase pipes with different water-gas ratios.In view of the above problems,on the basis of a large number of literature research,for high temperature and high pressure gas reservoirs,the deviation factor of gas Wells and viscosity calculation model are optimized.The unsteady temperature model in the process of well opening and shut-in is established by using the wellbore-formation unsteady heat transfer model and fluid thermodynamics model.The single-phase flow pressure calculation model was optimized,and the multi-phase flow pressure model was optimized under different gas-water ratios.The coupling model of temperature and pressure is established,and the model is verified and analyzed.The research results of this paper are as follows:(1)According to the basic experimental data of high-temperature and high-pressure gas Wells,the calculation methods of deviation factors such as DAK,PR,HY and component model are compared with the viscosity calculation methods such as Lee,Dempsey,Standing and component model.The results show that when the pressure exceeds 95MPa,the component model is more suitable for the calculation of deviation factor and viscosity of high temperature and high pressure gas reservoirs.(2)The non-steady state temperature model is established in the process of well opening and shut-in,and the calculation method of relevant thermodynamic parameters required for their calculation is studied.(3)Optimization of the single-phase flow pressure model was performed,and the study showed that the cullender-smith model had a higher calculation accuracy;Compared with the two-phase flow pressure model under different gas-water ratios,it was found that when the gas-water ratio was greater than 2000m3/m 3,the modified cullender-smith model had higher accuracy.When the gas-water ratio is less than 2000m3/m3,the improved Hasan-Kabir model has higher calculation accuracy.(4)Considering that the unsteady temperature-pressure coupling model is more in line with the actual field engineering needs than the temperature and pressure calculated by the steady-state temperature-pressure model,it can also correct the abnormal pressure results in the shut-in process of the field high-temperature and high-pressure gas Wells,so that the well test interpretation results can be closer to the measured values.