Wellbore Gas Hydrate And Productivity Forecast In High Temperature And High Pressure Gas Reservoir

Some gas wells in high temperature and high pressure gas reservoirs are blocked by hydrates in the production process,which seriously affects the production.Therefore,it is of great practical value to carry out research on wellbore hydrate prediction and production capacity prediction for high temperature and high pressure gas reservoirs,and it is of great significance to the deployment of development plans.Taking block KS 9 of high temperature and high pressure gas reservoir as the research object,the composition model of high temperature and high pressure gas well was established by using PIPESIM software for hydrate prediction.Open flow method,gas production indicating curve method and nodal analysis method are respectively adopted to calculate the gas well productivity,and the following results are obtained:(1)The Hagedorn&Brown correlation formula is preferred as the calculation correlation formula of pipe flow pressure drop in the block,and the wellbore pressure distribution,wellbore temperature distribution,critical temperature and pressure curve of hydrate formation and hydrate formation location are predicted for the gas well KS 9.The prediction results show that there will be natural gas hydrate formation in the upper80m below the wellhead of well KS 9.(2)The effects of gas production,tubing size,formation pressure and other sensitive parameters on hydrate formation are simulated.The smaller gas production,the smaller the tubing size,the higher the formation pressure,are easier the formation of hydrates.(3)For the gas well with a depth of about 7500 m,a temperature of 178?and a pressure of 125 MPa,when the gas production is 30×10~4m~3/d,choose 4 in or 4 1/2 in tubing to avoid the formation of hydrates.When gas production is greater than or equal to 40×10~4m~3/d,no matter what size tubing is selected,hydrate formation will not occur.(4)The hydrate prevention technology for downhole throttling and pressure reduction was studied.The throttling nozzle diameter of 6 mm and the depth of 2500 m were optimized and designed as the throttling process parameters of KS 9 well,which solved the technical difficulties of hydrate prevention and control under high temperature and high pressure conditions.(5)By comparing and analyzing the calculation results of the unobstructed flow method,gas production indicator curve method and node analysis method,it is determined that the average reasonable productivity of a single well in the KS 9 block of the high-temperature and high-pressure gas reservoir is 76×10~4m~3/d.(6)Optimized the reasonable working system and production parameters of each gas well in block KS 9 to determine the best production status of high temperature and high pressure gas wells.The research results guide and apply to the preparation of the Tarim KS 9 block development plan,which has a strong guiding significance for the prediction and prevention of hydrates in similar gas reservoirs.