Downhole Throttling Technology In Eastern Sichuan Sour Gas Field

Gas wells containing hydrogen sulfide in East Sichuan areas usually are running through surface heating system, throttling depressurization system. Wellhead, pipeline and equipments in front of the throttling system are still under high pressure, which probably exists certain potential safety hazards. Meantime, it’s required to equip on-site desulfurization device to purify virgin gas for heating system, which leads to long term construction and more costs. Downhole throttling technology is a better technology to fiz the issue mentioned above, but the current downhole throttling tools can not meet the requirement for gas wells in East Sichuan areas which containing high hydrogen sulfide.According to the specificity of sour gas field of East Sichuan, we analyze the reasonable diameter of flow nipple and design method of throttling depth in the report, basing on the calculation of downhole throttling depressurization and temperature drop predication, emphasizing on the systematic evaluation research on sealing property and bearing resistance of current downhole throttling tools, erosion control and corrosion resistance of sitting sub flow nipple and rubber test sample. Combining the specificity of gas field in East Sichuan, we did lots of systematic researches such as optimizing the material and the structure of the downhole throttling tools, testing the intensity of the steel and indoor evaluation, then successfully developed downhole throttling tools meeting the requirements of sour gas field of East Sichuan. On-site application approved that the flowing tubing pressure dropped to3.0-7.5MPA, and the gas flow temperature of the wellhead were between23to35degree much higher than the temperature to creating hydrates under the pressure of ground gathering pipe. There is no hydrate created in wellbore and ground gathering pipe to all of test wells. Application of downhole throttling technology in sour gas field can achieve the purpose of prevention and control of the hydrate successfully, and it also can increase the production and economic efficiency, simplify the surface process and save the costs on single-well yard construction including surface throttling system and heating system which normally required around2M per well.